Synchronous Motor Questions and Answers

Synchronous Motor Questions and Answers 


MCQ type Questions And answers of synchronous motor is provided in this post which is more helpful in preparation of gate examination and also for competitive examination.

Synchronous Motor Questions and Answers 


Question And Answer (Synchronous Motor)




Q.1

Hunting in a synchronous motor takes
place

(a)when supply voltage fluctuates

(b)when load varies

(c)when power factor is unity

(d)motor is under loaded

Ans.

(b)when load varies



Q.2

When load on an over-excited or under-
excited synchronous motor is increased,
rate of change of its armature current
as compared with that of power factor
is

(a)more

(b)less

(c)equal

(d)twice

Ans.

(b)less



Q.3

The rotor copper losses, in a synchronous motor are met by

(a) D.C. source 

(b)armature input

(c)motor input 

(d)supply lines

Ans.

(a) D.C. source 



Q.4

The maximum power developed in a
synchronous motor occurs at a coupling
angle of

(a)30°

(b)60°

(c)90°

(d)180°

Ans.

(c)90°



Q.5

When the stator windings are connected in such a fashion that the number of poles are made half, the speed of the rotor of a synchronous motor

(a)remains same as the original value

(b)decreases to half the original value

(c)tends to becomes zero

(d)increases to two times the original
value

Ans.

(d)increases to two times the original
value



Q.6

In which of the following motors the
stator and rotor magnetic field rotate
at the same speed?

(a)Universal motor

(b)Synchronous motor

(c)Induction motor

(d)Reluctance motor

Ans.

(b)Synchronous motor



Q.7

Synchronizing power of a synchronous
machine is

(a)directly proportional to the synchronous reactance

(b)inversely proportional to the synchronous reactance

(c)equal to the synchronous reactance

(d)none of the above

Ans.

(b)inversely proportional to the synchronous reactance



Q.8

Synchronous motors are

(a)not-self starting

(b)self-starting

(c)essentially self-starting

(d)none of the above

Ans.

(a)not-self starting



Q.9

The standard full-load power factor ratings for synchronous motors are

(a)zero or 0.8 leading

(b)unity or 0.8 lagging

(c)unity or 0.8 leading

(d)unity or zero

Ans.

(c)unity or 0.8 leading



Q.10

A synchronous motor running with normal excitation adjusts to load increases essentially by increase in

(a)back e.m.f.

(b)armature current

(c)power factor 

(d)torque angle

Ans.

(b)armature current



Q.11

A synchronous motor has better power factor as compared to that of an equivalent induction motor. This is mainly because

(a)synchronous motor has no slip

(b) stator supply is not required to produce magnetic field

(c)mechanical load on the rotor remains constant

(d)synchronous motor has large air gap

Ans.

(b) stator supply is not required to produce magnetic field



Q.12

A synchronous motor working at leading
power factor can be used as

(a)voltage booster

(b)phase advancer

(c)noise generator

(d)mechanical synchronizer

Ans.

(b)phase advancer



Q.13

Slip rings are usually made of

(a)carbon or graphite

(b) brass or steel

(c)silver or gold

(d)copper or aluminum

Ans.

(b) brass or steel



Q.14

An over-excited synchronous motor is used for

(a)fluctuating loads

(b)variable speed loads

(c)low torque loads

(d)power factor corrections

Ans.

(d)power factor corrections



Q.15

When the voltage applied to a synchronous motor is increased, which of the following will reduce?

(a)Stator flux 

(b)Pull in torque

(c)Both(a)and(b)

(d)None of the above

Ans.

(d)None of the above

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Also Read Electrical Engineering Interview Questions:

Q.1 If the potential at point A is higher that at point B ( Va > Vb ) then the potential difference will be _________?

A. Negative

B. Positive

C. Zero

D. 6 volt

Ans.

B. Positive


Q.2 Electromotive force is measured in _________?

A. Volt

B. Volt . Meter

C. Volt / Meter

D. Volt / coulomb

Ans.

A. Volt


Q.3 How many electrons are carried in 1 coulomb charge?

