V - curve of synchronous machine shows the relation between?

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asked Mar 18, 2018 by anonymous

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asked Mar 18, 2018 by anonymous

If we change the excitation of synchronous machine will it affect on power factor?

Last answer: Yes, If we change the excitation of synchronous machine it will affect on power factor. If the synchronous motor is overexcited then it will have leading power factor and if the motor is underexcited then it will have lagging power factor.

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asked Mar 18, 2018 by anonymous

If we change the excitation of synchronous machine will it affect on motor speed?

Last answer: No, If we change the excitation of synchronous machine it will not affect on motor speed.

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2

asked Mar 18, 2018 by anonymous

Which machine is the exciter of synchronous machine?

Last answer: DC shunt machine is the exciter of synchronous machine.

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3

asked Mar 20, 2018 by anonymous

Synchronsizing power of a synchronous machine is?

Last answer: Synchronsizing power of a synchronous machine is inversely proportional to the synchronous reactance.

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4

asked Mar 20, 2018 by anonymous

A synchronous machine with low value of short-circuit ratio has?

Last answer: A synchronous machine with low value of short-circuit ratio has lower stability limit.

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5

asked Mar 18, 2018 by anonymous

Why synchronous machine is called doubly excited machine?

Last answer: Armature windings of synchronous machines either deliver 3 phase AC or absorb 3 phase AC source, whereas field windings are energized from DC source. Thus due to presence of AC on armature and DC on field windings, synchronous machines are often referred as doubly excited machines.

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asked Apr 28, 2018 by anonymous

Torque angle for the synchronous machine is the angle between

Torque angle for the synchronous machine is the angle between (A) stator magnetic field and rotor magnetic field (B) stator magnetic field and net magnetic field in the air gap (C) rotor magnetic field and net magnetic field in the air gap (D) excitation voltage and impedance voltage drop

Last answer: Torque angle for the synchronous machine is the angle between rotor magnetic field and net magnetic field in the air gap

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asked May 1, 2018 by anonymous

In a synchronous machine, if the field flux axis ahead of the armature field axis in the direction of rotation,

In a synchronous machine, if the field flux axis ahead of the armature field axis in the direction of rotation, the machine is operating as (1) synchronous motor (2) synchronous generator (3) asynchronous motor (4) asynchronous generator

Last answer: In a synchronous machine, if the field flux axis ahead of the armature field axis in the direction of rotation, the machine is operating as synchronous generator

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asked Apr 30, 2018 by anonymous

The 'Equal area criterion' for the determination of transient stability of a synchronous machine connected to

The 'Equal area criterion' for the determination of transient stability of a synchronous machine connected to an infinite bus (1) ignores line as well as synchronous machine resistance and shunt capacitances. (2) assumes accelerating power acting on the rotor as constant. (3) ignores the effect of voltage ... inherent damping present in the machine. (4) takes into consideration the possibility of machine losing synchronism after it has survived during the first swing.

Last answer: 1

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asked Apr 29, 2018 by anonymous

The armature current on symmetrical 3 phase short circuit of a synchronous machine (salient pole)

The armature current on symmetrical 3 phase short circuit of a synchronous machine (salient pole) (A) has q -axis current only (B) has d -axis current only (C) has both d and q axis currents (D) cannot be divided between q and d axis currents

Last answer: The armature current on symmetrical 3 phase short circuit of a synchronous machine (salient pole) has d -axis current only

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asked Apr 29, 2018 by anonymous

During a disturbance on a synchronous machine, the rotor swings form A to B before finally setting down to

During a disturbance on a synchronous machine, the rotor swings form A to B before finally setting down to steady state at point C on the power angle curve. The speed of the machine during oscillation is synchronous at point(s)

Last answer: During a disturbance on a synchronous machine, the rotor swings form A to B before finally setting down to steady state at point C on the power angle curve. The speed of the machine during oscillation is synchronous at point(s) only at C

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asked Mar 20, 2018 by anonymous

The coupling angle or load angle of synchronous motor is defined as the angle between the?

Last answer: The coupling angle or load angle of synchronous motor is defined as the angle between the rotor and the stator poles of opposite polarity.

