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1) Insertion of resistance in the stator of an induction motor___________? a. increases the load torque b. decreases the starting torque c. increases the starting torque d. none of the above
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2) The starting torque of a three phase induction motor can be increased by__________? a. increasing slip b. increasing current c. both A. and (b) d. none of the above
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3) The rotor of an induction motor runs at__________? a. synchronous speed b. below synchronous speed c. above synchronous speed d. any of the above
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4) In a star-delta starter of an induction motor___________? a. resistance is inserted in the stator b. reduced voltage is applied to the stator c. resistance is inserted in the rotor d. applied voltage perl stator phase is 57.7% of the line voltage
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5) Slip ring motor is preferred over squirrel cage induction motor where___________? a. high starting torque is required b. load torque is heavy c. heavy pull out torque is required d. all of the above
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6) Reduced voltage starter can be used with_____________? a. slip ring motor only but not with squirrel cage induction motor b. squirrel cage induction motor only but not with slip ring motor c. squirrel cage as well as slip ring induction motor d. none of the above
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7) A squirrel cage induction motor is not selected when___________? a. initial cost is the main consideration b. maintenance cost is to be kept low c. higher starting torque is the main consideration d. all above considerations are involved
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8) Less maintenance troubles are experienced in case of___________? a. slip ring induction motor b. squirrel cage induction motor c. both A. and (b) d. none of the above
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9) In a squirrel cage motor the induced e.m.f. is___________? a. dependent on the shaft loading b. dependent on the number of slots c. slip times the stand still e.m.f. induced in the rotor d. none of the above
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10) The purpose of using short-circuit gear is___________? a. to short circuit the rotor at slip rings b. to short circuit the starting resistances in the starter c. to short circuit the stator phase of motor to form star d. none of the above
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11) Temperature of the stator winding of a three phase induction motor is obtained by___________? a. resistance rise method b. thermometer method c. embedded temperature method d. all above methods
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12) For driving high inertia loads best type of induction motor suggested is_____________? a. slip ring type b. squirrel cage type c. any of the above d. none of the above
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13) Insertion of resistance in the rotor of an induction motor to develop a given torque? a. decreases the rotor current b. increases the rotor current c. rotor current becomes zero d. rotor current rernains same
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14) Insertion of reactance in the rotor circuit_______? a. reduces starting torque as well as maximum torque b. increases starting torque as well as maximum torque c. increases starting torque but maxi-mum torque remains unchanged d. increases starting torque but maxi-mum torque decreases
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15) An induction motor can run at synchronous speed when____________? a. it is run on load b. it is run in reverse direction c. it is run on voltage higher than the rated voltage d. e.m.f. is injected in the rotor circuit
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16) The low power factor of induction motor is due to___________? a. rotor leakage reactance b. stator reactance c. the reactive lagging magnetizing current necessary to generate the magnetic flux d. all of the above
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17) In induction motor, percentage slip depends on__________? a. supply frequency b. supply voltage c. copper losses in motor d. none of the above
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18) When /?2 is the rotor resistance, .X2 the rotor reactance at supply frequency and s the slip, then the condition for maximum torque under running conditions will be_____________? a. sR2X2 = 1 b. sR2 = X2 c. R2 = sX2 d. R2 = s2X2
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19) In case of a double cage induction motor, the inner cage has__________? a. high inductance arid low resistance b. low inductance and high resistance c. low inductance and low resistance d. high inductance and high resistance
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20) 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
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