8. The resistance and reactance per phase of the rotor of a 3-phase induction motor are 0.6 ohm and 5 ohms respectively. The induction motor has a star-connected rotor and when the stator is connected to a supply of normal voltage, the induced e.m.f. between the slip rings at standstill is 80 V. Calculate the current in each phase and the power factor at starting when (i) the slip-rings are shorted, (ii) slip-rings are connected to a star-connected resistance of 4 ohm per phase.

8. The resistance and reactance per phase of the rotor of a 3-phase induction motor are 0.6 ohm and 5 ohms respectively. The induction motor has a star-connected rotor and when the stator is connected to a supply of normal voltage, the induced e.m.f. between the slip rings at standstill is 80 V. Calculate the current in each phase and the power factor at starting when (i) the slip-rings are shorted, (ii) slip-rings are connected to a star-connected resistance of 4 ohm per phase.

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

Related questions

Q: Question 6 What is an ohm? O A measure of charge O A measure of EMF O A measure of electron flow O A…

A: In this question we need to choose a correct option

Q: A 33 kV, 50 Hz. 3-phase underground cable, 6 km long uses three single core cables. Each of the…

A: We have been given an 33 KV 50 Hz 3-phase underground cable as, Length (l) = 6 Km = 6000 m Line…

Q: Please answer in typing format solution

A: Principles of Power Quality in Electrical SystemsPower quality is crucial in electrical systems,…

Q: Shown in the figure, ahydroelectric plant has two devices, a turbine and a generator. If the…

A: Given Whole plat efficiency ηp = 80% = 0.8 generator efficiency ηg=93 % = 0.93 Asked to find…

Q: times

A: effective voltage =peak voltage/(√2) So by simplifying we get Effective voltage equals to 0.707…

Q: 9.3 A person is working on a steel structure while standing on the ground. An accident occurred…

Q: a) Inductors_________ oppose a change of current. a) always b) sometimes c) never d) all of the…

A: a) Inductors always oppose a change of current. The magnetic flux produced by a current, I flowing…

Q: Hot-spot effect in PV strings is advantage to PV efficiency. Select one: a. True. b. False.

A: Hot-spot effect in PV strings

Q: Consider the periodic message signal x(t) shown below, where the period is 3 sec: x(t) ... 2 5 1 4 t…

A: Periodic signal is one that repeats the sequence of values exactly after a certain amount of time.…

Q: If 3-phase transfomer configuration in figure in has the givens as listed below: E-line on high…

A: Since you have posted a question with multiple sub-parts, we will solve first three sub-parts for…

Concept explainers

KVL and KCL

KVL stands for Kirchhoff voltage law. KVL states that the total voltage drops around the loop in any closed electric circuit is equal to the sum of total voltage drop in the same closed loop.

Sign Convention

Science and technology incorporate some ideas and techniques of their own to understand a system skilfully and easily. These techniques are called conventions. For example: Sign conventions of mirrors are used to understand the phenomenon of reflection and refraction in an easier way.

Question

Answer 8

7.
The rotor resistances per phase of a 4-pole, 50-Hz, 3-phase induction motor are 0.024 ohm and 0.12
ohm respectively. Find the speed at maximum torque. Also find the value of the additional rotor
resistance per phase required to develop 80% of maximum torque at starting.
[1200 r.p.m. 0.036 Q] (Elect. Machines, A.M.I.E. Sec. B, 1990)
8.
The resistance and reactance per phase of the rotor of a 3-phase induction motor are 0.6 ohm and
5 ohms respectively. The induction motor has a star-connected rotor and when the stator is
connected to a supply of normal voltage, the induced e.m.f. between the slip rings at standstill is 80
V. Calculate the current in each phase and the power factor at starting when (i) the slip-rings are
shorted, (ii) slip-rings are connected to a star-connected resistance of 4 ohm per phase.
[(i) 9.17 amp, 0.1194 lag (i) 6.8 amp, 0.6765 lag||Rajiv Gandhi Technical University, Bhopal, 2000]

Expert Solution

This question has been solved!

