Which D.C. motor is preferred for elevators ?

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asked Mar 20, 2018 by anonymous

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

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Which method of braking is generally used in elevators ?

Last answer: Plugging method of braking is generally used in elevators.

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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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If a D.C. motor designed for 40°C ambient temperature is to be used for 50°C ambient temperature, then the motor?

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.

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

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asked Mar 20, 2018 by anonymous

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

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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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?

Last answer: By looking at Commutator 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

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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51 views 1 answer

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?

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

If a D.C. motor is to be selected for conveyors, which motor would be preferred ?

Last answer: If a D.C. motor is to be selected for conveyors, Series motor would be preferred.

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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

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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65 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...

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.

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115 views 1 answer

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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87 views 1 answer

asked Mar 20, 2018 by anonymous

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

Last 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

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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asked Mar 20, 2018 by anonymous

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

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

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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?

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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95 views 1 answer

asked Mar 20, 2018 by anonymous

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

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

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305 views 1 answer

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?

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.

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142 views 1 answer

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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71 views 1 answer

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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76 views 1 answer

asked Mar 20, 2018 by anonymous

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

Last answer: In a D.C. shunt motor, speed is independent of armature 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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75 views 1 answer

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

If a D.C. series motor is operated on A.C. supply, it will?

Last 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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63 views 1 answer

asked Mar 20, 2018 by anonymous

D.C. motor is to a drive a load which is almost nil for certain part of the load cycle...

D.C. motor is to a drive a load which is almost nil for certain part of the load cycle and peak value for short duration. We will select the?

Last answer: D.C. motor is to a drive a load which is almost nil for certain part of the load cycle and peak value for short duration. We will select the compound motor.

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75 views 1 answer

asked Mar 20, 2018 by anonymous

D.C. motor is to drive a load which has certain minimum value for most of the time and some peak value...

D.C. motor is to drive a load which has certain minimum value for most of the time and some peak value for short duration. We will select the?

Last answer: D.C. motor is to drive a load which has certain minimum value for most of the time and some peak value for short duration. We will select the series motor.

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asked Mar 20, 2018 by anonymous

For which types of D.C. motor, dynamic braking is generally used ?

Last answer: Shunt motors, Series motors, Compound motors

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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

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

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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?

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.

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148 views 1 answer

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

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

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

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50 views 1 answer

asked Mar 20, 2018 by anonymous

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

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.

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70 views 1 answer

asked Mar 20, 2018 by anonymous

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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111 views 1 answer

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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173 views 1 answer

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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378 views 1 answer

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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91 views 1 answer

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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75 views 1 answer

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.

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69 views 1 answer

asked Mar 19, 2018 by anonymous

Why thyristor are not preferred for inverter?

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432 views 0 answers

asked May 22, 2020 by anonymous

Explain the necessity of starter for D.C. motor. State various types of D.C. motor starter.

Last answer: Necessity of Starter for D.C. Motor: Armature current is given by equation Ia = (V−Eb)/Ra i) If the motor is at standstill or rest, back emf Eb is zero (as Eb= ZNP/(60A), at start speed N ... . Types of D.C. motor starters: i) Two point starter ii)Three point starter iii) Four point starter

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81 views 1 answer

asked Mar 20, 2018 by anonymous

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

Last answer: Series motor has got maximum self relieving property.

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129 views 1 answer

asked Sep 18, 2018 by anonymous

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

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asked Mar 26, 2018 by anonymous

The Eb/V ratio of a d.c. motor is an indication of its?

Last answer: The Eb/V ratio of a d.c. motor is an indication of its efficiency.

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531 views 1 answer

asked Mar 26, 2018 by anonymous

The normal value of the armature resistance of a d.c. motor is?

Last answer: asked Mar 26, 2018 by anonymous The normal value of the armature resistance of a d.c. motor is?

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757 views 2 answers

asked Mar 26, 2018 by anonymous

In a d.c. motor, unidirectional torque is produced with the help of?

In a d.c. motor, unidirectional torque is produced with the help of

Last answer: Commutator provides unidirectional torque and pulsating dc

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257 views 1 answer

asked Mar 20, 2018 by anonymous

If a D.C. shunt motor is working at full load and if shunt field circuit suddenly opens?

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.

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103 views 1 answer

anonymous · Answer 1 · 2018-03-20T20:00:49+0000

answered Mar 20, 2018 by anonymous

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

Which D.C. motor is preferred for elevators ?

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