A DC shunt machine generates 250 V on open circuit at 1000 RPM. Armature resistance is 0.5 Ω, field resistance 250 Ω. When running as a motor takes 4 A at 250 V. Calculate the efficiency when running as a motor taking 40 A at 250 V. Armature reaction weakens the field by 4%.

Electrical Machines
A DC shunt machine generates 250 V on open circuit at 1000 RPM. Armature resistance is 0.5 Ω, field resistance 250 Ω. When running as a motor takes 4 A at 250 V. Calculate the efficiency when running as a motor taking 40 A at 250 V. Armature reaction weakens the field by 4%.

78.5%

72.5%

67.5%

82.5%

78.5%

72.5%

67.5%

82.5%

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Electrical Machines
The supply voltage to an induction motor is reduced by 10%. By what percentage, approximately, will the maximum torque decrease?

40%

10%

19%

5%

40%

10%

19%

5%

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Electrical Machines
A transformer has resistance and reactance in per unit as 0.01 and 0.04 respectively. Its voltage regulation for 0.8 power factor lagging and leading will be

6% and -4%

3.2% and -1.6%

None of these

4.8% and -3.2%

6% and -4%

3.2% and -1.6%

None of these

4.8% and -3.2%

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Electrical Machines
The breakdown torque of a synchronous motor varies as

1/V

1/V²

V²

applied voltage V

1/V

1/V²

V²

applied voltage V

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Electrical Machines
In one 132 / 33 kV transformer the LV resistance is 0.02 per unit. The resistance referred to HV side is

0.01 pu.

0.08 pu.

0.16 pu.

0.02 pu.

0.01 pu.

0.08 pu.

0.16 pu.

0.02 pu.

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Electrical Machines
For an ideal transformer the winding should have

equal resistance on primary and secondary side

no ohmic resistance on either side

maximum resistance on primary side and least resistance on secondary side

minimum resistance on primary side and maximum resistance on secondary side

equal resistance on primary and secondary side

no ohmic resistance on either side

maximum resistance on primary side and least resistance on secondary side

minimum resistance on primary side and maximum resistance on secondary side

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Electrical Machines

Electrical Machines A DC shunt machine generates 250 V on open circuit at 1000 RPM. Armature resistance is 0.5 Ω, field resistance 250 Ω. When running as a motor takes 4 A at 250 V. Calculate the efficiency when running as a motor taking 40 A at 250 V. Armature reaction weakens the field by 4%.

Electrical Machines The supply voltage to an induction motor is reduced by 10%. By what percentage, approximately, will the maximum torque decrease?

Electrical Machines A transformer has resistance and reactance in per unit as 0.01 and 0.04 respectively. Its voltage regulation for 0.8 power factor lagging and leading will be

Electrical Machines The breakdown torque of a synchronous motor varies as

Electrical Machines In one 132 / 33 kV transformer the LV resistance is 0.02 per unit. The resistance referred to HV side is

Electrical Machines For an ideal transformer the winding should have

Electrical Machines
A DC shunt machine generates 250 V on open circuit at 1000 RPM. Armature resistance is 0.5 Ω, field resistance 250 Ω. When running as a motor takes 4 A at 250 V. Calculate the efficiency when running as a motor taking 40 A at 250 V. Armature reaction weakens the field by 4%.

Electrical Machines
The supply voltage to an induction motor is reduced by 10%. By what percentage, approximately, will the maximum torque decrease?

Electrical Machines
A transformer has resistance and reactance in per unit as 0.01 and 0.04 respectively. Its voltage regulation for 0.8 power factor lagging and leading will be

Electrical Machines
The breakdown torque of a synchronous motor varies as

Electrical Machines
In one 132 / 33 kV transformer the LV resistance is 0.02 per unit. The resistance referred to HV side is

Electrical Machines
For an ideal transformer the winding should have