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

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

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

## Related questions

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

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

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Description : 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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Description : The effect of increasing load on a synchronous motor running with normal excitation is (A) Increase both its Ia and power factor. (B) Decrease Ia, but increase power factor. (C) Increase Ia, but decrease power factor (D) Decrease both Ia and power factor.

Last Answer : The effect of increasing load on a synchronous motor running with normal excitation is Increase Ia, but decrease power factor

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Last Answer : Yes, we can make the power factor of synchronous motor leading by adjusting its excitation.

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Description : 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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Description : Salient pole rotor is use for which speed?

Last Answer : Salient pole rotor is use for low and medium speed prime movers.

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Description : In a synchronous generator if the excitation increased from a low value to normal value, with a fixed load  (A) The armature current increases and the power factor decreases  (B) The armature ... but is lagging  (D) The armature current decreases and the power factor increases and is leading

Last Answer : In a synchronous generator if the excitation increased from a low value to normal value, with a fixed load The armature current decreases and the power factor increases and is leading

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Last Answer : Reason is kinetic energy

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Last Answer : Starting winding of a single phase motor of a refrigerator is disconnected from the circuit by means of a magnetic relay.

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Description : The maximum reluctance power of a salient-pole synchronous motor having direct-axis reactance, 1.0 pu and quadrature-axis reactance, 0.5 pu, and input voltage, 1.0 pu is (A) 0.25 pu (B) 0.5 pu (C) 1.0 pu (D) 1.5 pu

Last Answer : The maximum reluctance power of a salient-pole synchronous motor having direct-axis reactance, 1.0 pu and quadrature-axis reactance, 0.5 pu, and input voltage, 1.0 pu is 0.5 pu

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Last Answer : For a D.C. shunt motor if the excitation is changed torque will change but power will remain constant.

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

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

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

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

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

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

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

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

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

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

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

Last Answer : Synchronous motor has more efficiency.

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Description : 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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Description : 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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Description : 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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Description : Hunting in synchronous motor cannot be due to?

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

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Description : 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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Description : 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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Description : 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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Description : An unexcited single phase synchronous motor is ?

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

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Description : 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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Description : In a synchronous motor which losses varies with load?

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

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Description : The back emf of synchronous motor depends on?

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

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Description : Synchronous motor always runs at which speed?

Last Answer : Synchronous motor always runs at synchronous speed.

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Description : 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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Description : 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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Description : Three phase synchronous motor will have how many sliprings?

Last Answer : Three phase synchronous motor will have two sliprings.

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Description : If the field circuits of an unloaded salient pole synchronous motor gets suddenly open circuited, then (A) The motor stops. (B) It continues to run at the same speed. (C) Its runs at the slower speed. (D) It runs at a very high speed.

Last Answer : Ans: B The motor continues to run at the same speed because synchronous motor speed does not depend upon load, Nα f.

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Description : The synchronous speed of an 8 pole induction motor supplied power from a 50 Hz source will be ?

Last Answer : Ns         equals        f/pair pole 50/4      - 12.5

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Description : With a neat sketch give the working of shaded pole induction motor.

Last Answer : Explanation: It has squirrel cage rotor and salient pole stator. The stator poles are shaded partially by short circuited conductor band to create the phase difference between the fluxes emerging from shaded ... rotating magnetic field in the air-gap and torque is exerted on the squirrel cage rotor.

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Description : State two applications of 1) Shaded pole motor 2) Universal motor

Last Answer : (i)Applications of Shaded pole motor: 1. Small fans 2. Toy motors 3. Hair dryers 4. Ventilators 5. Electric clocks 6. Record players 7. Motorized valves 8. Gramophones 9. Photocopying ... 5. Portable Drilling Machines 6. Electric Shavers 7. Mechanical computing Machines 8. Machine Tools etc.