Virtual Laboratory for Performing Tests on a Single

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Virtual Laboratory for Performing Tests on a SinglePhase Power Transformer a

b

b

Srimanti Roychoudhury , Anish Deb , Gautam Sarkar & Jitendranath Bera

b

a

Department of Electrical Engineering, Budge Budge Institute of Technology, Nischintapur, Budge Budge, Kolkata-700137, India b

Department of Applied Physics, University of Calcutta, Kolkata-700009, India Published online: 07 Aug 2014.

To cite this article: Srimanti Roychoudhury, Anish Deb, Gautam Sarkar & Jitendranath Bera (2014) Virtual Laboratory for Performing Tests on a Single-Phase Power Transformer, IETE Journal of Education, 55:1, 11-25, DOI: 10.1080/09747338.2014.921399 To link to this article: http://dx.doi.org/10.1080/09747338.2014.921399

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Virtual Laboratory for Performing Tests on a Single-Phase Power Transformer Srimanti Roychoudhury1, Anish Deb2, Gautam Sarkar2 and Jitendranath Bera2 1

Department of Electrical Engineering, Budge Budge Institute of Technology, Nischintapur, Budge Budge, Kolkata-700137, India, 2 Department of Applied Physics, University of Calcutta, Kolkata-700009, India

Downloaded by [University of Calcutta ] at 22:59 10 August 2014

ABSTRACT This paper presents a virtual laboratory for testing a single-phase power transformer using MATLAB Simulink environment. The models presented herein replicate the actual tests like no-load test, short-circuit test, load test, and short heat run test successfully well within tolerable accuracy. The rating of the transformer is taken to be 2 kVA, 230/115 V, 50 Hz which is a typical rating for transformers usually employed for practical classes in the Electrical Machine Laboratory for undergraduate courses. This model is attractive to students and they are able to gain insights into operational aspects of a single-phase power transformer. This model, in whole or part, may also be used as final year projects of engineering undergraduate students. Keywords: Single-phase transformer, Simulation, Virtual tests, Virtual laboratory.

1.

INTRODUCTION

In the undergraduate level study on electrical engineering, the transformer [1,2] is a one of the most important electrical machines. In electrical machine laboratory the students perform some basic experiments with single-phase transformer. These experiments include open-circuit test, short-circuit test, load test, and short heat run test [3,4]. In the present work, all of the above-mentioned tests are replicated via MATLAB Simulink [5] without the support of any hardware what so ever. From our experience as educators, we can assert that such simulated tests will provide better as well as detailed insight into the understanding of transformer operation under different conditions. In actual laboratory tests of a transformer, the students are required to draw a few characteristics and obtain some results related to transformer operation. With the presented Simulink model, the students can familiarize themselves with different characteristics for transformer operation and can easily compute any required data, e.g. efficiency, regulation, and maximum temperature rise. After performing the “virtual” tests, students can proceed to perform actual tests with a better insight. The transformer under study has the following specifications: 2 kVA, 230/115 V, single-phase, 50 Hz power transformer.

IETE JOURNAL OF EDUCATION | VOL 55 | NO 1 | JANJUN 2014

The MATLAB Simulink model of transformer was attempted by Ayasun and Nwankpa [6] wherein they have worked with the “linear transformer” model available in Simulink which works with a linear BH curve. Moreover, they could not draw different characteristics like we obtain in hardwarebased laboratory tests. They have used a single set of readings each for the no-load test and the shortcircuit test. These shortfalls are properly taken care of in the presented MATLAB Simulink model.

2.

THE TRANSFORMER MODEL

In the Simulink environment we have two types of transformer models: the linear transformer and the saturable transformer. These models have the symbols shown in Figure 1. For the “linear transformer” model, the magnetization curve is linear, and hence, saturation effects, as in practical transformers, cannot be implemented using this model. However, in the model of “saturable transformer“, we use the magnetization characteristic at our will, thus enabling us to realize the magnetization curve compatible to the transformer be used in practice in the laboratory. This is the main reason for selecting the “saturable transformer” model in our work.

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Roychoudhury S: Virtual Laboratory for Performing Tests on a Single-Phase Power Transformer

Figure 1: Transformer models available in MATLAB Simulink.


3.

