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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.

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If the field of a D.C. shunt motor gets opened while motor is running?
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Answer :

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

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asked Mar 20, 2018 by anonymous
The speed of a D.C. shunt motor can be increased by?
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Answer :

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

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In a D.C. shunt motor, under the conditions of maximum power, the current in the armature will be?
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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.

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asked Mar 20, 2018 by anonymous
In a D.C. shunt motor, speed is?
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Answer :

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

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asked Mar 20, 2018 by anonymous
The speed of a D.C. shunt motor more than its full-load speed can be obtained by?
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Answer :

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

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asked Mar 20, 2018 by anonymous
The armature torque of the D.C. shunt motor is proportional to?
Description :

Answer :

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

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asked Mar 20, 2018 by anonymous
As the load is increased the speed of D.C. shunt motor will?
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Answer :

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

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asked Mar 20, 2018 by anonymous
If a D.C. shunt motor is working at full load and if shunt field circuit suddenly opens?
Description :

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.

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asked Mar 20, 2018 by anonymous
If the speed of a D.C. shunt motor is increased, the back e.m.f. of the motor will?
Description :

Answer :

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

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asked Mar 20, 2018 by anonymous
A 240 V, dc shunt motor draws 15 A while supplying the rated load at a speed of 80 rad/s.
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

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asked May 8, 2018 by anonymous
A 200 V dc shunt motor is running at 1000 rpm and drawing a current of 10 A. Its armature winding resistance
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

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asked May 3, 2018 by anonymous
If field current is decreased in shunt dc motor, the speed of the motor
Description :

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.

Answer :

increases

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asked Aug 25, 2019 by anonymous
Why does the speed of a DC shunt motor decrease as the load increases?
Description :

Why does the speed of a DC shunt motor decrease as the load increases?

Answer :

Because if the load is increasing then the torque must also be increase. If not then the speed of motor will decrease.

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asked Jul 5, 2019 by anonymous
The effect of increasing load on a synchronous motor running with normal excitation is
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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

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asked Apr 28, 2018 by anonymous
DC shunt motor
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DC shunt motor

Answer :

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asked Apr 23, 2020 by anonymous
State any four applications of DC shunt motor.
Description :

State any four applications of DC shunt motor.

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

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asked Jul 27, 2019 by anonymous
Can we make power factor of synchronous motor leading by adjusting its excitation?
Description :

Answer :

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

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asked Mar 6, 2018 by anonymous
If we change the excitation of synchronous machine will it affect on motor speed?
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.

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asked Mar 18, 2018 by anonymous
In a differentially compounded D.C. motor, if shunt field suddenly opens?
Description :

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.

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asked Mar 20, 2018 by anonymous
If a D.C. shunt motor is working at no load and if shunt field circuit suddenly opens?
Description :

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.

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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?
Description :

Answer :

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

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asked Mar 20, 2018 by anonymous
what will happen when excitation of an unloaded salient pole synchronous motor suddenly gets disconnected?
Description :

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

Answer :

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

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asked Mar 18, 2018 by anonymous
The mechanical power developed by a shunt motor will be maximum when the ratio of back e.m.f. to applied voltage is?
Description :

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.

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In case of D.C. shunt motors the speed is dependent on back e.m.f. only because?
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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.

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asked Mar 20, 2018 by anonymous
In D.C. shunt motors as load is reduced?
Description :

Answer :

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

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asked Mar 20, 2018 by anonymous
The direction of rotation of a D.C. series motor can be changed by?
Description :

Answer :

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

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asked Mar 20, 2018 by anonymous
D.C. shunt motors are used for driving?
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Answer :

D.C. shunt motors are used for driving machine tools.

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asked Mar 20, 2018 by anonymous
If a D.C. motor designed for 40°C ambient temperature is to be used for 50°C ambient temperature, then the motor?
Description :

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.

