Armature Reaction In DC Motor


Armature reaction is effect of armature flux on main fi […]

Armature reaction is effect of armature flux on main field flux.


Basically there are two windings in a dc motor - Armature winding (on rotor) and field winding (on stator). When we excite the field winding, it produces a flux which links with the armature. This causes an emf and hence a current in the armature. This current in armature produces another flux which lags the main flux. This is referred to as armature reaction. It has two effects on the machine:


1. Demagnetising effect: It reduces the strength of the main flux.
2. Crossmagnetising effect: Its effect is that it bends/distortes the the main flux line along the conductor


The conversion of mechanical energy to the electrical energy in the electric dc motor or generator is due to this interaction.


Armature reaction causes the neutral plane, a plane parallel to armature windings with the magnetic flux, to shift in the direction of rotation. Thus armature reaction distort the magnetic flux and lead the applied field not radial which changes the efficiency of the output of the dc generator or dc motor.


Inorder to minimise the armature reaction, two simple methods can be taken up


1. Shifting of the position of the brushes such that its plane are in the neutral plane.
2. Installation of interpoles in the gene