A. 6.25 × (10) 12

B. 6.25 × (10) 15

C. 6.25 × (10) 18

D. 6.25 × (10) 21

Ans.

C. 6.25 × (10) 18


Q.4 What is the unit of resistivity?

A. Ohm

B. Mho

C. Ohm . Meter

D. Ohm/ Meter

Ans.

C. Ohm . Meter


Q.5 What is the resistivity of copper at 20 ° C ?

A. 1.72 × (10) -8

B. 2.82 × (10) -8

C. 1

D. 0

Ans.

A. 1.72 × (10) -8


Q.6 What is the actual equation of ohm's law ?

A. V= I R

B. I = V / R

C. VI = R

D. V / I = R

Ans.

D. V / I = R



Q.7 What is the equation of capacitor in series connection?

A. C = C1 +C2 + C3 + .....+ Cn

B. C = --C1 --C2 --C3 --......-- Cn

C. 1/C = 1/ C1 + 1/ C2 + 1/C3 +.....+ 1/ Cn

D. C = -C1 + C2 - C3 +....- Cn

Ans.

C. 1/C = 1/ C1 + 1/ C2 + 1/ C3 +....+ 1/ Cn


Q.8 Find the passive Element....

A. Current source

B. Resistor

C. Voltage source

D. Thermistor

Ans.

B. Resistor


Q.9 Which one is not Type of current?

A. Direct current

B. Sinusoidal current

C. Fluctuating current

D. Alternating current

Ans.

B. Sinusoidal current


Q.10 What is the unit of apparent power?

A. VA

B. VAR

C. KVR

D. Watt

Ans.

A. VA

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Also Read Electrical Engineering Interview Questions:

Q.1 What is the formula of power factor?

A. P.f = R / I

B. P.f = R / V

C. P.f = R / Z

D. P.f = V / I

Ans.

C. P.f = R / Z


Q.2 What is the resonance condition?

A. XL = - Xc

B. XL = Xc

C. - Xl = Xc

D. XL + Xc = 0

Ans. 

B. XL = Xc


Q.3 What is the unit of conductance?

A. Ohm B. Mho

C. Ohm . m D. Ohm / meter

Ans.

B. Mho


Q.4 What is the power factor at resonance condition?

A. One B. Two

C. Three D. Zero

Ans.

A. One ( unity power factor)


Q.5 Who is the first inventor of electricity?

A. Thomas Alva Edison

B. Charles coulomb

C. Benjamin Franklin

D. J. J. Thomson

Ans. 

C. Benjamin Franklin


Q.6 if the centrifugal switch of a two-value capacitor motor using two capacitors fails to open then,

(a) motor will not come up to speed

(b) motor will not carry the load

(c) current drawn by the motor will be excessively high

(d) electrolytic capacitor will, in all probability, suffer break down


Ans: d


Q.7 In a universal motor, the most common cause of brush sparking is

(a) open armature winding

(b) shorted armature winding

(c) shorted field winding

(d) high commutator mica

(e) all of the above


Ans: e


Q.8 If starting winding of a single-phase induction motor is left in the circuit, it will

(a) run faster

(b) spark at light loads

(c) draw excessive current and overheat

(d) run slower


Ans: c


Q.9 Most of the fractional horsepower motors have either

(a) hard and annealed bearings

(b) ball or roller bearings

(c) soft and porous bearings

(d) plain or sleeve bearings


Ans: d

Q.10 Which of the following statements regarding reluctance-start motor is incorrect ?
(a) It is similar to reluctance motor

(b) It is basically an induction motor and not a synchronous one

(c) So far as its basic working principle is concerned, it is similar to shaded pole motor

(d) the air-gap between rotor and salient poles is non- uniform


Ans: a

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Q.1

While conducting short-circuit test on a transformer the following side is short circuited

(A) High voltage side

(B) Low voltage side

(C) Primary side

(D) Secondary side

Ans.
B. Low voltage coil



Q.2

Which of the following is not a routine test on transformers?

