The rms value of the resultant current in a wire which carries a dc current of 10 A and a sinusoidal altering current of peak value 20 A is

1. 14.1 A

2. 17.3 A

3. 22.4 A

4. 30.0 A

View Answer

Correct Answer :

17.3 A

Explanation :
No Explanation available for this question

The Z matrix of a 2-port network as given by .The element Y22 of the corresponding Y matrix of the same network is given by

1. 1.2

2. 0.4

3. -0.4

4. 1.8

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Correct Answer :

1.8

Explanation :
No Explanation available for this question

The synchronous speed for the seventh space harmonic mmf wave of a 3-phase,8 pole,50 Hz induction machine is

1. 107.14 rpm in forward direction

2. 107.14 rpm in reverse direction

3. 5250 rpm in forward direction

4. 5250 rpm in reverse direction

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Correct Answer :

107.14 rpm in forward direction

Explanation :
No Explanation available for this question

A rotating lectrical machine having its self-inductances of both the stator and the rotor windlings,independent of the rotor position will be definitely not develop

1. starting torque

2. synchronizing torque

3. hysteresis torque

4. reluctance torque

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Correct Answer :

synchronizing torque

Explanation :
No Explanation available for this question

The armature resistance of a permanent magnet dc motor is 0.8Ω.At no load,the motor draws 1.5 a from a supply voltage of 25V and runs at 1500rpm.The efficiency of the motor while it is operating on load at 1500 rpm drawing a current of 305 A from the same source will be

1. 48.0%

2. 57.1%

3. 59.2%

4. 88.8%

View Answer

Correct Answer :

48.0\%

Explanation :
No Explanation available for this question

A 50 Kva,3300/230 V single-phase transformers is connected as an autotransformer shown in fig.the nominal rating of the autotransformer will be

1. 50.0 kVA

2. 53.5 kVA

3. 717.4 kVA

4. 767.4 kVA

View Answer

Correct Answer :

767.4 kVA

Explanation :
No Explanation available for this question

The resistance and reactance of a 100 kVA 11000|400V,-Y distribution transformer are 0.02 and 0.07 pu respectively.The phase impedance of the transformer reffered to the primary is

1. (0.02+j0.07)Ω

2. (0.55+j1.925)Ω

3. (15.125+j52.94)Ω

4. (72.6+j254.1)Ω

View Answer

Correct Answer :

(72.6+j254.1)Ω

Explanation :
No Explanation available for this question

A single-phase 230 V,50 Hz,4 pole,capacitor-start induction motor has the following stand still impedances Main winding Zm=6.0+j4.0Ω Auxiliary winding Za=8.0+j6.0Ω The value of the starting capacitor required to produce 90o phase difference between the currents in the main and auxillary windings will be

1. 176.84 µF

2. 187.24 µF

3. 265.26 µF

4. 280.86 µF

View Answer

Correct Answer :

176.84 µF

Explanation :
No Explanation available for this question

Two 3-phase,Y-connected alternators are to be paralleled to a set of common bus bars.The armature has a per synchronous reactance of 1.7Ω and negligible armature resistance.The line voltage of the first machines is adjusted to 3300 V and that of the second machine is adjusted to 3200 V,the machine voltages are in phase at the instant they are paralleled.Under this condition,the synchronizing current per phase will be

1. 16.98 A

2. 29.41 A

3. 33.96 A

4. 58.82 A

View Answer

Correct Answer :

16.98 A

Explanation :
No Explanation available for this question

A 400V,15Kw,4 POLE,50Hz,Y-connected induction motor has full load slip of 4%.the output torque of the machine at full load is

1. 1.66 Nm

2. 95.50 Nm

3. 99.47 Nm

4. 624.73 Nm

View Answer

Correct Answer :

99.47 Nm

Explanation :
No Explanation available for this question

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