The core of a two-winding transformer is subjected to a magnetic flux variation as indicated in the figure.  The induced emf(em) in the secondary winding as a function of time will be of the form

1.  

2.  

3.  

4.  

View Answer  
4
Correct Answer :


Explanation :
No Explanation available for this question

Voltage phasors at the two terminals of a transmission line of length 70 km have a magnitude of 1.0 perunit but are 180 degrees out of phase. Assuming that the maximum load current in the line is 1/5th of minimum 3-phase fault current, which one of the following transmission line protection schemes will NOT pick up for this condition

1.  Distance protection using mho relays with zone-1 set to 80% of the line impedance

2.  Directional overcurrent protection set to pick up at 1.25 times the maximum load current

3.  Pilot relaying system with directional comparison scheme

4.  Pilot relaying system with segregated phase comparison scheme

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4
Correct Answer :

Distance protection using mho relays with zone-1 set to 80\% of the line impedance


Explanation :
No Explanation available for this question

A lossless transmission line having Surge Impedance Loading (SIL) of 2280 MW is provided with a uniformly distributed series capcitive compensation of 30%. Then, SIL of the compensated transmission line will be

1.  1835 MW

2.  2280 MW

3.  2725 MW

4.  3257 MW

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4
Correct Answer :

2280 MW


Explanation :
No Explanation available for this question

A lossless power system has to serve a load of 250 MW. There are two generators (G1 and G2) in the system with cost curves C1 and C2 respectively defined as follows C1(PG1)=PG1+0.055×PG22 C2(PG2)=3PG2+0.03×PG22 where PG1 and PG2 are the MW injections from generator G1 and G2 respectively. Then the mini mum cost dispatch will be

1.  PG1 = 250 MW; PG2 = 0 MW

2.  PG1 = 150 MW; PG2 = 100 MW

3.  PG1 = 100 MW; PG2 = 150 MW

4.  PG1 = 0 MW; PG2 = 250 MW

View Answer  
4
Correct Answer :

PG1 = 100 MW; PG2 = 150 MW


Explanation :
No Explanation available for this question

A lossless single machine infinite bus power system is shown below The synchronous generator transfers 1.0 per unit of power to the infinite bus. Critical clearing time of circuit breaker is 0.28 s. If another identical syenchronous generator is connected in parallel to the existing egnerator and each generator is scheduled to supply 0.5 per unit of power. Then the critical clearing time of the circuit breaker will

1.  reduce to 0.14 s

2.  reduce but will be more than 0.14 s

3.  remain constant at 0.28 s

4.  4increase beyond 0.28 s

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4
Correct Answer :

reduce but will be more than 0.14 s


Explanation :
No Explanation available for this question

Single line diagram of a 4-bus single source distribution system is shown below. Branches e1, e2, e3 and e4 have equal impedances. The load current values indicated in the figure are in per unit. Distribution company's policy requires radial system operation with minimum loss. This can be achieved by opening of the branch

1.  e

2.  e2

3.  e3

4.  e4

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4
Correct Answer :

e4


Explanation :
No Explanation available for this question

A single phase fully controlled bridge converter supplies a load drawing constant and ripple free load current. If the triggering angle is 30°, the input power factor will be  

1.  0.65

2.  0.78

3.  0.85

4.  0.866

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4
Correct Answer :

0.78


Explanation :
No Explanation available for this question

A single-phase half controlled converter shown in the figure is feeding power to highly inductive load. The converter is operating at a firing angle of 600 If the firing pulses are suddenly removed, the steady state voltage (vn) waveform of the converter will become

1.  

2.  

3.  

4.  

View Answer  
4
Correct Answer :


Explanation :
No Explanation available for this question

A 220 V. 20 A, 1000 rpm, separately excited dc motor has an armature resistance of 2.5Ω. The motor is controlled by a step down chopper with a frequency of 1 kHz. The input dc voltage to the chopper is 250 V The duty cycle of the chopper for the motor to operate at a speed of 600 rpm delivering the rated torque will be

1.  0.618

2.  0.608

3.  0.852

4.  0.902

View Answer  
4
Correct Answer :

0.608


Explanation :
No Explanation available for this question

A 220 V. 1400 rpm, 40 A separately excited dc motor has an armature resistance of 0.4Ω. The motor is fed from a single phase circulating current dual converter with an input ac line voltage of 220 V (rms). The approximate firing angles of the dual converter for motoring operation at 50% of rated torque and 1000 rpm will be

1.  430, 1370

2.  430, 470

3.  390, 1410

4.  390, 510

View Answer  
4
Correct Answer :

390, 1410


Explanation :
No Explanation available for this question
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