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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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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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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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Description :

Consider a circuit with three parallel branches connected across a DC supply. What is the ratio of the branch currents I1 : I2 : I3 if the branch resistances are in the ratio of 2 : 3 : 4 respectively? A) 2 : 3 : 4 B) 6 : 4 : 3 C) 4 : 3 : 2 D) None of these

Answer :

Consider a circuit with three parallel branches connected across a DC supply. What is the ratio of the branch currents I1 : I2 : I3 if the branch resistances are in the ratio of 2 : 3 : 4 respectively? A) 2 : 3 : 4 B) 6 : 4 : 3 C) 4 : 3 : 2 D) None of these

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Answer :

Induction motor is a AC motor it is also known as asynchronous motor .

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Description :

Answer :

When a D.C. series motor is connected to A.C. supply, the power factor will be low because of high inductance of field and armature circuits.

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105 views 1 answer
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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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74 views 1 answer
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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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165 views 1 answer
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 :

In a A.C. series motor armature coils are usually connected to commutator through resistance.

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Description :

State the modification to be done in dc series motor to work satisfactorily as ac series motor. State applications of ac series motor.

Answer :

Modifications are necessary in a dc series motor so that it operates satisfactorily on ac supply. The modifications are as follows:  1) AC series motor is built with a few field turns as ... and grinders 5) High speed vacuum cleaners 6) Sewing machines 7) Food processors 8) Drilling machine 

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118 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 :

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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Description :

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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222 views 1 answer
Description :

Answer :

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

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116 views 1 answer
Description :

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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305 views 1 answer
Description :

Answer :

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

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118 views 1 answer
Description :

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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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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Answer :

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

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139 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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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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107 views 1 answer
Description :

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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Description :

Two 100W, 200V lamps are connected in series across a 200V supply. The total power consumed by each lamp will be in Watts

Answer :

4800

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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 :

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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Description :

Answer :

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

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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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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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Description :

Answer :

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

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Description :

Answer :

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

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Description :

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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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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Answer :

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

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

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

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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 :

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

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Answer :

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

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Answer :

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

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Description :

Answer :

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

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Description :

Answer :

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

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Description :

What are the parts of AC motor?

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Description :

What is the principle of AC motor?

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Description :

AC motor

Answer :

AC motor AC motor have two types one is Induction motor and second is synchronous motor. Induction motor have two types one is single phase induction motor and second is three phase ... self starting motor so using  external motor or we have to start it as induction motor.

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Description :

What will happen if the primary of a transformer is connected to D.C. supply?  (A) Transformer will operate with low efficiency (B) Transformer will operate with high efficiency (C) No effect (D) Transformer may start to smoke and burn 

Answer :

What will happen if the primary of a transformer is connected to D.C. supply?  (A) Transformer will operate with low efficiency (B) Transformer will operate with high efficiency (C) No effect (D) Transformer may start to smoke and burn 

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129 views 1 answer
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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113 views 1 answer
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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319 views 1 answer
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