The 18 th Ntionl onference on Electricl Drives NAE 2016 Prcticl implementtion of hlfridge SRM converter for low power pplictions Tieriu Rusu 1, Petre Dorel Teodosescu 1, Adrinornel Pop 2 1 Fculty of Electric Engineering, Technicl University of lujnpoc, Romni 2 Brose Fhrzeugteile GmH & o. Kommnditgesellschft, Advnced Development Drives, 2, Würzurg, Germny Astrct The pper is presenting the prcticl implementtion of hlfridge converter driving switched reluctnce motor. One of the dvntges of the proposed converter topology is tht it ensures independent control for ech motor phse. The mesurements re concentrted on two motor types, nmely four phse SRM nd on two phse, highspeed SRM. The min ojective of the pper is the working principle demonstrtion nd to point out the min dvntges/disdvntges of the proposed topology nd emphsize future developments. Keywords Hlfridge, SRM, ipolr drive, cpcitor, high speed 1. INTRODUTION The requirements from the customer side re continuously ecoming more stringent oth in terms of performnce s well s the cost. Meeting the performnce requirements in the given conditions is mndtory for n electric drive motor, ut very often its finl cost sed on which one chooses etween different ville options. Therefore the continuous struggle for improving the performnce chrcteristics of the PMless of PMfree mchines [1]. Due to wellknown issues, discussions nd limits (i.e. lower efficiency nd power density when compred to rre erthsed PMSMs, high torque ripple nd NVH) [2], for specific pplictions SRM cn e prt of the solution. The most used topology for switched reluctnce mchine is symmetric ridge topology which is two qudrnt converter [3], operting under unipolr current condition. It is generlly known tht this converter topology provides the iggest numer of dvntges nd the smllest numer of disdvntges when driving SRM [4]. However, the iggest drwck of the symmetric ridge topology is represented y the fct tht such topology contins two diodes nd two trnsistors per one phse, which mens higher cost when compred with conventionl converters for PMSM, wherein only two trnsistors per phse re used. One further spect from the semiconductors point of view is tht there re not mny stndrdized power modules on the mrket hving n symmetric ridge configurtion (2 trnsistors nd 2 diodes) compred to regulr hlf ridge configurtion. Therefore the usge of discrete components for symmetric ridge is necessry. Furthermore, specil cre hs to e pid when clculting the rtings of the dditionl power diodes s due to high internl resistnce the losses my exceed very fst the vlue corresponding to stle therml ehvior, thus either lrger diodes or expensive cooling is needed. The most of ville MOSFET nd IGBT trnsistors re mnufctured with uild in ntiprllel diode, fct tht cnnot e exploited in cost effective wy for SRM motor drive. The switched reluctnce mchine cn operte under ipolr excittion regime, since the torque is not dependent upon the direction of the current, therefore the possiility of using the conventionl voltge source inverter (VSI) to drive n SRM hve een exploited in [57], however with ig drwck considering the fct tht the use of Yconnection of the motor windings is incresing the mgnetic coupling etween the motor phses thus, eliminting the independent phse control cpility. In [8] ttempts hve een mde to drive 3 phse mchine y mens of 3 phse VSI used in conjunction with regulr hlfridge topology. Bipolr current excittion hs een pplied to the motor phses ut the motor cnnot hndle full independent current control nd the overlpping condition etween phses cn e difficult. In this work, method for eliminting this drwcks is proposed nd vlidted y mesurements on two types of SRMs hving different rnge of working speeds. The work is structured in four sections s follows. In Section II, the considered topology is studied nd the operting principle is explined y showing the current pths modes nd conducting switches. In section III the prcticl implementtion nd the ATA ELETROTEHNIA, Volume 57, Numer 34, 2016, Specil Issue, ISSN 23445637
