Due to presence of third harmonic component in the star-star connection of three phase transformer, the frequency of the circuit component becomes

One third of the circuit frequency

Three times of the circuit frequency

One third of the circuit frequency

Due to armature reaction magnetic neutral axis gets shifted by some angle. In case of motors the brushes are shifted

Forwards same as the direction of rotation

Backwards opposite to the direction of rotation

Differential compound motors are mainly used in

Not suitable for any practical application

Depending upon the reluctances offered along the direct axis and quadrature axis, the armature reaction flux will

In phase with the armature current

Lags behind the armature current

In phase with the armature current

D.C. series motors are used in electric traction. What happens to the speed and current of d.c motor if there is sudden slight drop in the mains voltage?

Speed decreases and current also decreases

Speed decreases and current increases

Speed increases and current decreases

Speed decreases and current remains same

Crawling in an induction motor is caused

During starting of an induction motor

Back emf in case of synchronous motor depends on the

Excitation given to the field winding

Applications of induction generators are

In railways for braking purpose

An induction motor when loaded from no load to full load, its slip also varies from s = 1 to s = 0. Then the torques in the low slip region and in high slip region is

Independent of slip, proportional to the slip

Both are directly proportional to the slip

Both are inversely proportional to the slip

Directly proportional to the slip, inversely proportional to the slip

Independent of slip, proportional to the slip

An autotransformer starter is suitable for

Delta connected induction motor

Ampere turns per pole for compensating winding in d.c. machines is equal to

(pole pitch / pole arc) * armature ampere turns per pole

(pole arc / pole pitch) * armature ampere turns per pole

(pole pitch / pole arc) * armature ampere turns per pole

(pole arc / pole pitch) * total ampere conductors per pole

Among the following sentences which is/are true about short pitch coils

Less amount of copper is required

Eliminates high frequency harmonics

Minimizes eddy current and hysteresis losses

According to double revolving field theory, any alternating quantity can be resolved into two rotating components. The directions and magnitude of these components are

Same directions, each having magnitude half of the maximum magnitude of alternating current

Same directions, each having magnitude equal to the maximum magnitude of alternating current

Opposite directions, each having magnitude equal to the maximum magnitude of alternating current

Opposite directions, each having magnitude half of the maximum magnitude of alternating current

Same directions, each having magnitude half of the maximum magnitude of alternating current

A star connected three phase transformer is provided with tertiary delta connected winding which allows the flow of

Fifth harmonic of exciting current

Second harmonic of exciting current

Third harmonic of exciting current

Fifth harmonic of exciting current

Seventh harmonic of exciting current

A series wound motor is also called as universal motor because

It will run well below and above rated speed

It will run equally well using either an ac or a dc voltage source

It will run well below and above rated speed

It can be used in all kinds of applications

A machine operating as motor may go into regenerative braking mode if its speed becomes

Sufficiently low to make back emf greater than supply voltage

Sufficiently high to make back emf greater than supply voltage

Sufficiently low to make back emf greater than supply voltage

Sufficiently high to make back emf half of the supply voltage

Sufficiently low to make back emf half of the supply voltage

A long shunt compound motor and a short shunt compound motor can be

Cumulative type, differential type

Differential type, cumulative type

Both can be either cumulative or differential type

354 + Mcqs in Electrical Machines Questions in Electrical Engineering Questions Page 7 McqOptions

301.	Due to presence of third harmonic component in the star-star connection of three phase transformer, the frequency of the circuit component becomes
A.	Three times of the circuit frequency
B.	One third of the circuit frequency
C.	Remains same
D.	None of these
Answer» B. One third of the circuit frequency

Discussion

302.	Due to armature reaction magnetic neutral axis gets shifted by some angle. In case of motors the brushes are shifted
A.	Forwards same as the direction of rotation
B.	Backwards opposite to the direction of rotation
C.	Either (a) or (b)
D.	Does not get shifted
Answer» C. Either (a) or (b)

Discussion

303.	Direct online starter also called D.O.L. starter is used for motors having capacity
A.	Less than 5 h.p.
B.	Less than 10 h.p.
C.	Greater than 10 h.p.
D.	For any capacity motor
Answer» B. Less than 10 h.p.