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asked Mar 20, 2018 by anonymous
In a synchronous generator if the excitation increased from a low value to normal value, with a fixed load
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 current decreases and the power factor also decreases  (C) The armature current decreases and the power factor increases but is lagging  (D) The armature current decreases and the power factor increases and is leading

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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asked Apr 29, 2018 by anonymous
In a manual shunt motor starter?
Description :

Answer :

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

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asked Mar 20, 2018 by anonymous
While keeping the excitation constant, if the steam supply of an alternator running in parallel with another
Description :

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 will fall back in phase with respect to the other machine (C) Its portion of share in load will increase (D) Its power factor would be decreased.

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

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asked Apr 28, 2018 by anonymous
The purpose of retardation test on D.C. shunt machines is to find out?
Description :

Answer :

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

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asked Mar 20, 2018 by anonymous
In a D.C. series motor, if the armature current is reduced by 50%, the torque of the motor will be equal to?
Description :

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.

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asked Mar 20, 2018 by anonymous
What will happen if the back e.m.f. of a D.C. motor vanishes suddenly?
Description :

Answer :

The armature may burn if the back e.m.f. of a D.C. motor vanishes suddenly.

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asked Mar 20, 2018 by anonymous
If a D.C. motor is connected across the A.C. supply it will?
Description :

Answer :

If a D.C. motor is connected across the A.C. supply it will burn due to heat produced in the field winding by eddy currents.

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asked Mar 20, 2018 by anonymous
If a D.C. series motor is operated on A.C. supply, it will?
Description :

Answer :

If a D.C. series motor is operated on A.C. supply, it will spark excessively, have poor efficiency, have poor power factor.

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asked Mar 20, 2018 by anonymous
In case the conditions for maximum power for a D.C. motor are established, the efficiency of the motor will be?
Description :

Answer :

In case the conditions for maximum power for a D.C. motor are established, the efficiency of the motor will be less than 50%.

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asked Mar 20, 2018 by anonymous
For starting a D.C. motor a starter is required because?
Description :

Answer :

For starting a D.C. motor a starter is required because it limits the starting current to a safe value.

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asked Mar 20, 2018 by anonymous
Which D.C. motor is generally preferred for cranes and hoists ?
Description :

Answer :

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

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asked Mar 20, 2018 by anonymous
The condition for maximum power in case of D.C. motor is?
Description :

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asked Mar 20, 2018 by anonymous
Which D.C. motor will be suitable along with flywheel for intermittent light and heavy loads?
Description :

Answer :

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

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119 views 1 answer
asked Mar 20, 2018 by anonymous
The type of D.C. motor used for shears and punches is?
Description :

Answer :

The type of D.C. motor used for shears and punches is cumulative compound D.C. motor.

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asked Mar 20, 2018 by anonymous
Which D.C. motor is preferred for elevators ?
Description :

Answer :

Cumulative compound D.C. motor is preferred for elevators.

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90 views 1 answer
asked Mar 20, 2018 by anonymous
The speed of a D.C. motor can be controlled by varying
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

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156 views 1 answer
asked Mar 20, 2018 by anonymous
At the instant of starting when a D.C. motor is put on supply, it behaves like?
Description :

Answer :

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

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75 views 1 answer
asked Mar 20, 2018 by anonymous
In case the back e.m.f. and the speed of a D.C. motor are doubled, the torque developed by the motor will?
Description :

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.

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159 views 1 answer
asked Mar 20, 2018 by anonymous
As there is no back e.m.f. at the instant of starting a D.C. motor, in order to prevent...
Description :

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?

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.

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133 views 1 answer
asked Mar 20, 2018 by anonymous
Sparking, is discouraged in a D.C. motor because?
Description :

Answer :

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

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118 views 1 answer
asked Mar 20, 2018 by anonymous
Sparking at the commutator of a D.C. motor may result in?
Description :

Answer :

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

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asked Mar 20, 2018 by anonymous
The speed of a D.C. series motor is?
Description :

Answer :

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

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asked Mar 20, 2018 by anonymous
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