Dec 14, 2014

Armature Reaction in DC Motor



Armature-reaction-in-DC motor
Similar to DC generator, armature reaction happens in a DC motor. This is often anticipated as a result of once current drifts through the armature conductors of a DC motor, it creates armature flux which on the flux created by the main poles. The polarity and direction of rotation of motor is same as that of generator, but the armature field direction is reversed.
In a Motor the armature current flows against the back EMF Eb, whereas in a generator the armature current flows in the direction of the generated EMF Eg. As a result, it ought to be anticipated that for identical field polarity and direction of rotation, the armature flux of the motor are going to be within the opposite direction to it of the generator. Thus rather than the main flux existence distorted within the direction of rotation as in a very generator, it's distorted opposite to the direction of rotation. We are able to determine that:
In a DC Generator the armature reaction strengthens the flux at a trialing tips and weakens the flux at a leading pole tips, whereas the armature reaction in a DC motor creates the opposite effects.
In terms of a DC generator, no commutating poles and brushes on G.N.A. used, the brushes should be moved within the direction of rotation for reasonable commutation. On the other hand, just in case of a DC motor, the brushes are shifted contrary to the direction of rotation.
The brushes are given a backward lead in a very DC motor and forward lead in a DC generator when there is no commutation poles are used.
DC machine will be operated with fixed brush positions for all conditions of load by using commutating poles. Meanwhile commutating poles windings transmit the armature current, then, once a machine changes from generator to motor, the polarities of commutating poles should be inverse sign.
For that reason, in a DC motor, the commutating poles should have identical polarity because the main poles right back of them. This is often the alternative of the corresponding kin in a DC generator.


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