Discussion

304.	Differential compound motors are mainly used in
A.	Drilling machines
B.	Elevators
C.	Electric traction
D.	Not suitable for any practical application
Answer» E.

Discussion

305.	Depending upon the reluctances offered along the direct axis and quadrature axis, the armature reaction flux will
A.	Lead the armature current
B.	Lags behind the armature current
C.	In phase with the armature current
D.	None of these
Answer» C. In phase with the armature current

Discussion

306.	Deep bar or double cage rotors are used in squirrel cage induction motor to obtain
A.	High starting current
B.	High starting torque
C.	Reduced starting current
D.	Reduced rotor resistance
Answer» C. Reduced starting current

Discussion

307.	Deep bar or double cage rotors make use of skin effect. The skin effect depends upon
A.	Nature of material
B.	Diameter of wire
C.	Shape of wire and frequency
D.	All of these
Answer» E.

Discussion

308.	D.C. shunt motor is also called as
A.	Constant flux motor
B.	Constant voltage motor
C.	Variable voltage motor
D.	Constant current motor
Answer» B. Constant voltage motor

Discussion

309.	D.C. series motors are used in electric traction. What happens to the speed and current of d.c motor if there is sudden slight drop in the mains voltage?
A.	Speed decreases and current also decreases
B.	Speed decreases and current increases
C.	Speed increases and current decreases
D.	Speed decreases and current remains same
Answer» E.

Discussion

310.	D.C. shunt motors are commonly used in
A.	Cranes
B.	Electric traction
C.	Elevators
D.	Lathe machines
Answer» E.

Discussion

311.	Cumulative compound motor is capable of developing large amount of torque at low speeds just like series motor. Can cumulative compound motor be run on light load or no load?
A.	Yes
B.	No
Answer» B. No

Discussion

312.	Crawling is a phenomena mainly associated with
A.	3rd harmonic
B.	5th harmonic
C.	7th harmonic
D.	2nd harmonic
Answer» D. 2nd harmonic

Discussion

313.	Crawling in an induction motor is caused
A.	During starting of an induction motor
B.	At the fraction of rated speed
C.	Due to insulation failure
D.	All of these
Answer» C. Due to insulation failure

Discussion

314.	Copper losses in a rotating machine are
A.	Variable losses
B.	Constant losses
C.	Both (a) or (b)
D.	None of these
Answer» B. Constant losses

Discussion

315.	Consider three transformers connected in delta-delta fashion and supplying their rated load. Now if one of the transformer is removed then each of the remaining two transformer is overloaded. The overload on each transformer is given as
A.	1
B.	1.232
C.	1.732
D.	1.872
Answer» D. 1.872

Discussion

316.	Consider a purely inductive load connected to the alternator having zero lagging power factor. In this case the effect of armature reaction will be
A.	Demagnetizing effect
B.	Cross magnetizing effect
C.	Both (a) and (b)
D.	None of these
Answer» B. Cross magnetizing effect

Discussion

317.	Compared to the two winding transformer, in an autotransformer the leakage reactance and copper losses is
A.	less, more
B.	less, less
C.	more, more
D.	more, less
Answer» C. more, more

Discussion

318.	Can synchronous motor rotate at any speed other than the synchronous speed?
A.	Yes
B.	No
Answer» C.

Discussion

319.	Can a d.c. series motor be used for applications in belt drives?
A.	Yes
B.	No
Answer» C.

Discussion

320.	“By adding external resistance to rotor till it becomes equal to rotor reactance, the maximum torque can be achieved at start”. This statement holds for
A.	Slip ring induction motor
B.	Squirrel cage induction motor
C.	Both a and b
D.	Neither a nor b
Answer» B. Squirrel cage induction motor

