IMPLEMENTATION OF AC-AC CONVERTER FOR INDUCTION HEATING USING LOW COST EMBEDDED CONTROLLER

Transcription

1 MPLEMENTATON OF AC-AC CONVERTER FOR NUCTON HEATNG USNG LOW COST EMBEE CONTROLLER.Kirubakaran S.Rama Reddy Jerualem college of Engineering, Centre for collaborative reearch with Anna Univerity,Chennai., ndia. Abtract: A ingle-witch parallel reonant converter for induction heating i imulated and implemented. The circuit conit of an input LC-filter, a bridge rectifier and a controlled power witch. The witch operate in the oft commutation mode and erve a a high frequency generator. The output power i controlled via witching frequency. A teady tate analyi of the converter operation i preented. The experimental reult are compared with the imulation reult. Key word: Electronic, AC-AC converter, induction heating, oft commutation, Embedded control.. ntroduction Static frequency converter have been extenively applied in indutry a a ource of medium frequency power upply for induction heating and melting intallation. They are applied in all branche of the military, machine-building indutrie, for jewellery, mithy heating, dometic heating, cooking device and other purpoe. The ordinary circuit of an AC-AC converter for induction heating, typically include a controlled rectifier and a frequency controlled current ource or a voltage ource inverter. t i a well known fact that the input rectifier doe not enure a ine wave input current, and i characterized by low power [-]. Recently many tudie of high power factor rectifier with a ingle witch have been made [4-5]. Thee cheme are alo characterized by a cloe to ine wave input current. Three phae AC to C converter with improved power quality i given by [7]. High frequency voltage fed inverter with phae hift control for induction heating i given in [8-]. The above literature doe not deal with embedded implementation of the AC to AC converter fed induction heater. n the preent work, an embedded controlled AC to AC converter i introduced and implemented. n the cheme (Fig.) of the AC-AC converter there are two main advantage: t i characterized by a high power factor and a ine wave input current, and On the other hand, the inverter circuit i contructed with a ingle controlled witch, which erve a a highfrequency generator for induction heating. Fig.. Single witch AC-AC converter. Principle of operation The operating principle of the circuit are illutrated by Fig.. a Mode (to-t) b. Mode (t-t)

2 . nterval : t<t<t The equivalent circuit i hown in Fig.b. Two diode, and the witch S are on. n thi interval the capacitor C dicharge via the circuit C--S-Lrload-. Thi interval end when the capacitor voltage reduce to zero. c. Mode (t -t ) Fig.. Equivalent Circuit The theoretical waveform are hown in Fig..We uppoe the witching frequency i much higher than the input line frequency and in the analyi we arbitrarily choe the time interval where vin>.. nterval : t<t<t The equivalent circuit i hown in Fig.a. Four diode -4 and the witch S are off. n thi interval the capacitor C charge up practically linearly at a rate and a polarity correponding to the intantaneou input voltage vin.. nterval : t<t<t The equivalent circuit i hown in Fig.c. All the diode and the witch S are on. n thi interval the current flow through witch S via two parallel bridge branche. Thi interval end when the witch current decreae to zero. At thi moment the witch turn off and the proce tart from the beginning..operation analyi An analyi of the circuit operation i baed on the commonly accepted aumption that all circuit component are ideal. The approximate analytical calculation are baed on two additional aumption: the witch current can be approximated by a emi inuoidal, and the load power i determined by the firt harmonic of the load voltage. n thi converter optimal range of normalized parameter wa choen. The maximum normalized value of witch voltage i (vwmax vwmax / vb 4 5). To provide thee value it i neceary to chooe the following range of the normalized circuit parameter: L L L r..; ω r L C r () 5; ω..9 ω B Evaluation of the relationhip between input and output voltage Mg Vo/Vin A A A i w.max in π ( + ). co( π ).co(π ) 4 π ( 4 ) w. max w. max R.max w..max + R ( ω / ω ) () () (4) π + Ro ( ω ) ( co( )) V... ω o m M r g A. A. A.π ( + ) V in. r. m (5) Fig.. deal Switching Waveform Thi relationhip i expreed in Fig..a.

3 The value of duty cycle and may alo be found from the approximate polynomial expreion ( ω ω R r +.ω r R + 7.4R o ω ) ( L r 5.5ω + 75.ω + 9.R + 75L r ω.rω ) (6) Fig..a. Factor Mg againt parameter Ro & ω 4. Simulation Reult The AC to AC converter fed induction heater i imulated uing the matlab imulink and the reult are preented here. The circuit model of the AC-AC converter i hown in Fig.4a.. Scope are connected to meaure output voltage, driving pule and capacitor voltage. The value of duty cycle and may be calculated from the plot Fig..b. Fig.4a. imulation Circuit Fig.4b. riving pule Fig..b. uty cycle againt parameter Lr, ω Fig.4c. Voltage acro Switch S (V d )

