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Electrical Engineering Objective Questions { Induction Motors }

323. No-load test on a 3-phase induction motor was conducted at different supply voltage and a plot of input power versus voltage was drawn. This curve was extrapolated to intersect the y-axis. This intersection point yields '
A. Core loss
B. Stator copper loss
C. Stray load loss
D. Friction and windage loss
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324.  A 3-phase Induction Motor is driving a constant torque load at rated voltage and frequency. If both voltage and frequency are halved, following statements relate to the new condition if stator resistance, leakage reactance and core loss are ignored P The difference between synchronous speed and actual speed remains same Q The airgap flux remains same R The stator current remains same S The p.u. slip remains same Among the above, correct statements are
A. All
B. P. Q & R
C. Q. R & S
D. P & S
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325. A single phase induction motor with only the main winding excited would exhibit the following response at synchronous speed.
A. Rotor current is zero
B. Rotor current is non-zero and is at slip frequency
C. Forward and backward dotating fields are equal
D. Forward rotating field is more than the backward rotating field
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326. The type of single-phase induction motor having the highest power factor at full load is
A. shaded pole type
B. split-phase type
C. capacitor-start type
D. capacitor-run type
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327. The direction of rotation of a 3-phase induction motor is clockwise when it is supplied with 3-phase sinusoidal voltage having phase sequence A-13-C. For counterclockwise rotation of the motor, the phase sequence of the power supply shold be
A. B-C-A
B. C-A-B
C. A-C-B
D. B-C-A or C-A-B
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328.  The synchronous speed for the seventh space harmonic mmf wave of a 3-phase, 8 pole, 50 Hz induction machine is-
A. 107.14 rpm in forward direction
B. 107.14 rpm in reverse direction
C. 5250 rpm in forward direction
D. 5250 rpm in reverse direction
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329.  A 400V, 15 kW, 4 pole, 50Hz, Y-connected induction motor has full load slip of 4%. The output torque of the machine at full load is
A. 1.66 Nm
B. 95.50 Nm
C. 99.47 Nm
D. 624.73 Nm
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