AC power plugs and sockets are devices for removably connecting electrically operated devices to the
power supplyMains is the general-purpose alternating current electric power supply. In the US, electric power is referred to by several names including household power, household electricity, powerline, domestic power, wall power, line power, AC power, city power, street power, and grid power...
. Electrical plugs and sockets differ by country in rating, shape, size and type of connectors. The types used in each country are set by national standards.
Generally the plug is the movable connector attached to an electrically operated device's
power cordA power cord, line cord, or mains cable is a cable that temporarily connects an appliance to the mains electricity supply via a wall socket or extension cord. The terms are generally used for cables using a power plug to connect to a single-phase alternating current power source at the local line...
, and the socket is a fixture on equipment or a building structure. Plugs have
maleIn electrical and mechanical trades and manufacturing, each half of a pair of mating connectors or fasteners is conventionally assigned the designation male or female...
circuit contacts, while sockets have female contacts. The plug has protruding prongs, blades, or pins that fit into matching slots or holes in the socket. Wall-mounted sockets are also called receptacles, outlets, or power points.
To reduce the risk of
electric shockElectric Shock of a body with any source of electricity that causes a sufficient current through the skin, muscles or hair. Typically, the expression is used to denote an unwanted exposure to electricity, hence the effects are considered undesirable....
, plug and socket systems can incorporate a variety of safety features. For example sockets can be designed to accept only compatible plugs and reject all others. There are many systems which block the socket holes with insulators when a plug is not inserted and some systems are designed such that dangerous voltage is never present on an exposed contact. Exposed contacts are present in some sockets, but are used exclusively for
groundingIn electrical engineering, ground or earth may be the reference point in an electrical circuit from which other voltages are measured, or a common return path for electric current, or a direct physical connection to the Earth....
(earthing).
Early history
When
electricityElectricity is a general term encompassing a variety of phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena, such as lightning, static electricity, and the flow of electrical current in an electrical wire...
was first introduced into the household, it was primarily used for lighting. At that time, many electricity companies operated a split-tariff system where the cost of electricity for lighting was lower than that for other purposes. This led to portable appliances (such as vacuum cleaners, electric fans, and hair driers) being connected to light bulb sockets.
However, as electricity became a common method of lighting houses and operating labour-saving appliances, a safe means of connection to the electric system other than using a light socket was needed. The original two pin electrical plug and socket was invented by
Harvey HubbellHarvey Hubbell II , was a U.S. inventor, entrepreneur and industrialist. His best known inventions are the electrical plug, and the pull-chain light socket....
and
patentA patent is a form of intellectual property. It consists of a set of exclusive rights granted by a sovereign state to an inventor or their assignee for a limited period of time in exchange for the public disclosure of an invention....
ed in 1904. The original socket into which the user inserted the appliance's plug (of Hubbell's design) itself screwed into the sort of socket used for light bulbs, rather than being directly connected to the building's fixed wiring. (US Patent #774,250) Other manufacturers adopted the Hubbell pattern and by 1915 they were widespread, although in the 1920s and even later, household and light commercial equipment was still powered through cables connected with Edison screw-base adapters to lampholders.
The grounded consumer plug has several claimants to its invention. The earliest patent for a grounded plug appears to be one applied for on January 11, 1915 by George P. Knapp, on behalf of the Harvey Hubbell company and granted on April 18, 1916. This patent covers the use of a grounding pin which extends further than the other two contacts to ensure that it is engaged first. However, the suggested configuration of the pins was that found in the Australian plug used today primarily in Australasia and China, which was not interoperable with existing two-contact ungrounded plugs. Other grounded plugs that are widely used today were developed later by others so as to be interoperable with ungrounded plugs.
The
Schuko"Schuko" is the colloquial name for a system of AC power plugs and sockets that is defined as "CEE 7/4". A Schuko plug features two round pins of 4.8 mm diameter for the live and neutral contacts, plus two flat contact areas on the top and bottom side of the plug for protective earth...
-system plug was invented by Albert Büttner, who patented it in 1926. The current American version of the grounded plug, with two vertical blades and a round grounding pin was invented by Philip F. Labre, while he was attending the
Milwaukee School of EngineeringThe Milwaukee School of Engineering is a private university located in downtown Milwaukee, Wisconsin. MSOE is best known for its applications-oriented curriculum, close association with business and industry, and extremely high placement rate...
(MSOE). It is said that his landlady had a cat which would knock over her fan when it came in the window. When she plugged the fan back in, she would get an
electric shockElectric Shock of a body with any source of electricity that causes a sufficient current through the skin, muscles or hair. Typically, the expression is used to denote an unwanted exposure to electricity, hence the effects are considered undesirable....
. Labre figured out that if the plug were grounded, the electricity would go to earth through the plug rather than through his landlady. He applied a patent on May 12, 1927 and was issued a US patent for grounding receptacle and plug in June, 1928. As the need for safer installations became apparent, earthed three-contact systems were made mandatory in most industrial countries.
Proliferation
During the first fifty years of commercial use of electric power, standards developed rapidly based on growing experience. Technical, safety, and economic factors influenced the development of all wiring devices and numerous varieties were invented. Gradually the desire for trade eliminated some standards that had been used only in a few countries. Former colonies may retain the standards of the colonising country, occasionally—as with the UK and a number of its former colonies—after the colonising country has changed its standard. Sometimes offshore industrial plants or overseas military bases use the wiring practices of their controlling country instead of the surrounding region. Hotels and airports may maintain receptacles of foreign standards for the convenience of travellers. Some countries have multiple voltages, frequencies and plug designs in use, which can create inconvenience and safety hazards.
Consolidation
Many countries have settled on one of a few
de facto standards, which became formalised as official national standards, although there remain older installations of obsolete wiring in most countries. Some buildings have wiring that has been in use for almost a century and which pre-dates all modern standards.
In Europe, since 1965 the International Commission on the Rules for the Approval of Electrical Equipment (CEE) has published a standard (CEE 7
Specification for Plugs and Socket-Outlets for Domestic and Similar Purposes ) describing the plugs and sockets used. In North America the
National Electrical Manufacturers' AssociationNéma is a town in southeastern Mauritania, close to the border with Mali. It is located at around . It is the capital of Hodh Ech Chargui Region and of the Néma Department....
publishes standards for plugs and sockets.
There has been some movement towards consolidation of standards for international interoperability. For example, the CEE 7/7 plug has been adopted in several European countries and is compatible with both CEE 7/5 and CEE 7/4 sockets, while the ungrounded and unpolarised
EuroplugThe Europlug is a flat, two-pole domestic AC power plug that is generally supplied moulded on the end of an appliance's flex or a power cord, designed for voltages up to 250 V and currents up to 2.5 A...
is compatible with an even greater proportion of European and other socket types.
IEC 60906-1IEC 60906-1 is an international standard for 230 V AC domestic power plugs and sockets. It was intended to become the common mains plug and socket standard, to be used one day everywhere in Europe and other regions with 230 V mains. The standard was published by the International...
has been proposed as a common standard for all 230
VThe volt is the SI derived unit for electric potential, electric potential difference, and electromotive force. The volt is named in honor of the Italian physicist Alessandro Volta , who invented the voltaic pile, possibly the first chemical battery.- Definition :A single volt is defined as the...
plugs and sockets worldwide but has only been adopted in Brazil to date. IEC 60906-2 recognizes the wide use of the NEMA 5-15 parallel blade plug and socket and recommends it as the standard for all 120 V applications.
Many manufacturers of electrical devices like
personal computerA personal computer is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end-user with no intervening computer operator...
s put an IEC 60320 inlet on the device, and supply for each country a
power cordA power cord, line cord, or mains cable is a cable that temporarily connects an appliance to the mains electricity supply via a wall socket or extension cord. The terms are generally used for cables using a power plug to connect to a single-phase alternating current power source at the local line...
with an IEC 60320 coupler on one end and a national power plug at the other. The electrical device itself is designed to adapt to a wide range of voltage and frequency standards. This has the practical benefit of reducing the amount of testing required for approval, and reduces the number of different product variations that must be produced to serve world markets.
Application issues
Design features of plugs and sockets have gradually developed to reduce the risk of electric shock and fire. Safety measures may include pin and slot composition to permit only the precise insertion of plug into socket, earth pins longer than power pins so the device becomes earthed before power is connected, electrical insulation of pin shanks to reduce live contact exposure when a plug is partially inserted in a socket, socket slot shutters that open only for the correct plug, as well as built in
fusesIn electronics and electrical engineering, a fuse is a type of low resistance resistor that acts as a sacrificial device to provide overcurrent protection, of either the load or source circuit...
and switches.
Grounding/earthing
A third contact may be provided for a connection to
earth groundIn electrical engineering, ground or earth may be the reference point in an electrical circuit from which other voltages are measured, or a common return path for electric current, or a direct physical connection to the Earth....
, intended to protect against insulation failure of the connected device. A common approach is for electrical sockets to have three holes, which can accommodate either 3-pin earthed or 2-pin non-earthed plugs. When grounded distribution systems became common, earlier ungrounded socket types were either replaced with new standards, or revised to include a grounding pin.
Different types of plugs are used for different IEC
appliance classesIn the electrical appliance manufacturing industry, the following IEC protection classes are used to differentiate between the protective-earth connection requirements of devices.-Class 0:...
. The assigned class depends on whether or not the device is earthed, and the degree of insulation it incorporates. Class I, for example, refers to earthed equipment which requires a third contact in the plug and socket, while Class II refers to unearthed equipment protected by double insulation.
Polarization
Some wiring systems have two circuit conductors, both of which have a significant potential with respect to earth ground. Where the wiring system defines a "neutral" conductor that is connected to earth ground, it is an advantage for appliance designers to maintain that distinction. This requires a plug that can only be connected in one way to the wall socket, so that the energized and neutral conductors are not interchanged. Such "polarized" plugs cannot be interchangeable with non-polarized receptacles.
Polarization is maintained by the shape, size, or position of plug pins and socket holes to ensure that a plug fits only one way into a socket. The (single pole) switch of the appliance is then connected in series with the energized wire. For an appliance such as a
toasterThe toaster is typically a small electric kitchen appliance designed to toast multiple types of bread products. A typical modern two-slice toaster draws anywhere between 600 and 1200 W and makes toast in 1 to 3 minutes...
