Integration of-virtual-learning-of-induction-machines-for-undergraduates


Abstract—In context of understanding problems faced by
undergraduate students while carrying out laboratory experiments
dealing with high voltages, it was found that most of the students are
hesitant to work directly on machine. The reason is that error in the
circuitry might lead to deterioration of machine and laboratory
instruments. So, it has become inevitable to include modern
pedagogic techniques for undergraduate students, which would help
them to first carry out experiment in virtual system and then to work
on live circuit. Further advantages include that students can try out
their intuitive ideas and perform in virtual environment, hence
leading to new research and innovations. In this paper, virtual
environment used is of MATLAB/Simulink for three-phase induction
machines. The performance analysis of three-phase induction
machine is carried out using virtual environment which includes
Direct Current (DC) Test, No-Load Test, and Block Rotor Test along
with speed torque characteristics for different rotor resistances and
input voltage, respectively. Further, this paper carries out computer
aided teaching of basic Voltage Source Inverter (VSI) drive circuitry.
Hence, this paper gave undergraduates a clearer view of experiments
performed on virtual machine (No-Load test, Block Rotor test and
DC test, respectively). After successful implementation of basic tests,
VSI circuitry is implemented, and related harmonic distortion (THD)
and Fast Fourier Transform (FFT) of current and voltage waveform
are studied.
Keywords—Block rotor test, DC test, no-load test, virtual
environment, VSI.
I. INTRODUCTION
ITH the advent of modern technology, the use of
induction motors has become quite common, and this
increase in the application of induction motor may be credited
to its rugged construction, reliable use, economic
consideration, and low maintenance requirements [4]. Hence,
it becomes need of an hour for an electrical engineer to carry
out performance analysis of such kind of motors. The
performance analyses of induction motors help us to
understand torque-speed characteristics, and performing
harmonic analysis. The harmonic analysis in turn serves as a
tool to reduce noise and vibration losses of an induction
motor. This means that selecting a proper topology of
switching sequence and filters, harmonics can be mitigated,
hence resulting in minimization of losses due to noise and
vibration in induction machine. Keeping all these goals in
mind, the following paper presents computer aided teaching of
three-phase induction machines for undergraduate students
Rajesh Kumar is with the Maharishi Markandeshwar University, Mullana,
133203, Haryana, India (corresponding author, phone: +918398069447; e-
mail: rjesh10391@gmail.com).
Puneet Aggrawal is with the Maharishi Markandeshwar University (phone:
+918059931096; e-mail:puneet241@gmail.com).
using MATLAB/Simulink environment. The role of computer
aided teaching is very crucial for teaching pedagogy, as it
gives engineering students an intuitive insight about what is
happening inside a machine [5], e.g. study of speed torque
characteristics, calculation of stator and rotor resistance,
performing no-load test and block rotor test. Computer aided
teaching is a tool of virtual learning on one side and reduces
human error and computation on the other side [2]. It may
reduce the chances of system damage due to change in system
dynamics. Virtual environment easily detects system dynamics
and produces an error. Hence, a necessary check is provided
before implementing on real time system [6].
II.STATOR AND ROTOR RESISTANCE
The aid of circulating a suitable current and measuring the
voltage drop across terminals resistance of all available
circuits is examined. The test, if taken with motor cold (at
room temperature), provides a check for calculated values or
basis of estimation of efficiency. By feeding the stator and
rotor windings successively under DC voltage [7], the
voltammetric method of resistance calculations until the
nominal intensity gave the following average values. R1 = 4.3
Ω and R2=1.33 Ω, respectively.
Fig. 1 Experimental setup for DC test
A.Stator Resistance Using Simulink
Implementing the DC test for calculation of stator resistance
can be done as shown in Fig. 2 [1]. The asynchronous motor
block in Simulink diagram as shown in Fig. 2 can be modeled
according to the values as shown in Table I.
Instead of voltmeter and ammeter shown in Fig. 1, current
and voltage measurement blocks are used in the Simulink
diagram shown in Fig. 2.
B.Rotor Resistance Using SIMULINK
Using the parameters as shown in Table I, three-phase
induction motor is modeled and following Simulink diagram
is used for calculating rotor resistance of three phase induction
motor.
Integration of Virtual Learning of Induction
Machines for Undergraduates
Rajesh Kumar, Puneet Aggarwal
W
World Academy of Science, Engineering and Technology
International Journal of Electrical, Computer, Energetic, Electronic and Communication Engineering Vol:11, No:5, 2017
464International Scholarly and Scientific Research & Innovation 11(5) 2017 scholar.waset.org/1999.5/10007101
InternationalScienceIndex,ElectricalandComputerEngineeringVol:11,No:5,2017waset.org/Publication/10007101

