The demagnetising component of armature reaction in a D.C. generator?

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1 Answer

Answer :

The demagnetising component of armature reaction in a D.C. generator reduces generator e.m.f.

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Armature reaction in a generator results in?

Last Answer : Armature reaction in a generator results in demagnetisation of leading pole tip and magnetisation of trailing pole tip.

The armature reaction in a synchronous generator supplying leading power factor load is

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

The armature core of a D.C. generator is usually made of?

Last Answer : The armature core of a D.C. generator is usually made of silicon steel.

A 200 V DC machine supplies 20 A at 200 V as a generator. The armature resistance is 0.2

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

Why is the armature of DC generator laminated?

Description : Why is the armature of DC generator laminated?

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

Armature reaction of an unsaturated D.C. machine is?

Last Answer : Armature reaction of an unsaturated D.C. machine is crossmagnetising.

Define armature reaction in an alternator. Explain the effect of armature reaction at various P.F. of loads of alternator.

Description : Define armature reaction in an alternator. Explain the effect of armature reaction at various P.F. of loads of alternator.

Last Answer : Armature Reaction: The effect of armature flux on main flux is called as armature reaction.  Armature Reaction at Various Power Factors: When armature is loaded, the armature flux modifies ... lagging p.f. For capacitive loads the effect of flux is partly distorting and partly strengthening.

In a 3 -phase alternator, if there is only magnetizing armature reaction, the load is :

Description : In a 3 -phase alternator, if there is only magnetizing armature reaction, the load is :  (A) capacitive (B) inductive (C) resistive (D) inductive and resistive

Last Answer : In a 3 -phase alternator, if there is only magnetizing armature reaction, the load is : capacitive 

What is the effect of armature reaction?

Description : What is the effect of armature reaction? A) Demagnetization of the main field B) Demagnetization of the brushes C) Cross-magnetization of the brushes D) None of these

Last Answer : What is the effect of armature reaction? A) Demagnetization of the main field B) Demagnetization of the brushes C) Cross-magnetization of the brushes D) None of these

For a D.C. generator when the number of poles and the number of armature conductors is fixed...

Description : For a D.C. generator when the number of poles and the number of armature conductors is fixed, then which winding will give the higher e.m.f. ?

Last Answer : Wave winding

Open circuited armature coil of a D.C. machine is?

Last Answer : Open circuited armature coil of a D.C. machine is identified by the scarring of the commutator segment to which open circuited coil is connected and indicated by a spark completely around the commutator.

The critical resistance of the D.C. generator is the resistance of?

Last Answer : The critical resistance of the D.C. generator is the resistance of field.

If residual magnetism is present in a D.C. generator, the induced e.m.f. at zero speed will be?

Description : If residual magnetism is present in a D.C. generator, the induced e.m.f. at zero speed will be?

Last Answer : If residual magnetism is present in a D.C. generator, the induced e.m.f. at zero speed will be zero.

A 220 V D.C. generator is run at full speed without any excitation. The open circuit voltage will be?

Last Answer : A 220 V D.C. generator is run at full speed without any excitation. The open circuit voltage will be about 2 V.

In a level compounded D.C. generator, full load terminal voltage is?

Last Answer : In a level compounded D.C. generator, full load terminal voltage is equal to no-load terminal voltage.

In a D.C. generator in case the resistance of the field winding is increased, then output voltage will?

Last Answer : In a D.C. generator in case the resistance of the field winding is increased, then output voltage will decrease.

A D.C. generator can be considered as?

Last Answer : A D.C. generator can be considered as rotating amplifier.

In a D.C. generator the critical resistance refers to the resistance of?

Last Answer : In a D.C. generator, the critical resistance refers to the resistance of field.

Flashing the field of D.C. generator means?

Last Answer : Flashing the field of D.C. generator means creating residual magnetism by a D.C. source.

If a D.C. generator fails to build up the probable cause could not be?

Last Answer : If a D.C. generator fails to build up the probable cause could not be field resistance less than the critical resistance.

In a D.C. generator the magnetic neutral axis coincides with the geometrical neutral axis, when?