, putting the exposed heating wires on the neutral side of the switch provides a small measure of extra protection against electrical shock; similarly, lamps with
Edison screwThe Edison screw fitting is a system of connectors used for light bulbs, developed by Thomas Edison and licensed starting in 1909 under the Mazda trademark. Most have a right-hand threading, so that it goes in when turned clockwise and comes out when turned counterclockwise, like a hardware screw...
bases will connect the screw shell of the lamp socket to the neutral conductor.
Interchange hazards
Plugs and sockets are designed as a system to meet standards for safety and reliability. Some types of receptacles may accept more than one type of plug; where this is an official, approved intention of the receptacle design, all the approved combinations will be tested to the applicable safety standards. Occasionally, plug and receptacle combinations may allow power to flow but may not meet product standards for mating force, grounding, current capacity, life expectancy, or safety. Improvised or user-modified connectors will not meet the product safety standards. Adapters between different standards can overcome mechanical incompatiblity.
Types in present use
There are two basic standards for voltage and frequency in the world. One is the North American standard of 120 volts at a
frequencyThe utility frequency, line frequency or mains frequency is the frequency at which alternating current is transmitted from a power plant to the end-user. In most parts of the world this is 50 Hz, although in the Americas it is typically 60 Hz...
of 60
HzThe hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....
, and the other is the European standard of 220–240 volts at 50 Hz. The differences arose for historical reasons as discussed in the article
Mains electricityMains is the general-purpose alternating current electric power supply. In the US, electric power is referred to by several names including household power, household electricity, powerline, domestic power, wall power, line power, AC power, city power, street power, and grid power...
. Usually
NEMANéma is a town in southeastern Mauritania, close to the border with Mali. It is located at around . It is the capital of Hodh Ech Chargui Region and of the Néma Department....
type receptacles and plugs are used on 60 Hz systems, and CEE and other types are used on 50 Hz systems, but exceptions exist.
Countries on other continents have adopted one of these two voltage standards, although some countries use variations or a mixture of standards. The outline maps show the different plug types, voltages and frequencies used around the world, color-coded for easy reference.
Types are sometimes designated by an arbitrary letter designation from a 1998 US government publication, which has no official standing but is useful as a de facto naming standard when comparing different AC power plugs and sockets.
Special purpose sockets may be found in residential, industrial, commercial or institutional buildings. Examples of systems using special purpose sockets include:
- "Clean" ground for use with computer systems,
- Emergency power supply,
- Uninterruptible power supply, for critical or life-support equipment,
- Isolated power for medical instruments,
- "Balanced" or "technical" power used in audio and video production studios,
- Theatrical lighting
- Outlets for electric clothes dryers, electric ovens, and air conditioners with higher current rating.
Depending on the nature of the system, special-purpose sockets may be just labelled or coloured to identify a reserved use of a system (for example, computer power), or may have different arrangements of pins or keying provisions to make them physically incompatible with general purpose plugs, to prevent use of unintended equipment.
Argentina IRAM 2073 (Argentinian 10 A/250 V) and compatible types
The
ArgentinianArgentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
plug is a three-wire earthed plug rated at 10 A (or 20A), 250 V defined by
IRAMThe Argentine Normalization and Certification Institute is the International Organization for Standardization member body for Argentina....
and used in Class 1 applications in Argentina. This plug is similar in appearance to the Australasian and Chinese plugs. The pin length is same as the Chinese version. The most important difference from the Australasian plug is that the Argentinian plug is wired with the live and neutral contacts reversed.
In Brazil, this kind of plug is still commonly found in high-power appliances like air conditioners, dishwashers, and household oven. Since the adopted
IEC 60906-1IEC 60906-1 is an international standard for 230 V AC domestic power plugs and sockets. It was intended to become the common mains plug and socket standard, to be used one day everywhere in Europe and other regions with 230 V mains. The standard was published by the International...
standard prescribes a high-current plug version, the original motivation to use the "Argentinian" plug ceased to exist, and the new standard should prevail in the long term.
Australian standard AS/NZS 3112 (Australasian 10 A/240 V)
This plug, used in
AustraliaAustralia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
,
New ZealandNew Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
,
FijiFiji , officially the Republic of Fiji , is an island nation in Melanesia in the South Pacific Ocean about northeast of New Zealand's North Island...
,
ArgentinaArgentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
, Solomon Islands and
Papua New GuineaPapua New Guinea , officially the Independent State of Papua New Guinea, is a country in Oceania, occupying the eastern half of the island of New Guinea and numerous offshore islands...
, has a grounding pin, and two flat current-carrying pins forming an upside down V-shape. The flat blades measure 6.5 by and are set at 30° to the vertical at a nominal pitch of 13.7 mm (0.539370078740158 in). Australian and New Zealand wall sockets almost always have switches on them for extra safety, as in the UK. An unearthed version of this plug with two angled power pins but no earthing pin is used with small double-insulated appliances, but the powerpoint (wall) outlets always have three pins, including a ground pin.
There are several AS/NZS 3112 plug variants, including ones with larger pins and/or differently shaped ground pins used for devices drawing 15, 20, 25 and 32 amps. These sockets accept plugs of equal or of a lower current capacity, but not of higher capacity. For example, a 10 A plug will fit all sockets but a 20 A plug will fit only 20, 25 and 32 A outlets.
Australasia's standard plug/socket system was originally codified as standard C112 (floated provisionally in 1937, and adopted as a formal standard in 1938), which was superseded by
AS 3112AS 3112 is an Australian standard for mains power plug. It is also known as a Type I plug.-Description:The plug matching the pictured socket, used in Australia, Argentina, New Zealand, Fiji, Papua New Guinea and Tokelau, has an earthing pin and two flat pins forming an inverted V-shape...
in 1990. As of 2005, the latest major update is AS/NZS 3112:2004, which mandated insulated pins by 2005 at the point of sale in all Australian States and New Zealand. However, equipment and cords made before 2003 can still be used.
BS 4573 (UK shaver)
In the
United KingdomThe United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
and
IrelandIreland , described as the Republic of Ireland , is a sovereign state in Europe occupying approximately five-sixths of the island of the same name. Its capital is Dublin. Ireland, which had a population of 4.58 million in 2011, is a constitutional republic governed as a parliamentary democracy,...
, there is a two-pin socket for use with electric shavers in bath or shower rooms. It derives from the unearthed version of 5/6 ampere British plug and it has 0.2 in (5.08 mm) diameter pins 5/8 in apart. The sockets for this plug are often designed to accept unearthed CEE 7/16, US or Australian plugs as well. Sockets are often able to supply either 230 V or 115 V. In wet zones, they must contain an
isolation transformerAn isolation transformer is a transformer used to transfer electrical power from a source of alternating current power to some equipment or device while isolating the powered device from the power source, usually for safety...
compliant with BS 3535.
5 Ampere
IndiaIndia , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
and
PakistanPakistan , officially the Islamic Republic of Pakistan is a sovereign state in South Asia. It has a coastline along the Arabian Sea and the Gulf of Oman in the south and is bordered by Afghanistan and Iran in the west, India in the east and China in the far northeast. In the north, Tajikistan...
have standardised on a plug which was originally defined in British standard
BS 546BS 546 is a pre-Second World War British Standard for domestic AC power plugs and sockets that is also the precursor of current Indian and South African plug standards. This plug is also used in Singapore to a limited extent...
. It has three large round pins in a triangular pattern. The BS 546 standard is also used in parts of the Middle East (Kuwait, Qatar) and parts of Asia and South East Asia that were electrified by the British. This type was also previously used in
South AfricaThe Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
, but has been phased out in favour of the 15 A version there. Similarly, in
GhanaGhana , officially the Republic of Ghana, is a country located in West Africa. It is bordered by Côte d'Ivoire to the west, Burkina Faso to the north, Togo to the east, and the Gulf of Guinea to the south...
,
KenyaKenya , officially known as the Republic of Kenya, is a country in East Africa that lies on the equator, with the Indian Ocean to its south-east...
and
NigeriaNigeria , officially the Federal Republic of Nigeria, is a federal constitutional republic comprising 36 states and its Federal Capital Territory, Abuja. The country is located in West Africa and shares land borders with the Republic of Benin in the west, Chad and Cameroon in the east, and Niger in...
, the plug has been mostly replaced by the British BS 1363. This 5 A plug, along with its smaller 2 A cousin, is sometimes used in the UK for centrally switched domestic lighting circuits, in order to distinguish them from normal power circuits. Both plugs have an unearthed variant, incompatible with 3-prong version because of the distance between pins.
15 Ampere
The 15 A version of the BS 546 plug has larger pins spaced at 7.05 by. Live and neutral are spaced 1 in (25.4 mm) apart, and earth is 1+1/8 in away from each of them. In
IndiaIndia , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
,
PakistanPakistan , officially the Islamic Republic of Pakistan is a sovereign state in South Asia. It has a coastline along the Arabian Sea and the Gulf of Oman in the south and is bordered by Afghanistan and Iran in the west, India in the east and China in the far northeast. In the north, Tajikistan...
,
Sri LankaSri Lanka, officially the Democratic Socialist Republic of Sri Lanka is a country off the southern coast of the Indian subcontinent. Known until 1972 as Ceylon , Sri Lanka is an island surrounded by the Indian Ocean, the Gulf of Mannar and the Palk Strait, and lies in the vicinity of India and the...
,
NepalNepal , officially the Federal Democratic Republic of Nepal, is a landlocked sovereign state located in South Asia. It is located in the Himalayas and bordered to the north by the People's Republic of China, and to the south, east, and west by the Republic of India...
and
NamibiaNamibia, officially the Republic of Namibia , is a country in southern Africa whose western border is the Atlantic Ocean. It shares land borders with Angola and Zambia to the north, Botswana to the east and South Africa to the south and east. It gained independence from South Africa on 21 March...
, the 15 A version is used for larger appliances. Some countries like
South AfricaThe Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
use it as the main domestic plug and socket, where sockets always have an on–off switch built into them. It is still commonly found in
Hong KongHong Kong is one of two Special Administrative Regions of the People's Republic of China , the other being Macau. A city-state situated on China's south coast and enclosed by the Pearl River Delta and South China Sea, it is renowned for its expansive skyline and deep natural harbour...
and
BotswanaBotswana, officially the Republic of Botswana , is a landlocked country located in Southern Africa. The citizens are referred to as "Batswana" . Formerly the British protectorate of Bechuanaland, Botswana adopted its new name after becoming independent within the Commonwealth on 30 September 1966...
