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%.

72.5%

78.5%

82.5%

67.5%

72.5%

78.5%

82.5%

67.5%

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Electrical Machines
Why are capacitors used with large AC induction motor?

Improve power factor.

Improve voltage level.

Improve current level.

Improve power level.

Improve power factor.

Improve voltage level.

Improve current level.

Improve power level.

ANSWER DOWNLOAD EXAMIANS APP

Electrical Machines
Hysteresis loop represents the area of

hysteresis loss

eddy current loss

copper loss

total iron losses

hysteresis loss

eddy current loss

copper loss

total iron losses

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Electrical Machines
The rotor of a three phase induction motor has an impedance of 0.4 + j4 ohm per phase at standstill the maximum torque occurs at a slip of _____________.

15 %.

25 %.

50 %.

10 %.

15 %.

25 %.

50 %.

10 %.

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Electrical Machines
Neglecting all losses, the developed torque (T) of DC separately excited motor, operating under constant terminal voltage is reduced to its output power (P) as

T ∝ P.

T ∝ √P.

T is independent of P.

T2 ∝ P3.

T ∝ P.

T ∝ √P.

T is independent of P.

T2 ∝ P3.

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Electrical Machines
Induction motors normally use cast aluminium rotor because aluminium is

easy to cast owing to its low melting point and is easily available.

lighter in weight.

cheaper in cost.

of low resistivity.

easy to cast owing to its low melting point and is easily available.

lighter in weight.

cheaper in cost.

of low resistivity.

ANSWER DOWNLOAD EXAMIANS APP

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 Why are capacitors used with large AC induction motor?

Electrical Machines Hysteresis loop represents the area of

Electrical Machines The rotor of a three phase induction motor has an impedance of 0.4 + j4 ohm per phase at standstill the maximum torque occurs at a slip of _____________.

Electrical Machines Neglecting all losses, the developed torque (T) of DC separately excited motor, operating under constant terminal voltage is reduced to its output power (P) as

Electrical Machines Induction motors normally use cast aluminium rotor because aluminium is

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
Why are capacitors used with large AC induction motor?

Electrical Machines
Hysteresis loop represents the area of

Electrical Machines
The rotor of a three phase induction motor has an impedance of 0.4 + j4 ohm per phase at standstill the maximum torque occurs at a slip of _____________.

Electrical Machines
Neglecting all losses, the developed torque (T) of DC separately excited motor, operating under constant terminal voltage is reduced to its output power (P) as

Electrical Machines
Induction motors normally use cast aluminium rotor because aluminium is