31. The open circuit test on a transformer gives
- equivalent resistance and leakage reactance
- magnetizing current and core loss at rated voltage
- copper losses
- windage losses
32. Which of the following tests are to be conducted for the determination of voltage regulation of a transformer
- load test
- OC and SC test
- retardation test
- polarity test
33. For a transformer to be tested at full load conditions but consuming only losses from the mains, we do
- load test
- OC and SC test
- back to back test
- none of the above
34. The efficiency of two identical transformers under load conditions can be determined by
- back to back test
- open circuit test
- short circuit test
- any of the above
35. The efficiency of power transformer can be determined indirectly by
- open circuit test
- short circuit test
- open circuit and short circuit test
- back to back test
36. The transformer efficiency at relatively light loads is quite low. This is due to
- small copper loss
- small secondary output
- high fixed loss in comparison to the output
- poor power factor
37. The transformer efficiency, under heavy loads, is comparatively low due to
- large increase in copper losses in comparison to the output
- large increase in iron losses
- drop in power factor
- none of the above
38. The full load copper loss and iron loss of a transformer are 6400 W and 500 W respectively. The above copper loss and iron loss at half load will be
- 3200 W and 250 W respectively
- 3200 W and 500 W respectively
- 1600 W and 125 W respectively
- 1600 W and 500 W respectively
39. Transformer will operate at maximum efficiency when
- hysteresis loss = eddy current loss
- eddy current loss = copper loss
- copper loss = iron loss
- hysteresis loss = copper loss
40. Power transformers are designed to have maximum efficiency around _______ full load.
- nearly
- 70% of
- 50% of
- 25% of