Sabata ino tikupitiliza ndi nkhani ya sabata yatha.

1.2 Ma capacitor a Electrolytic

Dielectric yomwe imagwiritsidwa ntchito mu ma capacitor a electrolytic ndi aluminiyamu oxide yomwe imapangidwa ndi dzimbiri la aluminiyamu, yokhala ndi dielectric constant ya 8 mpaka 8.5 ndi mphamvu ya dielectric yogwira ntchito ya pafupifupi 0.07V/A (1µm=10000A). Komabe, sizingatheke kukwaniritsa makulidwe otere. Kukhuthala kwa aluminiyamu kumachepetsa mphamvu ya capacitance (capacitance yeniyeni) ya ma capacitor a electrolytic chifukwa cholembera cha aluminiyamu chiyenera kujambulidwa kuti chipange filimu ya aluminiyamu oxide kuti chipeze mawonekedwe abwino osungira mphamvu, ndipo pamwamba pake padzakhala malo ambiri osafanana. Kumbali inayi, resistivity ya electrolyte ndi 150Ωcm ya voltage yotsika ndi 5kΩcm ya voltage yokwera (500V). Resistivity yayikulu ya electrolyte imaletsa RMS current yomwe electrolytic capacitor imatha kupirira, nthawi zambiri kufika pa 20mA/µF.

Pazifukwa izi, ma capacitor a electrolytic amapangidwira kuti magetsi azikhala ndi mphamvu ya 450V (omwe amapanga ma 600V okha). Chifukwa chake, kuti mupeze mphamvu yamagetsi yokwera, ndikofunikira kuikwaniritsa polumikiza ma capacitor motsatizana. Komabe, chifukwa cha kusiyana kwa kukana kwa insulation kwa capacitor iliyonse ya electrolytic, resistor iyenera kulumikizidwa ku capacitor iliyonse kuti igwirizane ndi mphamvu ya capacitor iliyonse yolumikizidwa. Kuphatikiza apo, ma capacitor a electrolytic ndi zida zozungulira, ndipo mphamvu ya reverse yomwe imagwiritsidwa ntchito ikapitirira nthawi 1.5 za Un, electrochemic reaction imachitika. Mphamvu ya reverse yomwe imagwiritsidwa ntchito ikapitirira nthawi 1.5 za Un, capacitor imatuluka. Pofuna kupewa izi, diode iyenera kulumikizidwa pafupi ndi capacitor iliyonse ikagwiritsidwa ntchito. Kupatula apo, mphamvu ya voltage ya ma capacitor a electrolytic nthawi zambiri imakhala nthawi 1.15 za Un, ndipo abwino amatha kufika nthawi 1.2 za Un. Chifukwa chake opanga ayenera kuganizira osati mphamvu ya steady-state yogwira ntchito komanso mphamvu ya surge voltage akamagwiritsa ntchito. Mwachidule, tebulo loyerekeza lotsatirali pakati pa ma capacitor a filimu ndi ma capacitor a electrolytic likhoza kujambulidwa, onani Chithunzi 1.

2. Kusanthula kwa Ntchito

Ma capacitor a DC-Link monga zosefera amafunikira mapangidwe amphamvu kwambiri komanso amphamvu kwambiri. Chitsanzo ndi makina akuluakulu oyendetsa galimoto yatsopano monga tafotokozera mu Chithunzi 3. Mu ntchitoyi, capacitor imagwira ntchito yolumikizana ndipo dera lili ndi mphamvu yayikulu yogwirira ntchito. Capacitor ya filimu ya DC-Link ili ndi ubwino wotha kupirira mphamvu zazikulu zogwirira ntchito (Irms). Tengani magawo a galimoto yatsopano yamphamvu ya 50~60kW mwachitsanzo, magawo ake ndi awa: mphamvu yogwirira ntchito 330 Vdc, mphamvu yothamanga 10Vrms, mphamvu yothamanga 150Arms@10KHz.

Kenako mphamvu yocheperako yamagetsi imawerengedwa motere:

Izi n'zosavuta kuziyika pakupanga ma capacitor a filimu. Ngati ma capacitor a electrolytic agwiritsidwa ntchito, ngati 20mA/μF yaganiziridwa, mphamvu yocheperako ya ma capacitor a electrolytic imawerengedwa kuti ikwaniritse zomwe zili pamwambapa motere:

Izi zimafuna ma capacitor ambiri a electrolytic omwe amalumikizidwa nthawi imodzi kuti apeze capacitance iyi.

