In synchronous motor the torque is proportional to

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Electrical Machines

In synchronous motor the torque is proportional to

1/P

P²

1/P²

Power P

1/P

P²

1/P²

Power P

The armature mmf in a dc machine is 1. stationary with respect to field poles 2. stationary with respect to armature 3. rotating with respect to field poles 4. rotating with respect to armature From these, the correct answer is

1, 3

2, 3

2, 4

1, 4

1, 3

2, 3

2, 4

1, 4

Electrical Machines

Which of the following is done in speed control of DC motor by field flux control?

Inserting resistance to armature circuit and field circuit.

Any of above.

Inserting an additional resistance in the field circuit.

Inserting an additional resistance in the armature circuit.

Inserting resistance to armature circuit and field circuit.

Any of above.

Inserting an additional resistance in the field circuit.

Inserting an additional resistance in the armature circuit.

Electrical Machines

In an induction motor, the no-load slip is generally equal to

1.5 %.

less than 1 %.

4 %.

zero.

1.5 %.

less than 1 %.

4 %.

zero.

Electrical Machines

The armature resistance of a permanent magnet dc motor is 0.8 Ohm. At no load, the motor draws 1.5 A from a supply voltage of 25 V and runs at 1500 rpm. The efficiency of the motor while it is operating on load at 1500 rpm drawing a current of 3.5 A from the same source will be

59.2%.

48.0%.

57.1%.

88.8%.

59.2%.

48.0%.

57.1%.

88.8%.

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%.

920 RPM

960 RPM

940 RPM

970 RPM

920 RPM

960 RPM

940 RPM

970 RPM

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In synchronous motor the torque is proportional to

The armature mmf in a dc machine is 1. stationary with respect to field poles 2. stationary with respect to armature 3. rotating with respect to field poles 4. rotating with respect to armature From these, the correct answer is

Which of the following is done in speed control of DC motor by field flux control?

In an induction motor, the no-load slip is generally equal to

The armature resistance of a permanent magnet dc motor is 0.8 Ohm. At no load, the motor draws 1.5 A from a supply voltage of 25 V and runs at 1500 rpm. The efficiency of the motor while it is operating on load at 1500 rpm drawing a current of 3.5 A from the same source will be

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%.

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