ELECTRICAL MACHINES QUIZ

In a loaded DC motor, if the brushes are given a shift from the interpolar axis in the direction of rotation, then the commutation will

deteriorate and the speed rises.

deteriorate and the speed falls.

improve and the speed falls.

improve and the speed rises.

TRUE ANSWER : ?
YOUR ANSWER : ?

What are slot wedges in a DC machine made of?

Silicon steel.

Mild steel.

Fibre.

Cast iron.

TRUE ANSWER : ?
YOUR ANSWER : ?

Which of the following relation is correct?

Xd = Xq.

None of these

Xd < Xq.

Xd > Xq.

TRUE ANSWER : ?
YOUR ANSWER : ?

A 250 volt dc series motor having an armature resistance of 0.2 Ω takes a load current of 60 A. What will be the torque produced at the shaft of the motor? Consider brush drop of 1V.

can not be determined.

234.76 N-m.

266.20 N-m.

133.22 N-m

TRUE ANSWER : ?
YOUR ANSWER : ?

A 3-phase, 2 pole, 12 slot synchronous machine is operating at synchronous speed. Find the slot angle?

20°

60°

30°

18°

TRUE ANSWER : ?
YOUR ANSWER : ?

If the armature electric current is increased to double its previous value, and the time of commutation is halved, how will the reactance voltage vary?

It will be halved.

It will remain the same.

It will be doubled.

It will becomes four times.

TRUE ANSWER : ?
YOUR ANSWER : ?

Under which of the following conditions hunting of synchronous motor is likely to occur ?

Over-loading for long period.

Over-excitation.

Periodic variation of load.

Small and constant load.

TRUE ANSWER : ?
YOUR ANSWER : ?

Conservator tank is used

None of these

to act as an oil storage.

to take up the expansion of oil due to temperature rise.

for better cooling of transformer.

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YOUR ANSWER : ?

The interpoles in dc machines have a tapering shape in order to

reduce the saturation in the interpole

reduce the overall weight

increase the acceleration of commutation

economise on the material required for interpoles and their windings

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YOUR ANSWER : ?

In the V curve shown in figure below for a synchronous motor, the parameter of Y and X coordinates are, respectively

Power factor and field current.

Armature current and torque.

Torque and field current.

Armature current and field current.

TRUE ANSWER : ?
YOUR ANSWER : ?

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