Electrical Machine MCQ #17

For more article and MCQ click here; 

Electrical Article

1) Which of the following material is used for magnetic core of the transformer?

      (a) silicon steel

      (b) iron

      (c) cast steel

      (d) cast iron

2) The magnetic core and yokes of the transformer is made up of laminated ______

      (a) cast steel

      (b) electrotechnics steel

      (c) cast iron

      (d) hard drawn copper

3) The transformer grade steel consisting of _______

      (a) 3.5% of silicon

      (b) 3.5% copper

      (c) 3.5% of iron

      (d) all of the above

4) The silicon content in transformer core also affect the

      (a) mechanical properties

      (b) electrical properties

      (c) chemical properties

      (d) all of the above

ANSWER: | 1-a | 2-b | 3-a | 4-a |

5) The steel used for transformer core may be

      (a) cast steel

      (b) hot rolled

      (c) cold rolled

      (d) B or C

6) Generator transformers are ____________

      (a) Step-up transformers

      (b) Step-down transformers

      (c) Auto-transformers

      (d) One-one transformers

7) Station transformers are generally used for __________

      (a) Providing generator voltage to transmission

      (b) Providing power to load from transmission

      (c) Isolating DC

      (d) To supply power section auxiliary

8) On-load power factor for generator transformer is __________

      (a) high

      (b) low

      (c) can’t define

      (d) zero

ANSWER: | 5-d | 6-a | 7-d | 8-a |

9) A star connected three phase transformers is provided with tertiary delta connected winding which allows the flow of 

      (a) Second harmonic of exciting current

      (b) Third harmonic of exciting current

      (c) Fifth harmonic of exciting current

      (d) Seventh harmonic of exciting current

10) In a step-down autotransformer, if the transformation ratio increases then the saving of copper

      (a) Increases

      (b) Decreases

      (c) Remains same

      (d) None of these

11) Overheating of transformer windings and of load are due to ________

      (a) third harmonic currents

      (b) third harmonic voltages

      (c) fifth harmonic currents

      (d) fifth harmonic voltages

12) In 4-wire star connection 3rd harmonic currents may flow through __________

      (a) lines

      (b) phases

      (c) from fourth wire to neutral

      (d) all connections

ANSWER: | 9-b | 10-a | 11-a | 12-d |