, alongside BS 1363. BS 546 was almost universally used in the UK and Ireland for indoor dimmable theatre and architectural lighting installations, but there is now a widespread move to using CEE 16 A industrial sockets in new installations. It was also often used for non-dimmed but centrally controlled sockets within such installations, or where an unfused plug was desired. This plug is also widely used in
IsraelThe State of Israel is a parliamentary republic located in the Middle East, along the eastern shore of the Mediterranean Sea...
,
SingaporeSingapore , officially the Republic of Singapore, is a Southeast Asian city-state off the southern tip of the Malay Peninsula, north of the equator. An island country made up of 63 islands, it is separated from Malaysia by the Straits of Johor to its north and from Indonesia's Riau Islands by the...
,
Sri LankaSri Lanka, officially the Democratic Socialist Republic of Sri Lanka is a country off the southern coast of the Indian subcontinent. Known until 1972 as Ceylon , Sri Lanka is an island surrounded by the Indian Ocean, the Gulf of Mannar and the Palk Strait, and lies in the vicinity of India and the...
and
Malaysia for
air conditionersAn air conditioner is a home appliance, system, or mechanism designed to dehumidify and extract heat from an area. The cooling is done using a simple refrigeration cycle...
and
clothes dryerA clothes dryer or tumble dryer is a household appliance that is used to remove moisture from a load of clothing and other textiles, generally shortly after they are cleaned in a washing machine....
s.
A socket has been developed for the Indian subcontinent that accepts both 5A and 15 A BS 546 plugs, with adjacent holes of the appropriate gauge.
BS 1363
The
British StandardsBritish Standards are the standards produced by BSI Group which is incorporated under a Royal Charter...
1363 plug is used in the
United KingdomThe United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
and other countries. Compatible plugs standards are IS 401 and 411 (Ireland), MS 589 (Malaysia) and SS 145 (Singapore), and SASO 2203 (Saudi Arabia).
This plug, commonly known as a
13 amp plug, is a large plug that has three rectangular pins forming a triangle. Live and neutral are 17.4 mm (0.68503937007874 in) long, and spaced 22.2 mm (0.874015748031496 in) apart. 9 mm (0.354330708661417 in) of insulation at the trailing ends of the pins prevents accidental contact with a bare connector while the plug is partially inserted. The earth pin is approximately 3.97 by and 22.2 mm (0.874015748031496 in) long.
The plug has a 1 in (25.4 mm) long
fuseIn electronics and electrical engineering, a fuse is a type of low resistance resistor that acts as a sacrificial device to provide overcurrent protection, of either the load or source circuit...
to protect the appliance flexible cable from overload. British wiring standards allow up to 32A ring main circuits, so circuit protection of the fixed wiring cannot protect relatively small flexible cable conductors. Sockets are wired with neutral on the left and live on the right (viewed from the front of the socket) so that the fuse in the plug disconnects the live feed if it blows. The same convention is used for all British sockets connected directly to "mains" wiring.
UK wiring regulations (
BS 7671British Standard BS 7671 "Requirements for electrical installations" is the national standard in the United Kingdom for low voltage electrical installations....
) require sockets in homes to have shutters over the live and neutral connections to prevent the insertion of objects other than electric plugs. On Class II appliances, the earth pin is often
plasticA plastic material is any of a wide range of synthetic or semi-synthetic organic solids used in the manufacture of industrial products. Plastics are typically polymers of high molecular mass, and may contain other substances to improve performance and/or reduce production costs...
and serves only to open the shutters and to enforce the correct orientation of live and neutral pins. Opening the shutters with a screwdriver to insert other plugs may be dangerous if the plugs do not have a fuse or do not fit properly.
BS 1363 plugs and sockets started appearing in 1946 and BS 1363 was first published in 1947. By the end of the 1950s, it had replaced the earlier BS 546 in new installations, and by the end of the 1960s, most earlier installations had been rewired to BS 1363 standards. Outlets usually include switches on the live side for convenience and safety.
CEE 7/4 (German "Schuko" 16 A/250 V grounded)
CEE 7/4, commonly called "
Schuko"Schuko" is the colloquial name for a system of AC power plugs and sockets that is defined as "CEE 7/4". A Schuko plug features two round pins of 4.8 mm diameter for the live and neutral contacts, plus two flat contact areas on the top and bottom side of the plug for protective earth...
" socket, has a recessed round shape with two symmetrical round receptacles and two grounding clips on the sides of the socket. The Schuko connection system is symmetrical and unpolarised by design, allowing live and neutral to be reversed. Its dimensions are compatible with CEE 7/5 (french plug/socket) except that the female ground contact is omitted. The socket also accepts Europlugs and CEE 7/17 plugs. It supplies up to 16 amperes. It is used in
AlbaniaAlbania , officially known as the Republic of Albania , is a country in Southeastern Europe, in the Balkans region. It is bordered by Montenegro to the northwest, Kosovo to the northeast, the Republic of Macedonia to the east and Greece to the south and southeast. It has a coast on the Adriatic Sea...
,
AustriaAustria , officially the Republic of Austria , is a landlocked country of roughly 8.4 million people in Central Europe. It is bordered by the Czech Republic and Germany to the north, Slovakia and Hungary to the east, Slovenia and Italy to the south, and Switzerland and Liechtenstein to the...
,
Bosnia and HerzegovinaBosnia and Herzegovina , sometimes called Bosnia-Herzegovina or simply Bosnia, is a country in Southern Europe, on the Balkan Peninsula. Bordered by Croatia to the north, west and south, Serbia to the east, and Montenegro to the southeast, Bosnia and Herzegovina is almost landlocked, except for the...
,
BulgariaBulgaria , officially the Republic of Bulgaria , is a parliamentary democracy within a unitary constitutional republic in Southeast Europe. The country borders Romania to the north, Serbia and Macedonia to the west, Greece and Turkey to the south, as well as the Black Sea to the east...
,
ChileChile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...
,
CroatiaCroatia , officially the Republic of Croatia , is a unitary democratic parliamentary republic in Europe at the crossroads of the Mitteleuropa, the Balkans, and the Mediterranean. Its capital and largest city is Zagreb. The country is divided into 20 counties and the city of Zagreb. Croatia covers ...
,
EstoniaEstonia , officially the Republic of Estonia , is a state in the Baltic region of Northern Europe. It is bordered to the north by the Gulf of Finland, to the west by the Baltic Sea, to the south by Latvia , and to the east by Lake Peipsi and the Russian Federation . Across the Baltic Sea lies...
,
FinlandFinland , officially the Republic of Finland, is a Nordic country situated in the Fennoscandian region of Northern Europe. It is bordered by Sweden in the west, Norway in the north and Russia in the east, while Estonia lies to its south across the Gulf of Finland.Around 5.4 million people reside...
,
GermanyGermany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
,
GreeceGreece , officially the Hellenic Republic , and historically Hellas or the Republic of Greece in English, is a country in southeastern Europe....
,
HungaryHungary , officially the Republic of Hungary , is a landlocked country in Central Europe. It is situated in the Carpathian Basin and is bordered by Slovakia to the north, Ukraine and Romania to the east, Serbia and Croatia to the south, Slovenia to the southwest and Austria to the west. The...
,
IcelandIceland , described as the Republic of Iceland, is a Nordic and European island country in the North Atlantic Ocean, on the Mid-Atlantic Ridge. Iceland also refers to the main island of the country, which contains almost all the population and almost all the land area. The country has a population...
,
IndonesiaIndonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...
,
ItalyItaly , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
,
LatviaLatvia , officially the Republic of Latvia , is a country in the Baltic region of Northern Europe. It is bordered to the north by Estonia , to the south by Lithuania , to the east by the Russian Federation , to the southeast by Belarus and shares maritime borders to the west with Sweden...
,
LuxembourgLuxembourg , officially the Grand Duchy of Luxembourg , is a landlocked country in western Europe, bordered by Belgium, France, and Germany. It has two principal regions: the Oesling in the North as part of the Ardennes massif, and the Gutland in the south...
,
Republic of MacedoniaMacedonia , officially the Republic of Macedonia , is a country located in the central Balkan peninsula in Southeast Europe. It is one of the successor states of the former Yugoslavia, from which it declared independence in 1991...
, the
NetherlandsThe Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...
,
NorwayNorway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
,
PakistanPakistan , officially the Islamic Republic of Pakistan is a sovereign state in South Asia. It has a coastline along the Arabian Sea and the Gulf of Oman in the south and is bordered by Afghanistan and Iran in the west, India in the east and China in the far northeast. In the north, Tajikistan...
,
PortugalPortugal , officially the Portuguese Republic is a country situated in southwestern Europe on the Iberian Peninsula. Portugal is the westernmost country of Europe, and is bordered by the Atlantic Ocean to the West and South and by Spain to the North and East. The Atlantic archipelagos of the...
,
RomaniaRomania is a country located at the crossroads of Central and Southeastern Europe, on the Lower Danube, within and outside the Carpathian arch, bordering on the Black Sea...
,
RussiaRussia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
,
SerbiaSerbia , officially the Republic of Serbia , is a landlocked country located at the crossroads of Central and Southeast Europe, covering the southern part of the Carpathian basin and the central part of the Balkans...
,
SloveniaSlovenia , officially the Republic of Slovenia , is a country in Central and Southeastern Europe touching the Alps and bordering the Mediterranean. Slovenia borders Italy to the west, Croatia to the south and east, Hungary to the northeast, and Austria to the north, and also has a small portion of...
,
South KoreaThe Republic of Korea , , is a sovereign state in East Asia, located on the southern portion of the Korean Peninsula. It is neighbored by the People's Republic of China to the west, Japan to the east, North Korea to the north, and the East China Sea and Republic of China to the south...
,
SpainSpain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...
,
SwedenSweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....
,
TurkeyTurkey , known officially as the Republic of Turkey , is a Eurasian country located in Western Asia and in East Thrace in Southeastern Europe...
,
UkraineUkraine is a country in Eastern Europe. It has an area of 603,628 km², making it the second largest contiguous country on the European continent, after Russia...
and
UruguayUruguay ,officially the Oriental Republic of Uruguay,sometimes the Eastern Republic of Uruguay; ) is a country in the southeastern part of South America. It is home to some 3.5 million people, of whom 1.8 million live in the capital Montevideo and its metropolitan area...