USING THE VARIABLE AC VOLTAGE SOURCE

In the open-circuit and short-circuit tests, we need a variable AC voltage source for providing input to the transformer. This is because, for all the characteristics to be drawn from these two tests the independent variable is either the primary voltage or the primary current. This variable voltage source should change its magnitude gradually from zero with time with supply frequency remaining constant. In the case of open-circuit test, the final value of the input voltage should be the rated voltage, while for short-circuit test the input voltage is increased until the rated currents flow in the primary and secondary of the transformer. This subsystem forming the variable AC voltage source is built in the following way. In MATLAB, there are mainly two types of sinusoidal voltage sources: one is (1) Sine Wave (Simulink address: Simulink ! Sources ! Sine Wave) and the other is (2) AC Voltage Source (Simulink address: SimPowerSystem ! Electrical Sources ! AC Voltage Source). Referring to Figure 2, if we choose the first block we cannot build a variable AC voltage source, because it turns out a voltage with respect to time only and cannot represent a voltage as a phasor. Since a transformer requires as input a voltage phasor, in SimPowerSystem environment, the controlled voltage source model cannot automatically convert the time-domain signal into its equivalent phasor signal. Figure 3 represents such a non-functioning system built with sine wave blocks. Figure 3: (a) “Variable AC voltage source” providing input to the transformer model and (b) “subsystem1” made by sine wave blocks.

Figure 2: Two sinusoidal voltage source models available in MATLAB Simulink.

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Hence, the variable AC voltage source model was built using the second block shown in Figure 2. The final model of the input voltage using the AC voltage source model of SimPowerSystem is shown in Figure 4. IETE JOURNAL OF EDUCATION | VOL 55 | NO 1 | JANJUN 2014


Here, in the new subsystem of variable AC voltage source, individual AC voltage source models of the same supply frequency are utilized. Magnitudes of the voltages of these component sources are gradually increased, so that while operated as a conglomerate system, it can increase the input voltage of the transformer model by small steps as is done with a variac in practice. Component voltage sources are added one by one through switching operation with the help of breaker models (Simulink address: SimPowerSystem ! Elements ! Breaker).


In designing such a sub-system, we have used any particular amplitude of the supply voltage for a specified period of time. Thus, every breaker model may have equal time slots (of course, it is not a necessity) moving along the increasing time scale.

4.

STUDY OF BH CURVES IN SIMULINK

In Simulink environment, the saturable transformer model, once selected, considers automatically the magnetizing characteristic of the core. This characteristic, in turn, generates a specific characteristic of the magnetizing current Im. However, for any saturable transformer model, the hysteresis or saturation characteristic may easily be chosen with the help of Hysteresis Design Tool of the Powergui block. This increases the computational burden of that Simulink model; and as a result, the overall simulation process greatly slows down. To avoid this problem, we have selected the required hysteresis characteristic manually according to our choice. On the characteristic the magnetizing current Im in per unit is the x-axis and flux Fm in per unit is represented along the y-axis. Since Im is proportional to the electric field H and Fm is proportional to Bm, the flux density, the plot obtained with Fm and Im is essentially the BH curve. In drawing this saturation characteristic we consider the presence or absence of residual flux at our will. If we neglect the residual flux, the characteristic will obviously start from the origin. Otherwise, it will start from a point above it.

Figure 4: (a) New “variable AC voltage source” providing input to transformer model and (b) subsystem made by AC voltage source model of SimPowerSystem.


We have designed many types of BH curves like in Figures 5(a) to 5(e) and have run the Simulink model using each characteristic. Most of the curves ended up with distorted as well as unrealistic no-load current (I0) characteristics. This indicated that these BH curves are not suitable for this transformer. As a typical example, in Figure 5(f), we have shown one impractical no-load current characteristic obtained using the magnetization curve of Figure 5(e). However, by trial and error, we have constructed the BH curve of 13


Figure 5(g) which gives a realistic no-load current characteristic, shown in Figure 5(h). Thus, the BH curve of Figure 5(g) is accepted as the right choice for the Simulink based transformer. This curve was used for building the saturable transformer model.

5.

SELECTING THE PROPER BH CURVE

6.

