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A Computer-Aided EducationalTool for Induction MotorsCETIN
GENCER,1 MEHMET GEDIKPINAR2
1Department of Electrical&Electronic Engineering, Tunceli
University, Tunceli 62000, Turkey
2Faculty of Technical Education, Department of
Electronic&Computer Education, Firat University, Elazig 23119,
Turkey
Received 24 November 2009; accepted 18 January 2010
ABSTRACT: The computer-aided educational tools have gained
popularity in the last years with successfulimplementation in many
areas, including in engineering education. These tools are aimed to
help the studentsfor visualization of the concepts and to provide
the graphical feedback during the learning process. This
paperpresents a computer-aided educational tool for induction
motors, which is a part of laboratories in the electricalmachinery
courses. This tool helps to students and educators in subject to
teaching/of the equivalent circuit, andthe vector/phasor diagrams
in induction motors. The tool software was prepared in DELPHI
environment. It hasexible structure which is enable to users to
change motor label values, and to solve equivalent circuit
parametersand winding account. The proposed educational tool was
utilized in laboratories of electric machinery coursesand well
received by students. 2010 Wiley Periodicals, Inc. Comput Appl Eng
Educ; Published online in WileyInterScience
(www.interscience.wiley.com); DOI 10.1002/cae.20418
Keywords: computer-aided educational tool; induction motor;
equivalent circuit; DELPHI
INTRODUCTION
The quality of education which has been given in universities,
espe-cially in faculties of engineering can be increased by using
modernteaching techniques. Computer-aided educational tools are one
ofthe modern teaching techniques and have been increasingly usedby
the students of engineering subjects, such as the electrical,
com-puter, mechanical and civil engineering. Most of the subjects
taughtin these faculties, consist of the theoretical and practical
studies.The quality of education in these theoretical and practical
subjectsis increased by using computer-aided educational tools [14]
andthe topics which are difficult to compute by students, became
morevisual with the aid of some computer programs [57].
Computer-aided teaching process has been increased the interaction
betweenthe student and educator and enhanced the learning processes
ofmany students [8].
Several well-known commercial software packages such
asMatlab-Simulink, Auto-CAD, Mathcad, OrCAD PcPice, RT-LABoffers
many other useful toolboxes for many electrical machinesin
engineering subjects [914]. The direct use of these
softwarepackages is a major advancement in simplifying simulation
proce-dures for many practicing engineers as well as for
undergraduateengineering students [4]. However, some of these
software pack-ages can be expensive and time consumer for both
educators and
Correspondence to C. Gencer ([email protected]). 2010 Wiley
Periodicals, Inc.
students. In addition, some of these packages require code and
alsoassistance for simulation tools [13].
In this paper, a computer-aided educational tool for induc-tion
motor is presented for cost effective education and training.The
results of introducing educational software are now used asa
teaching tool in the laboratories of the electrical
machinerycourses at Firat University, in Turkey. The program is
pre-pared in DELPHI environment and setup files are available
fromweb.firat.edu.tr/cgencer.
Using this software, the equivalent circuit parameters of
athree-phase induction motor can be calculated and
vector/phasordiagrams can be drawn easily. This educational tool
can be suc-cessfully applied to the laboratory of electric
machinery coursesand used by educators for curriculum development
and teaching.
EQUIVALENT CIRCUIT AND VECTOR/PHASORDIAGRAM OF THE INDUCTION
MOTORS
Induction motors are important topics of the electric
machinerycourses. These motors are robust, easily maintained, and
cheap.Most of the books on the electrical machines, presents the
equiv-alent circuit of induction motors in a similar way to that of
atransformer [15]. Generally, the stator and the rotor circuits are
firstpresented separately and few are said about the
electromagneticcoupling when the motor is operating [16].
