Electrical Machines
φA DC shunt machine generates 250 V on open circuit at 1000 RPM. Armature resistance is 0.5 Ω, field resistance 250 Ω. When running as a motor takes 4 A at 250 V. Calculate the speed when running as a motor taking 40 A at 250 V. Armature reaction weakens the field by 4%.

 920 RPM
 960 RPM
 970 RPM
 940 RPM

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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

 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

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Electrical Machines
In a step down transformer which one of the following statements is true?

 Secondary power is less than primary power.
 Number of secondary turns is more than that of primary.
 Secondary current is less than primary current.
  Number of secondary turns is less than primary turns.

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