SELECTING Im

Power transformers of small ratings usually have a noload current of the order of 3%5% of the rated current. In our model, the rating of the transformer is taken as 2 kVA, 230/115 V, 50 Hz. For our transformer model, the no-load current I0 is chosen as about 3% of the rated primary current, whereas, by trial and error, we finally converged upon the suitable BH curve, vide Figure 5(g), and from the model the magnetizing current Im turns out to be 2.34% of the rated current.


For selection of the proper BH curve, we have used each of the BH curves to run the transformer model for the open-circuit test. By inspection of the no-load current characteristics obtained for each BH curve,

we have selected the most suitable magnetization characteristic.

Figure 5: Panels (a) to (d) show four unsuitable BH curves. Panel (e) shows another wrong choice of BH characteristic while panel (f) shows the distorted unrealistic I0 characteristics obtained from the BH curve of panel (e). Panel (g) shows the right choice of BH curve along with the acceptable I0 characteristic (panel (h)) it produced.

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Figure 5: (Continued)

The pattern of magnetizing current Im and no-load current I0 are shown in Figure 6. From Figure 6, we see that both the magnetizing component and the no-load current have non-sinusoidal pattern. This is due to the saturation effect of the magnetization characteristic. The form factors of these current waveforms obviously deviate from that of a pure sinusoid. Computation of true rms values of these currents is not possible via Simulink measurement blocks. However, to have an idea about the rms values, we employ regular rms meters available in MATLAB Simulink.

7.

SELECTING Ia AND ro

For a realistic transformer, the active component of noload current, Ia, is much less than the magnetizing current Im. With I0 3% and Im 2.34%, the active component Ia is about 2% of the rated primary current. Attempt to IETE JOURNAL OF EDUCATION | VOL 55 | NO 1 | JANJUN 2014

reduce Ia further made the model to run extremely slowly. This restricted us to settle upon the value of Ia as 2% of the rated primary current. Rated primary voltage (Vp) D 230 V. Rated primary current ðIp Þ ¼

2000 ¼ 8:695 A: 230

The active component of no-load current, Ia D 2% of rated current D 0.1739 A. The value of resistance r0 ¼

230 ¼ 1322:6 V. 0:1739

Thus, the value of r0 is approximately 1320 V.

8.

MULTIMETER

In our Simulink models, we use many function blocks available in MATLAB Simulink. Table 1 tabulates 15


measurement blocks) is shown in Figure 8. In this model, the secondary of the transformer is kept open and a variable AC supply of constant frequency is fed to the primary side. Here, the current measurement block reads the no-load current I0, voltage measurement block reads the primary voltage Vp and a subsystem of wattmeter gives us no-load power P0, which gives the value of approximate rated core loss. Another voltmeter is employed on the secondary side to measure the output voltage.


The variation of no-load current I0, no-load power P0 and secondary voltage Vs are plotted against the variable input voltage Vp. These curves are shown in Figure 9. When the rated voltage is reached at the primary side, the readings from Simulink model meters are as follows: Figure 6: (a) Pattern of no-load current I0 and (b) magnetizing component of no-load current Im.

some major function blocks and their addresses, frequently used to build up Simulink models. Of these, the “multimeter” block is used for measurement of primary voltage, secondary voltage, primary current, secondary current, no-load current, magnetizing current and flux F in different circuit models. The use of “multimeter” block, instead of a number of “current measurement” blocks and “voltage measurement” blocks, leads to faster simulation.

Vp ¼ 229:5 V; I0 ¼ 0:2682 A; P0 ¼ 40:03 W; cosf0 ¼ 0:6506; Vs ¼ 114:75 V: From these virtual test results, we can determine the values of resistance r0 and reactance x0 of the equivalent transformer model. However, the calculated value of power factor from above values of Vp, I0 and P0 is given as follows: cosf0 ¼

P0 ¼ 0:65034: Vp I0

Using all these values, the useful variables are determined as follows:

Whenever a “multimeter” block is used in any circuit model, we have to specify our measurement requirement before the first run. Otherwise, the operation will lead to “mismatch in input/output port dimensions in the multimeter block”.

