Figure shows an ideal single-phase transformer.The primary and secondary coils are wound on the core as shown in the figure.Turns ratio ( )=2.The correct phasors of voltages E1,E2 currents I1,I2 and core flux are as shown in the figure

1.

2.

3.

4.

4

Explanation :
No Explanation available for this question

To conduct load test on a dc shunt motor,it is coupled to a generator which is identical to the motor.The field of the generator is also connected to the same supply as the motor.The armature of the generator is connected to a load resistance.The armature resistance id 0.02 p.u. armature reaction and mechanical losses can be neglected with rated voltage across the motor,the load resistance across the generator is adjusted to obtain rated armature current in both motor and generator.The p.u. value of this load resistance is

1.  1.0

2.  0.98

3.  0.96

4.  0.94

4

0.96

Explanation :
No Explanation available for this question

Figure shows a Δ-Y-connected 3-phase distribution transformer used to step down the voltage.from 11000 V to 415 V line-to-line.It has two switches S1 and S2.Under  normal conditions S1 is closed and S2 is open.under certain special conditions S1  is open and S2 is closed.In such cases the magnitude of the voltage across the LV terminals a and c is

1.  240 V

2.  480 V

3.  415 V

4.  0 V

4

0 V

Explanation :
No Explanation available for this question

Figure shows an ideal three-winding transformer.The three windings 1,2,3 of the transformer are wound on the same core as shown.The turns ratio N1:N2:N3 is 4:2:1.A resistor of 10Ω is connected across winding-3.widing-1 is connected across a 400 V,ac supply.If the supply voltage phasor V1=400 0O the supply current phasor I1 is given by

1.  (-10+j10)A

2.  (-10-j10)A

3.  (10+j10)A

4.  (10-j10)A

4

(10-j10)A

Explanation :
No Explanation available for this question

Following are some of the properities of rotating electrical machines P stator winding current is dc,rotor-winding current is ac Q stator winding current is ac,rotor-winding current is dc R  stator winding current is ac,rotor-winding current is ac S stator has salient poles and rotor has commutator T Rotor has salient poles and rotor has commutator U Both stator and rotor have poly-phase windings DC machines.Synchronous machines and induction machines exhibit some of the above properities as given in the following table.Indicate the correct combination from this table.DC machines Synchronous machines Induction machines

1.  P.S Q.T R.U

2.  Q.U P.T R.S

3.  P.S R.U Q.T

4.  R.S Q.U P.T

4

P.S Q.T R.U

Explanation :
No Explanation available for this question

When stator and rotor windings of a 2-pole rotating electrical machine are excited each would produce a sinusoidal mmf distribution in the air gap with peak values FS and Fr respectively.The rotor mmf lags stator mmf by a space angle δ at any instant as shown in the figure.Thus,half of stator and rotor surfaces will form onepole with the other half forming the second pole.Further,the direction of torque acting on the rotor can be clockwise or counter-clockwise direction. The following table gives four sets of statements as regards poles and torque.select the correct set corresponding to the mmf axis as shown in the figure. Stator surface Stator surface Rotor surface Rotor surface Torque is ABC forms     CDA forms     cda forms          cda forms

1.  North pole south pole North pole south pole clock wise

2.  south pole north pole north pole south pole counter clock wise

3.   North pole south pole south pole north pole counter clock wise

4.   south pole north pole south pole north pole counter clock wise

4

North pole south pole south pole north pole counter clock wise

Explanation :
No Explanation available for this question

A 4-pole,3-phase,double layer winding is housed in a 36-slot stator for an arc machine with 60o phase spread.Coil span is 7 slot pitches.Number of slots in which top and bottom layers belongs to different phases is

1.  24

2.  18

3.  12

4.  0

4

12

Explanation :
No Explanation available for this question

A 3-phase inductor motor is driving a constant torque load at rated voltage and frequency.if both voltage and frequency are halved,following statements relate to the new condition if stator resistance,leakage reactance and core loss are ignored. P The difference between synchronous speed and actual speed remains same Q The air-gap flux remains same R The stator current remains same S The p.u slip remains same Among the above,correct statements are

1.  All

2.  P,Q and R

3.  Q,R and S

4.  P and S

4

P,Q and R

Explanation :
No Explanation available for this question

A dc series motor driving an electric train facesa constant power load.It is running at rated speed and rated voltage.If the speed has to be brought down to 0.25 p.u the supply voltage has to be approximately brought down to

1.  0.75 p.u

2.  0.5 p.u

3.  0.25 p.u

4.  0.125 p.u

4

0.5 p.u

Explanation :
No Explanation available for this question

1.  ∞Ω

2.  2000Ω

3.  105.26 Ω

4.  1052.6Ω

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