# ONLINE Multiple Choice Questions – Electric Machine Design PART 11

151. When D is the diameter and L is the length of
rotor of an induction motor, the best power factor can be obtained when
(P = no. of poles)
(A) D=L
(B) D = PF
(C) D = √(PL)
(D) D = 1.35 P √L.

152. The power factor of the induction motor will
be __________ if the magnetizing current is __________
(A) low……low
(B) high……..high
(C) high…..low
(D) low ……. high.

153. The magnetizing current of an induction motor will be __________ for __________ air gap
(A) larger ………. smaller
(B) larger ……… larger
(C) smaller……. larger
(D) smaller ……….. smaller.

154. In induction motors, small air gap __________
power factor and __________ noise level
(A) increases ………. reduces
(B) reduces ………. increases
(C) reduces……….also reduces
(D) increases……….also increases.

155. In induction motors, larger air gap __________
noise level and __________ cooling
(A) increases ………. improves
(B) reduces ………. improves
(C) reduces……….jeopardises
(D) increases……….jeopardises.

156. In case of induction motors, phase reactance
of the winding is __________ proportional to the
number of slots per pole per phase
(A) directly
(B) inversely.

157. In the design of induction motors, normally the number of slots per pole per phase is taken as
(A) two
(B) three
(C) three or more
(D) three or less.

158. Normally open type stator slots in induction motors are not provided because
(A) exciting current increases
(B) coils cannot be slid through the top
(C) time required for the winding will be large
(D) none of the above.

159. In induction motors provided with open type
slots the exciting current is __________ and power
factor is __________
(A) high……….high
(B) low……….low
(C) high……….low
(D) low ………. high.

160. Which type of slots are generally used in induction motors ?
(A) Open type
(B) Semi-closed type
(C) Closed type
(D) None of the above.

161. In induction motors, the difference between the number of stator and rotor slots should not be
(A) P
(B) 2 P
(C) 5P
(D) any of the above.

162. For avoiding cogging in induction motor the difference between the number of stator and rotor slots should not be
(A) P
(B) 3P
(C) 5 P
(D) any of the above.

163. In induction motor which of the following depends on the leakage reactance ?
(A) starting torque
(B) maximum torque
(C) starting current
(D) all of the above.

164. Leakage reactance in induction motors may result from
(A) slot leakage flux
(B) overhang leakage flux
(C) differential leakage flux
(D) all of the above.