.
"Schuko" is an abbreviation for the
GermanGerman is a West Germanic language, related to and classified alongside English and Dutch. With an estimated 90 – 98 million native speakers, German is one of the world's major languages and is the most widely-spoken first language in the European Union....
word
Schutzkontakt, which means "Protective (that is, grounded) contact".
Some countries, notably Finland, Norway and Sweden, require child-proof outlet shutters; the German
Schuko"Schuko" is the colloquial name for a system of AC power plugs and sockets that is defined as "CEE 7/4". A Schuko plug features two round pins of 4.8 mm diameter for the live and neutral contacts, plus two flat contact areas on the top and bottom side of the plug for protective earth...
standard does not have this requirement.
CEE 7/5 (French)
FranceThe French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
,
BelgiumBelgium , officially the Kingdom of Belgium, is a federal state in Western Europe. It is a founding member of the European Union and hosts the EU's headquarters, and those of several other major international organisations such as NATO.Belgium is also a member of, or affiliated to, many...
,
PolandPoland , officially the Republic of Poland , is a country in Central Europe bordered by Germany to the west; the Czech Republic and Slovakia to the south; Ukraine, Belarus and Lithuania to the east; and the Baltic Sea and Kaliningrad Oblast, a Russian exclave, to the north...
,
Czech RepublicThe Czech Republic is a landlocked country in Central Europe. The country is bordered by Poland to the northeast, Slovakia to the east, Austria to the south, and Germany to the west and northwest....
,
SlovakiaThe Slovak Republic is a landlocked state in Central Europe. It has a population of over five million and an area of about . Slovakia is bordered by the Czech Republic and Austria to the west, Poland to the north, Ukraine to the east and Hungary to the south...
and some other countries have standardized on a round plug with two round pins measuring 4.8 by, spaced 19 mm (0.748031496062992 in) apart and with a hole for the socket's ground pin. This standard will also accept Europlugs and CEE 7/17 plugs. Sockets are installed with the earth pin upwards. Although the plug is polarised, there is no universally observed standard for connecting the live and neutral. In the former Czechoslovakia Standard ČSN 33 2180:1979, section 6.2.2. required live to be on the left side of socket. Child-resistant outlet shutters are required by French and Belgian standards, however they are not required in all countries where this type is used.
CEE 7/5 plugs are not compatible with the CEE 7/4 socket because grounding in the CEE 7/5 socket is effected by a round male pin permanently mounted in the socket.
This type has been authorised in
DenmarkDenmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...
since 1 July 2008, but sockets of this kind are not yet common.
CEE 7/7 plug
In order to bridge the differences between German and French standards, the CEE 7/7 plug was developed. It is polarised to prevent the live and neutral connections from being reversed when used with a French CEE 7/5 outlet, but allows polarity reversal when inserted into a German CEE 7/4 socket. The plug is rated at 16 A.
It has grounding clips on both sides to connect with the CEE 7/4 socket and a female contact to accept the grounding pin of the CEE 7/5 socket. It is also used in Spain and Portugal. Currently, appliances are sold with non-rewireable CEE 7/7 plugs attached. This means that the plugs are now identical between countries like France and Germany, but the sockets are different.
CEE 7/16 Europlug
This two-pin plug is popularly known as the
EuroplugThe Europlug is a flat, two-pole domestic AC power plug that is generally supplied moulded on the end of an appliance's flex or a power cord, designed for voltages up to 250 V and currents up to 2.5 A...
. The plug is ungrounded and has two round 4 mm (0.15748031496063 in) pins, which usually converge slightly towards their free ends. It is described in CEE 7/16 and is also defined in
ItalianItaly , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
standard CEI 23-5 and
RussiaRussia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
n standard
GOST 7396GOST 7396 is a series of Soviet and later Russian standards that specify basic dimensions and safety requirements for power plugs and sockets used in Russia and other former Soviet Republics, as well as for export to markets that use American or British plugs.Many official standards in Eastern...
. This plug is intended for use with devices that require 2.5 amperes or less. Because it is unpolarised, it can be inserted in either direction into the socket, so live and neutral are connected arbitrarily. The separation and length of the pins allow its safe insertion in most CEE 7/5, CEE 7/4 "Schuko", Israeli, CEE 7/7, Swiss, Danish and Italian outlets, as well as BS 4573 UK shaver sockets. It can be forced into BS 546 (5 amperes) and some BS 1363 sockets, if the shutters are opened, though the connection may be neither reliable in either case, nor safe.
The Europlug itself is used in Class II applications throughout continental Europe. It is also used in the Middle East (Iran), most African nations, South America (Brazil, Chile, Argentina, Peru and Bolivia), Asia (India, Bangladesh, Sri Lanka, Indonesia, Pakistan, South Korea, and the Philippines) as well as Russia and the former Soviet republics, such as Ukraine, Armenia, Georgia, and many developing nations. It is also used alongside the BS 1363 in many nations, particularly former British colonies.
Variations in sockets
Europlug sockets have no ground provisions and consequently have been phased out in most countries. For example, in Germany, ungrounded outlets are rare, found only in very old installations, whereas in the Netherlands they are common in "dry areas" such as in bedrooms or living rooms. Standards also vary between countries as to whether child-resistant shutters are required. Depending on the country and the age of the socket these sockets may have 4.0 or 4.8 mm receptacles. The latter accept CEE 7/5 and CEE 7/4 plugs in addition to Europlugs, though without ground connection. Countries using the CEE 7/5 and CEE 7/4 standards vary in whether ungrounded Europlug sockets are still permitted in environments where the need for grounding is less critical. Adaptors and trailing sockets and power strips designed to accept only Europlugs with 4 mm (0.15748031496063 in) pins may also have plastic barriers in place to prevent CEE 7/17,
Schuko"Schuko" is the colloquial name for a system of AC power plugs and sockets that is defined as "CEE 7/4". A Schuko plug features two round pins of 4.8 mm diameter for the live and neutral contacts, plus two flat contact areas on the top and bottom side of the plug for protective earth...
or French plugs from entering.
CEE 7/17 (German/French 16 A/250 V ungrounded)
This plug also has two round pins but the pins are 4.8 mm (0.188976377952756 in) in diameter like CEE 7/5 and CEE 7/4 and the plug has a round plastic or rubber base that stops it being inserted into small sockets intended for the Europlug. Instead, it fits only into large round sockets intended for CEE 7/5 and CEE 7/4. The base has holes in it to accommodate both side contacts and socket earth pins. It is used for large appliances, and in South Korea for all domestic non-earthed appliances. It is also defined in Italian standard CEI 23-5. Can also be inserted in to Israeli SI 32 with some difficulty.
China CPCS-CCC (Chinese 10 A/250 V)
The standard for Chinese plugs and sockets is set out in GB 2099.1–2008 and GB 1002–2008. As part of China's commitment for entry into the WTO, the new CPCS (Compulsory Product Certification System) has been introduced, and compliant Chinese plugs have been awarded the
CCC MarkThe China Compulsory Certificate mark, commonly known as CCC Mark, is a compulsory safety mark for many products sold on the Chinese market. It became effective on May 1, 2002...
by this system. The plug is three wire, earthed, rated at 10 A, 250 V and used for Class 1 applications (But a 16 A version also existes). Although the pins on the Chinese plug are 1 mm (0.0393700787401575 in) longer, the Australasian plug can be used with
mainland ChineseChina , officially the People's Republic of China , is the most populous country in the world, with over 1.3 billion citizens. Located in East Asia, the country covers approximately 9.6 million square kilometres...
socket. The pins in Chinese plugs are slightly thinner than those in Australian plugs, so a plug or adaptor claiming to be suitable for use in both Chinese and Australian plugs may not fit either outlet correctly. A Chinese plug may tend to fit loosely in an Australian socket, while the relatively thick pins of an Australian plug may not fit easily into a Chinese socket. In China, the sockets are installed upside-down relative to the Australasian ones. China also uses American/Japanese NEMA 1–15 sockets and plugs for Class-II appliances. However, the voltage at a Chinese socket of any type is 220.
Danish Section 107-2-D1 (10/13/16 A/250 V earthed)
This
DanishDenmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...
standard plug is described in the Danish Plug Equipment Section 107-2-D1 Standard sheet (SRAF1962/DB 16/87 DN10A-R). The plug is similar to the French CEE 7/5 except that it has an earthing pin instead of an earthing hole (and vice versa on the socket). This makes the Danish socket more unobtrusive than the French socket which is a cavity into the wall to protect the earthing pin from mechanical damage (and to protect from touching the live pins). The Danish standard provides for outlets to have child-resistant shutters.
The Danish socket will also accept the CEE 7/16 Europlug or CEE 7/17 Schuko-French hybrid plug. CEE 7/4 (Schuko), CEE 7/7 (Schuko-French hybrid), and grounded CEE 7/5 French plugs will also fit into the socket but should not be used for appliances that need earth contact. The current rating on both plugs is 13 A.
A variation (standard DK 2-5a) of the Danish plug is for use only on surge protected computer outlets.
It fits into the corresponding computer socket and the normal socket, but normal plugs deliberately don't fit into the special computer socket. The plug is often used in companies, but rarely in private homes.
There is a variation for hospital equipment with a rectangular left pin, it is used for life support equipment.
Traditionally all Danish sockets were equipped with a switch to prevent touching live pins when connecting/disconnecting the plug. Today, sockets without switch are allowed, but then it is a requirement that the sockets have a cavity to prevent touching the live pins. However, the shape of the plugs generally makes it difficult to touch the pins when connecting/disconnecting.
Since the early 1990s grounded outlets have been required in all new electric installations in Denmark. Older outlets need not be grounded, but all outlets, including old installations, must be protected by
ground-fault interruptersA Residual Current Device is a generic term covering both RCCBs and RCBOs.A Residual-Current Circuit Breaker is an electrical wiring device that disconnects a circuit whenever it detects that the electric current is not balanced between the energized conductor and the return neutral conductor...
(HFI or HPFI in Danish) by 1 July 2008.
As of 1 July 2008, wall outlets for French 2-pin, female earth CEE 7/5 are permitted for installations in Denmark. This was done because no electrical equipment sold to private users is equipped with a Danish plug.
