φA 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 speed when running as a motor taking 40 A at 250 V. Armature reaction weakens the field by 4%.

Electrical Machines
φA 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 speed when running as a motor taking 40 A at 250 V. Armature reaction weakens the field by 4%.

940 RPM

920 RPM

970 RPM

960 RPM

940 RPM

920 RPM

970 RPM

960 RPM

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Electrical Machines
Example of double excited machine is

Synchronous motor.

Both are correct.

None of these

DC Shunt Motor

Synchronous motor.

Both are correct.

None of these

DC Shunt Motor

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Electrical Machines
The counter (or back) emf in a dc machine is 1. the same as generated emf in a dc motor 2. proportional to field flux and armature speed 3. not the same as generated emf in a dc motor 4.inversely proportional to field flux 5. proportional to number of armature conductors 6. constant from no load to full load From these, the correct answer is

2, 3, 6

3, 4, 5

2, 4, 5, 6

1, 2, 5

2, 3, 6

3, 4, 5

2, 4, 5, 6

1, 2, 5

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Electrical Machines
The factors that are responsible for decrease in terminal voltage of a shunt generator are

armature resistance, effect of armature reaction.

reduction in field current, effect of armature reaction, armature.

armature resistance, inter poles, armature.

armature resistance, effect of armature reaction.

reduction in field current, effect of armature reaction, armature.

armature resistance, inter poles, armature.

armature resistance, effect of armature reaction.

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Electrical Machines
Which of the following induction motor has the highest starting torque?

None of these

Squirrel cage induction motor.

Same in both induction motors.

Slip ring induction motor.

None of these

Squirrel cage induction motor.

Same in both induction motors.

Slip ring induction motor.

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Electrical Machines
Commutators in DC machines have a role of which converts

Both AC to DC and DC to AC.

AC to DC.

none of these.

high voltage DC to low voltage DC.

Both AC to DC and DC to AC.

AC to DC.

none of these.

high voltage DC to low voltage DC.

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Electrical Machines

Electrical Machines φA 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 speed when running as a motor taking 40 A at 250 V. Armature reaction weakens the field by 4%.

Electrical Machines Example of double excited machine is

Electrical Machines The factors that are responsible for decrease in terminal voltage of a shunt generator are

Electrical Machines Which of the following induction motor has the highest starting torque?

Electrical Machines Commutators in DC machines have a role of which converts

Electrical Machines
φA 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 speed when running as a motor taking 40 A at 250 V. Armature reaction weakens the field by 4%.

Electrical Machines
Example of double excited machine is

Electrical Machines
The factors that are responsible for decrease in terminal voltage of a shunt generator are

Electrical Machines
Which of the following induction motor has the highest starting torque?

Electrical Machines
Commutators in DC machines have a role of which converts