474 The 18 th Ntionl onference on Electricl Drives NAE 2016 mesurements re done for two SRM topologies. Finlly the conclusions re drwn in the lst section. T5 Tn 2. ONVERTER TOPOLOGY DESRIPTION Lph 1 Lph3 Lph n The considered converter topology sed on regulr hlf ridge configurtion for driving n SRM ws t first introduced in [9]. It promises independent phse control nd is mde y using commonly found trnsistor nd diode in chip, which is the stteofthert technique in hlf ridge converter topologies, such s VSI used for driving 3 phse PMSM. A single phse representtion of the hlf ridge converter topology driving the SRM is shown in Fig. 1. In Fig. 2 the converter is illustrted for three phse mchine ut it cn e strightforwrdly extended for ny numer of phses needed. ph1 Fig. 1. One phse representtion of the considered converter Phse 1 ph1 T6 Fig. 2 Extention of the proposed topology for three phse SRM The operting modes possile (Fig. 4, Fig. 4, Fig. 5, Fig. 5) for such converter topology cn e explined ccording to the presumptive timing wveforms (depicted in Fig 3) over the time intervls t k s follows: Time intervls, re defined s tt 2kk1 with kk = (0,1,..4), in which the phse fluxing is ccomplished y turning ON the high side trnsistor, wheres the low side trnsistor is kept in OFF stte. Over these time periods, the cpcitor connected in series with the phse is chrging from the us power ril. For this mode of opertion (positive cycle fluxing), the current circultion pth is shown in Fig. 4. During the time intervls defined s tt 2kk2 with kk = (0,1,..4), the high side trnsistor () is put in the OFF stte, forcing the phse to e defluxed through the ntiprllel diode from the trnsistor which ecme forwrded ised. At the eginning of the positive cycle period, the cpcitor hving low mount of energy stored, the defluxing current hve lower slope of Phse 2 Lph3 Tn1 Phse n ph n Phse pcitor Voltge Voltge HVA Phse Voltge Phse urrent t 1 t 2 t 3 t 4 t 5 t 6 t 7 t 8 t 9 t 10 t 11 t 12 t 13 t 14 t 15 t 16 t 17 t 18 t 19 t 20 t 21 Positive ycle Negtive ycle Fig. 3 Presumtive wveforms for SRM phse ATA ELETROTEHNIA, Volume 57, Numer 34, 2016, Specil Issue, ISSN 23445637
The 18 th Ntionl onference on Electricl Drives NAE 2016 475 descending s well. When the voltge level cross the cpcitor hs n incresed vlue, the slope of the defluxing current is incresing. The cpcitor chrges during the defluxing period. The converter current circultion pth for this operting mode of is shown in Fig. 4. During the time intervls defined s tt 11, the oth trnsistors re in the OFF stte nd there is no current flow in the motor phse. The voltge cross the cpcitor during this period of time reches its mximum vlue. During the time intervls defined s tt 2kk2 with kk = (4,5,..8),the phse fluxing is ccomplished y switching ON the low side trnsistor, while the trnsistor from the upper side is kept OFF. The current in the mchine phse during this operting mode hve negtive vlues its circultion pth eing shown in the Fig. 5. During the time intervls defined s tt 2kk1 with kk = (6,7,..10), the low side trnsistor () is put in the OFF stte, forcing the phse to e defluxed through the ntiprllel diode of the trnsistor. At the eginning of the negtive cycle period, the cpcitor hs the mximum stored energy; the defluxing current of the phse is mde with lower slope. When the voltge level cross the cpcitor hs n incresed vlue, the slope of the defluxing current is higher. The current pth for this operting mode converter is presented in Fig. 5. ph1 