How the poles of a dc generator affect the current capacity of the generator?

Interpoles are small poles fixed in between the main poles.They are wound with comparatively few heavy gauge Cu wire turns connected in series with the armature so that they carry full armature current. Their polarity , in the case of generator, is the same as that of the main pole ahead in the direction of rotation.

As their polarity is the same as that of the main pole ahead ,they induce an e.m.f in the coil which helps the reversal of current.The e.m.f induced by the compoles is known as reversing e.m.f. As interpoles carry armature current, their commutating e.m.f is proportionalto the armature current. The illustrate the manner in which the interpole flux oppose the armature flux.
The interpoles are connected in a manner similar to the series field of a dc generator;i.e, the load current passes through the coils of the interpoles and produces flux.Thus the greater the current through the armature con-doctors , the greater the distortion of the flux ; also the greater the e.m.f of self-induction. The strength of the interpole will also be greater , to produce the required increase in flux.

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