Sockets for the Schuko will not be permitted. The reason is that a large number of currently used Danish plugs (coincidentally made by the afore mentioned Lauritz Knudsen monopoly) will jam when inserted into a Schuko socket. This may cause damage to the socket. It may also result in a bad connection of the pins, with resultant risk of overheating and fire. Many international travel adapter sets sold outside Denmark match CEE 7/16 (Europlug) and CEE 7/7 (Schuko-French hybrid) plugs which can readily be used in Denmark.
Israel SI32
This plug, defined in SI 32 (IS16A-R), is unique to
IsraelThe State of Israel is a parliamentary republic located in the Middle East, along the eastern shore of the Mediterranean Sea...
. It has three flat pins to form a Y-shape. Live and neutral are spaced 19 mm (0.748031496062992 in) apart. The plug is rated at 16 A. In 1989, the standard was revised to use three round 4.5 mm (0.177165354330709 in) pins in the same locations, allowing the socket to accept the Europlugs used in Europe and Israel for non-earthed appliances. Sockets made since 1989 accept both flat and round pins for compatibility with both old and new plugs. As of 2008, pre-1989 sockets which accept only old-style plugs are very rare in Israel.
This plug is also used in the areas controlled by the
Palestinian National AuthorityThe Palestinian Authority is the administrative organization established to govern parts of the West Bank and Gaza Strip...
in the
West BankThe West Bank ) of the Jordan River is the landlocked geographical eastern part of the Palestinian territories located in Western Asia. To the west, north, and south, the West Bank shares borders with the state of Israel. To the east, across the Jordan River, lies the Hashemite Kingdom of Jordan...
and all of the
Gaza Stripthumb|Gaza city skylineThe Gaza Strip lies on the Eastern coast of the Mediterranean Sea. The Strip borders Egypt on the southwest and Israel on the south, east and north. It is about long, and between 6 and 12 kilometres wide, with a total area of...
.
Italian standards
Italy CEI 23-16/VII
The
ItalianItaly , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
earthed plug/socket standard, CEI 23-16/VII, includes two models rated at 10A and 16A that differ in contact diameter and spacing (see below for details). Both are symmetrical, allowing the live and neutral contacts to be inserted in either direction.
The double standard was initially adopted because in Italy, up to the second half of the twentieth century, the electric power used for lamps (
Luce = lighting) and the one used for all other appliances (
Forza =
electromotive forceIn physics, electromotive force, emf , or electromotance refers to voltage generated by a battery or by the magnetic force according to Faraday's Law, which states that a time varying magnetic field will induce an electric current.It is important to note that the electromotive "force" is not a...
; or
Uso Promiscuo = general purpose) were sold at different fares, charged with different taxes, accounted with separated electricity meters, and sent on different wire lines that ended with different sockets. Even though the two electric lines (and respective fares) were definitively unified during the summer of 1974 many houses kept twin wires and twin electricity meters for years thereafter. The two gauges for plugs and sockets thus became a
de facto standardA de facto standard is a custom, convention, product, or system that has achieved a dominant position by public acceptance or market forces...
which is still in use today and has been standardized with CEI 23-16/VII. Older installations often have sockets that are limited to either the 10A or the 16A style plug, requiring the use of an adapter if the other gauge needs to be connected.
CEE 7/16 unearthed Europlugs are also in common use; they are standardized in Italy as CEI 23-5 and fit most of the appliances with low current requirement and double insulation.
Appliances with CEE 7/7 Schuko-French plugs are often sold in Italy too; however not every socket will accept them since the pins of the CEE 7/7 Schuko-French plugs are thicker than the Italian ones. Adapters are cheap and commonly used to connect CEE 7/7 plugs to CEI 23-16/VII sockets, though the power rating may be mismatched (16A to 10A) and may lead to potentially unsafe connection in some cases.
The current Italian standards provide for outlets to have child-resistant shutters.
10 A
The 10 ampere style extends CEE 7/16 by adding a central earthing pin of the same gauge. Thus, CEI 23-16-VII 10A sockets can accept CEE 7/16 Europlugs. This is the plug shown in the first picture.
16 A
The 16 ampere style looks like a magnified version of the 10A style, identical in shape. However, the pins are 5
millimetreThe millimetre is a unit of length in the metric system, equal to one thousandth of a metre, which is the SI base unit of length....
s thick (being 4mm thick in 10A type), 8mm apart (while 5.5mm apart in 10A type) and 7mm longer. The packaging of these plugs in Italy may claim they are a "North European" type. In the past they were also referred to as
per la forza motrice (for electromotive force, see above) or sometimes
industriale (industrial), although the latter has never been a correct definition as factories used preminently three-phase current and specialized connectors.
Multiple standard sockets
Given that the plug with which appliances are fitted and sold varies, in modern installations in Italy (and in other countries where CEI 23-16/VII plugs are used) it is likely to find sockets that can accept more than one standard.
The simpler type has a central round hole and two 8-shaped holes above and below. This design allows the connection of both styles of CEI 23-16/VII plugs (10A and 16A) and the CEE 7/16 Europlug. The advantage of this socket style is its small, compact face. VIMAR brand claims to have patented this socket first in 1975 with their
Bpresa™The trademark symbol, designated by ™ , is a symbol used to provide notice that the preceding mark is a trademark. Use of this symbol does not mean that the trademark has been registered. Registered trademarks are indicated using the Registered trademark symbol...
model; however soon other brands started selling similar products mostly naming them with the generic term
presa bipasso (twin-gauge socket) that is now of common use.
A second, quite common type looks like a CEE 7/4 (German) socket, but adds a central grounding hole. This design can accept CEE 7/4 (German), CEE 7/5 (French), CEE 7/7 (German/French) and CEI 23-16/VII italian 10A plugs. Some of these sockets may also have 8-shaped holes to accept CEI 23-16/VII italian 16A plugs as well. Its drawback is that it’s twice as large as a normal CEI 23-16/VII italian socket.
Other types may push compatibility even further. The VIMAR-brand
universale (all purpose) socket, for example, accepts CEE 7/4 (German), CEE 7/5 (French), CEE 7/7 (German/French), both CEI 23-16/VII italian 10A and 16A plugs, and also NEMA 1-15 (USA/Japan) plugs.
Other countries
Outside of Italy, CEI 23-16/VII plugs are found in
AlbaniaAlbania , officially known as the Republic of Albania , is a country in Southeastern Europe, in the Balkans region. It is bordered by Montenegro to the northwest, Kosovo to the northeast, the Republic of Macedonia to the east and Greece to the south and southeast. It has a coast on the Adriatic Sea...
, Canary island,
ChileChile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...
,
EthiopiaEthiopia , officially known as the Federal Democratic Republic of Ethiopia, is a country located in the Horn of Africa. It is the second-most populous nation in Africa, with over 82 million inhabitants, and the tenth-largest by area, occupying 1,100,000 km2...
,
LibyaLibya is an African country in the Maghreb region of North Africa bordered by the Mediterranean Sea to the north, Egypt to the east, Sudan to the southeast, Chad and Niger to the south, and Algeria and Tunisia to the west....
,
MaldivesThe Maldives , , officially Republic of Maldives , also referred to as the Maldive Islands, is an island nation in the Indian Ocean formed by a double chain of twenty-six atolls oriented north-south off India's Lakshadweep islands, between Minicoy Island and...
,
San MarinoSan Marino, officially the Republic of San Marino , is a state situated on the Italian Peninsula on the eastern side of the Apennine Mountains. It is an enclave surrounded by Italy. Its size is just over with an estimated population of over 30,000. Its capital is the City of San Marino...
, São Tomé e Príncipe,
SyriaSyria , officially the Syrian Arab Republic , is a country in Western Asia, bordering Lebanon and the Mediterranean Sea to the West, Turkey to the north, Iraq to the east, Jordan to the south, and Israel to the southwest....
,
UruguayUruguay ,officially the Oriental Republic of Uruguay,sometimes the Eastern Republic of Uruguay; ) is a country in the southeastern part of South America. It is home to some 3.5 million people, of whom 1.8 million live in the capital Montevideo and its metropolitan area...
,
Vatican CityVatican City , or Vatican City State, in Italian officially Stato della Città del Vaticano , which translates literally as State of the City of the Vatican, is a landlocked sovereign city-state whose territory consists of a walled enclave within the city of Rome, Italy. It has an area of...
, sporadically in
North AfricaNorth Africa or Northern Africa is the northernmost region of the African continent, linked by the Sahara to Sub-Saharan Africa. Geopolitically, the United Nations definition of Northern Africa includes eight countries or territories; Algeria, Egypt, Libya, Morocco, South Sudan, Sudan, Tunisia, and...
(
TunisiaTunisia , officially the Tunisian RepublicThe long name of Tunisia in other languages used in the country is: , is the northernmost country in Africa. It is a Maghreb country and is bordered by Algeria to the west, Libya to the southeast, and the Mediterranean Sea to the north and east. Its area...
), and occasionally in older buildings in
SpainSpain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...
.
NEMA 1-15 (15 A/125 V ungrounded)
This plug and socket, with two flat parallel non-coplanar blades and slots, is used in most of
North AmericaNorth America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
and on the east coast of
South AmericaSouth America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
on devices not requiring a ground connection, such as lamps and double insulated small appliances. It is standardized in the US by the
National Electrical Manufacturers Associationis the association of electrical and medical imaging equipment manufacturers. Founded in 1926 and headquartered near Washington, D.C., its approximately manufacture products used in the generation, transmission, distribution, control, and end use of electricity. These products are used in utility,...
(NEMA) Ungrounded NEMA 1–15 sockets have been prohibited in new construction in the United States and Canada since 1962, but remain in many older homes and are still sold for replacement. NEMA 1-15 plugs are still very common because they are also compatible with newer NEMA 5-15 (grounding) sockets.
Initially, both of the the plug blades were the same width, so the plug could be inserted into the socket either way around. Most plugs manufactured from the 1950s onward are polarized by means of a neutral blade wider than the live blade, so the plug can be inserted only the right way. Polarized NEMA1-15 plugs will not fit into unpolarized sockets, which possess only narrow slots. NEMA 1-15 plugs will fit NEMA 5-15 grounded sockets. Some devices that do not distinguish between neutral and live, such as internally isolated electronic power supplies, are still produced with unpolarized pins (both narrow).
