Kuleli sonto siyaqhubeka nesihloko sangesonto eledlule.

1.2 Ama-capacitor e-electrolytic

I-dielectric esetshenziswa kuma-capacitor e-electrolytic yi-aluminium oxide eyakhiwe ukugqwala kwe-aluminium, ene-dielectric constant engu-8 kuya ku-8.5 kanye namandla e-dielectric asebenzayo angaba ngu-0.07V/A (1µm=10000A). Kodwa-ke, akunakwenzeka ukufeza ukujiya okunjalo. Ubukhulu besendlalelo se-aluminium kunciphisa i-capacity factor (i-capacitance ethile) yama-capacitor e-electrolytic ngoba i-aluminium foil kufanele iqoshwe ukuze kwakhiwe ifilimu ye-aluminium oxide ukuze kutholakale izici ezinhle zokugcina amandla, futhi ubuso buzokwakha izindawo eziningi ezingalingani. Ngakolunye uhlangothi, ukumelana kwe-electrolyte kungu-150Ωcm we-voltage ephansi kanye no-5kΩcm we-voltage ephezulu (500V). Ukumelana okuphezulu kwe-electrolyte kunciphisa ugesi we-RMS ongamelana nawo i-capacitor ye-electrolytic, ngokuvamile ku-20mA/µF.

Ngenxa yalezi zizathu, ama-capacitor kagesi aklanyelwe i-voltage ephezulu engu-450V evamile (abanye abakhiqizi baklama ama-600V). Ngakho-ke, ukuze uthole ama-voltage aphezulu kuyadingeka ukuwafinyelela ngokuxhuma ama-capacitor ochungechungeni. Kodwa-ke, ngenxa yomehluko wokumelana nokushisa kwe-capacitor ngayinye ye-electrolytic, i-resistor kumele ixhunywe ku-capacitor ngayinye ukuze ilinganise i-voltage ye-capacitor ngayinye exhunywe ochungechungeni. Ngaphezu kwalokho, ama-capacitor kagesi ayimishini ehlanganisiwe, futhi lapho i-voltage ebuyela emuva esetshenziswayo idlula izikhathi ezingu-1.5 ze-Un, kwenzeka ukusabela kwe-electrochemic. Lapho i-voltage ebuyela emuva esetshenziswayo inde ngokwanele, i-capacitor izochitheka. Ukuze kugwenywe lesi simo, i-diode kufanele ixhunywe eduze kwe-capacitor ngayinye lapho isetshenziswa. Ngaphandle kwalokho, ukumelana nokwanda kwe-voltage kwama-capacitor kagesi ngokuvamile kuphindwe izikhathi ezingu-1.15 ze-Un, kanti amahle angafinyelela izikhathi ezingu-1.2 ze-Un. Ngakho-ke abaklami akufanele bacabangele i-voltage yokusebenza eqinile kodwa futhi ne-voltage yokwanda lapho beyisebenzisa. Ngamafuphi, ithebula lokuqhathanisa elilandelayo phakathi kwama-capacitor efilimu nama-capacitor e-electrolytic lingadwetshwa, bheka uMfanekiso 1.

2. Ukuhlaziywa Kwesicelo

Ama-capacitor e-DC-Link njengezihlungi adinga ukwakheka kwamandla aphezulu kanye nomthamo ophezulu. Isibonelo uhlelo oluyinhloko lokushayela imoto entsha yamandla njengoba kushiwo ku-Fig.3. Kulesi sicelo, i-capacitor idlala indima yokuhlukanisa futhi isekethe inomthamo ophezulu wokusebenza. I-capacitor ye-DC-Link yefilimu inenzuzo yokukwazi ukumelana nemisinga emikhulu yokusebenza (i-Irms). Thatha amapharamitha emoto entsha yamandla angu-50~60kW njengesibonelo, amapharamitha alandelayo: i-voltage yokusebenza engu-330 Vdc, i-voltage ye-ripple engu-10Vrms, i-ripple current engu-150Arms@10KHz.

Khona-ke umthamo kagesi omncane ubalwa kanje:

Lokhu kulula ukukusebenzisa ekwakhiweni kwe-capacitor yefilimu. Uma kusetshenziswa ama-capacitor e-electrolytic, uma kucatshangelwa i-20mA/μF, umthamo omncane wama-capacitor e-electrolytic ubalwa ukuze uhlangabezane nemingcele engenhla kanje:

Lokhu kudinga ama-capacitor amaningi e-electrolytic axhunywe ndawonye ukuze kutholakale lo mthamo.

