7 th International Conference on DEVELOPMENT AND APPLICATION SYSTEMS S u c e a v a, R o m a n i a, M a y 27 29,

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1 7 h Inernaional Conference on DEVEOPMENT AND APPICATION SYSTEMS S u c e a v a, o m a n i a, M a y 27 29, THEE-PHASE AC CHOPPE WITH IGBT s Ovidiu USAU 1, Mihai UCANU, Crisian AGHION, iviu TIGAEU Gh. ASACHI Technical Universiy of Iasi omania, Faculy of Elecronics and Telecommunicaions sr.bulevardul Carol I, nr.11, O Iasi 1) ovidiu@ec.uiasi.ro Absrac. This paper describes wo circuis hree-phase ac chopper realised wih IGBT s wih high carrier wave frequency (chopper frequency). The firs circui described in his aricle is a hree-phase chopper funcioning wih inducive load. In boh siuaions he power sources are symmerically hree-phases. Also, he simulaion waveforms of he load and inpu currens for he power circuis are presened. Inroducion A.C. Choppers have been widely used o conrol average load power from a fixed ac source. The common applicaions are indusrial heaing, ligh dimming, and ac moor speed conrol. The advanages of he ac choppers are simpliciy, abiliy of conrolling large amoun of power, and high efficiency. The IGBT s conrols for boh circuis are made using uniform echnique PWM, presened in deail in (e.g. [5] ), where he conrol signal is obained by comparing a riangular wave wih a reference volage used for modifying he duy facor D and, implicily, he load volage. The conrol volages and are opposie signals. In order o obain idenical volages on he hree-phase sysem, he index of modulaion m mus be muliple of six The chopper frequency was chosen o be f S = 6kHz. The power circuis wih filers are used o obain he sinewave of he inpu curren. Power circui Figure 1 shows he power circui of he hreephase ac chopper in he case of resisive load. The circui conains one ac swich Q wih IGBT and six diodes. The IGBT conrol sraegy is presened in Figure 2. Suppose he ac-inpu volage is expressed as: v v S v T i i S i T 1 2 C C 2 i S S S v S v SS v ST Vcom1 Figure 1. Power circui of hree-phase ac chopper for resisive loads. v = V 2 cosω, ϖ = 2π. i = I 2 cos( ω ϕ ) T 2π vs = V 2 cos( ω ) (1) 2π i = I 2 cos( ω ϕ ) 4π vt = V 2 cos( ω ) 4π it = I 2 cos( ω ϕ ) ϕ - represen he shif angle beween he volage and he curren of he power sources. For a symmerical hree-phase sysem, we have v v + v = 0 ; i + i + i = 0 (2) + S T S T The index of modulaion is: f s m = = 6 l, l Ν () f Q 159

2 v S v SS v ST IGBT s Q 1, Q 2, Q regulaes he power delivered DT S T S 4 8.1A 25.8A 2 Source curren i wih =5uF 1 =2mH D= A D=0. T -2 Figure 2 The waveforms of he load volage and he conrol signal Considering he condiion () he waveforms of he load volage are presened in Figure 2. The mos cases in pracice he load has an inducive characer. In his case, for a hreephase sysem, he load can be conneced in he shape of riangle or of a sar. Figure presens he circui of a hree-phase ac chopper in which he load is conneced in he shape of a sar wihou a ground wire ms V 60ms 70ms 80ms 90ms 100ms Figure 4. Source curren i waveforms. oad curren i oad volage v S v v S i i S 1 2 C Q 1 Q 2 C ' 1 C ' i v vs V 60ms 65ms 70ms 75ms 80ms v T C 2 i T Q C ' 2 v T Figure 5. oad curren i and load volage vs Figure. Three-phase ac chopper for an inducive load conneced in he shape of a sar wihou ground wire The chopper in Figure is realised by using nine swiching diodes and four IGBT s. The hree Q 1, Q 2, and Q IGBT s direcly conneced o he hree-phase sysem are conrolled simulaneously wih he conrol signal and he Q 4 IGBT wih he conrol signal. The Q 4 o he load, IGBT Q 4 provides he freewheeling pah o discharge he sored energy when he series swich is urned off. The capaciies C 1, C 2 and C are mean o ensure he freewheeling pah o he load currens saring wih he momen when he IGBT s Q 1, Q 2, Q, are off and he IGBT Q 4 is on. For he wo circuis presened in Figure 1 and Figure, he inducors 1, 2, and he capaciies, C 2, C form inpu filers and are mean o approximae he absorpion of he sinusoidal curren from he sources v, v S and v T. 160