Mu ntchito zogwiritsa ntchito mphamvu zambiri, monga njanji yopepuka, basi yamagetsi, sitima yapansi panthaka, ndi zina zotero. Poganizira kuti mphamvu zimenezi zimalumikizidwa ndi pantograph ya locomotive kudzera mu pantograph, kukhudzana pakati pa pantograph ndi pantograph kumakhala kosalekeza panthawi yoyenda. Pamene ziwirizi sizikugwirizana, magetsi amathandizidwa ndi DC-L inki capacitor, ndipo pamene kukhudzanako kwabwezeretsedwa, mphamvu zambiri zimapangidwa. Choyipa kwambiri ndi kutulutsa kwathunthu ndi DC-Link capacitor ikachotsedwa, pomwe mphamvu yotulutsa imakhala yofanana ndi mphamvu ya pantograph, ndipo pamene kukhudzanako kwabwezeretsedwa, mphamvu zambiri zomwe zimachitika zimakhala pafupifupi kawiri kuposa momwe Un imagwirira ntchito. Kwa ma capacitor amafilimu, DC-Link capacitor ikhoza kuyendetsedwa popanda kuganizira zina. Ngati ma capacitor a electrolytic agwiritsidwa ntchito, mphamvu zambiri ndi 1.2Un. Tengani chitsanzo cha Shanghai metro. Un = 1500Vdc, kuti capacitor ya electrolytic iganizire mphamvu ndi:

Kenako ma capacitor asanu ndi limodzi a 450V ayenera kulumikizidwa motsatizana. Ngati kapangidwe ka capacitor ya filimu kagwiritsidwa ntchito mu 600Vdc mpaka 2000Vdc kapena 3000Vdc kumakhala kosavuta. Kuphatikiza apo, mphamvu ikatulutsidwa mokwanira, capacitor imapanga kutulutsa kwafupipafupi pakati pa ma electrode awiriwa, ndikupanga mphamvu yayikulu yolowera kudzera mu DC-Link capacitor, yomwe nthawi zambiri imakhala yosiyana kuti ma capacitor a electrolytic akwaniritse zofunikira.

Kuphatikiza apo, poyerekeza ndi ma capacitor a electrolytic, ma capacitor a filimu ya DC-Link amatha kupangidwa kuti akwaniritse ESR yotsika kwambiri (nthawi zambiri pansi pa 10mΩ, komanso yotsika kwambiri <1mΩ) ndi LS yodziyimira yokha (nthawi zambiri pansi pa 100nH, ndipo nthawi zina pansi pa 10 kapena 20nH). Izi zimalola kuti capacitor ya filimu ya DC-Link iikidwe mwachindunji mu module ya IGBT ikagwiritsidwa ntchito, zomwe zimathandiza kuti basi iphatikizidwe mu capacitor ya filimu ya DC-Link, motero kuchotsa kufunikira kwa capacitor yodzipereka ya IGBT ikagwiritsa ntchito ma capacitor a filimu, zomwe zimapangitsa kuti wopangayo asunge ndalama zambiri. Chithunzi 2. ndi 3 chikuwonetsa tsatanetsatane wazinthu zina za C3A ndi C3B.

3. Mapeto

Kale, ma capacitor a DC-Link anali makamaka ma capacitor a electrolytic chifukwa cha mtengo ndi kukula.

Komabe, ma capacitor a electrolytic amakhudzidwa ndi mphamvu yamagetsi ndi mphamvu yolimbana ndi mphamvu yamagetsi (ESR yokwera kwambiri poyerekeza ndi ma capacitor amafilimu), kotero ndikofunikira kulumikiza ma capacitor angapo amagetsi motsatizana komanso motsatizana kuti mupeze mphamvu yayikulu ndikukwaniritsa zofunikira pakugwiritsa ntchito mphamvu yayikulu. Kuphatikiza apo, poganizira kusinthasintha kwa zinthu za electrolyte, ziyenera kusinthidwa nthawi zonse. Kugwiritsa ntchito mphamvu zatsopano nthawi zambiri kumafuna moyo wa chinthucho wa zaka 15, kotero chiyenera kusinthidwa kawiri mpaka katatu panthawiyi. Chifukwa chake, pali mtengo waukulu komanso zovuta muutumiki wogulitsa pambuyo pogulitsa makina onse. Ndi chitukuko cha ukadaulo wopaka zitsulo ndi ukadaulo wa capacitor wamafilimu, zatheka kupanga ma capacitor a DC filter okhala ndi mphamvu yayikulu yokhala ndi mphamvu kuyambira 450V mpaka 1200V kapena kupitirira apo ndi filimu yopyapyala kwambiri ya OPP (yopyapyala kwambiri ya 2.7µm, ngakhale 2.4µm) pogwiritsa ntchito ukadaulo woteteza kutentha kwa filimu. Kumbali inayi, kuphatikiza ma capacitor a DC-Link ndi bus bar kumapangitsa kuti kapangidwe ka inverter module kakhale kakang'ono kwambiri ndipo kumachepetsa kwambiri kusokonekera kwa circuit kuti ikwaniritse bwino circuit.