606. A 400/200 volts transformer has pu impedance of 0.05. The HV side voltage required to circulate full load current during short circuit test is
A. 20 V
B. 40 V
C. 10 V
D. 5 V
Ans.: A
607. Non-loading heat run test on transformers is performed by means of
A. SC test
B. OC test
C. Core balance test
D. Sumpner’s test
Ans.: D
608. A three phase induction motor is driving full-load torque which is independent of
speed. If the line voltage drops to 90% of the rated value, % increase in motor copper
losses
A. 23%
B. –18%
C. 123%
D. None of these
Ans.: A
609. A synchronous generator is feeding power to infinite bus bars at unity power factor. Its excitation is now increased. It will feed
A. The same power but at a leading power factor
B. The same power but at a lagging power factor
C. More power at unity power factor
D. Less power at unity power factor
Ans.: B
610. The steam input in to a turbo-generator connected to infinite bus is increased. Which of the events will take place?
A. The generator will feed more leading KVAR to bus bar and power angle will not change
B. The generator will feed more real power to bus bar and power angle will increase
C. The generator will feed more power to bus bar and power angle will decrease
D. The generator will feed more lagging KVAR to bus bar and power angle will not
Change
Ans.: B
611. In an ideal transformer, which of the following statement is correct?
A. no voltage drops in resistance or leakage reactance
B. mmf required to maintain main flux is small
C. no core loss
D. all the above are correct
Ans.: D
612. The voltage applied to a transformer primary is increased keeping v/f fixed. How
will core loss and magnetizing current change?
A. Core loss will increase and magnetizing current remain same
B. Core loss will remain same and magnetizing current will remain same
C. Core loss will decrease and magnetizing current will increase
D. Core loss will remain same and magnetizing current will decrease
Ans.: A
613. Frequencies in the UHF range normally propagate by means of
A. Ground waves
B. Sky waves
C. Surface waves
D. Space waves
Ans.: D
614. Indicate the antenna that is not wideband
A. Discone
B. Folded dipole
C. Helical
D. Marconi
Ans.: D
615. The depth of penetration of a wave in a lossy dielectric increases with increasing
A. Conductivity
B. Permeability
C. Wavelength
D. Permittivity
Ans.: C
616. Copper behaves as a
A. Conductor always
B. Conductor or dielectric depending on field strength
C. Conductor or dielectric depending on frequency
D. Conductor or dielectric depending on the electric current density
Ans.: A
617. Assuming constant transmission efficiency, if voltage is increased ‘n’ times, the size of the conductor would be
A. Reduced to 2 1 n that of the original
B. Increased to 2 n that of the original
C. Reduced to 1 n that of the original
D. Increased to n times that of the original
Ans.: A
618. Shunt conductance in overhead power transmission lines is primarily due to
A. Leakage over the insulators
B. Leakage over the conductors
C. Leakage over the poles
D. Leakage between ground and conductors
Ans.: A
619. The dielectric strength of SF6 gas (used in circuit breakers) is approximately
A. Same as that of air
B. 2 to 3 times more than air
C. 10 to 20 times more than air
D. 2 to 3 times less than air
Ans.: B
620. Ferranti effect states that under certain conditions, the sending end voltage is
A. Less than receiving end voltage
B. Greater than receiving end voltage
C. Equal to receiving end voltage
D. Not having any impact on the receiving end voltage
Ans.: A