Electric Drives Mcqs


Calculate the PIV for the Full-wave bridge rectifier if the peak value of the supply voltage is 50.

A) 72.5 V B) 72.8 V
C) 70.7 V D) 76.1 V
Answer & Explanation Answer: C) 70.7 V

Explanation: The peak inverse voltage for the Full-wave bridge rectifier is Vm = √2×230=70.7 V. The peak inverse is the maximum negative voltage across the thyristor.

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Calculate the maximum frequency for ASCI using the data: R=1 kΩ, C=1 μF.

A) 250 Hz B) 280 Hz
C) 300 Hz D) 320 Hz
Answer & Explanation Answer: A) 250 Hz

Explanation: The minimum time period for ASCI is a 4×R×C=4×1×1×.001=4 msec. The total time is the sum of charging and discharging time. The maximum frequency is 1÷f=250 Hz.

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Load interrupter operated at ________

A) No-load B) Full load
C) Half of the full load D) One-fourth of the full load
Answer & Explanation Answer: B) Full load

Explanation: Load interrupter is used to avoid overloading conditions. It separates the under-stressed area from the line. It operates at full load.

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Reactance relay is used in _______

A) Medium line B) Short transmission line
C) Lossless line D) Long transmission line
Answer & Explanation Answer: B) Short transmission line

Explanation: Reactance relay is used in a short transmission line. Reactance relay is independent of the resistance value. It protects the short transmission line from any fault.

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Calculate the value of the fault impedance if the fault voltage is 2 V and fault current is 4 A.

A) .5 ohm B) .2 ohm
C) .4 ohm D) .6 ohm
Answer & Explanation Answer: A) .5 ohm

Explanation: The value of the fault impedance is the ratio of fault voltage and fault current. It is expressed in ohms. Z=V/I=2/4=.5 ohm.

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Inter turn fault can be detected by using __________

A) Oil circuit breaker B) Split phase relay
C) SF6 circuit breaker D) Vertical breaker
Answer & Explanation Answer: B) Split phase relay

Explanation: Inter turn fault mainly occurs in the winding of the rotor side of the alternator. They can be detected by using the split-phase relaying technique.

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Full form of LED is _____________

A) Light Emitting Diode B) Light Emission Digital
C) Light Energy Diode D) Light Energy Digital
Answer & Explanation Answer: A) Light Emitting Diode

Explanation: The full form of LED is a light-emitting diode. It converts light energy into electrical energy. It works in the reverse bias region.

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Mho relay is used in the medium transmission line.

A) True B) False
Answer & Explanation Answer: B) False

Explanation: Mho relay is an inherent directional relay. It is used in the long transmission line. It is less affected by power surges.

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