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12

asked Mar 20, 2018 by anonymous

To limit the operating temperature an electrical machine should have proper?

Last answer: To limit the operating temperature an electrical machine should have proper current rating.

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13

asked May 8, 2018 by anonymous

A 200 V DC machine supplies 20 A at 200 V as a generator. The armature resistance is 0.2

A 200 V DC machine supplies 20 A at 200 V as a generator. The armature resistance is 0.2 Ohm. If the machine is now operated as a motor at same terminal voltage and current but with the flux increased by 10%, the ratio of motor speed to generator speed is

Last answer: A 200 V DC machine supplies 20 A at 200 V as a generator. The armature resistance is 0.2 Ohm. If the machine is now operated as a motor at same terminal voltage and current but with the flux increased by 10%, the ratio of motor speed to generator speed is 0.87

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asked Mar 20, 2018 by anonymous

The efficiency of a properly designed synchronous motor will usually fall in range?

Last answer: The efficiency of a properly designed synchronous motor will usually fall in range 85 to 95%.

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15

asked Mar 20, 2018 by anonymous

The operating speed of a synchronous motor can be changed to new fixed value by?

Last answer: The operating speed of a synchronous motor can be changed to new fixed value by changing frequency.

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16

asked Mar 20, 2018 by anonymous

In case one phase of a three-phase synchronous motor is short-circuited the motor will?

Last answer: In case one phase of a three-phase synchronous motor is short-circuited the motor will not start.

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17

asked Mar 20, 2018 by anonymous

The size of a synchronous motor decreases with the increase in?

Last answer: The size of a synchronous motor decreases with the increase in flux density.

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18

asked Mar 20, 2018 by anonymous

The duration of sudden short-circuit test on a synchronous motor is usually about?

Last answer: The duration of sudden short-circuit test on a synchronous motor is usually about one second.

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19

asked Mar 20, 2018 by anonymous

The construction of a synchronous motor resembles?

Last answer: The construction of a synchronous motor resembles an alternator.

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20

asked Mar 20, 2018 by anonymous

If the field winding of an unloaded salient pole synchronous motor is open circuited, the motor will?

Last answer: If the field winding of an unloaded salient pole synchronous motor is open circuited, the motor will stop.

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21

asked Mar 20, 2018 by anonymous

The maximum torque which a synchronous motor will develop at rest for any angular position of the rotor...

The maximum torque which a synchronous motor will develop at rest for any angular position of the rotor, at rated stator supply voltage and frequency, is known as?

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22

asked Mar 20, 2018 by anonymous

The armature current of the synchronous motor?

Last answer: The armature current of the synchronous motor has large values for low and high excitation.

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23

asked Mar 18, 2018 by anonymous

How can we reverse the direction of rotation of synchronous motor?

Last answer: By reversing supply phase sequence we can reverse the direction of rotation of synchronous motor.

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asked Mar 18, 2018 by anonymous

What is the maximum value of torque angle in synchronous motor?

Last answer: The maximum value of torque angle in synchronous motor is 90 degrees electrical.

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asked Mar 18, 2018 by anonymous

If the load of the normally excited synchronous motor is increased the power factor will?

Last answer: If the load of the normally excited synchronous motor is increased the power factor will become lagging.

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asked Mar 18, 2018 by anonymous

If the field of synchronous motor is under excited, power factor will be?

Last answer: If the field of synchronous motor is under excited, power factor will be lagging.

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27

asked Mar 18, 2018 by anonymous

The back emf of synchronous motor depends on?

Last answer: The back emf of synchronous motor depends on load angle.

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asked Mar 20, 2018 by anonymous

A synchronous motor has better power factor as compared to that of an equivalent induction motor...

A synchronous motor has better power factor as compared to that of an equivalent induction motor. This is mainly because?

Last answer: A synchronous motor has better power factor as compared to that of an equivalent induction motor. This is mainly because stator supply is not required to produce magnetic field.

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29

asked Mar 20, 2018 by anonymous

Exciters of synchronous machines are?

Last answer: Exciters of synchronous machines are d.c. shunt machines.

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30

asked Mar 18, 2018 by anonymous

what will happen when excitation of an unloaded salient pole synchronous motor suddenly gets disconnected?

