Which of the following factors improve commutation in a dc machine ? 1. High contact resistance of brushes 2. High inductance of the coils undergoing commutation 3. Shifting of brushes in the direction of rotation for a generator and in the opposite direction For a motor 4. Narrow width for the commutation bars Select the correct answer using the codes given below : Codes :

Electrical Machines
Which of the following factors improve commutation in a dc machine ? 1. High contact resistance of brushes 2. High inductance of the coils undergoing commutation 3. Shifting of brushes in the direction of rotation for a generator and in the opposite direction For a motor 4. Narrow width for the commutation bars Select the correct answer using the codes given below : Codes :

1, 2 and 4

1, 2, and 3

1 and 3

2, 3 and 4

1, 2 and 4

1, 2, and 3

1 and 3

2, 3 and 4

ANSWER DOWNLOAD EXAMIANS APP

Electrical Machines
Maximum power developed depends on

reactance

both 1and 2

load angle

voltage

reactance

both 1and 2

load angle

voltage

ANSWER DOWNLOAD EXAMIANS APP

Electrical Machines
In a dc machine, the demagnetizing effect of armature reaction is due to

uneven air-gap length

component of armature mmf along field axis

magnetic saturation in half of the field pole

non-sinusoidal nature of armature mmf

uneven air-gap length

component of armature mmf along field axis

magnetic saturation in half of the field pole

non-sinusoidal nature of armature mmf

ANSWER DOWNLOAD EXAMIANS APP

Electrical Machines
The maximum power developed in cylindrical synchronous machine is occurs at a load angle of

Greater than 90o.

90o.

0o.

less than 90o.

Greater than 90o.

90o.

0o.

less than 90o.

ANSWER DOWNLOAD EXAMIANS APP

Electrical Machines
Ward Leonard control provides speed control

below rated speed.

above rated speed.

in one direction only.

in both direction.

below rated speed.

above rated speed.

in one direction only.

in both direction.

ANSWER DOWNLOAD EXAMIANS APP

Electrical Machines
If the applied voltage of a certain transformer is increased by 50% and the frequency is reduced by 50%, the maximum flux density will (assuming that the magnetic circuit remains unsaturated)

changes to 0.5 times the original value

changes to 1.5 times the original value

changes to three times the original value

remain the same as the original

changes to 0.5 times the original value

changes to 1.5 times the original value

changes to three times the original value

remain the same as the original

ANSWER DOWNLOAD EXAMIANS APP

Electrical Machines

Electrical Machines Maximum power developed depends on

Electrical Machines In a dc machine, the demagnetizing effect of armature reaction is due to

Electrical Machines The maximum power developed in cylindrical synchronous machine is occurs at a load angle of

Electrical Machines Ward Leonard control provides speed control

Electrical Machines If the applied voltage of a certain transformer is increased by 50% and the frequency is reduced by 50%, the maximum flux density will (assuming that the magnetic circuit remains unsaturated)

Electrical Machines
Maximum power developed depends on

Electrical Machines
In a dc machine, the demagnetizing effect of armature reaction is due to

Electrical Machines
The maximum power developed in cylindrical synchronous machine is occurs at a load angle of

Electrical Machines
Ward Leonard control provides speed control

Electrical Machines
If the applied voltage of a certain transformer is increased by 50% and the frequency is reduced by 50%, the maximum flux density will (assuming that the magnetic circuit remains unsaturated)