Cheater plugA cheater plug, AC ground lifter or three-prong/two-prong adapter is an adapter that allows a NEMA 5-15P grounding-type plug to connect to a NEMA 1-15R non-grounding receptacle . The use of such an adapter avoids the need to replace receptacles, but is potentially hazardous, if the grounding tab...
adapters allow a grounding 5-15 plug to be fitted to a non-grounded 1-15 receptacle.
JIS C 8303, Class II (Japanese 15 A/100 V ungrounded)
The
JapanJapan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
ese plug and socket appear physically identical to NEMA 1–15. However, the Japanese system incorporates stricter dimensional requirements for the plug housing, different marking requirements, and mandatory testing and approval by
MITIThe Ministry of International Trade and Industry was one of the most powerful agencies of the Government of Japan. At the height of its influence, it effectively ran much of Japanese industrial policy, funding research and directing investment...
or JIS.
Many Japanese outlets and multi-plug adapters are unpolarized — the slots in the sockets are the same size — and will accept only unpolarized plugs. Japanese plugs generally fit into most North American outlets without modification, but polarized North American plugs may require adapters or replacement non-polarized plugs to connect to older Japanese outlets. However, in Japan the voltage is 100 volts, and the frequency in eastern Japan is 50 rather than 60 Hz. Therefore, many North American devices which can be physically plugged into Japanese sockets may not function properly.
NEMA 5-15(15 A/125 V grounded)
The NEMA 5-15 plug has two flat parallel blades like NEMA 1-15, but also adds a grounding blade. It is rated for 15 amperes at 125 volts. The ground pin is longer than the live and neutral blades, so the device is grounded before the power is connected. Both current-carrying blades on grounding plugs are narrow, since the ground pin enforces polarity. NEMA 1-15 plugs are also compatible with NEMA 5-15 sockets.
The 5–15 socket is standard in Canada, the United States, and Mexico. It is also used in Central America, the Caribbean, northern South America (Colombia, Ecuador, Venezuela and part of Brazil), Japan, Taiwan and
Saudi ArabiaThe Kingdom of Saudi Arabia , commonly known in British English as Saudi Arabia and in Arabic as as-Sa‘ūdiyyah , is the largest state in Western Asia by land area, constituting the bulk of the Arabian Peninsula, and the second-largest in the Arab World...
. Looking directly at a NEMA 5-15 outlet with the ground at the bottom, the neutral slot is on the left, and the live slot is on the right. Outlets may be installed in any orientation.
In some parts of the United States and all of Canada, tamper-resistant outlets are now required in new construction. These prevent contact by objects like keys or paper clips inserted into the receptacle.
In
theater lightingModern stage lighting is a flexible tool in the production of theatre, dance, opera and other performance arts. Several different types of stage lighting instruments are used in the pursuit of the various principles or goals of lighting. Stage lighting has grown considerably in recent years...
, this connector is sometimes known as
PBG for
Parallel Blade with Ground,
Edison or
Hubbell, the name of a common manufacturer.
NEMA 5–20 (North American 20 A/125 V grounded)
This is a 20 amperes receptacle. The NEMA 5–20 A has a T-slot for the neutral blade which allows either 15 amperes parallel-blade plugs or 20 amperes plugs to be used.
JIS C 8303, Class I (Japanese 15 A/100 V grounded)
Japan also uses a NEMA 5-15 plug similar to the North American one. However it is less common than its NEMA 1-15 equivalent.
NEMA 14–30
A 30 amperes, 3 wire single-phase grounding receptacle is often used for electric clothes dryers. 240 volts from the
split phaseA split-phase electricity distribution system is a 3-wire single-phase distribution system, commonly used in North America for single-family residential and light commercial applications. It is the AC equivalent of the original Edison 3-wire direct current system...
system is used for the heating elements, and the motor and controls run on 120 volts.
NEMA 14–50
A 50 amperes 3 wire single-phase grounding outlet is usually installed in kitchens and used for electric cooking ranges and ovens. As for dryers, lighting and motors run on 120 V and the main heating element is connected for 240 V. Many plug-in cars use this type of outlet to charge in the owner's garage.
Thai 3 pin plug TIS 166–2549 (2006)
Thai Industrial Standard (TIS) 166–2547 and its subsequent update TIS 166-2549 stipulated a modification of the IEC 60906-1 plug, replacing prior standards which were based on NEMA 1–15 and 5–15, as Thailand uses 220 V electricity. The plug has two round power pins 4.8 mm in diameter and 19 mm in length, insulated for 10 mm and spaced 19 mm apart, with a grounding pin of the same diameter and 21.4 mm in length, located 11.89 mm from the line connecting the two power pins. It was designed to provide compatibility with prior hybrid three-pin sockets, which accept NEMA 1-15, NEMA 5-15 and Europlugs, all of which have been variably used in Thailand. The hybrid socket is also defined in TIS 166-2547, in addition to a plain three-round-pin socket, with plans to replace the former and phase out support for NEMA-compatible plugs. It is polarised so that when the socket is installed with the ground connector upwards, the live connector is to the left (as in NEMA 5-15). The plug is similar to but not interchangeable with the Israeli plug.
Soviet standard GOST 7396 C 1 (6 A or 16 A /250 V ungrounded)
This Soviet plug, still widely used in modern Russia, has pin dimensions and spacing equal to the Europlug, but lacks the insulation sleeves. Unlike the Europlug, it was rated for 6 A. It has a round body like the French CEE 7/5 or flat body with a round base like CEE 7/17. The round base has no notches. The pins are parallel and do not converge. The body is made of fire resistant thermoset plastic. The corresponding 6 A socket accept the Europlug, but not others as the 4.5 holes are too small to accept the 4.8 mm pins of CEE 7/4, CEE 7/5 or CEE 7/7 plugs.
There were also moulded rubber plugs available for devices up to 16 A similar to CEE 7/17, but with a round base without any notches. They could be altered to fit a CEE 7/5 or CEE 7/4 socket by cutting notches with a sharp knife.
Swiss SEV 1011 (Swiss 10 A/250 V)
SwitzerlandSwitzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....
has its own standard which is described in SEV 1011. (ASE1011/1959 SW10A-R) This plug is similar to the Europlug (CEE 7/16), except that it has an offset earth pin and the pin shanks are not necessarily insulated (the pins of most modern appliances are), so plugs partially inserted into non-recessed sockets present a
shockElectric Shock of a body with any source of electricity that causes a sufficient current through the skin, muscles or hair. Typically, the expression is used to denote an unwanted exposure to electricity, hence the effects are considered undesirable....
hazard. Sockets used in kitchens, bathrooms and other wet areas are recessed, while those used elsewhere are not (after 2015, only recessed sockets are allowed to be installed in any setting, minimizing the risk of electric shocks). Some plugs and adaptors have a tapered form and can be used in either environment, while others will fit only the non-recessed sockets. Swiss sockets accept Swiss plugs or Europlugs (CEE 7/16). There is also a non-earthed two-pin variant with the same pin shape, size, and spacing as the SEV 1011's live and neutral pins, but with a more flattened hexagonal form. It fits into Swiss sockets and CEE 7/16 sockets, and is rated for up to 10 A.
A less-common variant has 3 square pins and is rated for 16 amperes. Above 16 amperes, equipment must either be hardwired to the electrical supply system with appropriate branch circuit protection, or connected to the mains with an appropriate high power industrial connector.
Proposed common standard
In 1986, the International Electrotechnical Commission published IEC 60906-1, the specification for a plug that looks similar but is not identical to the Swiss plug. This plug was intended to one day become the common standard for all of Europe and other regions with 230 V mains, but the effort to adopt it as a European Union standard was put on hold in the mid 1990s.
BrazilBrazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
, which had been using mostly Class II Europlugs (while households also commonly presenting socket fittings for the NEMA 1–15 and NEMA 5–15 standards), set out IEC 60906-1 as the national standard in 2001 under specification NBR 14136. However, this standard was never really enforced or encouraged in that country until 2007, when the adoption of IEC 60906-1 was made optional for manufacturers. Also, it helped domestic consumers that most of Class II plugs fitted in the new IEC 60906-1 socket.
Since January 1, 2010, new electrical appliances in Brazil must now comply with the new IEC 60906-1 requirement. End-user stores and resellers can sell equipment without adoption deadlines, but importers will no longer be allowed to bring in nonconforming devices, nor will manufacturers be able to sell them in Brazil.
There are two types of sockets and plugs in this system: one for 10 A, with a 4mm pin diameter, and another for 20 A, with a 4.8 mm pin diameter, the latter used for heavier appliances such as microwave ovens.
South AfricaThe Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
has also introduced the IEC 60906 standard as SANS 164-2.
IEC 60906-2 designated the NEMA 5-15 grounded 15 ampere socket and plug as the standard for 120 volt applications; it is a recognition that the NEMA parallel blade plug and socket is already in universal use in North America.
Comparison of sockets
| Type1 |
Socket standard |
Power rating |
Grounded |
Polarised |
Fused |
Insulated pins |
| A |
NEMA 1–15 unpolarised |
15 A/125 V |
|
|
|
|
| NEMA 1–15 polarised |
15 A/125 V |
|
|
|
|
| JIS C 8303, Class II |
15 A/100 V |
|
|
|
|
| B |
NEMA 5–15 |
15 A/125 V |
* |
|
|
|
| NEMA 5–20 |
20 A/125 V |
* |
|
|
|
| JIS C 8303, Class I |
15 A/100 V |
* |
|
|
|
| C |
CEE 7/16 (Europlug) The Europlug is a flat, two-pole domestic AC power plug that is generally supplied moulded on the end of an appliance's flex or a power cord, designed for voltages up to 250 V and currents up to 2.5 A...
|
2.5 A/250 V |
|
|
|
|
| CEE 7/17 |
16 A/250 V |
|
2 |
|
|
| GOST 7396 GOST 7396 is a series of Soviet and later Russian standards that specify basic dimensions and safety requirements for power plugs and sockets used in Russia and other former Soviet Republics, as well as for export to markets that use American or British plugs.Many official standards in Eastern...
C 1 |
6 A/250 V
16 A/250 V |
|
|
|
|
| D and M |
BS 546 (2 pin) |
2 A/250 V
5 A/250 V = BS 4573 |
|
|
|
|
| BS 546 (3 pin) |
2 A/250 V
5 A/250 V
15 A/250 V = SABS 164
30 A/250 V |
|
|
|
|
| E |
CEE 7/5 ‡ |
16 A/250 V |
* |
3 |
|
† |
| F |
CEE 7/4 Schuko "Schuko" is the colloquial name for a system of AC power plugs and sockets that is defined as "CEE 7/4". A Schuko plug features two round pins of 4.8 mm diameter for the live and neutral contacts, plus two flat contact areas on the top and bottom side of the plug for protective earth...