4 R. The gate ignal i connected to port pin P.. Variou tep involved in the firing pule generation i hown in Fig.4.h. n the flow chart delay i reflecting the turn on interval of witch during which pule will be logic, wherea delay reflecting the turn off interval of witch during which pule will be logic. Start Fig.4d. Current through Switch S Switching pule are hown in Fig 4b.Voltage and current waveform of the witch are hown in Fig.4c & Fig 4d repectively. Output of converter i hown in fig. 4.e. Port initialization Turn on witch S Call delay Turn off witch S Fig. 4e. Output voltage Call delay U VN VOUT V U VN VOUT 5V TX N45 N45 L78/TO L785/TO R k Short jump VAMPL V V FREQ 5HZ 4 N45 5 N45 C E-6 LE C5 E- C7 Y ZTB U4 P./AN P./RX 4 P./AN P./TX 6 5 P. P./NT 7 6 P. P./NT 8 7 P.4 P.4/T 9 8 P.5 P.5/T 9 P.6 P.7 P XTAL XTAL RST/VPP VCC E 47E-6 47E-6 U 7 HN HO LN LO SHN 6 COM VB 9 VCC 5 V VS VSS R Fig.4.h Flow chart The comparion on the performance of conventional AC-AC converter and ingle witch AC-AC converter i preented in Table. The reult confirm that the ingle witch converter deliver the better performance than any other converter in achieving the better efficiency. E- R k SW SW C PUSHBUTTON E-6 AT89C5 Fig 4.g 89C5 baed control circuit The ATMEL 89C5 baed control circuit i hown in Fig. 4.g. Atmel microcontroller 89C5 wa ued to generate driving pule for the MOSFET witche. They are amplified uing the driver C nput voltag e in volt Table Performance comparion Output voltage Efficency in volt in % Convent- Single Conve- -ional witch -ntional converter converter converter Single witch converter

5 When the propoed converter and the previouly developed one are operating under the condition of maximum output power, the power lo analyi i hown in table-. The power lo diipation of the newly developed converter i comparatively lower than the previouly developed one. Table Power loe analyi in the circuit component evice and Power diipation component Newly Previouly developed developed Switch 49W 69W Filter inductor 8W 5W H load 58W 58W Bridge rectifier W 7W 5. Experimental Verification The ingle-witch AC-AC converter wa built and teted at V. The experimental etup of the AC to AC converter i hown in Fig.5. The circuit parameter are R6Ω; L5µH; C.5µF; LrµH; Li8.mH; Cin.94µF and the witching frequency ωs (6-) x -.The experimental waveform of the output voltage i hown in Fig.6. The input voltage and current are hown in Fig.7. t implie power factor i cloe to unity. The output power control wa alo checked and it dependency on the witching frequency i hown in Fig.8. The output power increae with an increae in the witching frequency. Fig. 5. Hardware layout Fig.6 Ocillogram of output voltage Fig 7. Experimental nput voltage and current Fig.8. Output power v/ witching frequency 6. Concluion An embedded controlled AC-AC converter circuit for induction heating ha been imulated and teted. The converter input current i practically inuoidal and it power factor i cloe to unity. The circuit topology i very imple ince it include only one power witch. Thi witch operate in a oft commutation mode. The converter provide a widerange power control. Thi converter ha advantage like reduced hardware, reduced tree and high power denity. The imulation and experimental reult demontrate the actual converter capability to control the heat. The experimental reult agree cloely with the imulation reult. Reference. AWSON,F.P., and JAN,P.: A comparion of load commutated inverter ytem for induction hearting and melting application. EEE Tan. on Power Electron., 99, 6, pp CHUNOVSKY, V., AXELOR,.B., and SHENKMAN, A. : An approximate analyi of a tarting proce of a current ource parallel inverter with a high-q induction heating, EEE Tran. on Power Electron., 997,, pp KAML, M., YAMAMOTO, S., and ABE, M.: A 5-5 khz half bridge inverter for induction heating application, EEE Tran. on Power Electron., 5

6 996, 4, pp JANG, Y., and ERCSON, R.W.: New ingle witch three phae high power factor rectifier uing multireonant zero-current witching, EEE Tran. Power Electron., 998, PE-, pp SML, E.H., OLVERA, C.M., and ERCSON, R.W.: A low ditortion three phae multireonant boot rectifier with zero current witching. EEE Tran. Power Electron., 998, PE -, pp Singh, B.; Singh, B.N.; Chandra, A.; Al-Haddad, K.; Pandey, A.; Kothari,.P.: A review of ingle-phae improved power quality AC-C converter. EEE Tran. nd. Electron., Vol. 5, No. 5, October, pp Singh, B.; Singh, B.N.; handra, A.; Al-Haddad, K.; Pandey, A.; Kothari,.P.: A review of three-phae improved power quality AC-C converter. EEE Tran. nd. Electron., Vol. 5, No., June 4, pp Mollov, S.V.; Theodoridi, M.; Foryth, A.J.: High frequency voltage-fed inverter with phae-hift control for induction heating, EE Proc.-Electr. Power Appl., Vol. 5, No., January 4, pp J.M. Burdio, F.Monterde, J.R. Garcia, A two output erie-reonant inverter for induction heating cooking appliance, EEE Tarn. Power Electron., vol., no.4, pp 85-8, Jul.5..J. Acero, R. Alonjo, and J.M. Burdio Modeling of planar piral inductor between two multilayer media for induction heating application, EEE Tran.Magn., vol.4,no., pp 79-79, Nov. 6...B.Saha, K.Y. Suh, S.K. Kwon, and M.Nakaoka, Selective dual duty cycle controlled high frequency inverter uing reonant capacitor in parallel with an auxiliary revere blocking witch, J.Power Elecctron., vol.7, no., pp8-, Apr. 7..RajKumar Ann baed over-modulated pace vector pule width modulator for vcim drive,journal of Electrical Engineering, Volume 8 /8 Edition..Jammuna V, Rama Reddy S Ann controlled energy aver for induction motor drive,journal of Electrical Engineering, Volume 8 /8 Edition 4. Mr..Kirubakaran ha obtained M.E. degree from Bharathidaan Univerity in. He i preently doing hi reearch in the area of AC-AC converter for induction heating. He ha year of teaching experience. He i a life member of STE. r. S. Ramareddy ha obtained M.E. degree from Anna Univerity in 989. He ha done hi reearch in the area of reonant converter in the year 995. He ha year of indutrial experience and 8 year of teaching experience. He i a life member of E, ETE, STE, SSR, SPE. He ha authored text book on power Electronic and Electronic circuit. He ha publihed paper in the area of power electronic and FACT. 6