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Answer :

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

Related questions

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.

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.

Description : 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

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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Last 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 

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

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.

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

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

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

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

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.

Description : Armature control of DC motor

Last Answer : Armature control of DC motor

Last Answer : The power factor of a single-phase induction motor is usually lagging.

Last Answer : In a shaded pole motor, the shading coil usually consist of a single turn of heavy copper wire which is short-circuited and carries only induced current.

Last Answer : The efficiency of a properly designed synchronous motor will usually fall in range 85 to 95%.

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

Last Answer : The normal value of the armature resistance of a d.c. motor is 0.5.

Last Answer : When the armature of a D.C. motor rotates, e.m.f. induced is back e.m.f.

Last Answer : In a synchronous motor, the armature current has large values for high and low excitation.

Last Answer : The armature current of the synchronous motor has large values for low and high excitation.

Description : 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

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 :

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

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

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

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

Description : From which material field coils of DC generator are made of?

Last Answer : Field coils of DC generator are usually made of copper.

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.

Last 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.

Last Answer : The commutator segments are connected to the armature conductors by means of copper lugs.

Description : Which of the following does not have a commutator? A) Dynamo B) Induction motor C) Universal motor D) None of these

Last Answer : Which of the following does not have a commutator? A) Dynamo B) Induction motor C) Universal motor D) None of these

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

Description : AC motor

Last 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.

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

Last 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 : Brake test on DC series motor

Last Answer : .embed-container { position: relative; padding-bottom: 56.25%; height: 0; overflow: hidden; max-width: 100%; } .embed-container iframe, .embed-container object, .embed-container embed { position: absolute; top: 0; left: 0; width: 100%; height: 100%; }

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

Last Answer : motor

Last Answer : The two pressure coils of a single phase power factor meter have the same dimensions and the same number of turns.

Description : The purpose of providing dummy coils in a generator is?

Last Answer : The purpose of providing dummy coils in a generator is to provide mechanical balance for the rotor.

Description : A 200 V DC machine supplies 20 A at 200 V as a generator. The armature resistance is 0.2 Ohm. If the machine is now operated as a motor at same terminal voltage and current but with the flux increased by 10%, the ratio of motor speed to generator speed is

Last Answer : A 200 V DC machine supplies 20 A at 200 V as a generator. The armature resistance is 0.2 Ohm. If the machine is now operated as a motor at same terminal voltage and current but with the flux increased by 10%, the ratio of motor speed to generator speed is 0.87

Description : In a synchronous machine, if the field flux axis ahead of the armature field axis in the direction of rotation, the machine is operating as  (1) synchronous motor (2) synchronous generator (3) asynchronous motor (4) asynchronous generator

Last Answer : In a synchronous machine, if the field flux axis ahead of the armature field axis in the direction of rotation, the machine is operating as synchronous generator 

Description : In dc machines, the armature windings are placed on the rotor because of the necessity for  (1) electromechanical energy conversion (2) generation of voltage (3) commutation (4) development of torque

Last Answer : 3  Commutation

Description : The armature current on symmetrical 3 phase short circuit of a synchronous machine (salient pole)  (A) has q -axis current only (B) has d -axis current only (C) has both d and q axis currents (D) cannot be divided between q and d axis currents

Last Answer : The armature current on symmetrical 3 phase short circuit of a synchronous machine (salient pole) has d -axis current only

Description : The induced emf in the armature of a lap -wound four -pole dc machine having 100 armature conductors rotating at 600 rpm and with 1 Wb flux per pole is  (1) 1000V (2) 100V (3) 600V (4) 10,000V

Last Answer : The induced emf in the armature of a lap -wound four -pole dc machine having 100 armature conductors rotating at 600 rpm and with 1 Wb flux per pole is 1000V

Description : Aluminium is not used as winding wire for the armature of a dc machine because  (1) aluminium has low resistivity (2) a large winding space is taken by aluminium conductors and creates ... ) the thermal conductivity of aluminium is low (4) aluminium has low conductivity as compared to copper

Last Answer : Aluminium is not used as winding wire for the armature of a dc machine because  (2) a large winding space is taken by aluminium conductors and creates jointing problems (3) the thermal conductivity of aluminium is low (4) aluminium has low conductivity as compared to copper

Description : The armature reaction in a synchronous generator supplying leading power factor load is (A) magnetizing (B) demagnetizing (C) demagnetizing and cross-magnetizing (D) magnetizing and cross-magnetizing

Last Answer : The armature reaction in a synchronous generator supplying leading power factor load is magnetizing and cross-magnetizing

Description : Why is the armature of DC generator laminated?

Last Answer : The armature of DC generator is laminated to reduce eddy current losses.

Description : State the function of commutator in DC generator and name the material used for commutator.

Last Answer : Function of Commutator: Commutator converts AC induced in armature winding into DC for external load. Material: i) Commutator segments are made up of Copper. ii) Commutator segments are insulated from each other by Mica.

Description : Number of commutator bars for a 4-pole, 2-layer, DC lap winding with 24 slots and one conductor per layer is (A) 48 (B) 24 (C) 192 (D) 96

Last Answer : Number of commutator bars for a 4-pole, 2-layer, DC lap winding with 24 slots and one conductor per layer is 24

Last Answer : To avoid formation of grooves in the commutator of a D.C. machine the brushes of opposite polarity should track each other.

Last Answer : The number of brushes in a commutator depends on amount of current to be collected.

Last Answer : The insulating material used between the commutator segments is normally mica.

Last Answer : The material for commutator brushes is generally carbon.