### Electrical Engineering Objective Questions And Answers On Power systems | Mcqs on Power Systems | only4electrical

1).A shunt reactor at 100MVAr is operated at 98% of its rated voltage and at 96% of its rated frequency. the reactive power absorbed by the reactor is.

a)
98 MVAr.

b)
104.02 MVAr.

c)
96.04 MVAr.

d)
100.04 MVAr.

2).The percentage resistance and percentage reactance of a 10KVA,400 V/200 v,3-phase transformer are 2% and 10% respectively. if the constant losses in the machine are 1% the maximum possible percentage efficiency of the transformer is.

a)
98.32%.

b)
96.85%.

c)
97.25%.

d)
96.12%.

3).Determine a minimum circuit breaker trip rating and interrupting capacity for a 10KVA single phase transformer with 4% impedance, to be operated from a 480 volt 60Hz source.

a)
420 AMP.

b)
520 AMP.

c)
530 AMP.

d)
480 AMP.

4).A star connected 440V,the 50Hz alternator has pre phase synchronous reactance of 10Ω. it supplies a balanced load current of 20A, as shown in the per phose equivatent circuit diagram below. it is desirable to have zero voltage regulation the load power factor should be.

a)
0.82.

b)
0.62.

c)
0.50.

d)
0.92.

5).The synchronous motor connected to an infinite bus takes power at a lag p.f. it its excitation is increased.

a)
Terminal voltage increase.

b)
load angle increase.

c)
power factor increase.

d)
None of the above.

6).if transformer frequency is changed from 50Hz to 60Hz the ratio of eddy current loss 50Hz to 60Hz, at constant voltage will be.

a)
1.

b)
2.

c)
5/6.

d)
25/36.

7).A 100KM long transmission line is loaded at 110KV. if the loss of line is 5 MW and the load is 150 MVA,the resistance of the line is.

a)
8.06 ohms per phase.

b)
8.806 ohms per phase.

c)
0.0806 ohms per phase.

d)
80.6 ohms per phase.

8).whenever the conductors are dead-ended of there is a change in the direction of the transmission line, the insulator.used are the.

a)
pin type.

b)
strain type.

c)
shackle type.

d)
suspension type.

9).with 100% inductive shunt compensation, the voltage profile is flat for.

a)
100% loading on the line.

b)
50% loading on the line.

c)
Zero% loading of the line.

d)
Any of the above.

10).The low voltage winding of a 400/230 V,1-phase, 50Hz transformer is to be connected to a 25Hz, the supply voltage shouid be.

a)
230 V.

b)
250 V.

c)
115 V.

d)
100 V.

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