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Q1: Fill in the blank the correct answer: 1- A 3-phase,50 Hz induction motor runs at 960 rpm, the number of poles are (a) 2 (b)4 (c) 6 (d) 8 2- If full load copper losses in a 3- phase,50 Hz, 4 pole induction motor running at 1425 rpm are 500 W, the rotor input power is (a) 5 kW (b) 10 kW (c) 20 kW (d) 50 kW 3- Frequency of rotor current in three phase induction motor at starting is --------- frequency (a) supply (b) less than supply (c) greater than supply (d) slip 4- If the rotor bars of a 3- phase induction motor are made deeper, R2 is (a) increased at starting (b) decreased at starting (c) increased at running (d) decreased at running 5-The full load slip of a 3-phase induction motor ranges from ----- (b) 20% to 30% (a) 10% to 20% 6- The advantages of squirrel cage induction motor is that (b) it requires less maintenance (a) has low starting current (c) 2% to 5% (d) 0.5% to 1% (c) it has good cooling (d) external resistance can be inserted in the rotor circuit 7- The maximum voltage is induced in the rotor of a 3-phase induction motor when is ------ (a) runs at no load (b) runs at full load (c) blocked (d) reversed direction 8- The rotor reactance of a 3-phase induction motor is maximum at ---------- (a) full load (b) starting (c) no load (d) half load 9- Friction an windage losses of a 3-phase induction motor are (a) maximum at no load (b) minimum at no load (c) maximum at full load (d) remain the same at all loads 10-If supply voltage of a 3-phase induction motor is increased 2 times, then torque is---------- (a) increased 2 times (b) decreased 2 times (c) increased 4 times (d) decreased 4 times [25 Marks]

Q1: Fill in the blank the correct answer: 1- A 3-phase,50 Hz induction motor runs at 960 rpm, the number of poles are (a) 2 (b)4 (c) 6 (d) 8 2- If full load copper losses in a 3- phase,50 Hz, 4 pole induction motor running at 1425 rpm are 500 W, the rotor input power is (a) 5 kW (b) 10 kW (c) 20 kW (d) 50 kW 3- Frequency of rotor current in three phase induction motor at starting is --------- frequency (a) supply (b) less than supply (c) greater than supply (d) slip 4- If the rotor bars of a 3- phase induction motor are made deeper, R2 is (a) increased at starting (b) decreased at starting (c) increased at running (d) decreased at running 5-The full load slip of a 3-phase induction motor ranges from ----- (b) 20% to 30% (a) 10% to 20% 6- The advantages of squirrel cage induction motor is that (b) it requires less maintenance (a) has low starting current (c) 2% to 5% (d) 0.5% to 1% (c) it has good cooling (d) external resistance can be inserted in the rotor circuit 7- The maximum voltage is induced in the rotor of a 3-phase induction motor when is ------ (a) runs at no load (b) runs at full load (c) blocked (d) reversed direction 8- The rotor reactance of a 3-phase induction motor is maximum at ---------- (a) full load (b) starting (c) no load (d) half load 9- Friction an windage losses of a 3-phase induction motor are (a) maximum at no load (b) minimum at no load (c) maximum at full load (d) remain the same at all loads 10-If supply voltage of a 3-phase induction motor is increased 2 times, then torque is---------- (a) increased 2 times (b) decreased 2 times (c) increased 4 times (d) decreased 4 times [25 Marks]

Electric Motor Control
Electric Motor Control
10th Edition
ISBN:9781133702818
Author:Herman
Publisher:Herman
Chapter3: Magnetic Starters
Section: Chapter Questions
Problem 18SQ
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Q1: Fill in the blank the correct answer: 1- A 3-phase,50 Hz induction motor runs at 960 rpm, the number of poles are (a) 2 (b)4 (c) 6 (d) 8 2- If full load copper losses in a 3- phase,50 Hz, 4 pole induction motor running at 1425 rpm are 500 W, the rotor input power is (a) 5 kW (b) 10 kW (c) 20 kW (d) 50 kW 3- Frequency of rotor current in three phase induction motor at starting is --------- frequency (a) supply (b) less than supply (c) greater than supply (d) slip 4- If the rotor bars of a 3- phase induction motor are made deeper, R2 is (a) increased at starting (b) decreased at starting (c) increased at running (d) decreased at running 5-The full load slip of a 3-phase induction motor ranges from ----- (b) 20% to 30% (a) 10% to 20% 6- The advantages of squirrel cage induction motor is that (b) it requires less maintenance (a) has low starting current (c) 2% to 5% (d) 0.5% to 1% (c) it has good cooling (d) external resistance can be inserted in the rotor circuit 7- The maximum voltage is induced in the rotor of a 3-phase induction motor when is ------ (a) runs at no load (b) runs at full load (c) blocked (d) reversed direction 8- The rotor reactance of a 3-phase induction motor is maximum at ---------- (a) full load (b) starting (c) no load (d) half load 9- Friction an windage losses of a 3-phase induction motor are (a) maximum at no load (b) minimum at no load (c) maximum at full load (d) remain the same at all loads 10-If supply voltage of a 3-phase induction motor is increased 2 times, then torque is---------- (a) increased 2 times (b) decreased 2 times (c) increased 4 times (d) decreased 4 times [25 Marks]
Transcribed Image Text:Q1: Fill in the blank the correct answer: 1- A 3-phase,50 Hz induction motor runs at 960 rpm, the number of poles are (a) 2 (b)4 (c) 6 (d) 8 2- If full load copper losses in a 3- phase,50 Hz, 4 pole induction motor running at 1425 rpm are 500 W, the rotor input power is (a) 5 kW (b) 10 kW (c) 20 kW (d) 50 kW 3- Frequency of rotor current in three phase induction motor at starting is --------- frequency (a) supply (b) less than supply (c) greater than supply (d) slip 4- If the rotor bars of a 3- phase induction motor are made deeper, R2 is (a) increased at starting (b) decreased at starting (c) increased at running (d) decreased at running 5-The full load slip of a 3-phase induction motor ranges from ----- (b) 20% to 30% (a) 10% to 20% 6- The advantages of squirrel cage induction motor is that (b) it requires less maintenance (a) has low starting current (c) 2% to 5% (d) 0.5% to 1% (c) it has good cooling (d) external resistance can be inserted in the rotor circuit 7- The maximum voltage is induced in the rotor of a 3-phase induction motor when is ------ (a) runs at no load (b) runs at full load (c) blocked (d) reversed direction 8- The rotor reactance of a 3-phase induction motor is maximum at ---------- (a) full load (b) starting (c) no load (d) half load 9- Friction an windage losses of a 3-phase induction motor are (a) maximum at no load (b) minimum at no load (c) maximum at full load (d) remain the same at all loads 10-If supply voltage of a 3-phase induction motor is increased 2 times, then torque is---------- (a) increased 2 times (b) decreased 2 times (c) increased 4 times (d) decreased 4 times [25 Marks]
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