ELECTRICAL MACHINES QUIZ

In a three phase star - delta transformer, what is the angle difference between primary and secondary phase voltages?

Star side leads by 30°.

Star side lags by -30°.

Delta side lags by -30°.

Delta side leads by 30°.

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Rotor resistance speed control is used in

synchronous motor.

slip ring induction motor.

squirrel cage induction motor.

dc shunt motor.

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Which of the following motor is suitable for frequent starting and stoppings?

All of these

Resistance split phase motor

Capacitor start motor

Capacitor start capacitor run motor

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The overall power factor of an on load transformer

is always unity.

is always leading.

depends on the power factor of the load.

is always lagging.

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A synchorous generator connected to an infinite bus is over excited. Considering only the reactive power from the point view of the system the machine acts as

A capacitor.

A resistor.

None of these.

an inductor.

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At slip s = 1 torque developed in machine is

electromagnetic torque.

starting torque.

none.

maximum torque.

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What is the shunt resistance component equivalent circuit obtained by no load test of an induction motor representative of ?

core loss only

windage and friction loss

both 1 and 2

Copper loss

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In above question, find rms line voltage for delta connection?

100 V.

399 V.

230.2 V.

50 V.

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Two generators operating in parallel with rating 50MW and 100MW respectively. Both their respective governor settings are identical as 4%, consider same no load frequency. How will the machine share a common load of 100 MW

66.67 MW and 33.33 MW respectively

33.33 MW and 66.67 MW respectively

50 MW and 50 MW respectively

any of the above

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Which of the following statements are correct ?

None of these

A small value of leakage reactance will increase the maximum power output of motor.

Both 1 and 2.

The leakage reactance of the induction motor should be small.

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