Faculty of Engineering Ain Shams University – ICHEP
Energy and Renewable Energy
EPM 222
Electrical Machines (2)
Induction Motor Simulation on
MATLAB/Simulink
Submitted by
Ziad Ahmed Oraby
20P3700
Submitted to
Dr. Ahmed Mohy
Eng. Amr Saleh
May 2023
INTRODUTION
A plant consisting of a resistive and motor load is fed at 2400 V from a distribution 25 kV network
through a 6 MVA 25/2.4 kV Wye-Delta transformer and from an emergency synchronous
generator/diesel engine unit. The 25 kV network is modeled by a R-L equivalent source with a shortcircuit level of 1000 MVA and with a 5 MW load. A three-phase to ground fault occurs on the 25 kV
system, causing opening of the 25kV circuit breaker.
Required: To examine the system performance of the following cases: (Run the simulations for 30
seconds)
Case (1): The system runs normally as depicted in the figure.
Case (2): The resistive load power is reduced by 50%.
Case (3): The resistive load power is increased by 50%.
Case (4): The generator reference speed is varied by ±3%.
Case (5): The generator reference voltage is varied by ±5%.
I.
Tabulate the Induction motor parameters values (resistance, inductance, total inertia, friction
torques coefficient)
II.
For the cases above, run the Simulink file and after reaching a steady-state condition,
determine the following:
1. Plot against time: the induction motor torque, speed, currents, terminal voltage, generator
mechanical power, generator output electrical power.
2. Tabulate the steady state values of the above measurements.
3. Comment on the motor speed and torque variation.
2
I.
Tabulate the Induction motor parameters values (resistance,
inductance, total inertia, friction torques coefficient)
Figure 1 : Motor Parameters
Stator
Resistance
(ohm)
Rotor
Resistance
(Ohm)
Stator
Inductance
(H)
Rotor
Inductance
(H)
Mutual
Inductance
(H)
Total
Inertia
(kg.m^2)
Friction
Torque
Coefficient
0.029
0.022
0.226/377
0.226/377
13.04/377
63.87
0
3
CASE 1 : The System Runs Normally
Case 1 model
1. Plot against time: the induction motor torque, speed, currents, terminal voltage, generator
mechanical power, generator output electrical power.
2. Comment on the motor speed and torque variation.
Currents
4
Generator mechanical power (second curve)
Genrator output Power
5
Motor Speed
-
The Motor speed increased at starting then reached steady state value after about 3
seconds.
Motor terminal voltage
6
Motor Torque
-
The motor torque fluctuated at starting due to the fault but then reached steady state value
after nearly 1 or 2 seconds.
3. Tabulate the steady state values of the above measurements.
We can get the steady state values from the graphs or from display blocks.
Motor Torque
Speed (RPM)
(N.m)
Generator output
Generator
power (p.u)
mechanical power
(p.u)
7965
1789
0.8155
7
0.8159
CASE 2 : The resistive load power is reduced by 50%
Case 2 model
-
To reduce the resistive load by 50%, We used two circuit breakers and two resistive loads (
1MW , 0.5 MW ), so that at the beginning The 1 MW load is connected and after 15 seconds,
this load is disconnected using the cricuit breaker and the 0.5 MW load is connected .
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1. Plot against time: the induction motor torque, speed, currents, terminal voltage, generator
mechanical power, generator output electrical power.
2. Comment on the motor speed and torque variation.
Currents and Motor Speed at the beginning
Generator mech Power
9
-
After 15 seconds , The generator input mech power decreased , beacause when the resistive
load decreased, the current drawn by the load decreased, so the output electrical power
decreased.
Generator Output power
Motor Currents and Speed
-
The motor Speed increased just after switching but then returned to the original speed at
steady state.
10
Terminal voltage
Motor Torque
-
The Torque value remained constant after switching but it is lower than the torque value in
Case 1.
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3. Tabulate the steady state values of the above measurements.
Motor Torque
Motor Speed
Generator output
Generator
(N.m)
(RPM)
power (p.u)
mechanical power
(p.u)
7958
1789
0.6548
12
0.6556
CASE 3 : The Resistive load Power is Increased By 50 %
Case 3 model
-
The same model as Case 2 , but we used a 1.5 MW load instead of the 0.5 MW load.
13
1. Plot against time: the induction motor torque, speed, currents, terminal voltage, generator
mechanical power, generator output electrical power.
2. Comment on the motor speed and torque variation.
Currents and Speed
14
-
The motor Speed decreased just after switching but then returned to the original speed at
steady state.
-
After 15 seconds , The generator input mech power increased , beacause when the resistive
load increased, the current drawn by the load increased, so the output electrical power
increased.
Generator mech power
Generator output power
15
Motor Terminal voltage
-
Terminal Voltage remained constant.
Torque
-
The Torque value remained constant after switching but it is higher than the torque value in
Case 1.
