Natural oil cooling is used for transformers up to a rating of____________?

Related Mcqs:

1. Two transformers are connected in parallel. These transformers do not have equal percentage impedance. This is likely to result in____________?

   A. short-circuiting of the secondaries
   B. power factor of one of the transformers is leading while that of the other lagging
   C. transformers having higher copper losses will have negligible core losses
   D. loading of the transformers not in proportion to their kVA ratings

2. The changes in volume of transformer cooling oil due to variation of atmospheric temperature during day and night is taken care of by which part of transformer?

   A. Conservator
   B. Breather
   C. Bushings
   D. Buchholz relay

3. Gas is usually not liberated due to dissociation of transformer oil unless the oil temperature exceeds?

   A. 50°C
   B. 80°C
   C. 100°C
   D. 150°C

4. Sumpner’s test is conducted on transformers to determine_____________?

   A. temperature
   B. stray losses
   C. all-day efficiency
   D. none of the above

5. Power transformers are designed to have maximum efficiency at___________?

   A. nearly full load
   B. 70% full load
   C. 50% full load
   D. no load

6. What will happen if the transformers working in parallel are not connected with regard to polarity ?

   A. The power factor of the two trans-formers will be different from the power factor of common load
   B. Incorrect polarity will result in dead short circuit
   C. The transformers will not share load in proportion to their kVA ratings
   D. none of the above

7. Power transformers are generally designed to have maximum efficiency around__________?

   A. no-load
   B. half-load
   C. near full-load
   D. 10% overload

8. Star/star transformers work satisfactorily when________________?

   A. load is unbalanced only
   B. load is balanced only
   C. on balanced as well as unbalanced loads
   D. none of the above

9. The efficiencies of transformers compared with that of electric motors of the same power are____________?

   A. about the same
   B. much smaller
   C. much higher
   D. somewhat smaller
   E. none of the above

10. The efficiency of two identical transformers under load conditions can be determined by_______________?

    A. short-circuit test
    B. back-to-back test
    C. open circuit test
    D. any of the above