A 75 kW, 440 V, Y-connected ,3-phase, 6-pole, 50 Hz wound rotor induction motor has a full load slip of 0.04 and the slip at maximum torque of 0.2 when operating at rated voltage and frequency with rotor winding short circuited at the slip rings. Take X1=X2= 0.5 0 /ph ,and assume the stator resistance to be negligible. Find: maximum torque ,and starting torque? If the rotor resistance is now doubled by adding an external series resistance, determine: maximum torque ?

A 75 kW, 440 V, Y-connected ,3-phase, 6-pole, 50 Hz wound rotor induction motor has a full load slip of 0.04 and the slip at maximum torque of 0.2 when operating at rated voltage and frequency with rotor winding short circuited at the slip rings. Take X1=X2= 0.5 0 /ph ,and assume the stator resistance to be negligible. Find: maximum torque ,and starting torque? If the rotor resistance is now doubled by adding an external series resistance, determine: maximum torque ?

Delmar's Standard Textbook Of Electricity

7th Edition

ISBN:9781337900348

Author:Stephen L. Herman

Publisher:Stephen L. Herman

Chapter35: Harmonics 916

Section: Chapter Questions

Problem 3RQ: Would a positive-rotating harmonic or a negative-rotating harmonic be more harmful to an induction...

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Would a positive-rotating harmonic or a negative-rotating harmonic be more harmful to an induction motor? Explain your answer.
1. 2. 4. 4. •.. .... ..... .... E.g. • 2. A 3 phase, 460 V, 10hp, 60 Hz, four-pole induction machine delivers rated output power at a slip of 0.05. determine the a. Synchronous speed and motor speed b. speed of the rotating air gad field c. frequency of the rotor circuit d. Slip in rpm e. Speed of the rotor field relative to the i. rotor structure ii. Stator structure iii Stator rotating field f. haft torque of this motor at the rated load? ... .... Equivalent Circuit • The induction motor consists of a two magnetically connected systems: Stator and rotor • This is similar to a transformer that also has two magnetically connected systems: primary and secondary windings. • The induction motor is similar to the transformer with the excention that its secondarv windings are free to.
1. Explain the term air-gap power or power developed in the rotor and shaft power. How these terms are related to each other?2. Derive an expression for the rotor copper loss in terms of slip and input to the rotor?3. What are the various losses in an induction motor? On what factors do they depend?4. List the different types of stray load losses in an induction motor.
1.5 A 10‐pole, 380 ‐V, 50 Hz, D‐connected three‐phase induction motor is rotating a quarry belt conveyor. The machine has the following parameters, referred to the stator, on a per phase basis: Stator Parameters Winding Resistance................0.19 Ω ......... Winding Reactance.................1.12 Ω.......... Rotor Parameters Winding Resistance......................0.29 Ω Winding Reactance.....................1.12 Ω Magnetising Reactance................................16.8 Ω Equivalent Core‐loss Resistance....................900 Ω. The friction and windage losses are 320 W. When the motor runs at its rated slip of 2.6 %. Determine: 1.5.1 The stator current. 1.5.2 Estimate the Output torque of the motor under the rated conditions. 1.5.3 The Motor…
Q / What is the benefit, purpose and conclusions of making single-phase induction motors ..?
An 8 pole, 50 Hz slip ring induction motor runs at a slip of 2.67% on full load. The rotor resistance per phase of the winding is 0.2 ohm. What external resistance per phase must be added in the rotor circuit so that the motor now runs ate a slip of 17.33% such that the torque remains same in both the cases. (Ans: 1.1 ohm)
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 .....
An 3-phase induction motor(IM) has full load slip = 0.5%. If the rotor circuit resistance is increased so that R2new =2R2old, then the slip at which the motor develops the same full load torque is=.. * ......
I.What is the effect of load on the efficiency of an induction motor? II. Explain the term air-gap power or power developed in the rotor and shaft power. How these terms are related to each other? III. Derive an expression for the rotor copper loss in terms of slip and input to the rotor? IV. What are the various losses in an induction motor? On what factors do they depend? V. List the different types of stray load losses in an induction motor.
Example -4. A three-phase. 60-Hz induction motor runs at 890 r/min at no load and at 840 r/min at full load. (a) How many poles does this motor have? (b) What is the slip at rated load? (c) What is the speed at one-quarter of the rated load? (d) What is the rotor's electrical frequency at one-quarter of the rated load?
1- To control the speed of an induction motor, the supply frequency is reduced by 10%. For the same magnetizing current to remain constant, the supply voltage must be....... a) Reduced by 10%, b) Reduced by 20%, c) Increased by 10%, d) Increased by 20% 2. When maximum starting torqua ic ohtoinod
What is the relationship between slip s) and load (Pa) in an induction motor? Please explain.