Design & performance of six pulse voltage multipliers 2

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  • 1. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 3, April (2013), © IAEME33DESIGN & PERFORMANCE OF SIX PULSE VOLTAGEMULTIPLIERSShaziaFathima1Associate Professor, Head of the EEE Department,Green Fort Engineering College,Bandlaguda, HyderabadDr. Sardar Ali 2Professor & Head - EEE Department,Royal Institute of Technology & Science, Chevella, R.R. Dist., Hyderabad, A.P., IndiaABSTRACTElectronic systems quite often require that higher DC voltages be generated internally fromthe supply voltage. Voltage multipliers can be used to generate bias voltages of a few volts or tens ofvolts or millions of volts for purposes such as high-energy physics experiments and lightning safetytesting.The most common application of the high voltage outputs of voltage multipliers is the anodeof cathode-ray tubes (CRT), which are used for radar scope presentations, oscilloscope presentations,or TV picture tubes. The dc output of the voltage multiplier ranges from 1000 volts to 30,000 volts.The actual voltage depends upon the size of the CRT and its equipment application.In this paper an attempt has been made to design a 3-phase or 6-pulse voltage multipliercircuit to produce an output voltage of about 4000v at different load currents from a 440v 3-phsupply. The performance of 6-pulse has been compared with that of single-pulse multiplier bysimulation and found to be far better. The prototype model requires a step-up transformer ofrating100VA, 440V/1150V. The 3-ph voltage is applied to the step-up transformer which is given asinput the voltage multiplier circuit. The multiplier circuit used here is a 4-stage which multiplies theoutput of step-up transformer four times. Simulation has been done using SIMPLORER software. Theresults of simulation have been compared with the hardware and found to be in coincidence.1 INTRODUCTIONA voltage multiplier is an electrical circuit that converts AC electrical power from a lowervoltage to a higher DC voltage by means of capacitors and diodes combined into a network.One of the cheapest and popular ways of generating high voltages at relatively low currents isthe classic multistage diode/capacitor voltage multiplier, known as Cockcroft Walton multiplier,INTERNATIONAL JOURNAL OF ADVANCED RESEARCH INENGINEERING AND TECHNOLOGY (IJARET)ISSN 0976 - 6480 (Print)ISSN 0976 - 6499 (Online)Volume 4, Issue 3, April 2013, pp. 33-40© IAEME: Impact Factor (2013): 5.8376 (Calculated by GISI)www.jifactor.comIJARET© I A E M E
  • 2. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 3, April (2013), © IAEME34named after the two men who used this circuit design to be the first to succeed in performing the firstnuclear disintegration in 1932-James Douglas Cockcroft and Ernest Thomas Sinton Walton.Unlike transformers this method eliminates the requirement for the heavy core and the bulk ofinsulation/potting required. By using only capacitors and diodes, these voltage multipliers can step uprelatively low voltages to extremely high values, while at the same time being far lighter and cheaperthan transformers. The biggest advantage of such circuit is that the voltage across each stage of thiscascade, is only equal to twice the peak input voltage, so it has the advantage of requiring relativelylow cost components and being easy to insulate.They have various practical applications and find their way in laser systems, CRT tubes, hvpower supplies, LCD backlighting, power supplies, x-ray systems, travelling wave tubes, ion pumps,electrostatic systems, air ionisers, particle accelerators, copy machines, scientific instrumentation,oscilloscopes, and many other applications that utilize high voltage DC.2 TYPES OF VOLTAGE MULTIPLIERSVoltage multipliers are alternating current (AC) to direct current (DC) converters that producehigh-potential DC voltage from a lower voltage, AC