SIMULATION AND PROJECT OF HIGH FREQUENCY TRANSFORMER APPLIED TO A PLASMA PLANT

Transcription

1 SIMULATIO AD PROJECT OF HIGH FREQUECY TRASFORMER APPLIED TO A PLASMA PLAT Giancarlos Costa Barbosa 1, Andrés Ortiz Salazar 2, Jean Paul Dubut 3, José Alberto Díaz Amado 4 1 Instituto Federal do Rio Grande do orte - IFR - Campus Caicó - Rodovia R 288 s/nº Caicó - R - Brasil 2 Universidade Federal do Rio Grande do orte - UFR - Campus Universitário, s/nº atal - R - Brasil 3 Instituto acional de Pesquisas Espaciais - IPE/CR - Av. Salgado Filo, nº Caixa Postal atal - R - Brasil 4 Instituto Federal da Baia - Campus Vitória da Conquista - Av. Amazonas, nº Vitória da Conquista - BA - Brasil 1 giancarlos.barbosa@ifrn.edu.br, 2 andres@dca.ufrn.br, 3 jean@crn.inpe.br, 4 jose_diaz@ifba.edu.br Abstract Tis paper describes te project of a transformer wit PCB (Printed Circuit Board) windings (50 k operating at te nominal frequency of 450 khz) for using in a plasma inertization plant. Te plant is composed basically of RF (Radio Frequency) power supply and a ICP (Inductively Coupled Plasma) torc. Te transformer will make te coupling between te RF power supply and te ICP torc. To evaluate te performance of te transformer will be made simulations taking into account parameters suc as temperature, magnetic flux density, waveform voltage and parasitic effects. Keywords - ICP torc, PCB windings, Series Resonant Inverter, Transformer, 3D Simulation. I. ITRODUCTIO One of te most serious ecological problems faced by te umanity is te environment pollution by residues generated in te production process and use of goods suc as: residues produced of raw materials and rendered services; urban waste and sewer, and used goods tat sould be discarded, besides te residues originated in te sanitary sewer treatment.[1] One solution to tis problem is to eliminate tese products cleanly and safely. Termal treatment tecnologies ave been widely used to treat tese residues and termal plasma as been gaining importance in te processing of dangerous residues. Plasma complements or substitutes traditional tecnologies, is a clean, definitive, safe and competitive option, and, more importantly, does not generate any oter residues. A toxic waste inertization plant is currently in te development pase. Te plant is composed of an ICP torc, two reactors (main and secondary), a torc refrigeration system, a gas cleaning system, a gas exaust system and a feed source operating in te radio frequency range.[2] Te RF power supply is composed of a tree-pase AC-DC boost converter and a single-pase DC-AC series resonant inverter. Te diagram of plasma inertization plant, including te transformer, is sown in Figure 1. Fig. 1. Diagram of plasma inertization plant. Tis study is te development of a transformer tat as excellent performance at ig frequencies (450 khz) and power (50 k), wic permits te impedance matcing between te RF power supply and te main reactor (plasma torc) ensuring te transfer energy wit minimum losses. Te transformer wit PCB windings was cosen because of te following caracteristics: excellent performance at ig frequencies, reduction of parasitic reactances and te skin effect.[3] For purposes of analysis, we used a software, Ansoft MAXELL 3D, were te transformer was subjected to te desired operating conditions. II. SERIES RESOAT IVERTER Four identical 50k inverters constitute te main part of te ig frequency series resonant converter. Eac inverter structure is rated to te nominal value of 50k and uses a dual SEMIKRO SKM100GB125D ultra-fast IGBT module.[4] Te Figure 2 sows te simplified circuit diagram of te ig frequency series resonant converter and its principal connections wit te resonant load and te DSP module /11/$ IEEE 695

2 CT n + 2 ( T ) ct ct T 0 1 n ct T 2 n = (2) ere ct, ct 0 1 e ct 2 are te constants dependents of magnetic losses in core. IV. PROJECT OF TRASFORMER Fig. 2. Simplified circuit diagram of te ig frequency series resonant load converter. Te full-bridge resonant inverters are designed to constitute a modular system. In order to minimize te parasitic inductances and provide a better space arrangement, te four inverter modules are vertically grouped and distributed around te DC bus, assuring te necessary symmetry to te inverter set. Te ig frequency transformer is built on a ferrite C core wit te primary and secondary windings constituted by PCB. In Figure 3 can be seen te waveforms of te inverter output. For te design of te transformer is needed specifies te effective (rms) values of voltages in primary (V 1rms ) and secondary (V 2rms ) windings, te effective value of current in secondary (I 2rms ), te frequency and temperature.[5] Te design begins wit te coice of te core to be used. For te transformer in study were used ferrite cores of material IP6 of Tornton. e used 16 cores of te type C- 100/57/25 so tat te arrangement of tese form a core equivalent to te type E. It is estimated, ten te maximum number of conductive layers, te of turns per layer and total turns. Tese values are limited by te geometric dimensions of te core and depend on te tecnology used for te manufacture of circuit boards in wic te windings are printed. Te maximum number of conducting layers is given by (3): i = f (3) pcb Te Table I describes te symbols used in (3). TABLE I Symbols used in (3) Symbol Quantity Fig. 3. Output inverter waveforms. III. POER LOSSES I TRASFORMERS Te losses of a transformer are related to its windings and its magnetic core, including te loss by skin effect and eddy current. Suc losses are te difference between te power in te primary winding of te transformer and power in load. Te magnetic losses in ferrite cores (P m ) were calculated according to te frequency (f in Hz), peak magnetic flux density (B in T) and temperature ( T n in C), can be obtained by (1): x y P = C f B CT T ) (1) m m ( n ere Cm, x, and y are te constants for te material and CT, te correction factor for losses as a function of temperature, is given by (2): i pcb f umber of conductive layers Heigt of te window of te core Sum of te isolations Tickness of PCB (Printed Circuit Board) umber of conductive faces of PCB Due to te use of coupling, te turns ratio between primary and secondary transformer was defined by a ratio of 3:1, as te RF power supply as an impedance of 12 Ω and te plasma torc to an impedance of 1.5 Ω. For te accomplisment of te work were available printed circuit board wit double layers of copper wit tickness of 70 µm. e used an equal number of conductive layers for bot windings, so eac coil was wit 12 conductive layers (six PCB). In eac conductive layer is only used one turn. Te primary winding consists of tree turns, ad eac of its turns placed on two printed circuit boards connected in parallel, and tese turns connected in series. Since te 696

