Consider the following factors for a dc machine: 1. Interpole 2. Armature resistance 3. Reduction in field current Which of the above factors are responsible for decrease in terminal voltage of a shunt generator?

Option 2 : 2 and 3 only

Interpoles:

The interpoles are the auxiliary poles, which are placed between the main poles. The interpoles are fitted to the yoke and are known as commutating poles. The use of the interpoles helps in reducing the reactance voltage and nullifies the cross magnetization effect of armature reaction, which results in a reduction in sparking at the commutator.

Armature resistance and field current:

For s shunt generator,

Terminal voltage V_t = E_g – I_aR_a and I_a = I_L + I_f

I_a is armature current

R_a is armature resistance

I_f is the field current

I_L is the line current

With an increase in armature resistance (R_a), the voltage drop I_aR_a increases.

With the reduction in field current, the armature current increases, and hence the voltage drop I_aR_a increases.