Discussion

321.	Brushes in d.c. machines are made up of
A.	Cast iron
B.	Mild steel
C.	Copper
D.	Carbon
Answer» E.

Discussion

322.	Breather present in a transformer is used to
A.	Absorb atmospheric moisture
B.	Prevent insulation failure
C.	Cooling
D.	All of these
Answer» B. Prevent insulation failure

Discussion

323.	Blondel’s two reaction theory which gives the method of analysis of disturbing effects caused by
A.	Salient pole construction
B.	Non salient pole construction
C.	Both (a) and (b)
D.	None of these
Answer» B. Non salient pole construction

Discussion

324.	Back emf in case of synchronous motor depends on the
A.	Excitation given to the field winding
B.	Speed
C.	Both (a) and (b)
D.	None of the above
Answer» B. Speed

Discussion

325.	At start, the slip of the induction motor is
A.	1
B.	0
C.	0.5
D.	None of these
Answer» B. 0

Discussion

326.	As the value of load power factor of an alternator changes, the value of armature reaction reactance
A.	Remains constant
B.	Changes
C.	None of these
Answer» C. None of these

Discussion

327.	As the load on d.c. motor increases, the current drawn by motor
A.	Increases
B.	Decreases
C.	Remains same
D.	None of these
Answer» B. Decreases

Discussion

328.	Applications of induction generators are
A.	In railways for braking purpose
B.	Wind mils
C.	Drilling machines
D.	Only (a) and (b)
E.	None of these
Answer» E. None of these

Discussion

329.	An over excited synchronous motor operating on no load condition is called as
A.	Synchronous capacitor
B.	Synchronous condenser
C.	Both (a) and (b)
D.	None of these
Answer» D. None of these

Discussion

330.	An induction motor when loaded from no load to full load, its slip also varies from s = 1 to s = 0. Then the torques in the low slip region and in high slip region is
A.	Both are directly proportional to the slip
B.	Both are inversely proportional to the slip
C.	Directly proportional to the slip, inversely proportional to the slip
D.	Independent of slip, proportional to the slip
Answer» D. Independent of slip, proportional to the slip

Discussion

331.	An autotransformer starter is suitable for
A.	Star connected induction motor
B.	Delta connected induction motor
C.	Both (a) & (b)
D.	None of these
Answer» D. None of these

Discussion

332.	An armature of a three phase, 8 pole alternators has 120 slots. The distribution factor is equal to
A.	0.897
B.	0.946
C.	0.957
D.	1
Answer» D. 1

Discussion

333.	Ampere turns per pole for compensating winding in d.c. machines is equal to
A.	(pole arc / pole pitch) * armature ampere turns per pole
B.	(pole pitch / pole arc) * armature ampere turns per pole
C.	(pole arc / pole pitch) * total ampere conductors per pole
D.	None of these
Answer» B. (pole pitch / pole arc) * armature ampere turns per pole

Discussion

334.	Among the following sentences which is/are true about short pitch coils
A.	Less amount of copper is required
B.	Eliminates high frequency harmonics
C.	Minimizes eddy current and hysteresis losses
D.	All of the above
Answer» E.

Discussion

335.	According to double revolving field theory, any alternating quantity can be resolved into two rotating components. The directions and magnitude of these components are
A.	Same directions, each having magnitude equal to the maximum magnitude of alternating current
B.	Opposite directions, each having magnitude equal to the maximum magnitude of alternating current
C.	Opposite directions, each having magnitude half of the maximum magnitude of alternating current
D.	Same directions, each having magnitude half of the maximum magnitude of alternating current
Answer» D. Same directions, each having magnitude half of the maximum magnitude of alternating current

Discussion

336.	According to Blondel’s two reaction theory the armature mmf is divided into components, direct axis component and quadrature axis component. The component acting along quadrature axis is
A.	Magnetizing
B.	Demagnetizing
C.	Cross magnetizing
D.	None of these
Answer» D. None of these

Discussion

337.	According to Blondel’s two reaction theory, the armature mmf component acting along direct axis can be
A.	Demagnetizing
B.	Magnetizing
C.	Cross magnetizing
D.	Either (a) or (b)
Answer» E.

