Electrical Machines
For satisfactory parallel operation of two transformers which of the following conditions is most essential,

 voltage ratio of all transformers must be same.
  polarities of all transformers must be same.
 percentage impedance of all transformers must be same.
 MVA rating of all transformer inversely proportional to impedance.

ANSWER DOWNLOAD EXAMIANS APP

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

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

ANSWER DOWNLOAD EXAMIANS APP