A Simulation of Three Phase to Multi Phase Transformation using a Special Transformer

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International Journal of Science and Research (IJSR), India Online ISSN: 2319-7064

Volume 2 Issue 7, July 2013

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A Simulation of Three Phase to Multi Phase

Transformation using a Special Transformer

L. Srinivas Goud1, T. Srivani

2

1

Assistant Professor, Auoras Engineering College, Bhonigir, India

2M. Tech Scholar, Auroras Engineering College, Bhonigir, India

Abstract:The first five-phase induction motor drive system was proposed in the late 1970s for adjustable speed drive applications.Since then, a considerable research effort has been in place to develop commercially feasible multiphase drive systems. Since the three-

phase supply is available from the grid, there is a need to develop a static phase transformation system to obtain a multiphase supply

from the available three-phase supply. Thus, this paper pro-poses a novel transformer connection scheme to convert the three-phase grid

supply to a five-phase fixed voltage and fixed frequency supply. The proposed transformer connection outputs five phases and, thus, can

be used in applications requiring a five-phase supply. Currently, the five-phase motor drive is a commercially viable solution. The five-

phase transmission system can be investigated further as an efficient solution for bulk power transfer. The connection scheme is

elaborated by using the simulation and experimental approach to prove the viability of the implementation. The geometry of the

fabricated transformer is elaborated in this paper.

Keywords: Five phase multiphase, three phase, transformer,turn ratio.

1. IntroductionMultiphase (more than three phase) systems are the focus ofresearch recently due to their inherent advantages comparedto their three-phase counterparts. The applicability ofmultiphase systems is explored in electric power generation[2][8], transmission [9][15], and utilization [16][33]. The

research on six-phase transmission system was initiated dueto the rising cost of right of way for transmission corridors,environmental issues, and various stringent licensing laws.

Six-phase transmission lines can provide the same powercapacity with a lower phase-to-phase voltage and smaller,more compact towers compared to a standard double-circuit

three-phase line. The geometry of the six-phase compacttowers may also aid in the reduction of magnetic fields aswell [12]. The research on multiphase generators has startedrecently and only a few references are available [2][8]. Thepresent paper is used in other country which is used in theship yard for bulk power. The present work on multiphase

generation has investigated asymmetrical six-phase (two setsof stator windings with 30 phase displacement) inductiongenerator configuration as the solution for use in renewable

energy generation. As far as multiphase motor drives are

concerned, the first proposal was given by Ward and Harrerway back in 1969 [1] and since then, the research was slowand steady until the end of the last century.

Figure 1: Block representation of the proposed system.

The research on multiphase drive systems has gainedmomentum by the start of this century due to availability ofcheap reliable semi-conductor devices and digital signal

processors. Detailed reviews on the state of the art inmultiphase drive research are available in [18][22]. It is tobe emphasized here that the multi-phase motors areinvariably supplied by ac/dc/ac converters. Thus, the focus ofthe research on the multiphase electric drive is limited to themodeling and control of the supply systems (i.e., the inverters

[23][33]). Little effort is made to develop any static

transformation system to change the phase number fromthree to -phase (where 3 and odd). The scenario has now

changed with this paper, proposing a novel phasetransformation system which converts an avail-able three-phase supply to an output five-phase supply.

Multiphase, especially a 6-phase and 12-phase system isfound to produce less ripple with a higher frequency of ripple

in an acdc rectifier system. Thus, 6- and 12-phase trans-formers are designed to feed a multipulse rectifier system andthe technology has matured. Recently, 24-phase and 36-phase transformer systems have been proposed for supplyinga multipulse rectifier system [34][37]. The reason of choice

for a 6-, 12-, or 24-phase system is that these numbers aremultiples of three and designing this type of system is simpleand straightforward. However, increasing the number ofphases certainly enhances the complexity of the system.None of these designs are available for an odd number ofphases, such as 5, 7, 11, etc., as far as the authors know.

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Figure 2: (a) Proposed transformer winding arrangements

(star-star). (b) Pro-posed transformer winding connection(star).

Figure 3: Phasor diagram of the proposed transformerconnection (star-star).

The usual practice is to test the designed motor for a number

of operating conditions with a pure sinusoidal supply toascertain the desired performance of the motor [38].

Normally, a no-load test, blocked rotor, and load tests areperformed on a motor to determine its parameters. Althoughthe supply used for a multiphase motor drive obtained from amultiphase inverter could have more current ripple, there are

control methods available to lower the current distortion even

below 1%, based on application and requirement. Hence, themachine parameters obtained by using the pulse width-modulated (PWM) supply may not provide the precise truevalue. Thus, a pure sinusoidal supply system available fromthe utility grid is required to feed the motor. This paperproposes a special transformer connection scheme to obtain abalanced five-phase supply with the input as balanced three -

phase. The block diagram of the proposed system is shown inFig. 1. The fixed voltage and fixed frequency avail-able grid

supply can be transformed to the fixed voltage and fixedfrequency five-phase output supply. The output, however,may be made variable by inserting the autotransformer at theinput side. The input and output supply can be arranged in

the following manner:

1) Input Star, Output Star;2) Input Star, Output Polygon;3) Input Delta, Output Star;4) Input Delta, Output Polygon.Since input is a three-phase system, the windings are

connected in a usual fashion. The output/secondary sideconnection is discussed in the following subsections.

2. Winding Arrangement for Five-Phase StarOutput

Three separate cores are designed with each carrying one

primary and three secondary coils, except in one core whereonly two secondary coils are used. Six terminals of primariesare connected in an appropriate manner resulting in starand/or delta connections and the 16 terminals of secondaries

are connected in a different fashion resulting in star orpolygon output. The connection scheme of secondary

windings to obtain a star output is illustrated in Fig. 2 and thecorresponding phasor diagram is illustrated in Fig. 3. Theconstruction of output phases with requisite phase angles of72

between each phase is obtained using

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Figure 4: MATLAB/SIMULINK model of the three- to five-phase transformation.