Discussion

338.	A two phase servomotor is commonly used in feedback control system to drive the loads and as sensors to measure
A.	Speed of controlled element
B.	Position of controlled element
C.	Both (a) and (b)
D.	None of these
Answer» D. None of these

Discussion

339.	A transformer is said to be isolation transformer if its primary to secondary ratio is
A.	Equal to one
B.	More than one
C.	Less than one
D.	Equal to 0.5
Answer» B. More than one

Discussion

340.	A three phase 4 pole, induction motor is supplied from 50 Hz supply. Then its synchronous speed will be
A.	1000 rpm
B.	1500 rpm
C.	1600 rpm
D.	2000 rpm
Answer» C. 1600 rpm

Discussion

341.	A synchronous motor is started by using damper winding. When the motor runs at synchronous speed then the induced emf in the damper winding will be
A.	Zero
B.	Maximum
C.	Half of the terminal voltage
D.	None of these
Answer» B. Maximum

Discussion

342.	A synchronous motor is running at a load angle of 25 degree at rated frequency with negligible armature resistance. Now, if the supply frequency is increased by 15% keeping the other parameters constant, then the new load angle will be equal to
A.	26.89 degree
B.	29.07 degree
C.	32.05 degree
D.	38.20 degree
Answer» C. 32.05 degree

Discussion

343.	A synchronous motor draws 2 MVA at a power factor of 0.8 leading. If the efficiency developed in the motor is 90% then the power developed is equal to
A.	1212 kW
B.	1440 kW
C.	1676 kW
D.	1767 kW
Answer» C. 1676 kW

Discussion

344.	A synchronous generator has a direct axis and quadrature axis reactances of 0.6 per unit and 0.3 per unit respectively. What will be its total induced emf on open circuit if it is used to supply full load at rated voltage at 0.8 power factor ( Assume rated terminal voltage is equal to 1 pu, full load armature current be 1 pu and armature resistance to be 0).
A.	1.099 pu
B.	1.199 pu
C.	1.488 pu
D.	1.588 pu
Answer» B. 1.199 pu

Discussion

345.	A star connected three phase transformer is provided with tertiary delta connected winding which allows the flow of
A.	Second harmonic of exciting current
B.	Third harmonic of exciting current
C.	Fifth harmonic of exciting current
D.	Seventh harmonic of exciting current
Answer» C. Fifth harmonic of exciting current

Discussion

346.	A series wound motor is also called as universal motor because
A.	It will run equally well using either an ac or a dc voltage source
B.	It will run well below and above rated speed
C.	It can be used in all kinds of applications
D.	None of these
Answer» B. It will run well below and above rated speed

Discussion

347.	A machine operating as motor may go into regenerative braking mode if its speed becomes
A.	Sufficiently high to make back emf greater than supply voltage
B.	Sufficiently low to make back emf greater than supply voltage
C.	Sufficiently high to make back emf half of the supply voltage
D.	Sufficiently low to make back emf half of the supply voltage
Answer» B. Sufficiently low to make back emf greater than supply voltage

Discussion

348.	A machine without commutator, providing an ac emf to the external circuit is called as
A.	D.C. generator
B.	Alternator
C.	Synchronous motor
D.	Transformer
Answer» C. Synchronous motor

Discussion

349.	A long shunt compound motor and a short shunt compound motor can be
A.	Cumulative type, differential type
B.	Differential type, cumulative type
C.	Both can be either cumulative or differential type
D.	None of these
Answer» D. None of these

Discussion

350.	A load of 110kW at 0.8 power factor is to be shared by two single phase transformer with equal turns have impedances equal to (0.4 + j 0.2) and (0.6 + j 0.8) with respect to secondary. How will they share the load if they are operating in parallel?
A.	80kW, 30kW
B.	82.55kW, 28.45kW
C.	75.55kW, 24.45kW
D.	85.45kW, 24.55kW
Answer» E.

