Q2. a) A four-pole, 415 V 50Hz induction motor supplies its rated power to a constant load. The rated speed of the motor is 1470 rpm. i) Draw the equivalent electrical circuit of the motor ii) Calculate the slip frequency and slip iii) If the supply voltage is changed to 207.5 V_25 Hz, calculate the motor speed, slip frequency, and slip. iv) Sketch torque-speed characteristics of the motor when the supply voltages are 415 V 50 Hz, 207.5 V 25 Hz and 415 V 60 Hz respectively; Compare the peak torques of the 415 V 50 Hz case and the 415 V_60 Hz case.

Q2. a) A four-pole, 415 V 50Hz induction motor supplies its rated power to a constant load. The rated speed of the motor is 1470 rpm. i) Draw the equivalent electrical circuit of the motor ii) Calculate the slip frequency and slip iii) If the supply voltage is changed to 207.5 V_25 Hz, calculate the motor speed, slip frequency, and slip. iv) Sketch torque-speed characteristics of the motor when the supply voltages are 415 V 50 Hz, 207.5 V 25 Hz and 415 V 60 Hz respectively; Compare the peak torques of the 415 V 50 Hz case and the 415 V_60 Hz case.

Delmar's Standard Textbook Of Electricity

7th Edition

ISBN:9781337900348

Author:Stephen L. Herman

Publisher:Stephen L. Herman

Chapter32: Three-phase Motors

Section: Chapter Questions

Problem 6RQ: Name three factors that determine the torque produced by an induction motor.

See similar textbooks

Similar questions

6- In a stepper motor, how is the speed of rotation determined? a) By the current supplied to the motor. b) By the magnitude of the voltage applied. c) By the load applied to the motor. d) By the frequency of the waveforms used. 7- A transformer core is laminated to a) reduce hysteresis loss b) reduce eddy current losses c) reduce copper losses d) reduce all above losses 8- An induction motor with 580 r.p.m. speed at 60 Hz will have a) 8 poles b) 6 poles c) 4 poles d) 2 poles 9- If any two phases for an induction motor are interchanged a) the motor will run in reverse direction b) the motor will run at reduced speed c) the motor will not run d) the motor will burn 10- No-Load speed of which of the following motor will be highest? a) Shunt motor b) Series motor c) Short-Shunt compound motor d) Long-Shunt compound motor
An induction motor having full load torque of 60 Nm when delta-connected develops a starting torque of 120 Nm. For the same supply voltage, if motor is changed to star -connection, then starting torque developed will be Nm.
A three-phase induction motor used for a commercial application in Oman runs at 580 rpm at no load and at 552 rpm at full load. a) How many poles do this motor have? b) What is the percentage slip at full load? c) The frequency of the rotor currents when slip is 5 % d) The frequency of the rotor currents at standstill. a) b) c) d)
3.An induction motor has a rotor resistance and reactance at standstill of 0.1 ohm and 3.5 ohm respectively. At standstill the voltage induced to the rotor is 60volts per phase. If the slip is 5%, determine the rotor current
A 110-V, 1-phase, 4-pole, 60-Hz induction motor has the following circuit constants: R1 = R2’ = 1.6 ohm,X1 = X2’ = 1.8 ohm, Xm = 60 ohm; core loss is 16 W and friction and windage loss is 12 W. Determine theefficiency of the motor at 0.04 slip by using (a) the exact equivalent circuit and (b) the approximateequivalent circuit
A wound rotor, induction motor has a rotor resistance of 0.6 ohms per phase and a rotor leakage reactance of 8 ohms.a)What is the operating speed (rpm) of this 2-pole induction motor fed from a 50Hz supply if the slip is 5%?b)If maximum torque occurs when R2 = sX2, what is the slip at maximum torque?c)What resistance must be added to the rotor circuit to give maximum startingtorque?
6- Which of the following supply is given to the rotor winding of 3-Phase Induction Motor: a) DC Supply b) AC Supply c) No Supply d) Pulsating Supply 7- 3-Phase Induction Motor will have Starting Torque and Starting Current a) High, High b) Low, Low. c) High, Low d) Low, High 8- Which of the following method is used for controlling the speed of an induction motor: a) Changing number of stator poles b) Supply voltage control c) Frequency control d) All the options are correct 9- Which of the following method cannot be used for starting of 3-Phase Squirrel Induction Motor: a) Star-Delta Starting b) Line resistor startling c) transformer Starter d) Rotor Resistance Starting 10- The rotor of a stepper motor has no: a) windings b) commutator c) brushes d) all of the above
A 30 induction motor has a 4-pole, Y-connected stator winding. The motor runs on a 50Hz supply with 200V between lines. The rotor resistance and reactance per phase are 0.192 and 0.992 respectively. Calculate: a) The gross torque at 4% slip in N-m b) The maximum torque in ft-lbs The ratio of rotor to stator turns is 0.67.
L-1). The 3-phase wound-rotor induction motor has .... . a) high starting torque b) low starting current c) both "a" and "b" d) neither "a" nor "b" L-2). The 3-phase wound-rotor induction.........a) motor has a wire wound rotor b) motor's rotor can be connected to an external resistive load by way of slip rings and brushes c) motor requires more maintenance than the 3-phase squirrel-cage induction motor d) all of the above L-3). The 3-phase wound-rotor induction motor's rotor circuit's resistance should be adjusted so it is__________ during starting. a) low b) high c) either "a" or "b" d) neither "a" nor "b" L-4). Will a 3-phase wound-rotor induction motor start with no external circuit connected to its rotor leads? a) yes b) no
A four-pole induction motor drives a load at 2478 rpm. This is to be accomplished by using an electronic converter to convert a 400-V dc source into a set of three-phase ac voltages. Part A Find the frequency required for the ac voltages assuming that the slip is 4 percent. The load requires 2 hp. Express your answer to three significant figures and include the appropriate units. f= Submit Part B Value I = HA Request Answer Submit If the dc-to-ac converter has a power efficiency of 90 percent and the motor has a power efficiency of 80 percent, estimate the current taken from the dc source. Express your answer to three significant figures and include the appropriate units. HÅ Value Units Request Answer ? Units ?
Q2. a) A 415V, 50Hz, 3-phase induction motor supplies its rated power to a load. The rated speed of the motor is 980 rpm. (i) Identify the pole number of the motor and calculate the rate slip (ii) When the load torque is increased by 50% and the supply voltage is kept constant. Determine the motor speed. (iii) If the supply AC voltage is changed using constant ratio of voltage/frequency in order to control the motor speed back to 980 rpm at the load torque in (b). Determine the new supply voltage and frequency.
(b) The power input to a 3-phase, 50-Hz induction motor is 60 kW. The total stator loss is 1000 W and the rotational loss is 5640 W. It is observed that the rotor e.m.fmakes 120 complete cycles per minute. (i) Calculate the efficiency of the motor. (ii) Calculate the gross torque and shaft torque.