Isigaba sesi-3 – Uyiqonda kanjani incazelo ye-“protective impedance”

i-impedance yokuvikela: i-impedance exhunywe phakathi kwezingxenye ezibukhoma nezingxenye ezifinyelelekayo ezifinyelelekayo zezakhiwo zesigaba II ukuze okwamanje, ekusetshenzisweni okuvamile nangaphansi kwezimo ezingaba zephutha entweni, ikhawulelwe kunani eliphephile.

Icala 1:
Isimo sokuqala ngokuvamile yizimo ezithile ezidinga ukunikezwa kwamandla kagesi aphansi, njengemikhiqizo esebenza nge-adaptha. I-voltage ephumayo ye-adaptha yi-DC12V, DC24V noma i-DC5V. Lezi zingxenye ezinama-voltage aphansi ngokuvamile zingathintwa abasebenzisi ngenxa yokuthi ingxenye ye-DC low-voltage itholwa ngokuguqulwa kwe-transformer kanye nokulungiswa kwe-rectifier yamanje. Ngakho-ke, kuyadingeka ukuqinisekisa ukuthi ingxenye ye-high-voltage kanye nengxenye ye-voltage ihlukaniswe ngokuphumelelayo. Ebhodini lethu elivamile lokushintshwa kwamandla, lapho senza ukuhlolwa kwe-EMC conduction, ukuphazamiseka okukhiqizwa yi-primary ye-transformer kudlula i-parasitic capacitance phakathi kwe-primary and secondary, okuzokhiqiza ukuphazamiseka okwenziwe kwe-150k-30MHz futhi kufinyelele kwesibili. Lapha sisebenzisa ama-capacitor angu-Y ukwenza isignali yokuphazamiseka ibuyele kumthombo wamandla, yenze iluphu ukuze isuse ukuphazamiseka, ngaphandle kwalokho izobangela ukuhlolwa kokwenziwa kwehluleke. I-Y capacitor lapha yakha i-impedance evikelayo. Ama-capacitor angu-Y amabili akhethwe ebhokisini elibomvu esithombeni esingezansi ayisivikelo sokuvikela.

Ama-impedances amabili okuvikela axhumeke phakathi kokuvunguza okuyinhloko kanye nokujika kwesibili kwe-T2 transformer; umugqa onamachashazi esithombeni esingezansi ubonisa ukuhlukaniswa kwengxenye ye-voltage yokusebenza engu-220-240V kanye nengxenye ye-voltage esebenzayo ephansi(SELV).

Esithombeni esiboniswe ngezansi, ingabe i-CY1 ne-CY2 yizithiyo zokuvikela?

Kusukela encazelweni yezinga, i-impedance yokuvikela isetshenziswa ekwakhiweni kwesigaba II, lapho kukhona umhlaba. Uma ukufakwa komhlaba lapha kuchazwa njengokuvikela umhlaba, ngakho-ke kusobala ukuthi i-CY1 ne-CY2 ayikwazi ukuchazwa njenge-impedance yokuvikela, ngoba i-impedance yokuvikela isetshenziswa ekwakhiweni kwekilasi II, futhi nansi ukwakhiwa kwekilasi I. Uma i-earthing ne-nbsp;lapha kuchazwa njengokusebenza komhlaba, khona-ke kunezinkinga ezimbili. Okokuqala, lesi yisakhiwo sekilasi I, khona-ke i-CY1 ne-CY2 ayikwazi ukuchazwa njenge-impedance yokuvikela. Okwesibili, uma kuyisakhiwo sesigaba II, i-CY1 ne-CY2 ingachazwa njenge-impedance yokuvikela, bese kudingeka kuhlangatshezwane nezidingo ezifanele zokuvimbela ukuvikela. Umbono wami siqu ukuthi i-CY1 ne-CY2 akuzona izithiyo eziyisivikelo, futhi singazibheka ngokuqondile njengokuvala okuyisisekelo. Ekugcineni, ngamanye amazwi, umklamo oboniswe kumdwebo wesifunda awumukelwa yizinga? kanye nbsp;

Uma kuyizithiyo zokuvikela, khona-ke okudingeka kuhambisane nesigatshana sama-22.42 – “I-impedance yokuvikela izohlanganisa okungenani izingxenye ezimbili ezihlukene.”.

From the definition of the standard, the protective impedance is used in the class II construction, where there is earthing. If the earthing here is defined as protection earthing, then obviously, CY1 and CY2 cannot be defined as protection impedance, because protection impedance is used in class II construction, and here is class I construction. If the earthing here is defined as functional earthing, then there are two problems. First, this is a class I structure, then CY1 and CY2 cannot be defined as protection impedance. Second, if it is a class II structure, CY1 and CY2 can be defined as protection impedance, and then the relevant requirements of protection impedance need to be met. My personal opinion is that CY1 and CY2 are not protective impedances, and we can directly regard them as basic insulation. At the end, in other words, the design shown in the circuit diagram is not accepted by the standard? 

If they are protective impedances, then which is need to comply with clause 22.42 – “Protective impedance shall consist of at least two separate components.”.