Appropriate turn ratios, and the governing phasorequations are illustrated in (1)(10). The turn ratios are

different in each phase. The choice of turn ratio is the key

in creating the requisite phase displacement in the outputphases. The input phases are designated with letters XY, and Z and the output are designated with lettersA, B, C, D, and E. As illustrated in Fig. 3, theoutput phase A is along the input phase X. The outputphase B results from the phasor sum of winding voltage and , the output phase C is obtained by thephasor sum of winding voltages and . The

output phase D is obtained by the phasor addition ofwinding voltages and and similarly output

phase E results from the phasor sum of the windingvoltages and . In this way, five phases areobtained. The transformation from three to five and Vice-

versa is further obtained by using the relation given in

Table 1: Design of proposed transformer

Primary Secondary Turns ratio

Phase Xa1a2 1

a4a3 0.47

Phase Y

b1b2 0.68

b4b3 0.858

b5b6 0.24

Phase Z

c1c2 0.68

c4c3 0.858

c5c6 0.24

Where (10) is shown above

(10)

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Figure 5: MATLAB/SIMULINK model of the three-to-five phase transformation (delta-star)

3. Winding Arrangement for Five-Phase StarOutput

Three separate cores are designed with each carrying oneprimary and three secondary coils, except in one core whereonly two secondary coils are used. Six terminals of primariesare connected in an appropriate manner resulting in starand/or delta connections and the 16 terminals of secondaries

are connected in a different fashion resulting in star orpolygon output. In this above design the primary side of the

transformer is connected in a delta form.

The construction of output phases with requisite phase anglesof 72 between each phase is obtained using appropriate turnratios, and the governing phasor equations. The input phases

are designated with letters X Y, and Z and the outputare designated with letters A, B, C, D, and E.

Figure 6: MATLAB/simulation model of the three phases to multiphase transformation (delta-polygon)

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4. Winding Arrangement for Polygon-PhaseDelta Output

Three separate cores are designed with each carrying primary

and two secondary coils. In this design the phase difference will

be 60 . Six terminals of primaries are connected in anappropriate manner resulting in delta-polygon. Connections and

the 12 terminals of secondaries are connected in star-polygon

output. The turns ratios are different in each phase. The input

phases are designated with letters X Y, and Z and the

output are designated with letters A, B, C, D, E, andF. The three phases to six phase connection design model is

in the above fig. In this value of VA=Vx

Figure 7: MATLAB/simulation model of the three- phase to five phase transformations (star-polygon)

5. Winding Arrangement For Polygon-PhaseStar Output

Three separate cores are designed with each carryingprimary and two secondary coils. In this design the phase

difference will be 60. Six terminals of primaries areconnected in an appropriate manner resulting in delta-polygon. The three phases to six phase connection designmodel is in the above fig. In this value of VA=Vx

Connections and the 12 terminals of secondarys areconnected in star-polygon output. The turns ratios are

different in each phase. The input phases are designated withletters X Y, and Z and the output are designated withletters A, B, C, D, E, and F.

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Figure 5: (a)(d). (a) Input Vy and Vz phases and output Vbphase voltage wave-forms. (b) Input Vy and Vx phases and

output Vc phase voltage waveforms. (c) Input Vz and Vxphases and output Vd phase voltage waveforms (d) Input Vz

and Vy phases and output Ve phase voltage wave-forms.

6. MATLAB Based Simulation ResultsInput Voltage

Output Voltage

Output Voltage

Output Current

Output for Multi Phase

Output Voltage

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Output Current

7. ConclusionThis paper proposes a new transformer connection schemeto transform the three-phase grid power to a five-phase

output supply. The connection scheme and the phasor

diagram along with the turn ratios are illustrated. Thesuccessful implementation of the proposed connectionscheme is elaborated by using simulation andexperimentation. A five- Phase induction motor under aloaded condition is used to prove the viability of the

transformation system. It is expected that the proposedconnection scheme can be used in drives applications andmay also be further explored to be utilized in multiphasepower transmission system.

Reference

[1] E. E. Ward and H. Harer, Preliminary investigation ofan inverter-fed 5-phase induction motor, Proc. Inst.Elect. Eng., vol. 116, no. 6, 1969.

[2] D. Basic, J. G. Zhu, and G. Boardman, Transientperformance study of Brushless doubly fed twin stator

generator, IEEE Trans. Energy Convers., vol. 18, no.3, pp. 400408, Jul. 2003.

[3] G. K. Singh, Self excited induction generator research-a survey, Elect. Power Syst. Res., vol. 69, pp. 107114, 2004.

[4] O. Ojo and I. E. Davidson, PWM-VSI inverter-assistedstand-alone dual stator winding induction generator,IEEE Trans Ind. Appl., vol. 36, no. 6, pp. 16041611,

Nov./Dec. 2000

Author Profile

L. Srinivas Goud received the B. Tech. degree in

Electrical and Electronics Engineering from JNTUUniversity and M. Tech in Power System Engineeringfrom JNTU University Hyderabad. He is currently

working as an Assistant Professor in AurorasEngineering College. He is working towards the Ph.D. degree in

Electrical Engineering.

T. Srivani received the B. Tech. degree in Electrical

and Electronics Engineering from JNTU Universityand pursuing M. Tech in Power Electronics in

Auroras Engineering College (JNTU Hyderabad).

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A Simulation of Three Phase to Multi Phase Transformation using a Special Transformer