138 views

1 Answer

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.

Like 0 like

Please log in or register to answer this question.

Related questions

230 views

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

1 answer
113 views

Last 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.

1 answer
68 views

Description : Why the speed of synchronous motor is constant?

0 answers
125 views

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

1 answer
108 views

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.

1 answer
95 views

Description : Synchronous motor always runs at which speed?

Last Answer : Synchronous motor always runs at synchronous speed.

1 answer
210 views

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

2 answers
92 views

Description : Damper winding in a synchronous motor

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

1 answer
100 views

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

1 answer
583 views

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

1 answer
571 views

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

Last Answer : Leading

2 answers
75 views

Description : Why synchronous motor Cannot start itself?

0 answers
80 views

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

0 answers
74 views

Description : What is the principle of synchronous motor?

0 answers
70 views

Description : What is the use of synchronous motor?

0 answers
113 views

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

1 answer
519 views

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

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

1 answer
261 views

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

Last 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. 

2 answers
498 views

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

Last 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

1 answer
264 views

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

1 answer
265 views

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

Last 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 

1 answer
164 views

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

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

1 answer
67 views

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

1 answer
106 views

Last Answer : Series motor has the poorest speed control.

1 answer
424 views

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

Last 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

1 answer
137 views

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

1 answer
144 views

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

1 answer
166 views

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

1 answer
120 views

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

1 answer
92 views

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

1 answer
119 views

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

1 answer
108 views

Last 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.

1 answer
179 views

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

1 answer
174 views

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

1 answer
105 views

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

1 answer
273 views

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

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

2 answers
393 views

Description : speed control methods of three phase induction motor?

Last Answer : Speed control of three phase induction motor

2 answers
171 views

Description : List different starting methods of three phase synchronous motor. Explain any one of them.

Last Answer : Different Starting Methods of Three Phase Synchronous Motor: As synchronous motor is not self starting, different methods of starting are as follows: 1) By using an Induction (Pony) motor 2) ... . The rotor gets pulled into synchronism and starts running at constant speed as a synchronous motor. 

1 answer
527 views

Description : Draw and explain V and inverted V curves for synchronous motor.

Last Answer : V curves' and inverted V curves' for Synchronous Motor:  V curve:  V curve is a plot of the stator current versus field current for different constant loads. The graph is plotted ... Vcurves of synchronous motor. The highest point on each of these curves indicates unity power factor.

1 answer
129 views

Description : List different torques in synchronous motor. 

Last Answer : Different Torques in Synchronous Motor: 1) Starting torque 2) Running torque 3) Pull-in torque 4) Pull-out torque

1 answer
667 views

Description : In a self-controlled synchronous motor fed from a variable frequency inverter  (1) the rotor poles invariably have damper windings  (2) there are stability problems  (3) the speed of the rotor decides stator frequency  (4) the frequency of the stator decides the rotor speed

Last Answer : 2

2 answers
104 views

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

1 answer
77 views

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

1 answer
180 views

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.

1 answer
204 views

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

1 answer
119 views

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

1 answer
261 views

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

1 answer
151 views

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

1 answer
200 views

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

1 answer
154 views

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

1 answer
...