Top 150+ Solved Design of Electrical Machines MCQ Questions Answer

From 31 to 45 of 102

Q. With conventional hydrogen cooling it is possible to increase the rating of a single unitto

a. 50 MW

b. 100 MW

c. 200 MW

d. none ofthe above

  • c. 200 MW

Q. The noise produced by a ______ cooled machine is less as the rotor moves in a mediumof smaller density.

a. air

b. hydrogen

c. either (a) or (b)

d. none of the above

  • b. hydrogen

Q. Machines cooled by direct cooling method may be called

a. "supercharged"

b. "inner cooled"

c. "conductor cooled"

d. any of the above

  • d. any of the above

Q. In direct cooled system using hydrogen both stator and rotor conductors are made

a. solid

b. hollow

c. perforated

d. any ofthe above

  • b. hollow

Q. With direct water cooling it is possible to have ratings of about

a. 200 MW

b. 300 MW

c. 400 MW

d. 600 MW

  • d. 600 MW

Q. The resistivity of water should not be less than

a. 10 Q m

b. 100 Q m

c. 1000 Q m

d. 2000 Q m

  • d. 2000 Q m

Q. Direct water cooling of rotor winding presents

a. no mechanical difficulties

b. lesser mechanical difficulties

c. greater mechanical difficulties

d. none of the above

  • c. greater mechanical difficulties

Q. The time taken by the machine to attain 0.632 of its final steady temperature rise iscalled

a. heating time constant

b. cooling time constant

c. either (a) or (b)

d. none of the above

  • a. heating time constant

Q. In self cooled motors the cooling time constant is about ______ than the heating timeconstant because cooling conditions are worse at standstill.

a. 2 to 3 times greater

b. 3 to 4 times greater

c. 4 to 5 times greater

d. none of the above

  • a. 2 to 3 times greater

Q. By which of the following methods motor rating for variable load drives can bedetermined ?

a. Method of average losses

b. Equivalent current method

c. Equivalent torque method

d. All of the above.

  • d. All of the above.

Q. Which of the following methods does not take into account the maximum temperaturerise under variable load conditions ?

a. Equivalent power method

b. Equivalent current method

c. Method of average losses

d. Equivalent torque method

  • c. Method of average losses

Q. Which of the following methods is most accurate ?

a. Equivalent current method

b. Equivalent power method

c. Equivalent torque method

d. Method of average losses

  • a. Equivalent current method

Q. By which of the following methods the temperature rise of windings and other partsmay be determined ?

a. Thermometer method

b. Resistance method

c. Embedded temperature detector method

d. Any of the above

  • d. Any of the above

Q. The slot leakage can be calculated by making which of the following assumptions ?

a. The current in the slot conductors is uniformly distributed over their cross-section

b. The leakage path is straight across the slot and around the iron at the bottom

c. The permanence of air paths is only considered. The reluctance of iron paths is assumed as zero

d. All of the above

  • d. All of the above
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