3 1 1 (50.000Hz,12.784A) (6.010kHz,10.986A) Hz,89.485V) (6.1000kHz,76.644V) load volage v 5 2 (50.000Hz,25.54A) (50.000Hz, V) load volage v (6.001kHz,12.789A) 10 ( kHz,89.796V) (50.000Hz,8.142A) 0 20 (50.000Hz, V) load volage v 2 1 (6.1999kHz,4.172A) 10 (6.1997kHz,28.571V) Figure 6. Harmonic conens of Figure 7. Harmonic conens of load volage v Simulaion resuls The presened power circuis of he hree-phase ac choppers were esed by simulaion. A srong inducive load was considered wih = 7 ohms, = 2 mh, and ampliude of mains phase volage V 2 =1 Carrier frequency was f s = 1/T S = 6 khz and m = f S /f = 120. Figure 4 shows he waveforms of he source curren i for hree values of he duy facor D. Figure 5 presens he waveforms of he volage v S and of he curren i for. Figure 6 shows he harmonic conens of he for hree values of he duy facor D. Figure 7 shows he harmonic conens of he load volage v for hree values of he duy facor D A 7.8A 1.8A Source curren i wih =15uF, 1 =5mH D =0.9 D =0.6 D = ms 70.0ms 80.0ms 90.0ms 99.2ms Figure 8. Source curren i waveforms. In order o approximae he sinusoidal currens absorbed i, i S, i T, we have consider ha 1 = 2 = =2mH, and he capaciies = C 2 = C =16uF. Figure 10 represen he waveforms obained by

4 simulaion of he absorbed currens i,i S,i T, sum of hese currens i + i S + i T, and sum of he volages v + v S + v T. Obained resuls confirm heoreical affirmaion presened in relaion (2). 20.9A oad curren i wih =15uF, 1 =5mH D= A v +v S +v T =0 i +i S +i T =0 D=0. 7.4A 2 i i S i T 154.7ms 160.0ms 170.0ms 180.0ms 190.0ms 200.0ms ms 70.0ms 80.0ms 90.0ms 97.6ms Figure 9. oad curren i Figure 10. Source currens i, i S, i T waveforms, sum of he currens i + i S + i T and sum of he volages v + v S + v T Figure 11 shows he harmonic conens of he 2. (50.000Hz,1.9047A) source curren i (50.000Hz,7.4971A) (50.000Hz,14.616A) 1 (50.000Hz,8.0517A) source curren i Hz,20.946A) 1 2 (50.000Hz,18.117A) source curren i 1 Figure 11. Harmonic conens of source curren i Figure 12. Harmonic conens of he load curren i source curren i, Figure 12 presens he harmonic conens of he and Figure1 presens he harmonic conens of he load volage v for hree value of duy facor D. Figure 8 shows he inpu currens i, and figure 9 presens he wave forms of he for hree value of duy facor D, when he 162

5 power circui in Figure is used, wih = C 2 = C = 15μF, 1 = 2 = = 5mH, C 1 = C 2 = C = 1μF. Sinusoidal waveforms for i S have been obained. 40 load volage V V S V T 10 (50.000Hz,91.718V) (6.1999kHz,78.706V) load volage v 5 0Hz 5KHz 10KHz 15KHz 20KHz (50.000Hz, V) (6.2001kHz,86.4) load volage v V Hz, V) load volage v 1 5V + 10 (6.1997kHz,25.052V) 0Hz 5KHz 10KHz 15KHz 20KHz 25KHz Figure 1. Harmonic conens of he load volage Figure 14 represen he waveforms obained by simulaion of he load volage v,v S,v T, and he conrol signal,. Conclusion The simulaion resuls proved good performance of he hree-phase ac chopper wih IGBT s on high chopper frequency. A sinusoidal inpu curren was obained by using he power circui wih filer. In he case of a symmerical hree-phase sysem, he ground wire is unusable. For his reason, he ground wire was no necessary in he power circui. eferences [1] evankar, G.N, Trasi, D.S., (1977) Symmerical Puls Widh Modulaed A.C.Chopper I.E.E.E. Trans on Elecron Conr. Insrum. Vol.IECI-24, pp V 1 5V + 80ms 85ms 90ms 95ms 100ms Figure 14. oad volage v,v S,v T, and he conrol signal, for he duy facor [2] Jang, D., Choe, G.,(1991) Asymmerical PWM Mehod for A.C. Chopper wih Improved Inpu Power Facor, I.E.E.E.- PESC Conf. ec., pp [] Jang, D.H., Choe, G.H., Ehsani, M., (1995), Asymmerical PWM Technique wih Harmonic Eliminaion and Power Facor Conrol in A. C. Chopper,I.E.E.E. Trans. on Power Elecronics, Vol. 10, Nr. 2, pp [4] Choe, G., Park M. (1998), An Improved PWM Technique for A.C. Chopper IEEE Trans. on Power Elecronics, Vol.4, pp [5] ucanu, M., Ursaru, O., Aghion, C., (200), Single Phase AC Chopper wih IGBT s, I.E.E.E.- Proc. of SCS, IASI, Vol. 1, pp