ph1 Fig. 5. Working principles. ) Negtive cycle fluxing; ) Negtive cycle defluxing 3. EXPERIMENTAL RESULTS OF THE HALF BRIDGE BASED SRM ONVERTER Fig. 4. Working principles. ) Positive cycle fluxing ) Positive cycle defluxing ph1 ph1 The proposed converter topology hs een experimentlly tested on two different commercilly ville switched reluctnce mchines. Firstly, tests hve een conducted on four phse mchine hving numer of 8 sttor poles nd 6 rotor poles 8/6 SRM. In the second prt, the experimentl mesurements hve een mde on commercilly ville high speed twophse 4/2 SRM. After developing the required models in Simulink they were compiled in order to e loded on the dspaesed rpidcontrol prototyping pltform. In Fig. 6 one cn see the phse currents when the 8/6 SRM is supplied with ipolr current. The reference current for the test elow is set to 1.2A nd hysteresis nd of 0.25A is employed, wheres the speed of the motor is set to low vlue of 300 rpm. Fig.7. presents the cquired dt (using n oscilloscope) of some of the signls on the converter with respect to one phse. hnnel 1 is showing the phse current (phse 1), while hnnel 2 shows the phse cpcitor voltge. On hnnel 3, the upper trnsistor drinsource voltge is displyed, wheres the phse voltge is shown on chnnel 4. ATA ELETROTEHNIA, Volume 57, Numer 34, 2016, Specil Issue, ISSN 23445637
476 The 18 th Ntionl onference on Electricl Drives NAE 2016 Fig. 6 Experimentl results of the hlf ridge sed converter Bipolr phse currents pplied to n 8/6 SRM Fig. 7. Experimentl results of the hlf ridge sed converter Phse current nd voltge, control signls pplied to n 8/6 SRM The sme tests hve een successfully done, considering this time high speed switched reluctnce mchine (4/2 configurtion sttor poles over rotor poles), running t 12 000 rpm. The ojective ws to verify nd to ssess the ehviour of the proposed hlf ridge sed converter topology on such operting conditions. The simulted model ws developed nd dpted to this specific two phse mchine, nd fterwrds rel time implementtion hs een done. Some of the results cquired y mens of n oscilloscope re shown in Fig 8 nd Fig 9. In the wveforms depicted in Fig 8, one cn oserve on chnnel 1 the control signls pplied to the gte of the trnsistor from the upper leg of the hlf ridge. On chnnel 2 nd chnnel 3 the phse current nd phse voltge hve een displyed. Finlly on chnnel 4 on the grph the cpcitor voltge is shown. Similrly, tests hve een conducted t higher speeds, nd the otined results re shown in Fig. 8, Fig. 8c, Fig. 8d. In the Fig 9, the two phse currents re shown on chnnels 1 nd 2. On the chnnel 3 the phse voltge ssocited to the phse 1 is highlighted, wheres on the c d Fig. 8 Two phse SRM drive wveforms t different speeds ATA ELETROTEHNIA, Volume 57, Numer 34, 2016, Specil Issue, ISSN 23445637
The 18 th Ntionl onference on Electricl Drives NAE 2016 477 chnnel 4, phse voltge ssocited to the phse 2 is eing displyed. Fig. 9. Experimentl results of the 2 phse hlf ridge sed converter. Phse currents nd voltges pplied to n 4/2 SRM In this section the possiility of using modified hlf ridgesed converter topology, derived from conventionl VSI (used for driving of 3 phse PMSMs) hve een investigted t oth simultion nd experimentl level. An dvntge of employing such topology is represented y the possiility of using mssively produced threephse full or hlf ridge pckges, insted of conventionl converter for SRM, which does not hve stndrdized converter pckge. Moreover, if discrete components re used, the conventionl converter for SRM contins 2 more discrete diodes for ech phse, which hve closed price to tht of trnsistors, especilly where high current cpility is needed. By using the proposed converter, the elimintion of the discrete diodes is ccomplished, leding to price svings of