Interrupter
Encyclopedia
An interrupter in electrical engineering is a device used to interrupt the flow of a steady direct current
for the purpose of converting a steady electric field into a changing one. Frequently, the interrupter is used in conjunction with a coil to produce increased voltages either by a back emf effect or through transformer
action in an induction coil
.
designed his own interrupter circuit for delivering shocks to patients from a voltaic cell through an induction coil. Previously, the interrupter had been a mechanical device requiring the physician to manually turn a cog wheel, or else employ an assistant to do this. Bird wished to free his hands to better apply the electricity to the required part of the patient. His interrupter worked automatically by magnetic induction and achieved a switching rate of around (five times per second). The faster the interrupter switches, the more frequently an electric shock is delivered to the patient and the aim is to make this as high as possible.
A rather more cumbersome interrupter was constructed by the American Charles Page
slightly earlier in 1838 but Bird's work was entirely independent. Although there is little in common between the two interrupter designs, Page takes the credit for being the first to use permanent magnets in an automatic interrupter circuit. Bird's (and Page's) interrupter had the medically disadvantageous feature that current was supplied in opposite directions during the make and break operations, although the current was substantially less during the make operation than the break (current is only supplied at all while the switch is dynamically changing). Treatment often required that current was supplied in one specified direction only. A modified version of the interrupter was produced by Henry Letheby
which could output only the make, or only the break currents by a mechanism consisting of two spoked wheels. Bird also produced a uni-directional interrupter using a mechanism we would now call split-rings. The date of Bird's design is uncertain but may predate Letheby's. Both designs suffered from the disadvantage that automatic operation was lost and the interrupter had to once again be hand-cranked. Nevertheless, this arrangement remained a cheaper option than electromagnetic generators for some time.
Other early interrupters worked by clockwork mechanisms or (non-magnetic) reed switch
es operated by motion of the patient's limbs. One example of such a device is found in the Pulvermacher chain.
Direct current
Direct current is the unidirectional flow of electric charge. Direct current is produced by such sources as batteries, thermocouples, solar cells, and commutator-type electric machines of the dynamo type. Direct current may flow in a conductor such as a wire, but can also flow through...
for the purpose of converting a steady electric field into a changing one. Frequently, the interrupter is used in conjunction with a coil to produce increased voltages either by a back emf effect or through transformer
Transformer
A transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors—the transformer's coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core and thus a varying magnetic field...
action in an induction coil
Induction coil
An induction coil or "spark coil" is a type of disruptive discharge coil. It is a type of electrical transformer used to produce high-voltage pulses from a low-voltage direct current supply...
.
Medical use
The physician Golding BirdGolding Bird
Golding Bird was a British medical doctor and Fellow of the Royal College of Physicians of London. Bird became a great authority on kidney diseases and published a comprehensive paper on urinary deposits...
designed his own interrupter circuit for delivering shocks to patients from a voltaic cell through an induction coil. Previously, the interrupter had been a mechanical device requiring the physician to manually turn a cog wheel, or else employ an assistant to do this. Bird wished to free his hands to better apply the electricity to the required part of the patient. His interrupter worked automatically by magnetic induction and achieved a switching rate of around (five times per second). The faster the interrupter switches, the more frequently an electric shock is delivered to the patient and the aim is to make this as high as possible.
A rather more cumbersome interrupter was constructed by the American Charles Page
Charles Grafton Page
Charles Grafton Page was an American electrical experimenter and inventor, physician, patent examiner, patent advocate, and professor of chemistry....
slightly earlier in 1838 but Bird's work was entirely independent. Although there is little in common between the two interrupter designs, Page takes the credit for being the first to use permanent magnets in an automatic interrupter circuit. Bird's (and Page's) interrupter had the medically disadvantageous feature that current was supplied in opposite directions during the make and break operations, although the current was substantially less during the make operation than the break (current is only supplied at all while the switch is dynamically changing). Treatment often required that current was supplied in one specified direction only. A modified version of the interrupter was produced by Henry Letheby
Henry Letheby
Henry Letheby , analytical chemist and public health officer, was born at Plymouth in 1816, and studied chemistry at the Royal Cornwall Polytechnic Society. In 1837 he commenced the study of medicine, and became the assistant of Jonathan Pereira. He graduated M.B...
which could output only the make, or only the break currents by a mechanism consisting of two spoked wheels. Bird also produced a uni-directional interrupter using a mechanism we would now call split-rings. The date of Bird's design is uncertain but may predate Letheby's. Both designs suffered from the disadvantage that automatic operation was lost and the interrupter had to once again be hand-cranked. Nevertheless, this arrangement remained a cheaper option than electromagnetic generators for some time.
Other early interrupters worked by clockwork mechanisms or (non-magnetic) reed switch
Reed switch
The reed switch is an electrical switch operated by an applied magnetic field. It was invented at Bell Telephone Laboratories in 1936 by W. B. Ellwood. It consists of a pair of contacts on ferrous metal reeds in a hermetically sealed glass envelope...
es operated by motion of the patient's limbs. One example of such a device is found in the Pulvermacher chain.