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

960 RPM

970 RPM

940 RPM

920 RPM

960 RPM

970 RPM

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Electrical Machines
A commutator with a diameter of 50 cm rotating at 1000 rpm. For a brush width of 1.5 cm, find the time of commutation in ms.

0.443.

0.512.

0.649.

0.573.

0.443.

0.512.

0.649.

0.573.

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Electrical Machines
Which single phase motor is used for a refrigerator?

Split phase.

Repulsion.

Capacitor run.

Universal.

Split phase.

Repulsion.

Capacitor run.

Universal.

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Electrical Machines
A transformer has maximum efficiency at 3/4 load. The ratio of iron loss and full load copper loss is

16/9.

3/4.

4/3.

9/16.

16/9.

3/4.

4/3.

9/16.

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Electrical Machines
If s is the slip and f is the supply frequency of an induction motor, the frequency of rotor current is given by

sf.

s2.

f / s.

sf / 2.

sf.

s2.

f / s.

sf / 2.

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Electrical Machines
If in a sub Ã¢â‚¬â€œ station there is one 132 / 33 kV transformer whose secondary is connected with primary of one 33 / 11 kV transformer, the total transformation ratio of the sub Ã¢â‚¬â€œ station will be,

7.

4.

12.

3.

7.

4.

12.

3.

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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 A commutator with a diameter of 50 cm rotating at 1000 rpm. For a brush width of 1.5 cm, find the time of commutation in ms.

Electrical Machines Which single phase motor is used for a refrigerator?

Electrical Machines A transformer has maximum efficiency at 3/4 load. The ratio of iron loss and full load copper loss is

Electrical Machines If s is the slip and f is the supply frequency of an induction motor, the frequency of rotor current is given by

Electrical Machines If in a sub Ã¢â‚¬â€œ station there is one 132 / 33 kV transformer whose secondary is connected with primary of one 33 / 11 kV transformer, the total transformation ratio of the sub Ã¢â‚¬â€œ station will be,

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
A commutator with a diameter of 50 cm rotating at 1000 rpm. For a brush width of 1.5 cm, find the time of commutation in ms.

Electrical Machines
Which single phase motor is used for a refrigerator?

Electrical Machines
A transformer has maximum efficiency at 3/4 load. The ratio of iron loss and full load copper loss is

Electrical Machines
If s is the slip and f is the supply frequency of an induction motor, the frequency of rotor current is given by

Electrical Machines
If in a sub Ã¢â‚¬â€œ station there is one 132 / 33 kV transformer whose secondary is connected with primary of one 33 / 11 kV transformer, the total transformation ratio of the sub Ã¢â‚¬â€œ station will be,