Transformer. Part – 1

1. In a transformer routine efficiency depends upon

A. Supply frequency

B. Load current

C. Power factors of load

D. Both b and c

2. Transformer will operate at maximum efficiency when

A. Copper loss = iron loss

B. Hysteresis loss = eddy current loss

C. Eddy current loss = copper loss

D. Hysteresis loss = copper loss

3. No load test on a transformer is carried out to determine

A. Copper loss

B. Magnetizing current

C. Magnetizing current and losses

D. Efficiency of transformer

4. A transformer can have zero voltage regulation at

A. Leading power factor

B. Unity power factor

C. Lagging power factor

D. Zero power factor

5. Buchholz relay operates due to

A. Electromagnetic induction

B. Electrostatic charge

C. Flux in the core

D. Gas generated due to heating

6. In case of pole mounted three phase distribution transformers, the windings are generally

A. Delta/star

B. Star/star

C. Delta/delta

D. None of the above

7. For the same excitation voltage and winding currents, the auto transformer gives

A. Half of the output of two winding transformer

B. Less output than two winding transformer

C. More than the output of the two winding transformer

D. Equal to the output of two winding transformer

8. Open circuit test on a transformer yields

A. Leakage of reactance

B. Sum of core and copper losses

C. Copper losses

D. Core losses

9. Power input to a transformer at no load and rated voltage consists of

A. Eddy current loss

B. Copper loss

C. Hysteresis loss

D. Core loss

10. Possible three to three phase transformer connections for parallel operation

A. Δ–Ү to Δ–Ү

B. Δ Δ to Δ- Ү

C. Ү Ү to Δ-Ү

D. Δ-Ү to Ү-Δ