1. In a single-phase induction regulator, compensating winding is provided in order to
(A) Increase Efficiency
(B) Reduce the voltage drop due to reactance of the secondary winding to a negligible value
(C) give a wider variety of output voltage
(D) all of the above
Ans: (B) Reduce the voltage drop due to reactance of the secondary winding to a negligible value
2. Autotransformer can do the following :
(A) step-up voltage
(B) Step down the voltage
(C) Both (A) & (B)
(D) None of above
Ans: (C) Both (A) & (B)
3. In an auto transformer power is transfered, through
(A) conduction process only
(B) Induction process only
(C) Both conduction and induction process
(D) Mutual coupling
Ans: (C) Both conduction and induction process
4. Scott connection is used for
(A) Single-phase to three-phase transformation
(B) Three-phase to single-phase transformation
(C) Three-phase to two-phase transformation
(D) any of the above
Ans: (C) Three-phase to two-phase transformation
5. Scott connected transformer can convert
(A) 3 to 2 phases and 2 to 3 phases
(B) 2 to 4 phases and 2 to 5 phases
(C) Both (A) and (B)
(D) none of the above
Ans: (A) 3 to 2 phases and 2 to 3 phases
6. In Scott connections, the teaser transformer operates on 0.866 of its rated
(A) Impedance
(B) Current
(C) Voltage
(D) Power
Ans: (C) Voltage
7. In a transformer fed from a fundamental frequency voltage source the source of harmonics is the
(A) Overload
(B) poor insulation
(C) Iron loss
(D) Saturation of core
Ans: (D) Saturation of core
8. Zero sequence currents can flow from a line into a transformer bank if the winding are
(A) Grounded star/delta
(B) Delta/star
(C) Star/grounded star
(D) Delta/Delta
Ans: (A) Grounded star/delta
9. The harmonic currents in a power transformer does nit cause an increase in
(A) Secondary Voltage
(B) core loss
(C) Copper loss
(D) magnetic interference with protective relays
Ans: (A) Secondary Voltage
10. In which transformer, the tertiary winding is used?
(A) Star-delta
(B) Delta-delta
(C) Star-star
(D) Delta-star
Ans: (C) Star-star
11. The magnetizing current in a transformer is rich in
(A) 3 rd harmonic
(B) 5th harmonic
(C) 7th Harmonic
(D) 13 th harmonic
Ans: (A) 3 rd harmonic
12. Two transformers when operating in parallel will share the load depending upon which of the following?
(A) Magnetising current
(B) Leakage reactance
(C) Per unit impedance
(D) Efficiency
Ans: (C) Per unit impedance
13. Two transformers operating in parallel will share the load depending upon their
(A) ratings
(B) Leakage reactance
(C) efficiency
(D) per unit impedance
Ans: (D) per unit impedance