16
3. Tabulate the steady state values of the above measurements.
Motor Torque
Motor Speed
Generator output
Generator
(N.m)
(RPM)
power (p.u)
mechanical power
(p.u)
7970
1789
0.9698
17
0.9745
CASE 4 : The generator reference speed is varied by ±3%
Part 1 : The generator reference speed is increased by 3%
We used step block instead of constant block to increase the generator reference speed after 15
seconds.
1. Plot against time: the induction motor torque, speed, currents, terminal voltage, generator
mechanical power, generator output electrical power.
2. Comment on the motor speed and torque variation.
Currents
18
Currents and motor speed
The motor speed increased when the generator reference speed increased, because the diesel
engine governor controls the speed of the generator by controlling the input fuel (mechanical power)
to the prime mover of the generator and it does that by measuring the generator synchronus speed
and comparing it with the reference speed and increases input mechanical power until both speeds
are equal.
So When the generator speed increased at constant load, the generator output current increased ,
so the motor stator currrents increased so the speed of rotating field cutting the rotor increased
causing the motor speed to increase at constant load torque.
19
Generator mechanical power
Generator output power
20
Terminal Voltage
-
Motor Terminal Voltage remained constant.
Torque
-
Torque value remained constant .
21
3. Tabulate the steady state values of the above measurements.
Motor Torque
Motor Speed
Generator output
Generator
(N.m)
(RPM)
power (p.u)
mechanical power
(p.u)
7967
1842
0.8273
22
0.8306
Part 2 : The generator reference speed is decreased by 3%
We used step block instead of constant block to decrease the generator reference speed after 15
seconds.
1. Plot against time: the induction motor torque, speed, currents, terminal voltage, generator
mechanical power, generator output electrical power.
2. Comment on the motor speed and torque variation.
Currents
23
Currents and motor speed
The motor speed decreased when the generator reference speed decreased, because the diesel
engine governor controls the speed of the generator by controlling the input fuel (mechanical power)
to the prime mover of the generator and it does that by measuring the generator synchronus speed
and comparing it with the reference speed and decreases input mechanical power until both speeds
are equal.
So When the generator speed decreased at constant load, the generator output current decreased ,
so the motor stator currrents decreased so the speed of rotating field cutting the rotor decreased
causing the motor speed to decrease at constant load torque.
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Generator mechanical power
Generator output power
25
Terminal Voltage
-
Motor Terminal Voltage remained constant.
Torque
-
Torque value remained constant .
26
3. Tabulate the steady state values of the above measurements.
Motor Torque
Motor Speed
Generator output
Generator
(N.m)
(RPM)
power (p.u)
mechanical power
(p.u)
7967
1736
0.8273
27
0.7978
CASE 5 : The generator reference Voltage is varied by ±5%
Part 1 : The generator reference voltage is increased by 5%
We used step block instead of constant block to increase the generator reference voltage after 15
seconds.
1. Plot against time: the induction motor torque, speed, currents, terminal voltage, generator
mechanical power, generator output electrical power.
2. Comment on the motor speed and torque variation.
Currents
28
Motor Speed
The excitation block controls the field voltage of the synchronus generator by measuring the output
terminal voltage of the generator and comparing it with the reference voltage, so when the reference
voltage is increased after 15 seconds, the field voltage of the generator increases until the output
terminal voltage equals the desired reference voltage .
When the generator terminal voltage increases , the generator output power increases, the motor
currents increase , and its speed increases.
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Motor terminal voltage
The motor terminal voltage increased after 15 seconds.
Generator mech power
The generator mech power increased slightly after 15 seconds.
30
Generator output power
Torque
Motor Torque remained constant.
31
3. Tabulate the steady state values of the above measurements.
Motor Torque
Motor Speed
Generator output
Generator
(N.m)
(RPM)
power (p.u)
mechanical power
(p.u)
7956
1790
0.8484
32
0.8491
Part 2 : The generator reference voltage is decreased by 5%
We used step block instead of constant block to decrease the generator reference voltage after 15
seconds.
1. Plot against time: the induction motor torque, speed, currents, terminal voltage, generator
mechanical power, generator output electrical power.
2. Comment on the motor speed and torque variation.
Currents
33
Motor Speed
The excitation block controls the field voltage of the synchronus generator by measuring the output
terminal voltage of the generator and comparing it with the reference voltage, so when the reference
voltage is decreased after 15 seconds, the field voltage of the generator decreases until the output
terminal voltage equals the desired reference voltage .
When the generator terminal voltage decreases , the generator output power decreases, the motor
currents increase , and its speed increases.
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Motor terminal voltage
The motor terminal voltage decreased after 15 seconds.
Generator mech power
The generator mech power decreased slightly after 15 seconds.
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Generator output power
Torque
Motor Torque remained constant.
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3. Tabulate the steady state values of the above measurements.
Motor Torque
Motor Speed
Generator output
Generator
(N.m)
(RPM)
power (p.u)
mechanical power
(p.u)
7954
1788
0.7839
0.7843
Drive Link for simulation files:
https://drive.google.com/drive/u/0/folders/1_J5ejPC_EmJfeaQ-ijYFAuF8OeE3lAHh
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