Ia ¼ I0 cosf0 ¼ 0:17442 A; Vp r0 ¼ ¼ 1315:789 V; Ia qffiffiffiffiffiffiffiffiffiffiffiffiffiffi Im ¼ I02 ¡ Ia2 ¼ 0:20373 A;

To activate the multimeter block, we always select the measurements needed a priori. A double click on the multimeter block is needed to set up the measurement requirements. There will be two columns. On the left column, we have “available measurements” options. Depending on our requirement, we click on a specific option and then consequently on “>>”. This will store our measurement requirement on the right column. In this way the set of measurement variables is chosen. Finally, we click “Ok” to make the multimeter block functionally ready for simulation.

x0 ¼

DVs 100 ¡ 80 ¼ 0:5: ¼ DVp 200 ¡ 160 1 Hence; the turns ratio; a ¼ ¼ 2: m

9.

10. SHORT-CIRCUIT TEST

OPEN-CIRCUIT TEST

Here Figure 7 shows the equivalent circuit of the transformer under open-circuit condition, whereas the Simulink model for the open-circuit test (with its 16

ð1Þ

Vp ¼ 1126:49 V: Im

ð2Þ ð3Þ ð4Þ ð5Þ

From the Vp¡Vs curve shown in Figure 9(c), we can determine the turns ratio of the transformer by computing the slope of the curve. Thus; slope m ¼

ð6Þ ð7Þ

Figure 10 shows the equivalent circuit of the transformer under short-circuit condition, whereas the Simulink model for the short-circuit test (with its measurement IETE JOURNAL OF EDUCATION | VOL 55 | NO 1 | JANJUN 2014


Table 1: Address and function of frequently used basic blocks of MATLAB Simulink.


Measurement blocks

MATLAB address sequence

Purpose

SimPowerSystem ! Measurements ! Current Measurement

Used as an ammeter

SimPowerSystem ! Measurements ! Voltage Measurement

Used as a voltmeter

SimPowerSystem ! Extra Library !Measurements ! Active and Reactive Power

Measures active power and reactive power

SimPowerSystem ! Measurements ! Multimeter

Replaces many “current measurement” and “voltage measurement” blocks. Makes simulation faster

SimPowerSystem ! Extra Library ! Measurements ! RMS

Calculates rms values of currents and voltages

Simulink ! Sinks ! Scope

Records current, voltage, or power waveforms with time

Simulink ! Sinks ! Display

Displays numerical values of different measurements

Figure 7: Equivalent circuit of transformer under an open-circuit condition.


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Figure 8: (a) Simulink model for open-circuit test with (b) corresponding measurement blocks.

blocks) is shown in Figure 11. Here, the secondary of the transformer is shorted through an ammeter and a variable AC supply of constant frequency (as in the open-circuit test model) is applied to primary. The voltage is gradually varied until the rated current flows through the primary as well as secondary windings. In the short-circuit test model, current measurement block reads the short-circuit current Ip and the voltage measurement block reads the primary voltage Vpsc. A subsystem of wattmeter gives the full-load copper loss or short-circuit power Psc. The small core loss due to low-voltage operation is neglected compared to the copper loss. As shown in Figure 10, the secondary side resistance rs and reactance xs are transferred to the primary side to make analysis easier.

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Figure 9: (a) Variation of no-load current I0 with input voltage Vp, (b) variation of no-load power P0 with input voltage Vp, and (c) variation of secondary voltage Vs with input voltage Vp.



Figure 10: Equivalent circuit of transformer under short-circuit condition.


The readings from Simulink model meters are given as Vpsc ¼ 10:29 V; Ip ¼ 8:695 A; Is ¼ 17:39 A;

Under short-circuit condition, secondary current Is and related short-circuit power Psc are plotted against the primary current Ip. These curves are shown in Figure 12.

Psc ¼ 40:5 W; cos fsc ¼ 0:4528:

Figure 11: (a) Simulink model for short-circuit test with (b) corresponding measurement blocks.


Figure 12: (a) Variation of secondary current Is with primary current Ip and (b) variation of short-circuit power against the primary current.

