Sparking, is discouraged in a D.C. motor because?

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Sparking, is discouraged in a D.C. motor because?

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asked Mar 20, 2018 by anonymous

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Sparking at the commutator of a D.C. motor may result in?

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.

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asked Mar 20, 2018 by anonymous

Sparking occurs when a load is switched off because the circuit has high?

Sparking occurs when a load is switched off because the circuit has high?
Last Answer : Sparking occurs when a load is switched off because the circuit has high inductance.

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asked Mar 25, 2018 by anonymous

For starting a D.C. motor a starter is required because?

Last 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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Describe the reason of using dc series motor for electric trains.

Describe the reason of using dc series motor for electric trains.
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asked Sep 18, 2018 by anonymous

A 240 V, dc shunt motor draws 15 A while supplying the rated load at a speed of 80 rad/s.

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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

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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

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

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asked May 3, 2018 by anonymous

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

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

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asked Apr 29, 2018 by anonymous

The function of a brush and commutator arrangement in a dc motor is to

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

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asked Apr 29, 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?

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asked Mar 20, 2018 by anonymous

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

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

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asked Mar 20, 2018 by anonymous

The speed of a D.C. motor can be controlled by varying

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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asked Mar 20, 2018 by anonymous

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

Last 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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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?

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asked Mar 20, 2018 by anonymous

The speed of a D.C. shunt motor can be increased by?

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

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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...

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?
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asked Mar 20, 2018 by anonymous

The armature voltage control of D.C. motor provides?

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asked Mar 20, 2018 by anonymous

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

Last 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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asked Mar 20, 2018 by anonymous

In a differentially compounded D.C. motor, if shunt field suddenly opens?

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asked Mar 20, 2018 by anonymous

Flywheel is used with D.C. compound motor to reduce the peak demand by the motor, compound motor will have to be?

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.

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Which D.C. motor is generally preferred for cranes and hoists ?

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The condition for maximum power in case of D.C. motor is?

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If a D.C. shunt motor is working at no load and if shunt field circuit suddenly opens?

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.

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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?

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

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asked Mar 20, 2018 by anonymous

Which D.C. motor has got maximum self loading property?

Last Answer : Differentially compounded D.C. motor has got maximum self loading property.

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asked Mar 20, 2018 by anonymous

The current drawn by the armature of D.C. motor is directly proportional to?

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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?

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asked Mar 20, 2018 by anonymous

The speed of a D.C. series motor is?

Last 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

The starting resistance of a D.C. motor is generally?

Last Answer : The starting resistance of a D.C. motor is generally low.

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In case the conditions for maximum power for a D.C. motor are established, the efficiency of the motor will be?

Last 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

By looking at which part of the motor, it can be easily confirmed that a particular motor is D.C. motor?

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asked Mar 20, 2018 by anonymous

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

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.

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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?

Last 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

In a D.C. shunt motor, speed is?

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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?

Last 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

If a D.C. motor is connected across the A.C. supply it will?

Last 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

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

The type of D.C. motor used for shears and punches is?
Last 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

A D.C. series motor is that which?

Last Answer : A D.C. series motor is that which has its field winding consisting of thick wire and less turns.

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asked Mar 20, 2018 by anonymous

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

Last 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

Which D.C. motor is preferred for elevators ?

Last Answer : Cumulative compound D.C. motor is preferred for elevators.

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asked Mar 20, 2018 by anonymous

The direction of rotation of a D.C. series motor can be changed by?

Last 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

A.C. series motor as compared to D.C. series motor has?

Last Answer : A.C. series motor as compared to D.C. series motor has smaller brush width, less number of field turns, more number of armature turns, less air gap.

136 views 1 answer

asked Mar 20, 2018 by anonymous