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Centrifugal switch disconnects the auxiliary winding of the motor at about 70 to 80 percent of synchronous speed.

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Answer : A centrifugal switch is used to disconnect starting winding when motor has picked up about 50 to 70 per cent of rated speed.

Answer : If the centrifugal switch does not open at 70 to 80 percent of synchronous speed of motor, it would result in damage to the starting winding.

Answer : If the centrifugal switch of a two-value capacitor motor using two capacitors fails to open then Electrolytic capacitor will, in all probability, suffer break down.

Answer : In a single phase motor the centrifugal switch disconnects auxiliary winding of the motor.

Answer : In split-phase motor auxiliary winding is of thin wire placed at the top of the slots.

Description : Damper winding in a synchronous motor

Answer : Damper winding in a synchronous motor Serves to start the motor.

Description : In synchronous motor, does the winding losses vary with load?

Answer : No, in the synchronous motor the winding losses do not vary with load.

Answer : In case of a reluctance motor, when the load is increased so that it cannot maintain synchronous speed the motor will run as induction motor.

Description : Why the speed of synchronous motor is constant?

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

Description : The damping winding in synchronous motor is generally used to?

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

Description : Synchronous motor always runs at which speed?

Answer : Synchronous motor always runs at synchronous speed.

Answer : In a capacitor start and run motors the function of the running capacitor in series with the auxiliary winding is to improve power factor.

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

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

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

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

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

Description : Damper winding is provided in 3 phase synchronous motors to :

Answer : Damper winding is provided in 3 phase synchronous motors to : provide starting torque and prevent hunting

Description : A 200 V dc shunt motor is running at 1000 rpm and drawing a current of 10 A. Its armature winding resistance is 2 Ohm. It. is braked by plugging. The resistance to be connected in series with armature to restrict armature current to 10 A, is

Answer : A 200 V dc shunt motor is running at 1000 rpm and drawing a current of 10 A. Its armature winding resistance is 2 Ohm. It. is braked by plugging. The resistance to be connected in series with armature to restrict armature current to 10 A, is 36 Ohm

Answer : The starting winding of a single-phase motor is placed in stator.

Answer : If starting winding of a single-phase induction motor is left in the circuit, it will draw excessive current and overheat.

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

Answer : The purpose of stator winding in the compensated repulsion motor is to improve power factor and provide better speed regulation.

Answer : In split phase motor main winding is of thick wire placed at the bottom of the slots.

Description : A 240 V, dc shunt motor draws 15 A while supplying the rated load at a speed of 80 rad/s. The armature resistance is 0.5 W and the field winding resistance is 80 W. The net Voltage across armature resistance at the time of plugging will be

Answer : A 240 V, dc shunt motor draws 15 A while supplying the rated load at a speed of 80 rad/s. The armature resistance is 0.5 W and the field winding resistance is 80 W. The net Voltage across armature resistance at the time of plugging will be 474 V

Description : A three-phase synchronous motor connected to ac mains is running at full load and unity power factor. lf its shaft load is reduced by half and field current is held constant then its new power factor will be

Answer : Leading

Description : What are the speed control methods of dc motor?

Answer : Field control of DC motor Armature control of DC motor

Description : What is the principle of synchronous motor?

Description : What is the use of synchronous motor?

Description : what is the difference between synchronous and asynchronous motor?

Answer : Asynchronous motors and syncrouns motor are called as dc machines.  and also syncrouns motor called as induction motor. Asynonymous motor as are rotates with constant speed we not able to operate . ... It is able to operate. These are a small difference between syncrouns and asynchronous motors. 

Description : The speed of a three-phase induction motor is controlled by variable voltage variable frequency control (i.e. keeping V/f constant). As the frequency is reduced, the slip at maximum torque  (1) Decreases (2) Increases (3) Remains constant (4) None of the above

Answer : The speed of a three-phase induction motor is controlled by variable voltage variable frequency control (i.e. keeping V/f constant). As the frequency is reduced, the slip at maximum torque Increases 

Description : The speed of a 2-pole, 3-phase stepper motor operated by 1200 pulses/min (A) 100 rpm (B) 200 rpm (C) 400 rpm (D) 800 rpm

Answer : The speed of a 2-pole, 3-phase stepper motor operated by 1200 pulses/min 200 rpm

Answer : In variable speed motor a weaker commutating field is needed at low speed than at high speed.

Answer : Series motor has the poorest speed control.

Description : The speed of a D.C. motor can be controlled by varying  1. Its flux per pole 2. Resistance of armature circuit 3. Applied voltage 4. All of the above

Answer : The speed of a D.C. motor can be controlled by varying  1. Its flux per pole 2. Resistance of armature circuit 3. Applied voltage 4. All of the above

Answer : The speed of a D.C. shunt motor can be increased by increasing the resistance in field circuit.

Answer : As the load is increased the speed of D.C. shunt motor will reduce slightly.

Answer : For the same H.P. rating and full load speed, following motor has poor starting torque differentially compounded.

Answer : The speed of a D.C. series motor is inversely proportional to the armature current.

Answer : In a D.C. shunt motor, speed is independent of armature current.

Answer : The speed of a universal motor is usually reduced by using gearing.

Answer : Speed control of a universal motor is achieved by varying field flux with tapped field windings, connecting rheostat in series, applying variable voltage by means of silicon controlled rectifier, applying variable voltage by means of variable auto-transformer.

Answer : The speed/load characteristics of a universal motor is same as that of D.C. series motor.

Answer : Speed torque characteristic of a repulsion induction motor is similar to that of a D.C. compound motor.

Answer : The speed control of universal motor used for sewing machines is by varying the resistance.

Description : speed control methods of three phase induction motor?

Answer : Speed control of three phase induction motor

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

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

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.

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

Description : Why synchronous motor Cannot start itself?

Description : How can we improve power factor using synchronous motor?

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

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