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Miniproject 1

The document describes a mini-project assignment for an Advanced Electrical Machinery course. The assignment requires students to use Thevenin's equivalent circuit method to calculate the torque of an induction motor. It provides the equivalent circuit diagram of an induction motor and equations for determining maximum torque, slip at maximum torque, and other values. It also gives a sample induction motor problem, and asks students to determine its maximum torque, speed at maximum torque, starting torque, and plot torque-speed curves with the original and doubled rotor resistance using MATLAB.

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98 views4 pages

Miniproject 1

The document describes a mini-project assignment for an Advanced Electrical Machinery course. The assignment requires students to use Thevenin's equivalent circuit method to calculate the torque of an induction motor. It provides the equivalent circuit diagram of an induction motor and equations for determining maximum torque, slip at maximum torque, and other values. It also gives a sample induction motor problem, and asks students to determine its maximum torque, speed at maximum torque, starting torque, and plot torque-speed curves with the original and doubled rotor resistance using MATLAB.

Uploaded by

TERMIN8R Game
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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EPEG 302: ADVANCED ELECTRICAL MACHINERY

MINIPROJECT 1:

USE OF THEVENIN’S EQUIVALENT CIRCUIT TO FIND THE TORQUE OF AN


INDUCTION MOTOR

Released date: 06.12.2019 Submission date: 20.12.2019

Evaluation will be done on individual basis.

The assignment purpose is to show that numerous methods can be implemented to solve a given
induction motor with its equivalent circuit where Thevenin’s equivalent method is one of those to
calculate the torque ofan induction motor.

 Consider an Induction motor with its equivalent circuit referrd to stator as shown in figure 1
below.

Vφ = per phase voltage applied to stator.


I1 = stator current.
I2 = rotor current.
R1 = stator equivalenr resistance per phase.
X1 = stator equivalent reactance per phase.
Xm = magnetizing reactance per phase.
E1 = induced emf in stator.
R2 = rotor equivalenr resistance per phase referred to stator.
X2 = rotor equivalent reactance per phase refrrred to stator.
s = percentage slip.

Figure 1. Per phase equivalent circuit of an induction motor


Figure 2. Thevenin equivalent voltage of induction motor input.

Figure 3. Thevenin equivalent impedance

Figure 4. Thevenin’s equivalent circuit of an induction motor.


Figure 5. Torque speed curve of an IM
Figure 6. Torque speed curve of a wound rotor induction
motor with varying resistance

The value of slip at maximum torque is given as,

The value of maximum torque or pull out torque or breakdown torque is,
1. A 460-V. 25-hp. 60-Hz. four-pole. Y-connected wound-rotor induction motor has the
following impedances in ohms per phase referred to the stator circuit:
Rl = 0.641 0hm
Xl = 1.106 0hm
R2 = 0.3320hm
X2 = 0.464 0hm XM = 26.3 0hm
a. What is the maximum torque of this motor? At what speed and slip does it occur?
b. What is the starting torque of this motor?
c. When the rotor resistance is doubled. What is the speed at which the maximum
torque now occurs? What is the new starting torque of the motor?
[Answer: a. 0.198, 1444 rpm, 299 Nm b.104 Nm, c. 0.396, 1087 rpm, 170 Nm]

Plot the torque-speed characteristics of this motor both with the original rotor resistance
and with the rotor resistance doubled using MATLAB.

Note: To plot the torque slip curve use vary the value of slip can from 0-1 so that corresponding
torque can be obtained. Do not put the value of s = 0 initially as it may lead to division
error.

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