‡ |
16 A/250 V |
* |
|
|
† |
| G |
BS 1363BS 1363 is a British Standard which specifies the most common type of single-phase AC power plugs and sockets that are used in the United Kingdom. Distinctive characteristics of the system are shutters on the line and neutral socket holes, and a fuse in the plug...
, IS 401 & 411, MS 589, SS 145 |
13 A/230-240 V |
|
|
|
|
| H |
SI 32 |
16 A/250 V |
4 |
|
|
|
| TIS 166–2549 |
16 A/250 V |
|
|
|
|
| I |
AS/NZS 3112AS 3112 is an Australian standard for mains power plug. It is also known as a Type I plug.-Description:The plug matching the pictured socket, used in Australia, Argentina, New Zealand, Fiji, Papua New Guinea and Tokelau, has an earthing pin and two flat pins forming an inverted V-shape...
|
10 A/240 V
15 A/240 V
20 A/240 V
25 A/240 V
32 A/240 V |
* |
|
|
|
| CPCS-CCC |
10 A/250 V |
|
|
|
|
| IRAM 2073 |
10 A/250 V |
|
|
|
|
| J |
Swiss SEV 1011 |
10 A/250 V
16 A/250 V |
* |
|
|
|
| K |
Danish 107-2-D1 |
13 A/250 V |
* |
|
|
|
| L |
CEI 23-16/VII |
10 A/250 V
16 A/250 V |
* |
|
|
|
| − |
IEC 60906-1IEC 60906-1 is an international standard for 230 V AC domestic power plugs and sockets. It was intended to become the common mains plug and socket standard, to be used one day everywhere in Europe and other regions with 230 V mains. The standard was published by the International...
(2 pin) |
10 A and 20 A/250 V |
|
|
|
|
IEC 60906-1IEC 60906-1 is an international standard for 230 V AC domestic power plugs and sockets. It was intended to become the common mains plug and socket standard, to be used one day everywhere in Europe and other regions with 230 V mains. The standard was published by the International...
(3 pin) |
10 A and 20 A/250 V |
* |
|
|
|
- * There are common ungrounded plugs that work with the grounded sockets of this type.
- † Deep-wall socket prevents human contact with pins.
- ‡ CEE 7/7 specifies a grounded hybrid plug that will fit into both the CEE 7/4 and CEE 7/5 sockets. CEE 7/17 specifies an ungrounded hybrid plug that will fit into both the CEE 7/4 and CEE 7/5 sockets.
- 1 Type letters are from a US Department of Commerce report that sees widespread but not universal use to differentiate plug and socket types based on rough mechanical compatibility. Most, but not all common household plugs have an associated letter.
- 2 There are some CEE 7/17 plugs with special shape which are polarised when used with CEE 7/5 sockets (mechanically only).
- 3 Plug can only be inserted one way with French CEE 7/5, but lack of wiring convention means that the system is not ploarized.
- 4 Newer sockets can accept ungrounded Europlugs.
Multi-standard sockets
Sockets that take a variety of plug types can be found in various countries where market size or local market conditions make a specific plug standard impractical to implement. These socket accept plugs fitting various European, Asian and North American standards. Since many plug standards are also associated with corresponding voltages, multi-standard sockets do not safeguard against devices being damaged by the wrong voltage. This forces users to be aware of the voltage requirements of their appliances as well as the prevailing local voltage. Devices designed to adapt automatically to whatever voltage and frequency is supplied, and which don't require grounding, are generally safe to use with these sockets.
These sockets have one or more ground holes to allow 3-pin plugs. On properly wired circuits, the ground contact may be actually grounded; however, as with most other forms of plugs, they are not immune to poor wiring. They may also not provide grounding to all types of plugs, as is the case of Schuko or French plugs where the grounding pin that mates with the plug is part of the socket rather than the plug.
Adapters
To facilitate travelers' use of personal electric devices, adapters are available to permit the interconnection of normally incompatible plugs and sockets. Such adapters overcome only the physical incompatibilities between plugs and sockets built to different standards; often a
voltage converterA voltage converter changes the voltage of an electrical power source. It may be combined with other components to create a power supply.-AC and DC:...
is required for electrical compatibility.
Old Spanish sockets
Some older industrial buildings in Spain used sockets that took a particular type of plug which was rated for higher current and had two flat contacts and a round ground pin, somewhat similar in design to the ones found on American plugs but larger in size.
The live and neutral measure 9 by, and are 30 mm (1.181 in) apart. All three pins are 19 mm (0.748031496062992 in) long, and the earth pin is a cylinder of 4.8 mm (0.188976377952756 in) diameter.
While the plug resembles an American connector, the two flat contacts are much wider apart than on a standard American plug, which will therefore not fit in these sockets.
No domestic appliances were ever sold with these plugs.
UK electric clock connector
Fused plugs and sockets of various proprietary and non-interchangeable types are found in older public buildings in the UK, where they are used to feed AC electric wall clocks. They are smaller than conventional socket outlets, commonly being made to fit BESA junction boxes, and are often of very low profile. Early types were available fused in both poles, later types fused in the live only and provided an earth pin. Most are equipped with a retaining screw or clip to prevent accidental disconnection. The prevalence of battery powered
quartzA quartz clock is a clock that uses an electronic oscillator that is regulated by a quartz crystal to keep time. This crystal oscillator creates a signal with very precise frequency, so that quartz clocks are at least an order of magnitude more accurate than good mechanical clocks...
controlled wall clocks has meant that this connector is rarely seen in new installations.
NEMA 1-15 style 5-receptacle outlet
This is a very rare 5-way outlet from circa 1928, and is able to accept modern ungrounded polarized NEMA 1-15 plugs because the outlet itself is polarized. However, the outlet itself is still obsolete as the NEMA standard only provides for having at most 3 outlets from a single wallplate.
American 240 V "Australian" style
The American electrical supply manufacturers Hubbell, Eagle, and possibly others made outlets and plugs that would match Australian plugs and sockets exactly. These American outlets date back to at least 1915 (as seen in US Patent 1,179,728 filed in 1915), antedating the NEMA 5-15 sockets and plugs. They were meant for appliances that needed grounding (120 V at 15 amperes), and to be used in
laundry roomA laundry room is a room where clothes are washed. In a modern home, a laundry room would be equipped with an automatic washing machine and clothes dryer,and often a large basin, called a laundry tub, for hand-washing delicate articles of clothing such as sweaters, and an ironing board...
s for
washing machineA washing machine is a machine designed to wash laundry, such as clothing, towels and sheets...
s and gas
dryersA clothes dryer or tumble dryer is a household appliance that is used to remove moisture from a load of clothing and other textiles, generally shortly after they are cleaned in a washing machine....
(to power the motor). These did not become popular because NEMA 1-15 2-blade plugs would not fit.
Split current/voltage ratings
Many older North American receptacles have two different current and voltage ratings, most commonly 10 A 250 V/15 A 125 V. This has to do with a peculiarity of the National Electrical Code from 1923 to the 1950s. Originally, receptacles were rated at 10 A 250 V, because the NEC limited lighting circuits to 10 amperes. In 1923, the code changed to allow lighting circuits to be fused at 15 amperes; however, the old rule still applied to circuits over 125 volts. The higher voltages were rarely used for lighting and appliances. Most receptacles with this rating are of the "T-slot" type. This type of rating was phased out in the 1950s, and finally abolished in the 1960s with the adoption of the current NEMA standards.
Pre-NEMA
twist-lock devices can sometimes be found with split 250/600 V ratings. These are also obsolete.
US perpendicular outlet
Another obsolete outlet, made by Bryant, 125 V 15 A and 250 V 10 A rating. A
NEMAis the association of electrical and medical imaging equipment manufacturers. Founded in 1926 and headquartered near Washington, D.C., its approximately manufacture products used in the generation, transmission, distribution, control, and end use of electricity. These products are used in utility,...
5–20 125 V 20 A or 6–15 250 V 15 A plug with a missing ground pin would fit this outlet, but a NEMA 2–20 plug is slightly too big to fit.
The upper slots as seen in the illustration connect to silver-colored wiring screws on the upper side, and the lower slots connect to brass-colored wiring screws on the lower side.
In Australia, the same or similar T-configuration sockets are used for
DC power outletsA DC connector is an electrical connector for supplying direct current power. Unlike domestic AC power plugs and sockets, DC connectors are not generally standardized....
, such as in
stand-alone power systemA stand-alone power system , also known as remote area power supply , is an off-the-grid electricity system for locations that are not fitted with an electricity distribution system...
s (SAPS) or on boats.
In
Soviet UnionThe Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....
and now
RussiaRussia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
this socket is commonly used for wiring in places where the voltage is lowered for safety purposes, like in schools, gas stations or in wet areas, rated 42 V 10 A AC. Such an unusual connection is intended specifically to make the connection of standard higher-voltage equipment impossible.
US Combination duplex outlet
The parallel and tandem outlet accepts normal parallel
NEMAis the association of electrical and medical imaging equipment manufacturers. Founded in 1926 and headquartered near Washington, D.C., its approximately manufacture products used in the generation, transmission, distribution, control, and end use of electricity. These products are used in utility,...
1–15 plugs and also tandem NEMA 2–15 plugs. Both pair of receptacles are fed internally by the same supply.
A more recent and fairly common version of this type is the T-slot outlet, in which the locations of the tandem and the parallel slots were combined to create T-shaped slots. This version also accepts normal parallel NEMA 1–15 plugs and also tandem NEMA 2–15 plugs. Incidentally, a NEMA 5–20 (125 V, 20 A), a NEMA 6-15 (250 V, 15 A) or 6–20 (250 V, 20 A) plug with a missing ground pin would fit this outlet. This type is no longer available in retail shops since the 1960s.
UK Dorman & Smith (D&S)
The D&S plugs and sockets were rated at 13 amperes and were one of the early competing types for use on ring main circuits. They were never popular in private houses but were widely deployed in prefabricated houses and
council housingA council house, otherwise known as a local authority house, is a form of public or social housing. The term is used primarily in the United Kingdom and the Republic of Ireland. Council houses were built and operated by local councils to supply uncrowded, well-built homes on secure tenancies at...
