TasDia Network
TasDia Network

MCQs 1: In lamps dark method for synchronization of single phase alternator, if the frequency of two alternators is exactly same as well as their voltages are in exact phase opposition then the resultant voltage will be

Sum of the voltages of two alternators Equal to the voltage of alternators Zero None of these
Answer Explanation

MCQs 2: If the frequencies of the two alternators in lamp dark method for synchronization of alternators are unequal, then the two lamps will

Glow together Become alternately bright and dark Not glow at all None of the above
Answer Explanation

MCQs 3: For synchronization of single phase alternators which method gives the more accurate result?

Lamps dark method Lamps bright method Both (a) and (b) None of these
Answer Explanation

MCQs 4: While synchronization of three phase alternators by lamps bright and dark method, if the lamps pair become dark and bright simultaneously, it indicates

Incorrect phase sequence That the frequencies of alternators are different That voltage of the alternators are not in phase opposition All of these
Answer Explanation

MCQs 5: For synchronization of alternators, the most suitable method is

Lamps method Voltmeter Synchroscope None of the above
Answer Explanation

MCQs 6: What does the pointer of synchroscope indicate when it is rotating in anticlockwise direction and when it is rotating in clockwise direction?

Incoming machine is running slow, incoming machine is running faster Incoming machine is running faster, incoming machine is running slow Pointer rotates only in clockwise direction all of the above
Answer Explanation

MCQs 7: The electrical power output in case of synchronous machine is

Directly proportional to the power angle Inversely proportional to the power angle Directly proportional to the square of power angle None of these
Answer Explanation

MCQs 8: The electrical power output of an alternator will be maximum, if the power angle is equal to

0 degree 45 degree 90 degree 180 degree
Answer Explanation

MCQs 9: The synchronous generator supplies leading power factor and lagging power factor respectively when it is

Over excited, under excited Over excited, over excited Under excited, under excited Under excited, over excited
Answer Explanation

MCQs 10: Blondel’s two reaction theory which gives the method of analysis of disturbing effects caused by

Salient pole construction Non salient pole construction Both (a) and (b) None of these
Answer Explanation

MCQs 11: According to Blondel’s two reaction theory the armature mmf is divided into components, direct axis component and quadrature axis component. The component acting along quadrature axis is

Magnetizing Demagnetizing Cross magnetizing None of these
Answer Explanation

MCQs 12: According to Blondel’s two reaction theory, the armature mmf component acting along direct axis can be

Demagnetizing Magnetizing Cross magnetizing Either (a) or (b)
Answer Explanation

MCQs 13: The reluctance offered to the mmf wave is lowest when

It is aligned with the field pole axis It is oriented at 90 degree to the field pole axis Both (a) and (b) None of these
Answer Explanation

MCQs 14: Depending upon the reluctances offered along the direct axis and quadrature axis, the armature reaction flux will

Lead the armature current Lags behind the armature current In phase with the armature current None of these
Answer Explanation

MCQs 15: In a salient pole synchronous generator direct axis reactance is

Greater than quadrature axis reactance Less than quadrature axis reactance Equal to quadrature axis reactance None of the above
Answer Explanation

MCQs 16: A synchronous generator has a direct axis and quadrature axis reactances of 0.6 per unit and 0.3 per unit respectively. What will be its total induced emf on open circuit if it is used to supply full load at rated voltage at 0.8 power factor ( Assume rated terminal voltage is equal to 1 pu, full load armature current be 1 pu and armature resistance to be 0).

1.099 pu 1.199 pu 1.488 pu 1.588 pu
Answer Explanation

MCQs 17: A 3 phase star connected synchronous generator having direct axis reactance of 8 ohm and quadrature axis reactance of 6 ohm supplies current of 9 A with phase angle of 20 degree lagging at 415 V. Then its direct axis component of armature current and quadrature axis component of armature current are

8.04 A, 4.04 A 4.04 A, 6.84 A 6.84 A, 8.04 A 4.04 A, 8.04 A
Answer Explanation

MCQs 18: In case of salient pole alternators, maximum output power can be obtained when power angle (d) is

Less than 90 degree Equal to 90 degree Greater than 90 degree None of the above
Answer Explanation

MCQs 19: If a 3 phase alternator is short circuited at its terminal, then the initial value of short circuit current will be limited by

Synchronous reactance Transient reactance Sub transient reactance All of the above
Answer Explanation

MCQs 20: The change in excitation of the two alternators operating in parallel causes

Only the kVAR sharing of two alternators without disturbing kW sharing of the two machines Only the kW sharing of two alternators without disturbing kVAR sharing of the two machines Both the kVAR sharing and kW sharing of two alternators None of the above
Answer Explanation

MCQs 21: In case of hydro generators, the driving torque can be changed by controlling the

Gate opening Throttle opening Both (a) and (b) None of these
Answer Explanation

MCQs 22: The increase in mechanical torque in case of alternator will

Increase the armature current and reduce the power factor Increase the armature current and improve the power factor Decrease the armature current and improve the power factor Decrease the armature current and reduce the power factor
Answer Explanation

MCQs 23: When an alternator is connected to infinite bus bar, change in excitation for alternator will

Change the terminal voltage and power factor both Affect only terminal voltage and power factor remains unaffected Affect only power factor and terminal voltage remains unaffected Neither terminal voltage will get affected nor power factor
Answer Explanation

MCQs 24: If a three phase winding is displaced in space by 120 degree in a synchronous motor then the magnitude of resultant flux when it is rotated by Θ = 0 degree and Θ = 60 degree is

0, 1.5 times the magnitude of maximum flux 1.5 times the magnitude of maximum flux, 0 0.866 times the magnitude of maximum flux, 1.5 times the magnitude of maximum flux 1.5 times the magnitude of maximum flux, 1.5 times the magnitude of maximum flux
Answer Explanation

MCQs 25: For a half cycle of fluxes in a synchronous motor, the resultant flux has rotated through

0 degree 90 degree 180 degree 360 degree
Answer Explanation

MCQs 26: For a two pole, 50 Hz, 3 phase synchronous motor the speed of rotating magnetic field is

1000 rpm 2000 rpm 3000 rpm 3500 rpm
Answer Explanation

MCQs 27: A synchronous motor draws 2 MVA at a power factor of 0.8 leading. If the efficiency developed in the motor is 90% then the power developed is equal to

1212 kW 1440 kW 1676 kW 1767 kW
Answer Explanation

MCQs 28: Synchronous motor works on the principle of

Mutual induction Electromagnetic induction Magnetic locking None of these
Answer Explanation

MCQs 29: Synchronous motors are

Self starting Not self starting Both (a) and (b) None of these
Answer Explanation

MCQs 30: Can synchronous motor rotate at any speed other than the synchronous speed?

Yes No
Answer Explanation

Related Topics

About Us | Contact Us | Privacy Policy
ABOUT US
Category
Who We Are

TasDia Network, this platform not only provides you the best educational stuff but besides this, we are creating thousands of new ideas to making your signature and planning much more on a single platform.

© 2020-2023, TasDia Network

All rights of the publication are reserved by tasdia.com.