19



From the short-circuit test results, we can compute the equivalent impedance Zp, equivalent resistance Rp and finally the equivalent reactance Xp of the transformer model referred to the primary side. The different parameters are given as follows: Zp ¼

Vpsc ¼ 1:183 V; Ip

ð8Þ

Rp ¼

Psc ¼ 0:5356 V; Ip2

ð9Þ

Xp ¼

qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi Z2p ¡ R2p ¼ 1:0548 V:

ð10Þ

The calculated value of power factor from above values of Vpsc, Ip, and Psc is given as Psc cos fsc ¼ ¼ 0:4526: Vpsc Ip

ð11Þ

11. LOAD TEST For predetermination of percentage efficiency and percentage regulation of the transformer, we perform the load test. The equivalent circuit of the transformer under load test is shown in Figure 13. For conducting the test in the Simulink environment, we connect a subsystem of variable resistance in the secondary of the transformer as shown in Figure 14. The subsystem termed as “Variable Resistive Load” is constructed to vary the load of the transformer gradually. A typical portion of the variable resistive load is shown in Figure 15. Here we have utilized some switches and resistance branches from SimPowerSystem of MATLAB Simulink library. To achieve the desired operation, one particular resistance branch of the “Variable Resistive Load” is kept ON for one time period of the input voltage cycle.

It may be noted that an impedance load cannot be used in this model, because, to vary load current, variation of the impedance load is needed. This gives rise to switching of inductive current leading to high di dt and consequently undesired model output. During this time all other resistance branches are kept in OFF state. Following this switching pattern, we vary the connected resistive load continuously. This ensures a variable load current. Finally, we plot the transformer efficiency curves against load fraction at different power factors, shown in Figure 16(a). For clarity, a portion of the family of curves of Figure 16(a) is shown magnified in Figure 16(b). The efficiency of the transformer is given by %h ¼

x S cosf £100; x S cosf þ Pi þ x2 Pc

ð12Þ

where the symbols have their usual meaning. In the transformer model, rated copper loss Psc D 40.5 W (obtained from short-circuit test) and iron loss P0 D 40.03 W (obtained from no-load test). Obviously, the maximum efficiency occurs at the load fraction of rffiffiffiffiffi Pi x¼ ¼ 0:994: ð13Þ Pc Thus, for unity power factor, the maximum efficiency can be calculated from Eqs. 4(a) and 4(b) as %hmax ¼ 96:15%: For a particular time interval, the connected load being fixed, we obtain a particular value of efficiency. We use different loads for equal time duration occurring at different times, thus increasing the load current gradually. These load currents are plotted against respective efficiencies to obtain the efficiency (h) versus load fraction (x) curve. Three such curves, for three

Figure 13: Equivalent circuit of transformer under load test.

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Figure 14: (a) Simulink model of load test for determining transformer efficiency with (b) corresponding measurement blocks.

load power factors of 0.6, 0.8 and unity as chosen, are shown in Figure 16, whereas Figure 17 shows the variation of efficiency with increasing power factors at different load fractions of 0.6, 0.8 and unity as chosen. Figure 18 shows variation of percentage voltage regulation for the same power factors.

12. LOAD TEST FOR DETERMINING VOLTAGE REGULATION Voltage regulation of a transformer depends upon its load. It also depends upon the load power factor. IETE JOURNAL OF EDUCATION | VOL 55 | NO 1 | JANJUN 2014

Hence, for predetermination of regulation, we design the Simulink model in such a fashion that overall variation of voltage regulation with changing load power factor at different load fractions is obtained.

13. CALCULATION OF LOAD POWER FACTOR FOR ZERO REGULATION In this transformer model, the total resistance per unit is 2r D 0.02 pu and the total reactance per unit is 2x D 0.04 pu. 21



Figure 15: Subsystem of variable resistance connected in transformer secondary side.

Figure 17: (a) Curves showing the variation of transformer efficiency at different load power factors with load fractions of 1, 0.8, and 0.6. (b) Enlarged curve.

Figure 16: (a) Efficiency versus load fraction curves at different load power factors of 1, 0.8, and 0.6. (b) Enlarged efficiency versus load fraction curves.

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Figure 18: Curves showing variation of percentage voltage regulation with power factor angles, at different load fractions of 1, 0.8, and 0.6.



Per unit regulation is given as

load operation. Thus, we have

2 ¼ x ½ 2 r cos u § 2 x sin u: If regulation 2 ¼ 0; then tan u ¼

2r : 2x

ð14Þ

rated loss ¼ Ip2 Rp þ Pi ¼ I 2 Rp þ pi ;

ð15Þ

where Ip is the rated primary current of transformer, I is the overload current during short heat run test, Rp is the equivalent resistance of transformer referred to the primary, Pi is the rated core loss, and pi is the iron loss for low-voltage operation during the test.