3 secondary winding consists of one turn ad its six boards connected in parallel. It was observed tat in range of 60 to 80 C, te transformer operates wit minimal losses. Te specified and calculated values of transformer are sown in Table II. it tese data it was possible to implement a prototype of te transformer sown in Figure 4. It is possible to visualize in Figures 5 and 6 te values of voltages and currents in bot windings. TABLE II Specified and Calculated Values Specified Values Values Frequency (khz) 450 Voltage of Primary (V) 800 Voltage of Secundary (V) 260 Current of Secondary(A) 186 Cosen Core C 100/57/25 Calculated Values Values umber of turns of Primary 3 umber of turns of Secondary 1 Track widt of Primary (mm) 45 Track widt of secondary (mm) 45 Temperature ( C) 68 Fig. 5. aveforms of voltages in winding primary (blue line) and winding secondary (black line). Fig. 6. aveforms of currents in winding primary (blue line) and winding secondary (black line). Fig. 4. Prototype of Transformer. V. SIMULATIOS Te software Ansoft MAXELL 3D, tat it is based on te analysis of finite elements, it was used in te simulations. Te simulations were done considering a resistive load and sinusoidal supply. All te following analysis is based on energy losses, te beavior of te field and te magnetic induction and current density. As previously mentioned, te total losses are te difference between te primary power transformer and power te load are obtained troug (4). From te values of voltage and current is possible to obtain te power values in te input transformer and its output. Tus, it was found tat te transformer as an efficiency of about 94.4% in te simulations. In simulations was done using of (1) for te calculation of losses in te magnetic core. Te software provides a tool in te user enter only te values of te constants and it displays te results. it tese values of losses you can ceck te operating temperature of te transformer in wic tere is minimal losses. According to Figure 7, it can be observed tat te losses occur at a minimum temperature around 68 C, reacing a value of about P tot 1 = T T 0 [ V1 ( t) I1( t) VL ( t) I L ( t)] dt (4) 697

4 Fig. 7. Core losses in function of temperature. It is possible to also find te values of losses in te windings. As tese coils ave low impedance, te losses will be low. It was found a value of approximately 17. In te situation of operation indicated, te values of te vector magnetic flux density normal to te surface of te central core of te transformer can be seen in Figure 8. Fig. 10. Current density in te secondary winding. Fig. 11. Vector magnetic flux density in te core of te transformer. Fig. 8. Flux density in transformer. In order to sow te best distribution of current in te windings, we generated te Figures 9 and 10. It can be observed tat current is more evenly distributed trougout te trail of copper wit a consequent reduction of skin effect and improvement in efficiency. In Fig. 11 you can view te distribution of vector magnetic flux density in te core of te transformer. VI. COCLUSIOS From te data obtained in simulation was possible to confirm tat te transformer wit PCB windings is an effective solution for applications were you want optimum performance at ig frequencies and powers. As previously mentioned, work is currently being developed and ave not been made simulations taking into account te waveform of te inverter. Te waveform is square, differently from discussed in tis article. Future studies can be made a more detailed study of te influence of skin effect and proximity effect in te calculation of transformers losses. Fig. 9. Current density in te primary winding. 698

5 REFERECES [1] G. Prieto, O. Prieto, C. Gay and I. T. Yamamoto, Destruction of Residual Fumigant Using a Plasma Reactor, IEEE Transactions on Industry Applications, vol. 39, no. 1, pp , january/february [2] de Medeiros, Tiago Q., Alexandre M. F. Guimarães, Andrés O. Salazar and André L. Maitelli, Automation system applied to a plasma inertization plant, Eletrônica de Potência SOBRAEP, vol. 12, no. 1, pp , marc [3] J. Li, Y.Si, Z. iu and D. Zou Modeling Simulation and Optimization Design of PCB Planar Transformer, in Proc. of ICEMS, vol. 3, pp , [4] Dubut, J. P., Alexandre M. F. Guimarães, Marcelo Dantas Lopes, Pedro Ivo de A. do ascimento, Andrés O. Salazar and André L. Maitelli Hig Frequency Converter Based On Resonant Inverters For Exciting A 50k Inductive Coupled Plasma Torc, in Proc. of COBEP, pp , [5] C. Ebert,. Carpes Jr and J. Fagundes, Projeto de indutores e transformadores planares utilizados em fontes de alimentação caveadas, in Proc. of Induscon, pp. 1-6,