DC Motors MCQs

Question 1

1n a lap wound D.C. generator having p as number of poles and Z as number of conductors, the maximum number of equilizer rings will be

Accepted Answer

2Z

Answer

Z

Answer

p

Answer

2p

Question 2

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

Accepted Answer

crossmagnetisation as well as demagnetizing

Answer

demagnetisation only

Answer

cross magnetisation as well as magnetization

Answer

cross magnetisation only

Question 3

Armature reaction of an unsaturated D.C. machine is

Accepted Answer

crossmagnetising

Answer

demagnetizing

Answer

magnetizing

Answer

none of above

Question 4

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

Accepted Answer

all above

Answer

to avoid sudden loading of the primemover

Answer

to avoid mechanical jark to the shaft

Answer

to avoid burning of swith contacts

Question 5

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

Accepted Answer

relative rotation between field and armature

Answer

oscillating magnetic field

Answer

pulsating magnetic flux

Answer

all above

Question 6

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

Accepted Answer

all above

Answer

odour of burning insulation

Answer

unbalanced magnetic pull producing vibrations

Answer

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

Question 7

Equilizer rings are required in case armature is

Accepted Answer

lap wound

Answer

wave wound

Answer

delta wound

Answer

duplex wound

Question 8

1n the cas of lap winding resultant pitch is

Accepted Answer

difference of front and back pitches

Answer

multiplication of front and back pitches

Answer

division of front pitch by back pitch

Answer

sum of front and back pitches

Question 9

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

Accepted Answer

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

Answer

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

Answer

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

Answer

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