source. They are used with constant, high-impedance loads and in applications where input voltage stability is not critical. Voltage multiplierscan receive an input voltage directly from a power source, but often use a transformer to minimizepotential hazards.There are several types of multiplier circuits:1. Half Wave voltage doubler2. Full Wave voltage doubler3. Voltage tripler circuit3 SINGLE-PULSE VS SIX-PULSE MULTIPLIERS3.1 Single Pulse Voltage Multiplier3.2 WorkingThe Cockcroft Walton or Greinacher design is based on the Half-Wave Series Multiplier, orvoltage doubler. In fact, all multiplier circuits can be derived from its operating principles. It mainlyconsists of a high voltage transformer Ts, a column of smoothing capacitors (C2,C4), a column ofcoupling capacitors (C1,C3), and a series connection of rectifiers(D1,D2,D3,D4). The followingdescription for the 2 stage CW multiplier, assumes no losses and represents sequential reversals ofpolarity of the source transformer Ts in the figure shown below. The number of stages is equal to the
  • 3. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 3, April (2013), © IAEME35number of smoothing capacitors between ground and OUT, which in this case capacitors C2 are andC4.Let Vmax be the peak value of the secondary voltage of the high voltage transformer. Toanalyze the behaviour, let us consider that charging of capacitors actually takes place stage by stagerather than somewhat simultaneously. This assumption will not invalidate the result but will makeanalysis easier to follow. Consider the first part of the circuit containing the diode D1, the capacitorC1, and the secondary winding. During the first negative half cycle of the applied voltage, thecapacitor C1 charges up to voltage Vmax. Since during the positive half cycle which follows, thediode D1 is reverse biassed, the capacitor C1 will not discharge (or will not charge up in the otherdirection) and the peak of this half cycle, the point a will be at 2Vmax. During the following cycles,the potential at a will vary between 0 and 2Vmax, depending on whether the secondary voltage andthe capacitor voltage are opposing or assisting.5 SIMULATIONThe simulations of 1-pulse and 6-pulse voltage multipliers have been carried out using Simplorersoftware. The results of simulation of both multipliers have been presented to assess the performanceand for comparative study of these multipliers:5.1 Single-Pulse MultiplierFig 5.1.1: Simulation Of 1-Pulse MultiplierFig 5.1.2: Single-Pulse multiplier at No-load under transient state
  • 4. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 3, April (2013), © IAEME36Fig 5.1.3: Single-Pulse multiplier at No-load under steady state (VNL = 3.65KV)Fig 5.1.4: Single-Pulse multiplier under full load- steady stateFig 5.1.5: Single-Pulse multiplier at full-loadThe ripple & Regulation of 1-pulse multiplier can be calculated from its simulation graph of fullload(fig--)Ripple = (3.09 - 2.83)/3.09*100 = 8.4%Regulation = (3.65K – 2.96K)/3.65K*100 = 19.8%
  • 5. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 3, April (2013), © IAEME375.2 Six-Pulse MultiplierFig 5.2.1: Simulation circuit of 6-pulse multiplierFig 5.2.2: Six-pulse multiplier at no-load Fig 5.2.3: Six-pulse multiplierunder steady state(VNL=3.7KV) under transient stateFig 5.2.4: Six-pulse multiplier Fig 5.2.5: Six-pulse multiplierat full-load at full load(zoomed for clarity)Ripple = (3.25K – 3.07K) /3.7K*100 = 4.86%Regulation= (3.7K – 3.15K)/3.7K*100 = 14.4%
