4-pole,400-V, 50-Hz,1425 rpm, Y-connected, three-phase induction motor has the followingparameters in /phase: R1 = 0.4, R2 = 0.25, X1 = X2 = 0.5, and Xm = 15.5.Use the approximate equivalent circuit to determine at rated slip the following:(a) Motor input current, (b) Motor power factor, (c) Motor input power,(d) Stator copper loss, (e) Rotor copper loss, and (f) Developed torque?144

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Answered: 4-pole,400-V, 50-Hz,1425 rpm,…

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.

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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
Derive the torque equation for a three phase induction motor, with the help of torque speed characteristics curve briefly explain how an induction motor can operate in stable region.
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 single-phase, 120 V, 60 Hz, four-pole, split-phase induction motor has the following standstill impedances:Main winding: Zm =5+j6.25Auxiliary winding: Za =8+j6a) Determine the value of capacitance to be added in series with the auxiliary winding to obtainmaximum starting torque.b) Compare the starting torques and starting current with and without the added capacitance in theauxiliary winding circuit when operated from a 120V, 60Hz supply
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
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
A four-pole, single-phase, 120 V, 60 Hz induction motor gave the following standstill impedances when tested at rated frequency:Main winding : Zm =1.5+j4 ohmsAuxiliary winding : Za =3+j6 ohmsa) Determine the value of external resistance to be inserted in series with the auxiliary winding to obtain maximum starting torque as a resistor split-phase motor.b) Determine the value of the capacitor to be inserted in series with the auxiliary winding to obtain maximum starting torque as a capacitor-start motor.c) Determine the value of the capacitor to be inserted in series with the auxiliary winding to obtain maximum starting torque per ampere of the starting current as a capacitor-start motor.d) Compare the starting torques and starting currents in parts (a), (b), and (c) expressed as per unit of the starting torque without any external element in the auxiliary circuit, when operated at 120V, 60Hz.
A 4-pole induction motor drives a load at 2500 rpm. This is to be accomplished by using an electronic converter to convert 400 Volts DC into a set of 3-phase AC voltages. Find the frequency required for the AC voltages assuming that the slip is 4 percent. The load requires 2 hp. If the DC-to-AC converter has a power efficiency of 88 percent and the motor has a power efficiency of 80 percent, estimate the current taken from the DC source.
18. A single-phase, 120 V, 60 Hz, four-pole, split-phase induction motor has the following standstill impedances: Main winding: Zm =5+j6.25 Auxiliary winding: Za =8+j6 a) Determine the value of capacitance to be added in series with the auxiliary winding to obtain maximum starting torque. b) Compare the starting torques and starting current with and without the added capacitance in the auxiliary winding circuit when operated from a 120V, 60HZ supply.
A 3 – phase induction motor has a 4 – pole, star – connected stator winding. The motorruns on a 50 – Hz supply with 200 V between lines. The rotor resistance and standstillreactance power phase are 0.1 and 0.9 ohm respectively. The ratio of rotor to stator turnsis 0.67. Calculate (a) total torque at 4 % slip, (b) total mechanical power at 4 % slip, (c)maximum torque, (d) speed at maximum torque, (e) maximum m power
A four-pole induction motor drives a load at 2500 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. Find the frequency required for the ac voltages assuming that the slip is 4 percent. The load requires 2 hp. If the dc-to-ac converter has a power efficiency of 88 percent and the motor has a power efficiency of 80 percent, estimate the current taken from the dc source.
1a

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