Last answer: When excitation of an unloaded salient pole synchronous motor suddenly gets disconnected the motor will stop.

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31

asked Mar 20, 2018 by anonymous

The standard full-load power factor ratings for synchronous motors are?

Last answer: The standard full-load power factor ratings for synchronous motors are unity or 0.8 leading.

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32

asked Mar 20, 2018 by anonymous

In a synchronous motor, the armature current has large values for?

Last answer: In a synchronous motor, the armature current has large values for high and low excitation.

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33

asked Mar 20, 2018 by anonymous

The maximum constant load torque under which a synchronous motor will pull into synchronism...

The maximum constant load torque under which a synchronous motor will pull into synchronism at rated rotor supply voltage and frequency is known as?

Last answer: The maximum constant load torque under which a synchronous motor will pull into synchronism at rated rotor supply voltage and frequency is known as pull-in torque.

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34

asked Mar 20, 2018 by anonymous

If the synchronous motor, properly synchronised to the supply is running on no load and is having negligible loss then?

Last answer: If the synchronous motor, properly synchronised to the supply is running on no load and is having negligible loss then the stator current will be zero.

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35

asked Mar 18, 2018 by anonymous

The synchronous motor which works on leading power factor and does not drive any mechanical load is called?

Last answer: The synchronous motor which works on leading power factor and does not drive any mechanical load is called synchronous condenser.

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36

asked Mar 18, 2018 by anonymous

The damping winding in synchronous motor is generally used to?

Last answer: The damping winding in synchronous motor is generally used to provide starting torque and prevent hunting.

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37

asked Mar 18, 2018 by anonymous

Can we use the synchronous motor as the synchronous capacitor?

Last answer: Yes, we can use the synchronous motor as the synchronous capacitor when the synchrnous motor is overexcited.

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38

asked Mar 18, 2018 by anonymous

The synchronous motor will develop maximum power when the load angle is?

Last answer: The synchronous motor will develop maximum power when the load angle is 900.

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39

asked Mar 20, 2018 by anonymous

Slip-rings in a synchronous motor carry?

Last answer: Slip-rings in a synchronous motor carry direct current.

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asked Mar 20, 2018 by anonymous

A synchronous motor running with normal excitation adjusts to load increases essentially by increase in?

Last answer: A synchronous motor running with normal excitation adjusts to load increases essentially by increase in armature current.

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41

asked Mar 20, 2018 by anonymous

A synchronous motor can develop synchronous torque?

Last answer: A synchronous motor can develop synchronous torque at synchronous speed.

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42

asked Mar 20, 2018 by anonymous

Synchronous motors are generally not self-starting because?

Last answer: Synchronous motors are generally not self-starting because the direction of instantaneous torque reverses after half cycle.

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43

asked Mar 20, 2018 by anonymous

For power factor correction, synchronous motors operate at?

Last answer: For power factor correction, synchronous motors operate at no-load and greatly over-excited fields.

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44

asked Mar 18, 2018 by anonymous

Which motor have more efficiency, synchronous motor or induction motor?

Last answer: Synchronous motor has more efficiency.

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45

asked Mar 18, 2018 by anonymous

Hunting in synchronous motor cannot be due to?

Last answer: Hunting in synchronous motor cannot be due to windage friction.

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asked Mar 18, 2018 by anonymous

An unexcited single phase synchronous motor is ?

Last answer: An unexcited single-phase synchronous motor is reluctance motor.

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asked Mar 18, 2018 by anonymous

A synchronous motor can be made self starting by providing?

Last answer: A synchronous motor can be made self-starting by providing damper bar.

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asked Mar 18, 2018 by anonymous

In a synchronous motor which losses varies with load?

Last answer: In a synchronous motor, copper losses varies with load.

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asked Mar 18, 2018 by anonymous

Synchronous motor always runs at which speed?

Last answer: Synchronous motor always runs at synchronous speed.

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anonymous · Answer 1 · 2018-03-18T02:54:01+0000

V - curve of synchronous machine shows the relation between AC armature current and DC field current.

V - curve of synchronous machine shows the relation between?

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