semiconductors. However, the phse cpcitor of the proposed topology is needed to e discussed, since it cn ffect the totl cost of the converter. onsidering tht the price of the cpcitor is directly proportionl with its cpcitnce, low vlue cpcitnce is required for good price lnce. Furthermore the technology of the cpcitor (polrized or nonpolrized) cn e lso tken into discussion, since the polrized electrolytic cpcitors cn store higher energy, ut with disdvntge of lower life spn, while the unpolrized, hve lower energy cpcity, ut much higher reliility. With regrds to the possiility of using nonpolrized cpcitor, the pplictions suitle for such drive re in the low power rnge nd high speed. 4. ONLUSIONS From the ove presented results, one cn conclude tht the present converter topology hs limittions, one eing the fct tht is not llowing the utiliztion t the mximum of us voltge, which for utomotive industry (where low dc us voltge is ville) cn e determining fctor not to continue with the investigtion of it. However, due to its dvntges (highlighted in this work) it cn e stted tht there re some pplictions especilly for high speed nd low torque, such s electriclly driven superchrgers, highspeed hnddryers or vcuum cleners in which this topology cn e used successfully. Acknowledgments: This work ws prtilly supported y grnt from the Romnin Ntionl Authority for Scientific Reserch, MENUEFISDI, project PNIIPTPA201340914, No. 60/2014 in the frme of the project Innovtive electric power grid protection device ginst low power fctor electronic lods (IEDPF). This reserch ws prtilly finncilly supported y the Europen ommission under EU Frmework FP7 PEOPLE, suprogrmme re, Mrie urie Actions, IndustryAcdemi Prtnerships nd Pthwys in the frme of the project Optiml LowNoise EnergyEfficient Electricl Mchines nd Drives for Automotive Applictions (EMDALoOP). REFERENES 1. I. Bolde, L. N. Tutele, L. Prs, D. Dorrell Automotive Electric Propulsion Systems With Reduced or No Permnent Mgnets: An Overview, IEEE Trns. Ind. Electron., vol. 61, no. 10, pp. 5696 5711, Octoer 2014. 2. T. J. E. Miller, Switched Reluctnce Motors nd their ontrol, Oxford, Ed. Mgn Physics Pulishing, 1993. 3. R. Krishnn, Switched Reluctnce Motor Drives Modelling, Simul tion, Anlysis, Design nd Applictions, R Press, 2001. 4. T. J. E. Miller, Electronic ontrol of Switched Reluctnce Mchines, Newnes, August 2001. 5. K. Tungpimolrut, S. Kchpornkul, P. Jitkreeyrn, P. Somsiri, N. hy opitk, Distorting improving method for three phses full ridge converter sed switched reluctnce motor drive system, IEEE 14th Workshop on ontrol nd Modelling for Power Electronics (ompel), Slt Lke ity, USA, 2326 June, 2013. 6. W. M. d Silv,. Goldemerg, A. Vn. den Bossche, A New Three Phse Fullridge dump onverter Applied to Switched Reluctnce Motor Drives, IEEE 36th Power Electronics Specilists onference (PES), Recife, 16 June, 2005. 7. P. Somsiri, K. Tungpimolrut, P. Aree, ThreePhse Full Bridge on verters Applied to Switched Reluctnce Motor Drives with modified Switching Strtegy, Proceedings of Interntionl onference on Electricl Mchines nd Systems, Seoul, Kore, 811 Octoer, 2007. 8. Z. Gro, S. Vukosvic, E. Levi, A Novel Power Inverter for Switched Reluctnce Motor Drives, Fct Universittis Series: Electronics nd Energetics, vol. 18, no. 3, pp. 453 465, Decemer 2005. 9. P. D. Teodosescu, T. Rusu,. S. Mrtis, A.. Pop nd I. Vintiloiu, "onsidering hlf ridge converters for switched reluctnce motor drive pplictions," 2015 Intl Aegen onference on Electricl Mchines & Power Electronics (AEMP), 2015 Intl onference on Optimiztion of Electricl & Electronic Equipment (OPTIM) & 2015 Intl Symposium on Advnced Electromechnicl Motion Systems (ELETROMOTION), Side, 2015, pp. 186191. ATA ELETROTEHNIA, Volume 57, Numer 34, 2016, Specil Issue, ISSN 23445637