Thus, the usual explanation relates the equivalent circuit of
aninduction motor at standstill with that of the transformer,
replacing
1
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2 GENCER AND GEDIKPINAR
Figure 1 Equivalent circuit of a conventional induction
motor.
in both cases the actual rotor (actual secondary winding of
thetransformer), by an equivalent rotor (an equivalent
secondarymotor), having the same number of turns per phase,
disposed inthe same way, as those of the stator (the primary
winding) [1622].
The standard equivalent circuit for induction motors is shownin
Figure 1.
All quantities are referred to the stator and represent onphase
[16]. Vs is input voltage per phase, I is stator current perphase,
Rs is stator winding resistance per phase, (ms/2)Xs isstator
leakage reactance per phase, (ms/2)Xr is rotor leakagereactance per
phase referred to stator, Rr is rotor resistance perphase referred
to stator, RFe is the resistance representing the corelosses,
(ms/2)Xsm
(is ir
)is magnetizing reactance, ir is the rotor
current referred to stator per phase ms is number of stator
windingphase, mr is number of rotor phase and s is slip factor. The
rotorcurrent ir refers to the portion of the stator current that
flows tobalance the rotor magneto-motive force (MMF).
Vector/phasor diagrams are important to observe the
relationsbetween current and voltage phasors in different working
condi-tions and to find out their values [21]. These diagrams are
mostlyused to find the currents, the voltage or the parameters. The
vec-tor/phasor diagrams can be drawn by using Equations (1) and
(2).In these equivalences, iFe=0 and is ir = ism
Vs = (Rsis) +(jms
2Xsis
)+(jms
2Xsmism
)(1)
0 =(
Rriss
)+(jmr
2Xri
r
)(jms
2Xsmism
)(2)
Rs, Xs,ms, Xsm, Rr, Xr,mr, s, is0 = ismParameters are usually
known and Vs, ir, is,Qs, Er = Es can
be drawn in the vector/phasor diagrams as follow steps. The
vec-tor/phasor diagram in Figure 3, 20 V = 1 cm and 10 A = 1
cm.
Step 1: is0 current is taken, j(ms/2)Xsm ism = Er = 0BStep 2:
Rr, s, Xr,mr are known from tan r= ((mr/2)Xr)/
(Rr/2) and r is found and the direction of ir is drawn.Step 3:
Er = |j(ms/2)Xsmism| diametric circle is drawn and
the A point is shown.The A point shows that where the ir line
cuts the circle (Fig. 2).The reduced rotor current is found using
ir phasor equation
as in Equation (3).
A0 = Rr
sir (3)
The real rotor current ir is calculated as in Equation (4)
ir = msmr
ir (4)
Step 4: is = 0Q can obtain from is = ir + ism relation.Step 5:
OK = j(ms/2)Xsmism is drawn by taken Es = ErStep 6: OM = Vs can
obtain from Rsis = KL and
j(ms/2)Xsis = LM
Figure 2 Vector/phasor diagram of a three-phase induction
motor.
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COMPUTER-AIDED EDUCATIONAL TOOL 3
Figure 3 Label values window.
Figure 4 Experimental results window.
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4 GENCER AND GEDIKPINAR
Figure 5 Winding calculations window.
Figure 6 Equivalent circuit parameters calculation window.
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COMPUTER-AIDED EDUCATIONAL TOOL 5
Figure 7 The equivalent circuit of per phase of the induction
motor.
Figure 8 Vector/phasor diagram of the induction motor.
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6 GENCER AND GEDIKPINAR
THE OPERATIONAL PROCEDURE OF THEEDUCATIONAL TOOL
The software is developed using Delphi 7.0 visual package
pro-gram and it works in a Windows environment [23]. It is
preparedto help students to improve their knowledge about the
inductionmotors. The program operation can be observed on a PC
monitorand can be modified by choosing appropriate windows. A
mainwindow and other selected window can be seen simultaneously
byclicking desired button on the top of the screen.
MAIN WINDOW
A view of the main program window is shown in Figure 3. Thevalue
input window can be seen by operating the program. Thevalue input
window has three sub-windows. These windows areshown in Figures 35.
