Electrical Machines
For a DC machine having P no of pole pairs, Z no of conductors having length L of resistivity ρ and cross section S are arranged. what is the armature resistance for simple wave-winding ?

 PZL/4S
 PZL/4Sa²
 PZL/4Sp²
 PZL/ 4Sa

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Electrical Machines
A dc shunt generator, when driven without any excitation, showed an open circuit voltage of 12 V. When the field winding was excited, the voltage dropped to zero. It happened because

 there was a break in the armature circuit
 there was no residual magnetism in the field circuit
 field resistance was higher than critical resistance
 field winding was wrongly connected

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