Fig. 1 Stator resistance calculation using Simulink
Fig. 2 Rotor resistance calculation using Simulink
TABLE I
PARAMETER SPECIFICATIONS
PARAMETER VALUES
Nominal Power(L-L), Voltage
and Frequency
2588.2 VA, 415 V, 50 Hz
Stator(R1,L1) 4.3 Ω, 0.028 H
Rotor(R2,L2) 1.33 Ω, 0.072 H
Core Resistance Rc 562.98 Ω
Mutual Inductance Lm 0.225 H
Inertia, Friction, and Pair of Poles
0.03124 kgm2
, 0.00358
Nms, 4
III. NO-LOAD AND BLOCK ROTOR TEST
No-Load test is one of the most informative tests which
give the core and pulsation losses, friction and windage loss,
magnetizing current, and no-load power factor. Any
mechanical unbalance, noise, faulty connection etc. are
revealed. The stator connection is made to supply normal
frequency and variable voltage; instruments are included to
measure the voltage, input power, and current. After the start,
the motor is run in normal running condition, i.e. short
circuited, with brush gear raised in case of slipping motors
with this equipment. When the motor has run long enough for
its bearing to show distress if faulty, applied voltage is raised
to about 20% over normal voltage, input power and current are
observed. The readings are lower values of voltage down to
that at which the current starts again to rise [7].

Fig. 3 Experimental setup for no-load test
Fig. 4 Experimental setup for block rotor test
Fig. 5 No-load test using Simulink
Block Rotor test is analogous to short-circuit of a
transformer. The rotor is held stationary and short circuited
under its normal running conditions. The test consequently
reveals no mechanical defects, but is of importance furnishing
short circuit current and power factor, enables the current
diagram to be drawn. I2
R losses measured by the test are
necessary for estimation of efficiency by loss summation. The
stator is supplied with low voltage of normal frequency, to
avoid excessive currents. The position at which the rotor is
clamped may affect the current. If so, variations are noted