Last Answer : In a D.C. generator the magnetic neutral axis coincides with the geometrical neutral axis, when there is no load on|he generator.

The e.m.f. generated in a D.C. generator is directly proportional to?

Last Answer : The e.m.f. generated in a D.C. generator is directly proportional to speed of armature.

In a D.C. generator the number of mechanical degrees and electrical degrees will be the same when?

Last Answer : In a D.C. generator the number of mechanical degrees and electrical degrees will be the same when number of poles is 2.

D.C. generator generally preferred for charging automobile batteries is?

Last Answer : D.C. generator generally preferred for charging automobile batteries is long shunt compound generator.

In a D.C. generator the ripples in the direct e.m.f. generated are reduced by?

Last Answer : In a D.C. generator the ripples in the direct e.m.f. generated are reduced by using carbon brushes of superior quality.

If brushes of a D.C. generator are moved in order to bring these brushes in magnetic neutral axis, there will be?

Last Answer : If brushes of a D.C. generator are moved in order to bring these brushes in magnetic neutral axis, there will be crossmagnetisation as well as demagnetising.

In case of a 4-pole D.C. generator provided with a two layer lap winding with sixteen coils, the pole pitch will be?

Last Answer : In case of a 4-pole D.C. generator provided with a two layer lap winding with sixteen coils, the pole pitch will be 8.

In a D.C. generator, the iron losses mainly take place in?

Last Answer : In a D.C. generator, the iron losses mainly take place in armature rotor.

The condition for maximum efficiency for a D.C. generator is?

Last Answer : The condition for maximum efficiency for a D.C. generator is variable losses equal to constant losses.

The total losses in a well designed D.C. generator of 10 kW will be nearly?

Last Answer : The total losses in a well designed D.C. generator of 10 kW will be nearly 500 W.

A 200 V dc shunt motor is running at 1000 rpm and drawing a current of 10 A. Its armature winding resistance

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

In dc machines, the armature windings are placed on the rotor because of the necessity for

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

The induced emf in the armature of a lap -wound four -pole dc machine having 100 armature conductors

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

Aluminium is not used as winding wire for the armature of a dc machine because

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

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

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.

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

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

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

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

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.

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.

Armature control of DC motor

Description : Armature control of DC motor

Last Answer : Armature control of DC motor

In a separately excited generator supplying rated load the armature reaction?

Last Answer : In a separately excited generator supplying rated load the armature reaction is always present.

In D.C. generators on no-load, the air gap flux distribution in space is?

Last Answer : In D.C. generators on no-load, the air gap flux distribution in space is flat topped.

A sinusoidal voltage of 5 Hz is applied to the field of a shunt generator. The armature voltage wave?

Description : A sinusoidal voltage of 5 Hz is applied to the field of a shunt generator. The armature voltage wave?

Last Answer : A sinusoidal voltage of 5 Hz is applied to the field of a shunt generator. The armature voltage wave will be of 5 Hz.

The e.m.f. induced in the armature of a shunt generator is 600 V. The armature resistance is 0.1 ohm...

Description : The e.m.f. induced in the armature of a shunt generator is 600 V. The armature resistance is 0.1 ohm. If the armature current is 200 A, the terminal voltage will be?

Last Answer : The e.m.f. induced in the armature of a shunt generator is 600 V. The armature resistance is 0.1 ohm. If the armature current is 200 A, the terminal voltage will be 580 V.

Armature coil is short circuited by brushes when it lies?

Last Answer : Armature coil is short circuited by brushes when it lies along neutral axis.

The commutator segments are connected to the armature conductors by means of?

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

The resistance of armature winding depends on?

Last Answer : The resistance of armature winding depends on length of conductor, cross-sectional area of the conductor, number of conductors.

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

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.

The fall in speed of a dc generator due to increase in load can be corrected by

Description : The fall in speed of a dc generator due to increase in load can be corrected by  (1) cooling the armature.. (2) increasing the excitation. (3) reducing the load voltage. (4) increasing the input to the prime mover

Last Answer : It   can  be  corrected  by  increasing  the  input  to  the  prime  mover.