Mini electrical machines quiz

1➤ The power output of a synchronous motor is___.

inversely proportional to synchronous reactancedirectly proportional to synchronous reactance independent of synchronous reactance None of these

2➤ The construction of synchronous motor is similar to

D.C. compound motor . Alternatorslip-ring induction motor . shunt generator

3➤ In case one phase of 3-phase synchronous motor is short circuited the motor will ________

Not start Run with excessive vibrationRun at two-third of synchronous speedTake less than the rated load

4➤ A salient pole synchronous motor is running at no load. Its excitation is reduce to zero:

It will stop It will remain running at synchronous speed It will loose synchronism It is uncertain

5➤ Embedding the damper winding in the pole face serves which of the following purpose?

Reduce windage lossesEliminate losses on account of air frictionReduce bearing frictionEliminate hunting and provide adequate starting torque

6➤ For the following specifications of a synchronous motor, determine the ratio of no load speed to full load speed.

1 : 1 2 : 33 : 5 2 : 7

7➤ The regulation of a synchronous motor is

00.50.011

8➤ In a transformer the leakage flux:

contributes to transfer of energy from primary to secondarycontributes to transfer of energy from secondary to primary does not contribute to transfer of energy from primary to secondarycontributes to transfer of energy between both coils simultaneously

9➤ Centrifugal Methods of reconditioning transformer oil is effective for removal of___

waterdissolved gases solid impurities none of these

10➤ Compared to the secondary of a loaded step-up transformer, the primary has A. lxB. higher voltage and lower current C. lower voltage and lower current D. higher voltage and higher current

lower voltage and lower current. higher voltage and higher current lower voltage and higher currenthigher voltage and lower current

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