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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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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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Answer :

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

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

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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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Description :

Answer :

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

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Answer :

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

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116 views 1 answer
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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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114 views 1 answer
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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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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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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194 views 1 answer
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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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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2.6k views 1 answer
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

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429 views 1 answer
Description :

DC shunt motor

Answer :

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113 views 2 answers
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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Description :

Answer :

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

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88 views 1 answer
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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79 views 1 answer
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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74 views 1 answer
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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108 views 1 answer
Description :

Answer :

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

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114 views 1 answer
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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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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Description :

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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Description :

Answer :

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

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Description :

Answer :

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

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Answer :

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

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

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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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Description :

Answer :

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

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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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81 views 1 answer
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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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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120 views 1 answer
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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Description :

Answer :

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

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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
Description :

Answer :

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

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115 views 1 answer
Description :

Answer :

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

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90 views 1 answer
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
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
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
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
Description :

Answer :

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

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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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Description :

Answer :

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

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