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1) Short-circuit test on an induction motor cannot be used to determine___________? a. windage losses b. copper losses c. transformation ratio d. power scale of circle diagram
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2) The starting torque of a 3-phase squirrel cage induction motor is____________? a. twice the full load torque b. 1.5 times the full load torque c. equal to full load torque
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3) A 3-phase slip ring motor has____________? a. double cage rotor b. wound rotor c. short-circuited rotor d. any of the above
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4) 5 H.P., 50-Hz, 3-phase, 440 V, induction motors are available for the following r.p.m. Which motor will be the costliest ? a. 730 r.p.m. b. 960 r.p.m. c. 1440 r.p.m. d. 2880 r.p.m.
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5) A pump induction motor is switched on to a supply 30% lower than its rated voltage. The pump runs. What will eventually happen ? It will____________? a. stall after sometime b. stall immediately c. continue to run at lower speed without damage d. get heated and subsequently get damaged
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6) Which type of bearing is provided in small induction motors to support the rotor shaft ? a. Ball bearings b. Cast iron bearings c. Bush bearings d. None of the above
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7) The speed characteristics of an induction motor closely resemble the speedload characteristics of which of the following machines? a. D.C. series motor b. D.C. shunt motor c. universal motor d. none of the above
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8) It is advisable to avoid line starting of induction motor and use starter because____________? a. it will run in reverse direction b. it will pick up very high speed and may go out of step c. motor takes five to seven times its full load current d. starting torque is very high
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9) 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
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10) As load on an induction motor goes on increasing______________? a. its power factor goes on decreasing b. its power factor remains constant c. its power factor goes on increasing even after full load d. its power factor goes on increasing up to full load and then it falls again
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11) Slip ring motor is recommended where____________? a. speed control is required b. frequent starting, stopping and reversing is required c. high starting torque is needed d. all above features are required
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12) In an induction motor the relationship between stator slots and rotor slots is that_____________? a. stator slots are equal to rotor slots b. stator slots are exact multiple of rotor slots c. stator slots are not exact multiple of rotor slots d. none of the above
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13) 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
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14) A 3-phase induction motor delta connected is carrying too heavy load and one of its fuses blows out. Then the motor______________? a. will continue running burning its one phase b. will continue running burning its two phase c. will stop and carry heavy current causing permanent damage to its winding d. will continue running without any harm to the winding
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15) A 3-phase induction motor stator delta connected, is carrying full load and one of its fuses blows out. Then the motor_______________? a. will continue running burning its one phase b. will continue running burning its two phases c. will stop and carry heavy current causing permanent damage to its winding d. will continue running without any harm to the winding
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16) Size of a high speed motor as compared to low speed motor for the same H.P. will be__________? a. bigger b. smaller c. same d. any of the above
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17) Slip of an induction motor is negative when_____________? a. magnetic field and rotor rotate in opposite direction b. rotor speed is less than the synchronous speed of the field and are in the same direction c. rotor speed is more than the synchronous speed of the field and are in the same direction d. none of the above
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18) 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
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19) The ‘cogging’ of an induction motor can be avoided by____________? a. proper ventilation b. using DOL starter c. auto-transformer starter d. having number of rotor slots more or less than the number of stator slots (not equal)
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20) The power factor of an induction motor under no-load conditions will be closer to_____________? a. 0.2 lagging b. 0.2 leading c. 0.5 leading d. unity
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