Therefore, the power factor at which zero regulation occurs is given as ¡1 2 r p:f : ¼ cos tan : 2x

ð16Þ


Putting the numerical values, we obtain ¡ 1 0:02 p:f : ¼ cos tan ¼ 0:8944 ðleadÞ: 0:04

ð17Þ

14. SHORT HEAT RUN TEST In the short heat run test, we determine the maximum possible temperature rise of a transformer when it is continuously operated at full load. This operational situation is simulated in “short heat run test” without actually loading the transformer. The equivalent circuit of the short heat run test is shown in Figure 19. In the short heat run test, the transformer is operated under short-circuit condition and hence the input voltage is much smaller than the rated value. Due to such low-voltage operation, the core loss of the transformer is less than its core loss during full load. To simulate the condition of full-load operation, we need to make up for this short fall in core loss by adding extra copper loss to the system. To achieve this under short-circuit condition, the transformer is actually operated at overload (say, I > Ip). That is, the total watt loss under this condition is made equal to the watt loss during full-

ð18Þ

In the above equation, since Pi > pi, I > Ip. During short heat run test, the primary voltage of the transformer is gradually increased from zero until the wattmeter reads the total rated loss at full load. This loading condition is maintained for about 23 hours and the variation of temperature is plotted with time. Mathematically, this variation is represented by the following equation: u ¼ ua þ ðum ¡ ua Þð1 ¡ e ¡ t=a Þ;

ð19Þ

where u is the winding temperature of the transformer at time t, ua is the ambient temperature, um is the maximum temperature, and a is the heating time constant of the transformer. This experiment is performed on virtual platform to determine the maximum possible temperature rise in the designed transformer model. To draw the theoretical curve based upon the above equation, we need to have the heating time constant a of the transformer and also its um. Hence, we have used the values of a and um of a transformer of our laboratory. Using these values in the RHS of Eq. (19), we can plot the required timetemperature curve. This seems to be illogical, because to determine um, we are starting our simulation procedure with the knowledge of, supposedly unknown, um. However, in the virtual test, this is the only way to go about determining um.

Figure 19: Equivalent circuit of short heat run test.


23

Roychoudhury S: Virtual Laboratory for Performing Tests on a Single-Phase Power Transformer um ¡ ua du value of du dt ¼ a . Hence, knowing um, u a, and dt , the heating time constant a can be computed from the output graph of Simulink.

15. CONCLUSION


The presented MATLAB Simulink model of transformer is attempted by “saturable transformer” model available in Simulink which works with a nonlinear BH curve, from which we have drawn different characteristics like we obtain in hardware-based laboratory tests. We have modelled a separate variable AC voltage source which acts like a variac while operated as a conglomerate system. It is not a straightforward deal to model a variable AC voltage source via Simulink. This tricky part has been avoided in reference [6], whereas this designed variable AC voltage source play one of the major role in drawing different characteristics of a single-phase transformer like in practice. Here we have separately designed the magnetizing characteristic that will suit the transformer under consideration. From Figure 6, we see that both the magnetizing component and the no-load current have nonsinusoidal pattern that will give better understanding on saturation effect of the magnetization characteristic.

Figure 20: (a) Curve showing variation of temperature with time. (b) Change in temperature versus temperature curve.

However, for any practical transformer, the timetemperature curve is obtained via actual test only. The simulated curve for temperature rise of the transformer with time (in minutes) is shown in Figure 20(a). From this curve, we determine du dt at seven different points and plot the u ¡ du curve shown in Figure 20(b). dt The maximum temperature um is obtained by extrapolating the straight line of Figure 20(b). From the above two relations we can write u ¼ um ¡ a

du : dt

ð20Þ

When du dt is zero, the above equation will give the maximum temperature um. On the other hand at u D ua, the

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The virtual test models for open-circuit test, short-circuit test, load test, and short heat run test, presented herein, can be used in the software laboratories which obviously give detailed insights into different operational aspects of a single-phase power transformer. Parallel operation of two single-phase transformer using the presented model is currently under investigation.

REFERENCES 1.