when the rotor is locked at various positions, and mean
position is found. Alternatively, rotor may be allowed to rotate
very slowly during the progress of test. The voltage is raised
in steps with reading of current and power input, until the
current reaches twice the normal. The readings are taken
quickly to avoid overheating [7].
A.No- Load Test Using Simulink
For performing No-Load test using Simulink environment,
authors have modeled asynchronous machine in SI units
according to parameter values mentioned in Table I. The No-
Load test is performed using Simulink diagram as shown in
Fig. 6 [2].
B.Block Rotor Test Using Simulink
The Block Rotor test using Simulink can be performed by
modeling the asynchronous machine in SI units using the
tabulation of Table I. The Block Rotor test of three-phase
induction motor is carried out by making moment of inertia of
rotor to infinity, i.e. by modifying the inertia and friction
factor to 10,000 kgm2
and 10,000 N-ms, respectively and
using the following simulation diagram as shown in Fig. 7 [2].
Fig. 6 Block rotor test using Simulink
In the Simulink diagram shown in Figs. 6 and 7
respectively, three-phase programmable source is fed with
values of 415 V and 50 Hz, respectively. The motors are
driving DC generators debiting on resistive load of 10 Ω. The
DC generators shown in Fig. 7 are separately excited; along
with armature and field circuit respectively represented by A+,
A- and F+, F- and having an inductor and resistor in series
having electromagnetic force [2].
IV. VSI CONTROLLED INDUCTION MOTOR DRIVE
In AC grid connected drives, a common diode bridge
rectifier which would provide a pulsed DC voltage from the
mains is required. Here, the basic circuit might look simple
but problem of concern here is switching these devices
accurately. PWM inverters make it possible to control both
frequency and magnitude of voltage and current applied to a
motor. These inverter-powered motor drives are more variable
and offer in a wide range better efficiency and higher
performance as compared to fixed frequency motor drives [8].
PWM inverter delivers energy to the AC motors and is
controlled by applying PWM signals to the gates of power
MOSFET switches at different times to produce desired
output. Depending on the type of load and type of speed,
different methods are adopted for speed control of motors. To
perform stepless control for above and below the rated speed
with high torque and for eliminating harmonics, the most
suitable control is PWM inverter fed induction motor control
[8]. The block diagram of VSI fed Induction Motor is shown
in Fig. 8 [3].
Fig. 7 Block diagram using Simulink
A.VSI Fed Induction Motor Using Simulink
The PWM inverter has to generate a nearly sinusoidal
current, which can control the voltage and current with 120-
degree phase difference in each phase. The circuit of six-
switch three-phase inverter is shown in Fig. 9. In three-phase
voltage source fed inverter drive system, an uncontrolled
diode bridge rectifier is used to convert AC into DC. PWM
inverter is used to convert DC into variable voltage variable
frequency AC. And this is supplied to the motor gate pulses
for three-phase inverter as shown in Fig. 10 [3].

Fig. 8 VSI fed induction motor drive
Fig. 9 Input pulses applied at gate
V.RESULTS AND CONCLUSIONS
A.DC Test and No-Load Test
After successful implementation of DC test using Simulink
for calculation of stator and rotor resistances respectively, the
following results are yielded: Stator Resistance (R1) = 1.33 Ω
and Rotor Resistance (R2) = 4.26 Ω. Further, No-Load test
was carried by varying the input voltage and then tabulating
corresponding obtained parameters as shown in Table II.
The value of Pcore is calculated by subtracting Pmec from
Pcore+ Pmec , Pmec can be obtained by using MATLAB
commands Polyfit, Linspace, and Polyval. These commands
are used to obtain the best line passing through maximum
number of points. The intersection of these curves with y-axis
gives mechanical loss which is equal to 10.22 W [2]. This is
shown in Fig. 11. For different values of voltage, variation of
torque with respect to slip speed is observed as shown in Fig.
12.
TABLE II
RESULTS OF VIRTUAL NO-LOAD TEST
Uo(V) Io(A) Po(W) PSLC(W) Pcore+Pmec(W) Pcore(W)
415 3.045 444.2 35.4 408.8 398.57
380 2.577 377.2 25.36 351.9 341.67
300 2.214 242.3 18.73 223.6 213.37
280 1.986 211.4 15.06 196.3 186.07
260 1.899 175.5 13.77 161.7 151.47

Fig. 10 Separation of core and mechanical loss
Fig. 11 Torque vs slip for different voltages
As it can be observed from Fig. 12 torque is directly
proportional to the voltage level, as the voltage levels fall
down maximum torque also falls down. It can also be
observed that, for certain increase in slip speed, the torque
increases and then gradually starts decreasing, this is
inevitable as slip operation of motoring, braking, and
regeneration follows.
Now the variations of torque slip characteristics for
different rotor resistances can be observed in Fig. 13. The
torque speed characteristics for operational voltage and
resistance can be shown in Fig. 14.
B.VSI Fed Induction Motor Drive
After implementing the simulation of VSI fed induction
motor drives, the following results are obtained. The phase
current waveforms are shown in Fig. 15.
The output phase voltages so obtained are shown in Fig. 16.
The THD analysis of VSI fed induction motor drive was
done for voltage and current waveforms respectively which
are shown in Fig. 17 and Fig. 18, respectively.
From Figs. 17 and 18, it can be observed that THD for
phase voltage was found to be about 34.38%, and that phase
current was found to be about 8.75%.
Fig. 12 Torque speed curves for different resistance
Fig. 13 Torque slip for operational voltage
C.Conclusions
The simulation shown here is an attempt to make teaching
more interactive by making students to learn virtual
environment of machines and implementing them. The further
advantages are virtual environment which serves as a best tool
for students who are hesitant to work directly on machine, so
simulation tool will provide a check for students whether their
design is proper and they can proceed to carry out respective
tests. As in electrical engineering we deal with high voltages a
minor error in the live circuit may lead t chaos. Hence causing
economical and functional damage. Virtual environment also
boost up innovations as here we get an open source to try our
institutions with proper logic and hence observe the relation
with reality without much of financial stress on an individual.
Hence authors here propose to include these simulation tests in
to undergraduate courses to boost up their learning practices.

