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.Management Sciences
Category: Polyphase Induction Motors
In the squirrel-cage induction motor the rotor slots are usually given slight skew__________?
A. to reduce the magnetic hum and locking tendency of the rotor
B. to increase the tensile strength of the rotor bars
C. to ensure easy fabrication
D. none of the above
In an induction motor if air-gap is increased__________?
A. the power factor will be low
B. windage losses will be more
C. bearing friction will reduce
D. copper loss will reduce In an induction motor
Low voltage at motor terminals is due to____________?
A. inadequate motor wiring
B. poorely regulated power supply
C. any one of the above
D. none of the above
If an induction motor with certain ratio of rotor to stator slots, runs at 1/7 of the normal speed, the phenomenon will be termed as____________?
A. humming
B. hunting
C. crawling
D. cogging
Lubricant used for ball bearing is usually___________?
A. graphite
B. grease
C. mineral oil
D. molasses
If a 3-phase supply is given to the stator and rotor is short circuited rotor will move___________?
A. in the opposite direction as the direction of the rotating field
B. in the same direction as the direction of the field
C. in any direction depending upon phase squence of supply
The torque developed in the cage induction motor with autostarter is___________?
A. k/torque with direct switching
B. K x torque with direct switching
C. K2 x torque with direct switching
D. k2/torque with direct switching
In Ns is the synchronous speed and s the slip, then actual running speed of an induction motor will be___________?
A. Ns
B. s.N,
C. (l-s)Ns
D. (Ns-l)s
The speed of a squirrel-cage induction motor can be controlled by all of the following except_____________?
A. changing supply frequency
B. changing number of poles
C. changing winding resistance
D. reducing supply voltage
The complete circle diagram of induetion motor can be drawn with the help of data found from__________?
A. noload test
B. blocked rotor test
C. stator resistance test
D. all of the above
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