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

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

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

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

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.

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

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

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

Description : 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 :

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

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

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

Answer : In A.C. series motor compensating winding is employed to reduce sparking at the brushes.

Description : Why a dc series motor has a high starting torque?

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.

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.

Description : Brake test on DC series motor

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Description : What are the advantages of DC series motor?

Description : Why dc series motor should not be started at no load?

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

Description : In an AC. circuit, a low value of kVAR compared with kW indicates?

Answer : In an AC. circuit, a low value of kVAR compared with kW indicates high power factor.

Description : In case of conductively compensated D.C. series motors, the compensating winding is provided?

Answer : In case of conductively compensated D.C. series motors, the compensating winding is provided in series with armature winding.

Answer : When two D.C. series motors are connected in parallel, the resultant speed is normal speed.

Answer : H.R.C. fuse, as compared to a rewirable fuse, has no ageing effect, high speed of operation, high rupturing capacity.

Description : Write two applications of D.C. series motor.

Answer : The applications of D.C. series motor: 1. Cranes 2. Hoists 3. Trolley and cars 4. Conveyors 5. For traction work i.e. electric locomotives 6. Elevator 7. Air compressor

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.

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

Description : Explain series switching control of AC load. Single phase resistance load - Integral half cycle control Phase control - Resistance load

Description : What are the parts of AC motor?

Description : What is the principle of AC motor?

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.

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.

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

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.

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

Answer : If  equalising bar is connected to the 2 DC generators  the current will be equal in 2 generators irrespective of parallel connection so that we connect equaliser bar

Answer : During rheostat braking of D.C. series motors motor is run as a generator.

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

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

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

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.

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

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

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.

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

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

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

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.

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

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

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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