(A) Core insulation voltage test

(B) Impedance test

(C) Radio interference test

(D) Polarity test
Ans.
C. Radio interference test



Q.3

In a certain loaded transformer, the secondary voltage is one-fourth the primary voltage. The secondary current is

(A) one-fourth the primary current

(B) four times the primary current

(C) equal to the primary current

(D) one-fourth the primary current and equal to the primary current

Ans.
(B) four times the primary current


Q.4

The rating of transformer may be expressed in ____________.

(A) kVAR

(B) kW

(C) Horse power

(D) kVA
Ans.
(D) kVA


Q.5

The primary winding of a power transformer should always be

(A) open

(B) shorted

(C) switched

(D) fused
Ans.
(D) Fused


Q.6

A transformer is used for

(A) changes ac to dc

(B) changes dc to ac

(C) steps up or down dc voltages

(D) steps up or down ac voltages

Ans.
(D) step up or down ac voltages


Q.7

What is the working principle of transformer?

(A) Thermal

(B) Electromagnetic induction

(C) Electromagnetic radiation

(D) Thermal leakage

Ans.
(B) Electromagnetic radiation


Q.8

Which one term is not related to Transformer?

(A) core

(B) yoke

(C) pole

(D) winding

Ans.
(C) pole


Q.9

Which type of winding is used in shall type of transformer?

(A) sandwich winding

(B) circular winding

(C) rectangular winding

(D) square winding

Ans.
(A) sandwich winding


Q.10

How many magnetic circuit has a core type transformer?

(A) one

(B) two

(C) three

(D) Four

Ans.
(A) One



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Electrician Tool Kit Set


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5. Household Electrical Tool Kit Set


6. Multi Purpose Digital Line Meter


7. Wire Cutter or Striper

Also Read Electrical Engineering Interview Questions:

Q.1

Magnetism steel is normal difficult
because

(a)it corrodes easily

(b)it has high permeability

(c)it has high specific gravity

(d)it has low permeability

Ans.

(d)it has low permeability


Q.2

The left hand rule correlates to

(a)current, induced e.m.f. and direc-
tion of force on a conductor

(b)magnetic field, electric field and
direction of force on a conductor

(c)self induction, mutual induction
and direction of force on a conductor

(d).current, magnetic field and direc-
tion of force on a conductor

Ans.

(d).current, magnetic field and direc-
tion of force on a conductor


Q.3 

The unit of relative permeability is

(a)henry/meter

(b)henry

(c)henry/sq. m

(d)it is dimensionless

Ans.

(d)it is dimensionless


Q.4.

A conductor of length L has current I
passing through it, when it is placed
parallel to a magnetic field. The force
experienced by the conductor will be

(a)zero

(b)BLI

(c)B2LI

(d)BLI

Ans.

(a)zero


Q.5

The force between two long parallel
conductors is inversely proportional to

(a)radius of conductors

(b)current in one conductor

(c)product of current in two conductors

(d)distance between the conductors

Ans.

(d)distance between the conductors


Q.6

Materials subjected to rapid reversal of
magnetism should have

(a)large area of B-H loop

(b)high permeability and low hysteresis
loss

(c)high co-reactivity and high retentivily.

(d)high co-reactivity and low density


Ans.

(b)high permeability and low hysteresis
loss

 Q.7 

Indicate which of the following material
does not retain magnetism per-
manently.

(a)Soft iron

(b)Stainless steel

(c)Hardened steel

(d)None of the above

Ans.

(a)Soft iron

Q.8

The main constituent of perm alloy is

(a)cobalt

(b)chromium

(c)nickel

(d)tungsten

Ans.

(c)nickel


Q.9

The use of permanent magnets is not
made in

(a)magnetos

(b)energy meters

(c)transformers 

(d)loud-speakers

 Ans.

(c)transformers


Q.10

Paramagnetic materials have relative
permeability


(a)slightly less than unity

(b)equal to unity

(c)slightly more than unity

(d)equal to that ferromagnetic materials

Ans.

(c)slightly more than unity

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