DC GENERATOR

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DC GENERATOR

TEST NO - 2

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In case of D.C. machine winding, number of commutator segments is equal to

1 point

number of armature coils

number of armature coil sides

number of armature conductors

number of armature turns

Clear selection

If B is the flux density, I the length of conductor and v the velocity of conductor, then induced e.m.f. is given by

1 point

Blv

Blv2

Bl2v

Bl2v2

Clear selection

The material for commutator brushes is generally

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mica

copper

cast iron

carbon

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The insulating material used between the commutator segments is normally

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graphite

paper

mica

insulating varnish

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Armature reaction of an unsaturated D.C. machine is

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crossmagnetising

demagnetising

magnetising

none of above

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In D.C. generators, current to the external circuit from armature is given through

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commutator

solid connection

slip rings

none of above

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Equilizer rings are required in case armature is

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wave wound

lap wound

delta wound

duplex wound

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D.C. generators are connected to the busbars or disconnected from them only under the floating condition

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to avoid sudden loading of the primemover

to avoid mechanicaljerk to the shaft

to avoid burning of switch contacts

all above

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In the case of lap winding resultant pitch is

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multiplication of front and back pitches

division of front pitch by back pitch

sum of front and back pitches

difference of front and back pitches

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In D.C. generators, the brushes on commutator remain in contact with conductors which

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lie under south pole

lie under north pole

lie under interpolar region

are farthest from the poles

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A D.C. welding generator has

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lap winding

wave moving

duplex winding

any of the above

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The function of pole shoes in the case of D.C. machine is

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to reduce the reluctance of the magnetic path

to spread out the flux to achieve uniform flux density

to support the field coil

to discharge all the above functions

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Which of the following statement about D.C. generators is false ?

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Compensating winding in a D.C. machine helps in commutation

In a D. C. generator interpoles winding is connected in series with the armature winding

Back pitch and front pitch are both odd and approximately equal to the pole pitch

Equilizing bus bars are used with parallel running of D.C. shunt generators Ans: d

Clear selection

In case of D.C. machine winding, number of commutator segments is equal to

1 point

number of armature coils

number of armature coil sides

number of armature conductors

number of armature turns

Clear selection

Brushes of D.C. machines are made of

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carbon

soft copper

hard copper

all of above

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Welding generator will have

0 points

lap winding

wave winding

delta winding

duplex wave winding

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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

1 point

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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

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demagnetisation only

cross magnetisation as well as magnetisation

crossmagnetisation as well as demagnetising

cross magnetisation only

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In a D.C. machine, short-circuited field coil will result in

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odour of barning insulation

unbalanced magnetic pull producing vibrations

reduction of generated voltage for which excitation has to be increased to maintain the voltage

all above

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Eddy currents are induced in the pole shoes of a D.C. machine due to

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oscillating magnetic field

Optpulsating magnetic fluxion 2

relative rotation between field and armature

all above

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For a D.C. machines laboratory following type of D.C. supply will be suitable

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rotary converter

mercury are rectifier

induction motor D.C. generator set

synchronous motor D.C. generator set

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If B is the flux density, I the length of conductor and v the velocity of conductor, then induced e.m.f. is given by

1 point

Blv

Blv2

Bl2v

Bl2v2

Clear selection

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