  • 6. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 3, April (2013), © IAEME385.3 Comparison of ResultsThe ripple and regulation of 1-pulse and 6-pulse multipliers have been calculated from the simulationresults. It has been observed that the performance of 6-pulse multiplier is much better than 1-pulsemultipliers. Hence a six-pulse multiplier can be used to generate high DC voltages with comparativelyless ripple & regulation.6 DESIGN OF 6-PULSE MULTIPLIER6.1 Ripple and RegulationRipple and Regulation of a 6-pulse multiplier circuit are calculated as follows::Ripple Voltage = δV = nI/6fC= 133.33V% Ripple = δV/ Vmax*100= 3.33%Regulation = ∆V = nI/3fC[n2/6-n/4+1/3] = 533.33V% Regulation = ∆V/Vmax*100= 13.33%6.1 Components Required1. Step up transformer- 440V/1150V,100VA.2. Capacitors of 0.5µF, 2KV - 8Nos3. Diodes of PIV rating 2KV - 12 nos4. Load resistors:1mA load: 500K , 1W- 8Nos2mA load: 270K , 1.5W – 7 Nos3.2mA load: 125K , 1.5W - 10 Nos4mA load: 100K , 1.5W – 10Nos5mA load: 100K , 2.5W – 8 Nos6mA load: 100K , 4W – 6Nos5. Measuring resistor of 10M ,1W6. Micro Ammeter(0-50µA)7. Milli ammeter(0-10mA)6.2 Practical Implementation of 6-pulse MultiplierMaximum voltage the 3-ph multiplier can develop is calculated as follows:Transformer rating = 415V/1150V, 100VA, 3-ФPrimary Side: VL-L= 415VVph = 230VSecondary Side:VL-L=1150VVph= 660VVph= Vrms=660VVmax = Vrms*√2*nWhere n – number of stages of multiplier circuit = 4Vmax = 660*√2*4 = 3.8 kV =~ 4KVMaximum permissible load current = IL√3VLIL = 100VAIL = 100/ (√3*1150) = 50 mA
  • 7. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 3, April (2013), © IAEME39Fig 6.2.1: Main circuit & Load circuit of 6-Pulse multiplierFig 6.2.2: Complete practical kit of a 6-pulse multiplier (Input supply from a step-up transformer of440/1150V behind the vertical kit)6.3 Testing Of 6-Pulse Voltage MultiplierFig 6.3.1: Testing of 6-pulse multiplier using a potential divider arrangement
  • 8. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 3, April (2013), © IAEME40Fig 6.3.2: Ripple obtained at full load for input voltage of 230VThe ripple and regulations at different loads is measured and tabulated. The results obtained fromtheoretical calculation, experimental tests and simulation of a 6-pulse multiplier are compared with eachother and found to be almost equal.7 CONCLUSIONIn this paper, a 6-pulse voltage multiplier circuit has been successfully designed, implemented andsimulated using the SIMPLORER software. Its performance has been tested at different loads. The resultsobtained from theoretical calculations, practical observations and simulated graphs have been comparedand found to be in great coincidence.Simultaneously, the performance of 6-pulse multiplier has been compared with that of 1-pulsemultiplier. It is found that 6-pulse voltage multiplier gives a much better performance in terms of rippleand regulation. The theoretical, practical and simulated results of the 1-pulse multiplier shows a largeamount of ripple and high regulation, whereas in a 6-pulse multiplier the DC output obtained is muchbetter comparatively.Practically, it has been observed that the number of capacitors is reduced and thus the size of thecircuit and cost gets drastically reduced. The 6-pulse multipliers would prove more economical where 3-phtransformer and 3-ph variac are already present.Hence it can be concluded that the requirements of high quality DC can be better accomplished bymeans of 6-pulse voltage multipliers as compared to any of the multiplier circuits.8 REFERENCES1. High Voltage Engineering. Fundamentals. Second edition. ... E. Kuffel, W.S. Zaengl andJ. Kuffel 20002. MS Naidu and V. Kamaraju, High Voltage Engineering, Tata mcgraw Hill, 20013. CL Wadhwa, High Voltage Engineering, Wiley Eastern Ltd., 1994 .4. Sanjay M Trivedi, B. S. Raman and Dr. Mihir Shah, “Design of a Unified Timing Signal Generator(UTSG) for Pulsed Radar”, International journal of Electronics and Communication Engineering&Technology (IJECET), Volume 3, Issue 1, 2012, pp. 252 - 261, ISSN Print: 0976- 6464,ISSN Online: 0976 –64729. Vishnu Goyal and Dr. Sulochana Wadhwani, “Simulation of Six Pulse Cycloconverter ExcitedInduction Machine” International Journal of Electrical Engineering & Technology (IJEET),Volume 3, Issue 2, 2012, pp. 76 - 83, ISSN Print : 0976-6545, ISSN Online: 0976-6553.