# For a D.C. shunt motor if the excitation is changed?

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

## Related Questions

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

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
Last 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

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

Last Answer : The armature torque of the D.C. shunt motor is proportional to armature current.

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

Last Answer : In a D.C. shunt motor, under the conditions of maximum power, the current in the armature will be more than full-load current.

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

Last Answer : The speed of a D.C. shunt motor more than its full-load speed can be obtained by decreasing the field current.

Last Answer : If the field of a D.C. shunt motor gets opened while motor is running the motor will attain dangerously high speed.

DC shunt motor
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If field current is decreased in shunt dc motor, the speed of the motor (a) remains same. (b) increases. (c) decreases. (d) none of the above.

State any four applications of DC shunt motor.
Last Answer : Applications of DC shunt motor: 1) Lathe machines 2) drilling machines 3) milling machines 4) Printing machinery 5) Paper industry 6) centrifugal and reciprocating pumps 7) blowers 8)fans

Why does the speed of a DC shunt motor decrease as the load increases?
Last Answer : Because if the load is increasing then the torque must also be increase. If not then the speed of motor will decrease.

Last Answer : If a D.C. shunt motor is working at full load and if shunt field circuit suddenly opens this will make armature to take heavy current, possibly burning it.

Last Answer : If the speed of a D.C. shunt motor is increased, the back e.m.f. of the motor will increase.

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

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

Last Answer : The mechanical power developed by a shunt motor will be maximum when the ratio of back e.m.f. to applied voltage is 0.5.

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

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.

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.

Last Answer : In case of D.C. shunt motors the speed is dependent on back e.m.f. only because flux is practically constant in D:C. shunt motors.

Last Answer : In D.C. shunt motors as load is reduced the speed will remain almost constant.

Last Answer : In a manual shunt motor starter over load relay is connected in series and no volt relay in parallel with the load.

Last Answer : In a differentially compounded D.C. motor, if shunt field suddenly opens the motor will first stop and then run in opposite direction as series motor.

Last Answer : If a D.C. shunt motor is working at no load and if shunt field circuit suddenly opens this will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses.

Last Answer : The purpose of retardation test on D.C. shunt machines is to find out stray losses.

Last Answer : D.C. shunt motors are used for driving machine tools.

Last Answer : The direction of rotation of a D.C. series motor can be changed by interchanging field terminals.

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

While keeping the excitation constant, if the steam supply of an alternator running in parallel with another identical alternator is increased, then (A) It would over-run the other alternator (B) Its rotor ... (C) Its portion of share in load will increase (D) Its power factor would be decreased.
Last Answer : While keeping the excitation constant, if the steam supply of an alternator running in parallel with another identical alternator is increased, then Its portion of share in load will increase

Describe the reason of using dc series motor for electric trains.
Last Answer : Electric trains require an inverse torque speed characteristics for proper operation. That is a higher torque is required at start (when speed is nil or low) and as the train picks up ... torque - speed characteristics of DC series motors match, these motors are suitable for electric trains

In a 2 kW, 200 V, 1000 rpm. DC series motor the torque at full load was found to be 0.3 N -m. The torque at half full load in N -m is :
Last Answer : In a 2 kW, 200 V, 1000 rpm. DC series motor the torque at full load was found to be 0.3 N -m. The torque at half full load in N -m is : 0.075

The function of a brush and commutator arrangement in a dc motor is to  (1) produce unidirectional torque (2) produce unidirectional current in the armature (3) help in changing the direction of rotation of the armature (4) reduce sparking
Last Answer : The function of a brush and commutator arrangement in a dc motor is to produce unidirectional torque

Last Answer : If a D.C. motor designed for 40°C ambient temperature is to be used for 50°C ambient temperature, then the motor is to be derated by a factor recommended by manufacturer and select the next higher H.P. motor.

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

Last Answer : At the instant of starting when a D.C. motor is put on supply, it behaves like a low resistance circuit.

Last Answer : In case the back e.m.f. and the speed of a D.C. motor are doubled, the torque developed by the motor will remain unchanged.

As there is no back e.m.f. at the instant of starting a D.C. motor, in order to prevent a heavy current from flowing though the armature circuit?
Last Answer : As there is no back e.m.f. at the instant of starting a D.C. motor, in order to prevent a heavy current from flowing though the armature circuit a resistance is connected in series with armature.

Last Answer : The armature voltage control of D.C. motor provides constant torque drive.

Last Answer : Flywheel is used with D.C. compound motor to reduce the peak demand by the motor, compound motor will have to be cumulatively compounded.

Last Answer : Sparking, is discouraged in a D.C. motor because commutator gets damaged.

Last Answer : D.C. Series motor is generally preferred for cranes and hoists.

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Last Answer : Sparking at the commutator of a D.C. motor may result in damage to commutator segments, damage to commutator insulation, increased power consumption.

Last Answer : Cumulatively compounded D.C. motor will be suitable along with flywheel for intermittent light and heavy loads.

Last Answer : The current drawn by the armature of D.C. motor is directly proportional to the torque required.

Last Answer : In a D.C. series motor, if the armature current is reduced by 50%, the torque of the motor will be equal to 25% of the previous value.