1. A 3-0 motor is designed to run at 5% slip on full-load. If motor draws 6 times the full-load currer at starting at the rated voltage, estimate the ratio of starting torque to the full-load torque. [1.8] (Electrical Engineering Grad, I.E.T.E. Dec. 1986 2. A squirrel-cage induction motor has a short-circuit current of 4 times the full-load value and has full-load slip of 5%. Determine a suitable auto-transformer ratio if the supply line current is not

1. A 3-0 motor is designed to run at 5% slip on full-load. If motor draws 6 times the full-load currer at starting at the rated voltage, estimate the ratio of starting torque to the full-load torque. [1.8] (Electrical Engineering Grad, I.E.T.E. Dec. 1986 2. A squirrel-cage induction motor has a short-circuit current of 4 times the full-load value and has full-load slip of 5%. Determine a suitable auto-transformer ratio if the supply line current is not

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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Similar questions

Torque-speed characteristics for three phase induction motor 4. Discuss the following (rated torque, starting torque, break down torque).
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
B/ Fill in the blanks: TV ezur 1- In a three-phase induction motor iron losses in stator will be..... that in rotor. 2- In three-phase induction motors sometimes copper bars are placed deep in the rotor to........... 3- Blocked rotor test on induction motors is used to find out. R..., ke, X. 4- The maximum torque in an induction motor depends on .............and .....
Q.14. What is slip in an induction motor? Q.15. What is the value of slip at start in an induction motor?
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.
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.
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.
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 three phase induction motor designed for a rated voltage of V1 at 50 Hz is accidentally switched on directly to a voltage of V2 at 60 Hz. Stator impedance of the motor is negligible. Calculate the ratios of currents and torques at starting and maximum torques when V2 = V1. Also find the ratio of V2 to V1 to obtain the same values of starting current and torque at 60 Hz. (Ans: 0.834, 0.695, 0.695, ; 1.2)
What are the various losses in an induction motor? On what factors do they depend? IV. V. List the different types of stray load losses in an induction motor.
Draw the typical speed-torque characteristic of the induction motor and expain it.
Q4) What is the effect in series motor if you assume V = Eb , with low resistance fielding winding ? a) b) The given information about series motor on full – load (with that the flux is proportional to the field current) is a ) takes ( 78A) and runs at (850 r.p.m) , the series winding resistance is (0.04 2) , with diverter in parallel with the field winding is a (0.18 2) and the armature resistance is (0.09 S2). ( 220 V Neglected the iron, friction and windage losses. Determine the efficiency , speed when developing full load torque ,the maximum efficiency .