- Repulsion motor
A repulsion motor is a type of
electric motor for use onalternating current . It was formerly used as atraction motor forelectric train s but has been superseded by other types of motors and is now only of historical interest.Construction
The motor has a
stator and a rotor but there is no electrical connection between the two and the rotor current is generated by induction. The rotor winding is connected to a commutator which is in contact with a pair of short-circuited brushes which can be moved to change their angular position relative to an imaginary line drawn through the axis of the stator. The motor can be started, stopped and reversed, and the speed can be varied, simply by changing the angular position of the brushes.Most commutator motors are limited to about 1,500
volt s because higher voltages give rise to a risk ofarcing across the commutator. Repulsion motors can be used at higher voltages because the rotor circuit is not electrically connected to the supply.Types
Types of repulsion motor are listed below under the names ot their inventors. It is likely that the different types were developed to match the
torque /speed characteristics of the motor as closely as possible to the service it was required to provide.Elihu Thomson
The
Elihu Thomson motor is the original repulsion motor and is described in "Construction" above.Deri
The Deri motor is similar to the Elihu Thomson type but has two pairs of short-circuited brushes—one fixed and one moveable. This allows very fine control of speed.
Latour-Winter-Eichberg
This is the "compensated" repulsion motor devised independently by Latour and by Winter-Eichberg.
There are, again, two pairs of brushes but they are fixed at right angles to each other. One pair is short-circuited while the other pair is fed with variable-voltage
alternating current from tappings on the secondary winding of a smalltransformer . The primary winding of the transformer is in series with the stator winding of the motor. This motor has the same torque/speed characteristics as an ordinary series-wound motor.Atkinson
The Atkinson motor has two stator coils at right angles to each other. Speed control (by brush-shifting) is possible from 75% below synchronous speed to 10% above. Starting torque is about 2.5 times full-load torque with twice full-load current.
ee also
*
Electric_motor#AC_Motors
*SR Class CP electric multiple unit
*SR Class SL electric multiple unitources
* "The Electrical Year Book 1937," published by Emmott and Company Limited, Manchester, England, pp 79-82
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