Fig. 14 Phase current waveforms of VSI
Fig. 15 Output phase voltages of VSI

Fig. 16 FFT analysis of phase voltage
Fig. 17 FFT analysis of phase current
REFERENCES
[1] M. G. Say “The Performance and Design of Alternating Current
Machines”.
[2] Amar Bentounsi, Hind Djeghloud, Hocine Benalla, Tahar Birem, and
Hamza Amiar “Computer Aided Teaching Using MATLAB/Simulink
for Enhancing IM Course With Laboratory Tests,” IEEE Transaction on
Education, vol.54. August 2011.
[3] Dong-Choon Lee, and Young-Sin Kim “Control of Single Phase to
Three Phase AC/DC/AC PWM Converters for Induction Motor Drives,”
IEEE Transaction on Industrial Electronics. Vol. 54. No.2 April 2007.
[4] “Induction Motors”, electricmotors.machinedesign.com. Penton Media,
Inc. Archieved from original on 2007-11-16.
[5] S. Ayasun and C. O. Nwankpa, “Induction Motor Test Using
MATLAB/Simulink and their integratiion into undergraduate electric
machinery courses.” IEEE Trans. Educ., vol. 44, no. 2, pp. 165-169,
May 2001.
[6] “MATLAB Documentation”. Mathsworks. Retrieved 14th
Aug 2013.
[7] Y. Yanawati, I. Daut, S. Nor Shafiquin, I. Pungut, M. N. Syatirah, N.
Gomesh, A. R. Siti Rafidah, N. Haider “Efficiency Increment on
0.35mm and 0.50 mm Thickness of Non-Oriented Steel Sheets for 0.5Hp
Motor”, International Journal of Materials Engineering. FEB 2012.
[8] Atif Iqbal, Adoum Lamine, Imitiaz Ashraf, “MATLAB/SIMULINK
Model of Space Vector PWM for Three-Phase Voltage Source Inverter”,
IEEE Conference on Universties Power Engineering, June 2006.

Rajesh Kumar born in Kural, Bhiwani, Haryana, India on
10th
March 1992. He is currently pursuing Masters in
Technology on Electrical Engineering, Maharishi
Markandeshwar University, Mullana, Haryana, India He
completed his B. Tech on 2014 from National Institute of
Technology Goa, Ponda, Goa, India.
He did training on “Embedded Systems” from International Institute of
Information Technology, Pune. Mr. Kumar was a student Member of IEEE.
Mr. Kumar was Editor-In-Chief of The Electrical Student Luminous
Association (TESLA), National Institute of Technology Goa. He was Campus
Ambassador of Innovians Technology Greater Noida and organized National
Level Workshop on “Industrial Automation”. His areas of interest include
Control System, Power systems, Renewable energy, Power Electronics and
Drives.
Puneet Aggrawal born in Ambala Cantt., Haryana, India on
24th
November 1981. He is currently working as an A.P. in
Electrical Department, Maharishi Markandeshwar
Engineering College, Mullana, India. He completed his
Bachelor of Technology and Masters (M. Tech) in the years
2003 and 2010 respectively. His area of interest includes
Power Electronics and Drives, Networks, Operation
Research, and Application to Power Electronics and Power Systems.

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