ONLINE Multiple Choice Questions – Electric Machine Design PART 14

196. The materials in order of decreasing eddy current loss will be
(A) iron, wood, aluminium
(B) iron, aluminium, wood
(C) aluminium, iron, wood
(D) wood, aluminium, iron.

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197. For a 5 kW DC motor the number of slots per pole should be
(A) 4
(B) 8
(C) 12
(D) 16.

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198. In a synchronous generator in order to eliminate the fifth harmonic the chording angle should be
(A) 9°
(B) 18°
(C) 27°
(D) 36°.

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199. Inter poles in DC machines are provided to reduce
(A) sparking
(B) armature reaction
(C) iron loss
(D) efficiency.

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200. Skewing in the slots of an induction motor is provided to reduce
(A) iron loss
(B) noise
(C) harmonics
(D) temperature rise.

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201. Sometimes a reactor is connected in series with a transformer to
(A) improve regulation
(B) control fault current
(C) improve efficiency
(D) improve power factor.

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202. DC motor yoke is generally made of
(A) wood
(B) copper
(C) aluminium
(D) steel.

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203. For the same rating, the cost of an induction motor as compared to that of a DC motor is
(A) more
(B) less
(C) same
(D) nearly the same.

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204. In case of electrical machines, the intermittent rating as compared to its continuous rating is
(A) more
(B) less
(C) same.

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205. For the use of mush windings in 3φ induction motors, the slot should be
(A) semi-closed
(B) open
(C) closed
(D) either (a) or (b).

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206. A hunting sound is produced in a synchronous motor when
(A) load fluctuates
(B) supply frequency varies
(C) both (A) and (B) above
(D) none of the above.

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207. The transformer noise is mainly because of
(A) cooling oil
(B) sinusoidal current
(C) magnetic flux
(D) all of the above.

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208. Stampings in transformers are provided to reduce
(A) hysteresis loss
(B) eddy current loss
(C) copper loss
(D) all of the above.

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209. Which loss occurs in the yoke of a DC machine ?
(A) iron loss
(B) copper loss
(C) heat loss
(D) no loss.

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210. The losses occurring in the rotor of an induction motor are less than those in the stator because of
(A) small diameter of rotor
(B) less rotor frequency
(C) slot skewing
(D) none of the above.

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ONLINE Multiple Choice Questions - Electric Machine Design PART 15
ONLINE Multiple Choice Questions - Electric Machine Design PART 13

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