The contents of the value input windowchange according to the
chosen sub-windows. Although the usermay start the tool directly by
using default values of the programgiven for a specific parameters
of squirrel-cage induction motor,to start a new calculation should
be entered by the user.
The label values of three-phase induction motor can be seenin
label values window (Fig. 4). The values of locked-rotor and
no-load test experimental results can be seen in experimental
resultswindow (Fig. 5). The users have opportunity to change these
resultsvalues in both windows (Figs. 4 and 5). The winding
calculationwindow can be seen in Figure 6. This window can give
opportunityto user a change whether or not to calculate winding
parameters.
According to the default values, the phase resistance,
phaseimpedance, phase reactance, slip, power input, core losses,
cop-per losses, efficiency, and winding parameters of the
three-phaseinduction motor are estimated by clicking calculations
button inmain window (Fig. 6).
The Equivalent circuit of three-phase induction motor can
bedrawn by clicking circuit button in main window (Fig. 7).
The vector/phasor diagrams of three-phase induction motorcan be
drawn by clicking phasor diagram button in main window(Fig. 8).
THE EVALUATION OF THE EDUCATIONAL TOOL
The proposed educational tool utilized laboratory of
electricmachinery courses at Firat University, Turkey, and has been
wellreceived by our students. The tool is expected to achieve
followingeducational goals. One who uses this tool should be able
to:
Improve his/her knowledge on the induction motor
fundamen-tals.
Save in time while developing his/her knowledge. Interpret and
draw conclusions related to induction motor
parameters and vector/phasor diagrams. To draw of vector/phasor
diagrams as a result more easy.
The results obtained by using the tool and the results
obtainedwithout using the tool were compared. Students response to
the useof the tool was obtained through evaluation sheets. The
feedbackfrom the introduction of the educational tool was very
positive. Theaccuracy is well supported by the fact that the
computed resultsagree closely with the experimental results
[10,11,14,19]. The edu-cators also may develop new ideas and
teaching methods by using
the tool. With this philosophy, it is aimed that the tool is
availablefor everyone who wants to use or try it so that students
may use itin a laboratory of electric machinery or at home.
CONCLUSIONS
In this paper, computer-aided educational tool for the
three-phaseinduction motor is presented for cost-effective
education and train-ing. The tool helps students to improve their
trough understandingon equivalent circuit and vector/phasor diagram
of inductionmotor. It is intended as an aid to teaching and may be
used byeducators for curciculum development. The tool can be
installedon a PC operating in a Windows environment (Windows XP,
Vista,or NT) and freeware. The tool has flexible structure enables
usersto change motor label parameters and to solve winding
account.It can be used as a classroom teaching aid or as a
self-study tooloutside the classroom.
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M. Gedikpinar received the BS degree fromthe Department of
Electrical Education, Facultyof Technical Education, Gazi
University, Ankara,Turkey, in 1981, the MSc degree from Instituteof
Science and Technology, Firat University, in1998, and the PhD
degree from Institute of Sci-ence and Technology, Gazi University,
in 2002,respectively. He is currently teaching in Depart-ment of
Electronic and Computer Education, Fac-ulty of Technical Education,
Firat University. His
research interests include intelligent control, electrical
machines anddesigning, electronics instruments and measurements,
analyzing of circuit.
BIOGRAPHIES
C. Gencer received the BS degree from theDepartment of
Electrical Education, Faculty ofTechnical Education, Gazi
University, Ankara,Turkey, in 1995, the MSc degree from Instituteof
Science and Technology, Firat University, in1999, and the PhD
degree from Institute of Scienceand Technology, Gazi University, in
2005, respec-tively. He is currently teaching in Department
ofElectrical&Electronic Engineering, Tunceli Uni-versity. His
research interests include intelligent
control, electrical machines and drives, educational tools,
engineering tech-nology education, web-based distance learning.