M. G. Say, The Performance and Design of Alternating Current Machines, 3rd ed. New Delhi: CBS Publishers, 1983.

2.

A. C. Franklin, and D. P. Franklin, The J & P Transformer Books, 11th ed. New Delhi: Aditya Books, 1983.

3.

Standards, Specification of Power transformers, S2026 (Part I), 1977.

4.

International Standard IEC 60076-1, Edition 2.1, 2000-04 Power transformers Part 1: General.

5.

Duane Hanselman, and Bruce Littlefield, Mastering MATLAB 7. Delhi: Pearson Education, 2005.

6.

Ayasun Saffet, and Nwankpa, Chika O., “Transformer tests using MATLAB/Simulink and their integration into undergraduate electric machinery courses,” Comput. Appl. Eng. Educ. Vol. 14, pp. 14250, Jul. 2006; published online in Wiley InterScience. doi:10.1002/cae.20077. Available: http://www. interscience.wiley.com



Authors Srimanti Roy Choudhury did her BTech in 2006 from Jalpaiguri Government Engineering College, under West Bengal University of Technology, India and MTech (2010) from the Department of Applied Physics, University of Calcutta, India. During 2006 to 2007 she worked in the Jalpaiguri Government Engineering College in Department of Electrical Engineering as a part-time teacher. Presently she is an assistant professor (from 2010) in the Department of Electrical Engineering, Budge Institute of Technology and also acted as a guest lecturer in the Department of Polymer Science & Technology, University of Calcutta, India. Her research area includes control theory in general and application of ‘alternative’ orthogonal functions in different areas of systems and control. She has published four research papers in different national and international journals.


E-mail: [email protected]

Gautam Sarkar did his BTech in 1975, MTech. in 1977, and PhD (Tech) degree in 1991 from the Department of Applied Physics, University of Calcutta, India. He started his career as a research assistant in the Department of Applied Physics, University of Calcutta, India and joined the department as a lecturer in 1985. In 1998, he became reader in the same department. Presently he is in the chair of Labanyamoyee Das Professor (2002). His areas of research include automatic control, fuzzy systems, microprocessor based control of electric motors and application of piecewise constant basis functions in systems and control. He has published more than 40 research papers in different national and international journals. He is the coauthor of the book “Triangular orthogonal functions for the analysis of continuous time systems” published by Elsevier (India) in 2007 and Anthem Press (UK) in 2011. E-mail: [email protected]

Anish Deb (b.1951) did his BTech in 1974, MTech in 1976, and PhD (Tech) degree in 1990 from the Department of Applied Physics, University of Calcutta, India. He started his career as a design engineer (1978) in industry and joined the Department of Applied Physics, University of Calcutta, India as a Lecturer in 1983. In 1990, he became reader in the same Department. Presently he is a professor (1998). His research interest includes automatic control in general and application of ‘alternative’ orthogonal functions in systems and control. He has published more than 60 research papers in different national and international journals. He is the principal author of the books “Triangular orthogonal functions for the analysis of continuous time systems” published by Elsevier (India) in 2007 and Anthem Press (UK) in 2011, and “Power Electronic Systems: Walsh Analysis with MATLAB” to be published by CRC Press (USA) in March, 2014. E-mail: [email protected]

Jitendranath Bera has obtained his post-BSC, BTech and MTech degree in 1993 and 1995, respectively from the Department of Applied Physics, University of Calcutta with specialization in Electrical Machines and Power System. He has obtained his PhD in the year 2005, from Jadavpur University, Kolkata, India, in the field of multimedia wireless communication. He worked as Scientist-B in a project sponsored by ADA, GOI at the Institute of Radio Physics and Electronics, Calcutta University for a period of almost two years. Then he joined Premier Irrigation Equipment Limited as AGM and worked for a period of about 10 years. Since 2005, he is an associate professor in the Department of Applied Physics, University of Calcutta, Kolkata. His fields of interest are wireless communication, electrical drives and condition monitoring of electrical machines, embedded systems etc. His teaching experience is of about seven years. He has more than 55 national and international journal and conference papers. E-mail: [email protected]

DOI: 10.1080/09747338.2014.921399; Copyright © 2014 by the IETE


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Virtual Laboratory for Performing Tests on a Single

Virtual Laboratory for Performing Tests on a Single

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