Explore an expertly crafted, step-by-step solution for a thorough understanding of key concepts.

SEE SOLUTION Check out a sample Q&A here

Step 1

VIEW

Step 2

VIEW

Step by step

Solved in 2 steps

SEE SOLUTION Check out a sample Q&A here

Knowledge Booster

Learn more about

Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, electrical-engineering and related others by exploring similar questions and additional content below.

Similar questions

Would a positive-rotating harmonic or a negative-rotating harmonic be more harmful to an induction motor? Explain your answer.
200 +21. If maximum torque of an induction motor is kg-m at a slip of 12%, the torque at 6% slip would be...... kg-m. 1 (a) 100 (b) 160 (c) 50 (d) 40 B, 1993)
. Explain how the pulsating mmf of a single-phase induction motor may be considered equivalent to two oppositely-rotating fields. Develop an expression for the torque of the motor. A 125-W, 4-pole, 110-V, 50-Hz single-phase induction motor has the no-load rotational loss of 25 watts and total rotor copper loss at rated load of 25 watts at a slip of 0.06. At a slip s = 0.06, what is the power input to the machine ?
The resistance and reactance per phase of the rotor of a 3-phase induction motor are 0.6 ohm and 5 ohms respectively. The induction motor has a star-connected rotor and when the stator is connected to a supply of normal voltage, the induced e.m.f. between the slip rings at standstill is 80 V. Calculate the current in each phase and the power factor at starting when (i) the slip-rings are shorted, (ii) slip-rings are connected to a star-connected resistance of 4 ohm per phase.
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.
The amount of torque developed by a 3-phase squirrel-cage induction motor from no-load to rated-load is proportional to the amount of current flow through the rotor conductors. a) directly b) inversely If n
Three Phase Induction Mot... The relative speed of stator magnetic field with respect to rotor of a 30 induction motor with 4 pole, 50 Hz frequency. If the slip is 0.05.
7. The total rotational losses of an induction motor are a combination of ------- A) Friction losses B) Windage losses. D) Stray losses. C) Core losses. 8. The developed mechanical power can be calculated using the equation of- A) PAG - PRCL. B) PAG w sync C) (1-s) PAG. D) 3 E2Gc. 9. For an induction motor, if the synchronous speed is 1800 r/m, and the rotor speed 180rad/sec, then the slip will be: A) 5.5% C) 6% B) 4.5% D) 4% 10. The power losses in the stator part of the induction motor are B) Core losses D) Friction and windage losses A) Stator copper losses C) Air-gap losses
B) fill in the blanks : 1) When a synchronous motor is running at synchronous speed, the damper winding Produces...... torque. 2)The maximum power in cylindrical and salient pole machines is obtained respectively at load angles of...... 3)The primary winding of a 220/6 V, 50 Hz transformer is energized from 110 V, 60 Hz supply. The secondary output voltage will be.... 4)The relative speed between the magnetic fields of stator and rotor under steady state operation is zero for a.....machines. 6 G
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) Explain how the power flows in an induction machine, where losses occur and how they can be calculated, along with typical percentage values that you would expect to observe. b) Briefly explain the differences between synchronous motors and induction motors. You should describe the construction and operation of each motor, and how power is distributed to the rotor. c) A 415V star-connected synchronous induction motor has a stator resistance of 0.5ohms per phase and a combined rotor and exciter resistance of 2 ohms. On no-load and with unity power factor, the motor draws a line current of 5 amperes.If the excitation current is 10 amperes under no-load unity power factor conditions and 20 amperes under load condition, what is the efficiency of the motor when the line supply current is 100 amperes?
In an Induction motor, if the load is decreased, what happens to the power factor?Select one:a. Power factor increasesb. Power factor becomes instablec. Power factor has no relation with loadd. Power factor decreases