This set of Electric Drives Question Bank focuses on “Electrical Drive Systems and Components – Sequence Operations and Protection”.
1. Relay is an electromechanical switch.
Explanation: Relay is an electromechanical switch. It uses electrical signals as input and mechanical operation as an output.
2. Mho relay is used in the medium transmission line.
Explanation: Mho relay is an inherent directional relay. It is used in the long transmission line. It is less affected by power surges.
3. Full form of LED is _____________
a) Light Emitting Diode
b) Light Emission Digital
c) Light Energy Diode
d) Light Energy Digital
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.
4. Inter turn fault can be detected by using __________
a) Oil circuit breaker
b) Split phase relay
c) SF6 circuit breaker
d) Vertical breaker
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.
5. 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
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.
6. Reactance relay is used in _______
a) Medium line
b) Short transmission line
c) Lossless line
d) Long 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.
7. Load interrupter operated at ________
b) Full load
c) Half of the full load
d) One-fourth of the 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.
8. 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
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.
9. 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
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.
10. In single-phase, RLE load, calculate the Peak inverse voltage using the data: (Vs)r.m.s = 9 V, f = 50 Hz, E = 40 V.
a) 52.2 V
b) 52.7 V
c) 59.7 V
d) 52.9 V
Explanation: In a single phase, RLE load the peak inverse voltage across the thyristor VT = Vm+E = 52.7 V.
Sanfoundry Global Education & Learning Series – Electric Drives.
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