Discussion

Explore topic-wise MCQs in Electrical Engineering Questions.

Due to presence of third harmonic component in the star-star connection of three phase transformer, the frequency of the circuit component becomes

Due to armature reaction magnetic neutral axis gets shifted by some angle. In case of motors the brushes are shifted

Direct online starter also called D.O.L. starter is used for motors having capacity

Differential compound motors are mainly used in

Depending upon the reluctances offered along the direct axis and quadrature axis, the armature reaction flux will

Deep bar or double cage rotors are used in squirrel cage induction motor to obtain

Deep bar or double cage rotors make use of skin effect. The skin effect depends upon

D.C. shunt motor is also called as

D.C. series motors are used in electric traction. What happens to the speed and current of d.c motor if there is sudden slight drop in the mains voltage?

D.C. shunt motors are commonly used in

Cumulative compound motor is capable of developing large amount of torque at low speeds just like series motor. Can cumulative compound motor be run on light load or no load?

Crawling is a phenomena mainly associated with

Crawling in an induction motor is caused

Copper losses in a rotating machine are

Consider three transformers connected in delta-delta fashion and supplying their rated load. Now if one of the transformer is removed then each of the remaining two transformer is overloaded. The overload on each transformer is given as

Consider a purely inductive load connected to the alternator having zero lagging power factor. In this case the effect of armature reaction will be

Compared to the two winding transformer, in an autotransformer the leakage reactance and copper losses is

Can synchronous motor rotate at any speed other than the synchronous speed?

Can a d.c. series motor be used for applications in belt drives?

“By adding external resistance to rotor till it becomes equal to rotor reactance, the maximum torque can be achieved at start”. This statement holds for

Brushes in d.c. machines are made up of

Breather present in a transformer is used to

Blondel’s two reaction theory which gives the method of analysis of disturbing effects caused by

Back emf in case of synchronous motor depends on the

At start, the slip of the induction motor is

As the value of load power factor of an alternator changes, the value of armature reaction reactance

As the load on d.c. motor increases, the current drawn by motor

Applications of induction generators are

An over excited synchronous motor operating on no load condition is called as

An induction motor when loaded from no load to full load, its slip also varies from s = 1 to s = 0. Then the torques in the low slip region and in high slip region is

An autotransformer starter is suitable for

An armature of a three phase, 8 pole alternators has 120 slots. The distribution factor is equal to

Ampere turns per pole for compensating winding in d.c. machines is equal to

Among the following sentences which is/are true about short pitch coils

According to double revolving field theory, any alternating quantity can be resolved into two rotating components. The directions and magnitude of these components are

According to Blondel’s two reaction theory the armature mmf is divided into components, direct axis component and quadrature axis component. The component acting along quadrature axis is

According to Blondel’s two reaction theory, the armature mmf component acting along direct axis can be

A two phase servomotor is commonly used in feedback control system to drive the loads and as sensors to measure

A transformer is said to be isolation transformer if its primary to secondary ratio is

A three phase 4 pole, induction motor is supplied from 50 Hz supply. Then its synchronous speed will be

A synchronous motor is started by using damper winding. When the motor runs at synchronous speed then the induced emf in the damper winding will be

A synchronous motor is running at a load angle of 25 degree at rated frequency with negligible armature resistance. Now, if the supply frequency is increased by 15% keeping the other parameters constant, then the new load angle will be equal to

A synchronous motor draws 2 MVA at a power factor of 0.8 leading. If the efficiency developed in the motor is 90% then the power developed is equal to

A star connected three phase transformer is provided with tertiary delta connected winding which allows the flow of

A series wound motor is also called as universal motor because

A machine operating as motor may go into regenerative braking mode if its speed becomes

A machine without commutator, providing an ac emf to the external circuit is called as

A long shunt compound motor and a short shunt compound motor can be

A load of 110kW at 0.8 power factor is to be shared by two single phase transformer with equal turns have impedances equal to (0.4 + j 0.2) and (0.6 + j 0.8) with respect to secondary. How will they share the load if they are operating in parallel?