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4. List two design techniques to improve the efficiency of an induction motor. (2 marks)
high voltage techniques Q5. Calculate the efficiency of this High voltage motor. THREE PHASE INDUCTION MOTOR CEU CHINA ELECTRIC TYPE Y2-400-6 POWER FACTOR 0.82 RATED POWER 315 KW INSTALLATION STATOR 6000 V 39.5 A CONNY DUTY S 1 ROTORI A CONN INS.CL. F STANDARD JB/T10446 ALT. 1000 m TEMP 40 °C COOLING IC 411 FREQUENCY Hz PROTECTION CL IP55 WEIGHT kg 50 992 RATED SPEED r/min NO 25 DATE 18.10
(b) (i) Explain briefly why an induction motor can never run at synchronous speed? (2 Marks) (ii) If a six-pole induction motor supplied by a three-phase 50 Hz supply has a rotor frequency of 2.3 Hz, Calculate: (a)The percentage slip (b)The speed of the rotor in rpm (4 Marks) (iii)Draw a typical torque versus slip characteristic curve of an induction motor. If rotor resistance is increased show how the new torque versus slip curve deviates from the original one. (4...
QUESTION 2 [25 MARKS] a) Describe what will happen to the induction motor when the rotor speed is the same as the rotating magnetic field speed. 15 MARKS b) The following data in Table 2 was obtained from the no-load test, locked rotor test and DC test of a three-phase delta-connected, 450 V, 2-pole, 60 Hz, wound-rotor induction motor. The locked rotor test was done at 15Hz. No-load test Vyt = 450 V Ini - 30 A PNL-4.6 kW Table...
QUESTION 2 [25 MARKS] a) Describe what will happen to the induction motor when the rotor speed is the same as the rotating magnetic field speed. [5 MARKS] The following data in Table 2 was obtained from the no-load test, locked rotor test and DC test of a three-phase delta-connected, 450 V, 2-pole, 60 Hz, wound-rotor induction motor. The locked rotor test was done at 15Hz. b) Table 2 No-load test Locked rotor test DC test VNL = 450 V...
Question 3. (25 Marks) Parameters of a three-phase, 400 v, 50 Hz, 4-pole, star-connected induction motor are as follows: bl The sum of friction, windage and stray losses are 0.15 kW. The motor is running at 1440 rpm. (a) Calculate the input line current (b) Calculate the stator copper loss and rotor copper loss. (c) Calculate the output power and efficiency.
Question 11: (3 marks) A 6 pole, 60 Hz, star connected three-phase induction motor has a rating of Pm = 55 kW and line voltage = 420 V. The slip of the motor is 2% at 0.9 power factor lagging. If the full load efficiency is 95%, calculate the torque developed in the motor.
J. List two methods for overcoming starting problems in an Induction Motor. Briefly describe them
A three-phase induction motor delivers 500 hp at an efficiency of 0.91, the operating power factor being 0.76 lagging. A loaded synchronous motor with a power consumption of 100 kW is connected in parallel with the induction motor. Calculate the necessary kVA and the operating power factor of the synchronous motor if the overall power factor is to be unity. Answer should be 365 kVA, 0.274
4. The total frictional and windage loss of a 3-phase induction motor is 300 W. With a 2% slip, find the %efficiency of the motor when it draws 25 A current at 0.8 p.f. lagging from a 460-V supply and the equivalent rotor resistance referred to stator Rgap = 8.0 ohm
4.6. A 460-V, 75 kW, 4-pole, delta-connected, 60-Hz, three- phase induction motor has a full-load slip of 5 percent, an efficiency of 92 percent and a power-factor of 0.87 lagging at full-load. At start-up, the motor develops 1.9 times the full load developed torque but draws 7.5 times the rated current at the rated voltage. This motor is to be started with an auto- transformer reduced-voltage starter. Assume the stator resistance and the stator core loss to be negligible. Calculate...