Ezisetshenzisweni ze-over-voltage, njengesitimela esikhanyayo, ibhasi likagesi, isitimela esingaphansi komhlaba, njll. Uma ubheka ukuthi la mandla axhunywe kwi-locomotive pantograph nge-pantograph, ukuxhumana phakathi kwe-pantograph ne-pantograph kuyaphazamiseka ngesikhathi sokuhamba kwezokuthutha. Uma lokhu kokubili kungathintani, ukunikezwa kwamandla kusekelwa yi-DC-L inki capacitor, futhi lapho ukuxhumana kubuyiselwa, i-over-voltage iyakhiqizwa. Isimo esibi kakhulu ukukhishwa okuphelele yi-DC-Link capacitor uma inqanyuliwe, lapho i-discharge voltage ilingana ne-pantograph voltage, futhi lapho ukuxhumana kubuyiselwa, i-over-voltage ephumela cishe kabili kune-Un esebenza kahle. Kuma-capacitor efilimu i-DC-Link capacitor ingaphathwa ngaphandle kokucatshangelwa okwengeziwe. Uma kusetshenziswa ama-capacitor e-electrolytic, i-over-voltage ingu-1.2Un. Thatha i-Shanghai metro njengesibonelo. I-Un=1500Vdc, ukuze i-electrolytic capacitor icabangele i-voltage ingu:

Ngemuva kwalokho ama-capacitor ayisithupha angu-450V kufanele axhunywe ngokulandelana. Uma ukwakheka kwe-capacitor yefilimu kusetshenziswa ku-600Vdc kuya ku-2000Vdc noma ngisho naku-3000Vdc kutholakala kalula. Ngaphezu kwalokho, amandla uma ekhishwa ngokugcwele i-capacitor akha ukukhishwa kwesekethe esifushane phakathi kwama-electrode amabili, okukhiqiza ugesi omkhulu wokungena nge-capacitor ye-DC-Link, okuvame ukuhluka kuma-capacitor e-electrolytic ukuze ahlangabezane nezidingo.

Ngaphezu kwalokho, uma kuqhathaniswa nama-capacitor e-electrolytic, ama-capacitor efilimu e-DC-Link angaklanywa ukuze afinyelele i-ESR ephansi kakhulu (ngokuvamile ngaphansi kwe-10mΩ, ngisho nangaphansi kwe-<1mΩ) kanye ne-self-inductance LS (ngokuvamile ngaphansi kwe-100nH, futhi kwezinye izimo ngaphansi kwe-10 noma i-20nH). Lokhu kuvumela i-capacitor yefilimu ye-DC-Link ukuthi ifakwe ngqo kwimojula ye-IGBT uma isetshenziswa, okuvumela ibha yebhasi ukuthi ihlanganiswe ne-capacitor yefilimu ye-DC-Link, ngaleyo ndlela kuqedwe isidingo se-capacitor ye-absorber ye-IGBT ezinikele lapho kusetshenziswa ama-capacitor efilimu, okusindisa umklami imali eningi. Isibalo 2. kanye ne-3 sibonisa imininingwane yobuchwepheshe yeminye yemikhiqizo ye-C3A ne-C3B.

3. Isiphetho

Ezinsukwini zokuqala, ama-capacitor e-DC-Link ayeyi-capacitor ye-electrolytic ikakhulukazi ngenxa yezindleko kanye nosayizi.

Kodwa-ke, ama-capacitor e-electrolytic athintwa amandla okumelana ne-voltage kanye nogesi (i-ESR ephezulu kakhulu uma kuqhathaniswa nama-capacitor efilimu), ngakho-ke kuyadingeka ukuxhuma ama-capacitor e-electrolytic amaningana ngokulandelana nangokuhambisana ukuze kutholakale umthamo omkhulu futhi kuhlangatshezwane nezidingo zokusetshenziswa kwe-voltage ephezulu. Ngaphezu kwalokho, uma ucabangela ukuguquguquka kwezinto ze-electrolyte, kufanele kushintshwe njalo. Ukusetshenziswa kwamandla amasha ngokuvamile kudinga impilo yomkhiqizo yeminyaka eyi-15, ngakho-ke kumele kushintshwe izikhathi ezi-2 kuya kwezi-3 phakathi nalesi sikhathi. Ngakho-ke, kunezindleko ezinkulu kanye nokuphazamiseka kwensizakalo yangemva kokuthengisa yomshini wonke. Ngokuthuthuka kobuchwepheshe bokumboza insimbi kanye nobuchwepheshe be-capacitor yefilimu, kuye kwenzeka ukukhiqiza ama-capacitor e-DC filter ane-voltage ephezulu kusuka ku-450V kuya ku-1200V noma ngaphezulu ngefilimu ye-OPP encane kakhulu (encane kakhulu engu-2.7µm, ngisho no-2.4µm) kusetshenziswa ubuchwepheshe bokufudumeza ifilimu yokuphepha. Ngakolunye uhlangothi, ukuhlanganiswa kwama-capacitor e-DC-Link nebha yebhasi kwenza ukwakheka kwe-inverter module kube kuncane kakhulu futhi kunciphisa kakhulu ukugeleza kwesekethe ukuze kuthuthukiswe isekethe.