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

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Answer :

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

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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

Answer :

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

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Description :

Answer :

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

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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

Answer :

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

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83 views 1 answer
Description :

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

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.

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190 views 1 answer
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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

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

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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.

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

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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

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Description :

Why is the armature of DC generator laminated?

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

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Answer :

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

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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?

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.

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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. ?

Answer :

Wave winding

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Description :

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.

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139 views 1 answer
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Armature coil is short circuited by brushes when it lies along neutral axis.

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

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Answer :

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

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134 views 1 answer
Description :

Explain the nuclear chain reaction in a nuclear power plant.

Answer :

Nuclear chain reaction in a nuclear power plant: If a slow moving neutron hits unstable heavy nucleus of nuclear fuel U235 or Pu239 , the neutron is absorbed, the nucleus splits into two more ... chain reaction can be controlled and desired heat energy can be obtained in nuclear power plant. 

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Description :

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

Answer :

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

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Answer :

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

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Answer :

In case of a flat compounded generator voltage remains constant irrespective of the load.

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Answer :

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

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Description :

Answer :

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

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Answer :

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

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Description :

Answer :

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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Description :

Answer :

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

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Description :

Answer :

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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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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Description :

Answer :

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

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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.

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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.

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Answer :

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

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Answer :

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

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Answer :

In over compounded generator, full load terminal voltage is more than no load terminal voltage.

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The transfer of energy for reaction turbines is based on _______ A) Newton’s first law B) Newton’s second law C) Newton’s third law D) All the above

Answer :

The transfer of energy for reaction turbines is based on Newton’s third law

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Description :

The ratio of limiting friction and normal reaction is known as?

Answer :

The ratio of limiting friction and normal reaction is known as coefficient of friction.

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Answer :

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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Answer :

An exciter for a turbo generator is a shunt generator.

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Answer :

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

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Description :

Answer :

A cumulatively compounded long shunt generator when operating as a motor would be differentially compounded long shunt.

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Answer :

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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75 views 1 answer
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?

Answer :

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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Description :

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.

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Description :

Answer :

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

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Description :

Answer :

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

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Description :

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

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Description :

Answer :

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

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