# Electrical Machine 1

Electrical Engineering MCQ Question Papers: Campus Placement

Subject: Electrical Machine 1

Part 1: List for questions and answers of Electrical Machine I

Q1.Due to over damping, the instrument will become

a) Slow

b) Lethargic

c) Fast

d) Both (a) and (b)

Q2.A differential relay comparator used for the protection of three phase transformers has

a) One comparator

b) Two comparator

c) Three comparator

d) Six comparator

Q3.In double delta transformation, a double delta refers to the case where there are two delta transformations in

a) Parallel

b) Series

c) Both series and parallel

d) Neither series nor parallel

Q4.Most familiar application of zig – zag transformer is as

a) Ground reference on an ungrounded system

b) Converting single phase to two phase

c) Reducing harmonics

d) All of these

Q5.In a single phase, full wave bridge circuit and in three phase, delta full wave bridge circuit, the ripple voltage frequency is always

a) Twice the line frequency, six times the line frequency

b) Both will be twice the line frequency

c) Both will be six times the lines frequency

d) None of these

Q6.In Scott connection, the voltage across the teaser leads the mains by

a) 30 degree

b) 60 degree

c) 90 degree

d) 120 degree

Q7.Scott connection is used for the conversion of

a) Single phase to three phase

b) Three phase to single phase

c) Single phase to two phase

d) All of these

Q8.In T-T connection, the ratio of actual capacity to the available capacity is

a) 1

b) 0.928

c) 1.928

d) 0.5

Q9.In T-T connection, the percentage tapping of main transformer and teaser transformer are

a) 50%, 86.6%

b) 50%, 50%

c) 86.6%, 86.6%

d) 86.6%, 50%

Q10.With a bank of two single phase transformers connected in V – V fashion supplying a balanced three phase load with Cos? as power factor. The power factor of the two transformers is given by

a) Cos f , Cos f

b) Cos f, Cos(30+ f)

c) Cos(30- f), Cos(30+ f)

d) Cos(30- f), Cos f

Q11.The average power factor at which V-V bank is operating is less than that with the load. The power factor is

a) 57.7% of the balanced load power factor

b) 66.7% of the balanced load power factor

c) 86.6% of the balanced load power factor

d) None of theses

Q12. 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

Q13.The load carried by V – V connection is

a) 47.7% of the original load

b) 57.7% of the original load

c) 67.7% of the original load

d) 87.7% of the original load

Q14.The most commonly used connections for power systems as a step – up and step – down transformers are

a) Star – delta, star – star

b) Delta – star, star – delta

c) Star – star, delta – delta

d) Star – delta, delta – star

Q15.In case of delta-star connection of three phase transformer, secondary line voltage with respect of primary line voltage is at

a) 0 degree

c) 30 degree lagging

d) 60 degree lagging

Q16.For large low voltage transformers, the most commonly used connections are

a) Star – star connection

b) Delta – delta connection

c) V connection

d) All of these

Q17.If K is the transformation ratio, then the secondary phase voltage of delta-delta connected three phase transformer will be

a) 1 / K times of the primary phase voltage

b) Equal to the primary phase voltage

c) 1 / K ? 2 times of the primary phase voltage

d) K times the primary phase voltage

Q18.The phase shift in a star-star connected three phase transformer is

a) 0 degree

b) 30 degree

c) 60 degree

d) 120 degree

Q19.In star-star connection of three phase transformer, if VL is the line voltage and IL is the line current then phase voltage and phase current is given by

a) VL / root of 3, IL

b) VL , IL

c) root of 3VL , IL / root of 3

d) VL, IL / root of 3

Q20.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

Part 1: List for questions and answers of Electrical Machine I