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

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Answer :

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

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

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

Description :

A shunt generator running at 1000 r.p.m. has generated e.m.f. as 200 V. If the speed increases to 1200 r.p.m., the generated e.m.f. will be nearly?

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A shunt generator running at 1000 r.p.m. has generated e.m.f. as 200 V. If the speed increases to 1200 r.p.m., the generated e.m.f. will be nearly 240 V.

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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?

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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.

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

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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.

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

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

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

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

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

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Magnetic field in a D.C. generator is produced by electromagnets.

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

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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.

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

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

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

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A D.C. generator can be considered as rotating amplifier.

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

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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. ?

Answer :

Wave winding

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

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

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

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

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

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

Answer :

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

Description :

The eddy current loss in a dc generator is 400 W at 40 Hz frequency of reversal and constant flux density. When frequency is increased to 50 Hz., eddy current loss is :  (A) 256 W (B) 320 W (C) 500 W (D) 625 W

Answer :

The eddy current loss in a dc generator is 400 W at 40 Hz frequency of reversal and constant flux density. When frequency is increased to 50 Hz., eddy current loss is : 625 W

Description :

In a DC generator the windings of interpoles are connected :  (A) in series with main field winding, to create a pole,of same polarity as the main pole ahead in the direction of rotation.  (B) in series with main field winding, to create a pole of opposite polarity as the main pole ahead in the direction of ... in the direction of rotation.  (D) in series with the armature winding, to create a pole of opposite polarity as the main pole ahead in the direction of rotation.

Answer :

In a DC generator the windings of interpoles are connected :  in series with the armature winding, to create a pole of same polarity as the main pole ahead in the direction of rotation. 

Description :

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

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 :

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.

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

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 :

The terminal characteristics of a dc generator suitable for electric welders is (A) separately excited generator (B) shunt generator (C) series generator (D) differentially compounded generator

Answer :

The terminal characteristics of a dc generator suitable for electric welders is differentially compounded generator

Description :

What is the difference between an AC and DC generator?

Answer :

The generator which generates DC voltage is called DC generator and generator which generates AC voltage is called AC generator (or) Alternator. In DC generator armature is rotated and field winding ... generator. A DC generator can generate low voltages but an AC generator can generate upto 11kv.

Description :

What is the principle of DC generator?

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

Answer :

Field coils of DC generator are usually made of copper.

Description :

Why is the armature of DC generator laminated?

Answer :

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

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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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Answer :

In case of D.C. shunt motors the speed is dependent on back e.m.f. only because flux is practically constant in D:C. shunt motors.

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Answer :

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

Description :

The counter e.m.f. of a d.c. motor?

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The counter e.m.f. of a d.c. motor helps in energy conversion.

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Answer :

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

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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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The armature may burn if the back e.m.f. of a D.C. motor vanishes suddenly.

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

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Answer :

A separately excited generator as compared to a self-excited generator is amenable to better voltage control, more stable, has exciting current independent of load current.

Description :

Explain how sinusoidal AC voltage is generated by using simple one loop generator.

Answer :

An electric current produced by means of electrical machine is known as generator which converts mechanical energy into electrical energy. When conductor cuts the magnetic flux, emf induced in it. (Faraday' ... upon position of armature. The nature of emf is alternating as shown by the waveform. 

Description :

Answer :

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

Description :

Answer :

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

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