MULTIPLE CHOICE QUESTIONS
Q.1 If maximum torque of an induction motor is 200 kg-m at a slip of 12%, the torque at 6% slip would be ...... kg-m.
(A) 100
(B) 160
(C) 50
(D) 40
Q.2 The fractional slip of an induction motor is the ratio
(A) rotor Cu loss/rotor input
(B) stator Cu loss/stator input
(C) rotor Cu loss/rotor output
(D) rotor Cu loss/stator Cu loss
Q.3 The torque developed by a 3-phase induction motor depends on the following three factors:
(A) speed, frequency, number of poles
(B) voltage, current and stator impedance
(C) synchronous speed, rotor speed and frequency
(D) rotor emf, rotor current and rotor pf.
Q.4 If the stator voltage and frequency of an induction
motor are reduced proportionately, its
(A) locked rotor current is reduced
(B) torque developed is increased
(C) magnetising current is decreased
(D) both (a) and (b)
Q.5 The efficiency and p.f. of a SCIM increases in proportion to its
(A) speed
(B) mechanical load
(C) voltage
(D) rotor torque
Q.6 A SCIM runs at constant speed only so long as
(A) torque developed by it remains constant
(B) its supply voltage remains constant
(C) its torque exactly equals the mechanical load
(D) stator flux remains constant
Q.7 The synchronous speed of a linear induction motor does NOT depend on
(A) width of pole pitch
(B) number of poles
(C) supply frequency
(D) any of the above
Q.8 Thrust developed by a linear induction motor depends on
(A) synchronous speed
(B) rotor input
(C) number of poles
(D) both (a) and (b)
Q.9 The output current corresponding to maximum efficiency for a transformer having core loss of 100 W and equivalent resistance referred to secondary of 0.25 Ω is ....... ampere.
(A) 20
(B) 25
(C) 5
(D) 400
Q.10 The maximum efficiency of a 100-kVA transformer having iron loss of 900 kW and F.L. Cu loss of 1600 W occurs at ....... kVA.
(A) 56.3
(B) 133.3
(C) 75
(D) 177.7
