# ONLINE Multiple Choice Questions – Electric Machine Design PART 12

166. Stiff shaft is necessary in case of induction motors due to
(A) high operating speeds
(B) asynchronous-speed operation
(C) pulsating torque
(D) small air gap.

167. The average value of specific electric loading of induction motors is in the range
(A) 5 to 50 ampere conductors/meter
(B) 50 to 450 ampere conductors/meter
(C) 500 to 4500 ampere conductors/meter
(D) 5000 to 45000 ampere conductors/meter.

168. In case of induction motors the ratio of length to pole pitch for minimum cost, is taken as
(A)1.0
(B) 1.5 to 2
(C) 2 to 3
(D) 3 to 5.

169. In case of induction motors, the ratio of length to pole pitch for good efficiency is taken as
(A) 1.0
(B) 1.5
(C) 2.0
(D) 5.0.

170. For small induction motors, the ratio of length to pole pitch is taken as
(A) 0.6
(B) 1.5
(C) 1.5
(D) 2.0.

171. The number of parallel paths in an integral slot winding with P poles are
(A) P
(B) 2P
(C) P/2
(D) P/4.

172. The use of double squirrel cage winding on the rotor provides
(A) low noise
(B) reduced starting torque
(C) a large starting torque
(D) higher efficiency.

173. By providing deep narrow slots in the rotor punching in induction motor
(A) starting torque can be increased
(B) running torque can be reduced
(C) efficiency can be improved
(D) none of the above.

174. In induction motor if the number of rotor slots is equal to the stator slots then
(A) the motor will run smoothly
(B) the motor will mil at zero slip
(C) the noise level will be low
(D) the motor may refuse to start.

175. A __________ value of magnetizing current gives __________ power factor
(A) large……..poor
(B) large ……… better
(C) smaller……..poor
(D) smaller …….. larger.

176. Friction and windage loss in induction motor is usually
(A) 0.1% of the rated output
(B) 1% of the rated output
(C) 5% of the rated output
(D) 10% of the rated output.

177. In case of double cage rotor the upper cage which is near to the air gap is made of
(A) electrolytic copper
(B) annealed copper
(C) brass
(D) steel.

178. Losses due to harmonic currents produced in the cage rotor winding can be reduced by
(A) using skewed rotor
(B) using chorded stator winding
(C) proper slot combination of rotor and stator
(D) any of the above.

179. In squirrel cage motors, skin effect occurs in
(A) stator winding
(B) rotor winding
(C) both (A) and (B) above
(D) none of the above.