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A centrifugal switch is an electric switch that operates using the centrifugal force
Centrifugal force

In classical mechanics, centrifugal force is an outward force associated with rotation. Centrifugal force is one of several so-called pseudo-forces , so named because, unlike Fundamental interaction, they do not originate in interactions with other bodies situated in the environment of the particle upon which they act....
 created from a rotating shaft, most commonly that of an electric motor
Electric motor

An electric motor uses electrical energy to produce mechanical energy, nearly always by the interaction of magnetic fields and current-carrying conductors....
 or gasoline engine. The switch is designed to activate or de-activate as a function of the rotational speed of the shaft.

Perhaps the most common use of centrifugal switches is within single-phase
Single-phase electric power

In electrical engineering, single-phase electric power refers to the distribution of alternating current electric power using a system in which all the voltages of the supply vary in unison....
, split-phase induction motor
Induction motor

An induction motor is a type of asynchronous AC motor where power is supplied to the rotating device by means of Electromagnetic induction. Other commonly used name is squirrel cage motor due to the fact that the rotor bars with short circuit rings resemble a squirrel cage ....
s. Here, the switch is used to disconnect the starting winding of the motor once the motor approaches its normal operating speed.






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A centrifugal switch is an electric switch that operates using the centrifugal force
Centrifugal force

In classical mechanics, centrifugal force is an outward force associated with rotation. Centrifugal force is one of several so-called pseudo-forces , so named because, unlike Fundamental interaction, they do not originate in interactions with other bodies situated in the environment of the particle upon which they act....
 created from a rotating shaft, most commonly that of an electric motor
Electric motor

An electric motor uses electrical energy to produce mechanical energy, nearly always by the interaction of magnetic fields and current-carrying conductors....
 or gasoline engine. The switch is designed to activate or de-activate as a function of the rotational speed of the shaft.

Perhaps the most common use of centrifugal switches is within single-phase
Single-phase electric power

In electrical engineering, single-phase electric power refers to the distribution of alternating current electric power using a system in which all the voltages of the supply vary in unison....
, split-phase induction motor
Induction motor

An induction motor is a type of asynchronous AC motor where power is supplied to the rotating device by means of Electromagnetic induction. Other commonly used name is squirrel cage motor due to the fact that the rotor bars with short circuit rings resemble a squirrel cage ....
s. Here, the switch is used to disconnect the starting winding of the motor once the motor approaches its normal operating speed. In this case, the centrifugal switch consists of weights mounted to the shaft of the motor and held near the shaft by spring force. At rest, levers attached to the weights press a low-friction
Friction

File:Friction alt.svgFriction is the force resisting the relative lateral motion of solid surfaces, fluid layers, or material elements in contact....
, non-conductive
Electrical insulation

An insulator, also called a dielectric, is a material that resists the flow of electric current. An insulating material has atoms with tightly bonded valence electrons....
 plate against a set of electrical contacts mounted to the motor housing, closing the contacts and connecting the starting winding to the power source. When the motor approaches its normal operating speed, centrifugal force overcomes the spring force and the weights swing out, raising the plate away from the electrical contacts. This allows the contacts to open and disconnects the starting winding from the power source; the motor then continues operating solely using its running winding. Motors using such a centrifugal switch make a distinct clicking noise when starting and stopping as the centrifugal switch opens and closes.

A variation of the centrifugal switch used a changeover contact to ensure that the auxiliary windings remain in the circuit through a running capacitor. These motors are called two-value or capacitor start capacitor run motors
AC motor

An AC motor is an electric motor that is driven by an alternating current. It consists of two basic parts, an outside stationary stator having coils supplied with AC current to produce a rotating magnetic field, and an inside rotor attached to the output shaft that is given a torque by the rotating field....
.

Centrifugal switches were also used in early electric fans, particularly those made in the 1900s and early 1910s.

See also

  • Transfer switch
    Transfer switch

    Transfer switches allow switches from a primary power source to a secondary or tertiary power source and are employed in some electrical power distribution systems....