. The
BBCThe British Broadcasting Corporation is a British public service broadcaster. Its headquarters is at Broadcasting House in the City of Westminster, London. It is the largest broadcaster in the world, with about 23,000 staff...
also used them. D&S supplied the sockets to local authorities at very low cost, with the intention of making money out of the sales of plugs typically priced at 4 times the price of a BS1363 plug. It is not known exactly when D&S ceased manufacturing the plugs and sockets but some local authorities continued to use them in new installations until the late 1950s. Many D&S sockets were still in use until the early 1980s, although the difficulty in obtaining plugs for them after around 1970 often forced their users to replace them with BS1363 sockets. This generally violated local authority regulations on alterations to council housing. The D&S plug suffered from a serious design fault: the live pin was a fuse which screwed into the plug body and tended to come unscrewed on its own in use. A fuse that worked loose could end up protruding from the socket, electrically live and posing a shock hazard, when the plug was removed.
UK Wylex Plug
The Wylex plugs and sockets were produced by Wylex Electrical Supplies Ltd. as a competitor to the BS1363 and D&S sockets for use on ring main circuits. The plugs were available in both 5 A and 13 A versions, differing only by the widths of the live and neutral pins, and contained an internal fuse of the same rating as the plug. A plug had a central round earth pin and two flat pins, one on each side of the earth pin, for live and neutral. The two flat pins were slightly offset above and below the line cutting through the horizontal diameter of the earth pin. Wall sockets were rated at 13 amperes and took both 5 A and 13 A plugs. Many 13 A plugs had a socket on the back which took a 5 A plug, but would not take another 13 A plug because the slots for the live and neutral pins were narrower than those of the wall sockets, resulting in a stacked arrangement. Wylex sockets were used in council housing and public sector buildings, and for a short while in private housing. They were particularly popular in the
ManchesterManchester is a city and metropolitan borough in Greater Manchester, England. According to the Office for National Statistics, the 2010 mid-year population estimate for Manchester was 498,800. Manchester lies within one of the UK's largest metropolitan areas, the metropolitan county of Greater...
area although they were installed throughout England, mainly in schools, university accommodation, and government laboratories. Wylex plugs and sockets continued to be manufactured for several years after BS1363 sockets became standard and were commonly used by banks and in computer rooms during the 1960s and 70s for
uninterruptible power suppliesAn uninterruptible power supply, also uninterruptible power source, UPS or battery/flywheel backup, is an electrical apparatus that provides emergency power to a load when the input power source, typically mains power, fails...
or "clean" filtered mains supplies. It is not known exactly when Wylex ceased manufacturing its plugs and sockets; however plugs were available in electrical shops of the Manchester area until the mid 1980s.
Lampholder plug
A lampholder plug fits into the bayonet cap or
Edison screwThe Edison screw fitting is a system of connectors used for light bulbs, developed by Thomas Edison and licensed starting in 1909 under the Mazda trademark. Most have a right-hand threading, so that it goes in when turned clockwise and comes out when turned counterclockwise, like a hardware screw...
socket of a lampholder in place of a light bulb and enables an electrical appliance to be powered from a wall or ceiling light fitting. They were commonly used during the 1920s to 1960s when wall sockets were scarce in many houses and often nonexistent in some of the rooms (bathrooms, cellars, attics, etc.). Also, as in some countries (like Italy) electricity was supplied on a "split tariff" basis with electricity for lighting being charged at a lower fare than that for other purposes, lampholder plugs enabled the consumers to reduce their electricity costs and were thus in broad use.
Lampholder plugs were and are rarely fused.
In the UK, lighting circuits are protected with a 5 A or 6 A fuse or
circuit breakerA circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. Its basic function is to detect a fault condition and, by interrupting continuity, to immediately discontinue electrical flow...
. Wiring regulations in the UK and some other countries no longer approve lampholder plugs because of the risks of overheating and fire.
Edison screw lampholder adaptors (for NEMA 1-15 plugs) are still easily found and commonly used in the Americas.
Old Greek sockets
Called "Tripoliki" (τριπολικές) the 3 Pin round standard similar to Swiss SEV 1011 and post-1989 Israeli/Thai type, virtually abandoned by 1995. Previous to the large-scale adoption of Schuko plugs, this was the only way to use an earthed appliance.
NEMA 2–15 and 2–20
These ungrounded plugs with two flat parallel blades are variants of the 1–15 but are intended to deliver 240 volts instead of 120. The 2–15 has coplanar current blades (rotated 90° from ordinary American plugs), and is used for 240 V service at 15 amperes, while the 2–20 has the two current prongs rotated 90° relative to each other (one vertical, one horizontal) and is used for 240 V service at 20 amperes. NEMA 2 plugs and sockets are rare because they have been prohibited for household use in the United States and Canada for several decades. They have no ground or neutral, and in some cases plugs can be inserted into incorrect-voltage sockets. Prior to the adoption of the NEMA standard, a plug nearly identical to the 2–20 was used for 120 V at 20 A. That obsolete plug would fit into 5–20 and 6–20 sockets, which supply different voltages, but the NEMA 2-20 plug is dimensionally incompatible.
Soviet adaptor plugs
Some appliances sold in the
Soviet UnionThe Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....
had a flat unearthed plug with an additional pass-through socket on the top, allowing stacked arrangement of plugs. This design was very helpful (for the usual Soviet apartment of the 1960s had very few wall sockets), but completely unsafe, as the brass cylinders of the secondary socket were uncovered at the ends (to unscrew them easily), recessed only for 3 mm and provided bad contact because they relied on the secondary plug's bisected expanding pins. The pins of the secondary plug (without insulation sleeves) could not be inserted into the cylinders completely, and were accessible through a 5 mm gap between the primary and secondary plugs.
UK Walsall Gauge plug
Unlike the standard BS 1363 plugs found in the UK, the earth pin is on a horizontal axis and the live and neutral pins on a vertical axis. This style of plug/socket was used by University laboratories (from batteries) and the
BBCThe British Broadcasting Corporation is a British public service broadcaster. Its headquarters is at Broadcasting House in the City of Westminster, London. It is the largest broadcaster in the world, with about 23,000 staff...
, and is still in use on parts of the
London UndergroundThe London Underground is a rapid transit system serving a large part of Greater London and some parts of Buckinghamshire, Hertfordshire and Essex in England...
for 220V DC voltage supply.
Italian Bticino brand Magic security connector
This style of connector, produced by Italian brand Bticino, appeared in the 1960s and was intended as an alternative to the Europlug or CEI 23-16/VII connectors then in use. The socket is an almost rectangular receptacle, with one or more lateral key pins and indents to prevent inverting the plug (it is polarised), or connecting plugs and sockets with different ampere ratings. At least four models were produced: three single-phase general purpose connectors rated respectively 10 A, 16 A and 20 A; plus a three-phase industrial connector rated 10 A; all of them have different key-pin positioning so plugs and sockets cannot be mismatched. The socket is closed by a safety lid (bearing the word ‘’Magic’’ on it) which can be opened only with an even pressure on its surface, thus preventing the insertion of objects (except the plug itself) inside the socket. The contacts are blades positioned on both sides of the plug; the plug is energized only when it is inserted fully into the socket.
The obvious drawback of the system is that it is not compatible with Europlugs. As household appliances were never sold fitted with these security plugs and the use of adapters would defeat all of the newly introduced safety features, once this system is adopted all standard plugs must be cut off and replaced with the appropriate security connector. However, the
Magic security system had some success at first because its enhanced safety features appealed to customers; standard connectors of the day were considered not safe enough. The decline of the system occurred when safety lids similar to the Magic type were developed (VIMAR Sicury) and then applied to standard sockets by third brands and by Bticino itself.
In Italy, the system was never definitively abandoned and, though rarely seen today, is still marked as available in Bticino’s products catalogue.
In Chile, 10 A Magic connectors are commonly used for computer/laboratory power networks, as well as for communications or data equipment. This allows delicate electronics equipment to be connected to an independent circuit breaker, usually including a
surge protectorA surge protector is an appliance designed to protect electrical devices from voltage spikes. A surge protector attempts to limit the voltage supplied to an electric device by either blocking or by shorting to ground any unwanted voltages above a safe threshold...
or an
uninterruptible power supplyAn uninterruptible power supply, also uninterruptible power source, UPS or battery/flywheel backup, is an electrical apparatus that provides emergency power to a load when the input power source, typically mains power, fails...
backup. The different style of plug makes it more difficult for office workers to connect computer equipment to a standard unprotected power line, or to overload the UPS by connecting other office appliances.
In Iceland, Magic plugs were widely used in homes and businesses alongside Europlug and Schuko installations. Their installation in new homes was still quite common even in the late 1980s.
Single phase electric stove plugs and sockets
The plugs and sockets used to power
electric stoveAn electric stove converts electricity into heat to cook and bake.- History :On September 20, 1859, George B. Simpson was awarded US patent #25532 for an 'electro-heater' surface heated by an platinum-wire coil powered by batteries; in his words, useful to "warm rooms, boil water, cook...
s from a single-phase line have to be rated for greater current values than ones for three-phase system because all the power has to be transferred through a single line. Electric stoves are often hardwired to the electrical supply system, connected to the mains with an appropriate high power industrial connector or with non-standard high power proprietary domestic connector (as some countries do not have wiring regulations for single-phase electric stoves). In Russia an electric stove can be often seen connected with an 25–32 amperes connector.
See also
- AC adapter
The AC adapter, AC/DC adapter or AC/DC converter is a type of external power supply, often enclosed in what looks like an over-sized AC plug. Other names include plug pack, plug-in adapter, adapter block, domestic mains adapter, line power adapter, or power adapter...
- DC connector
A DC connector is an electrical connector for supplying direct current power. Unlike domestic AC power plugs and sockets, DC connectors are not generally standardized....
- Industrial and multiphase power plugs and sockets
Industrial and multiphase plugs and sockets provide a connection to the electrical mains rated at higher voltages and currents than household plugs and sockets...
- Polyphase system
A polyphase system is a means of distributing alternating current electrical power. Polyphase systems have three or more energized electrical conductors carrying alternating currents with a definite time offset between the voltage waves in each conductor. Polyphase systems are particularly useful...
- Stage pin connector
A stage pin connector is a standard cable type for theatrical lighting in North America.-Uses:...
- Two-phase electric power
External links