AC vs DC Capacitors: The Essential Engineering Guide to Selection and Safety

1. Selelekela: Ho utloisisa AC le DC Capacitors

Phapang lipakeng tsa li-capacitor tsa AC le DC ke ea bohlokoa moralong oa elektroniki. Leha ka bobeli ba boloka matla a motlakase, sebopeho sa bona sa kahare, lisebelisoa tsa dielectric, le matla a ho sebetsana le motlakase ha li fetohe. Ho sebelisa capacitor ea DC potolohong ea AC ho ka lebisa ho hloleheng ho matla joalo ka ho chesa haholo, ho putlama ha motlakase oa reverse-voltage, kapa ho phatloha.

Tataiso ena e hlalosa dipharologanyo tsa bohlokwa tsa sebopeho, thepa, le ditekanyetso pakeng tsa di-capacitor tsa AC le DC mme e fana ka temohisiso e sebetsang ya kgetho bakeng sa baenjiniere ba sebetsang ka di-elektroniki tsa motlakase, di-drive tsa di-motor, le di-switching power supplies. Kutlwisiso e hlakileng ya ditekanyetso tsa VAC ha e bapiswa le VDC ke ya bohlokwa bakeng sa ho sebedisa di-capacitor ka polokeho le ka botshepehi.

2. AC Capacitors ke Eng? Moralo bakeng sa Khatello ea Maikutlo a Bipolar

2.1 Molao-motheo oa Ts'ebetso: Phetoho e Tsoelang Pele ea Polarity

Li-capacitor tsa AC li hahiloe hore li mamelle ho fetoha ha motlakase oa bi-directional, ho mamella phetoho e sa feleng ea polarity moleng kapa maqhubu a phahameng. Sena se hloka li-dielectric tse se nang polar tse nang le matla a phahameng a ho koala le ntho e fokolang haholo ea ho qhala (tan δ) ho fokotsa mocheso oa mocheso nakong ea ts'ebetso e tsoelang pele ea AC.

2.2 Sebopeho le Lisebelisoa

Li-capacitor tsa filimi tsa polypropylene (PP) ke mefuta e tloaelehileng ea AC ka lebaka la tahlehelo ea bona ea dielectric e seng polar le e tlase. Mohaho oa filimi o entsoeng ka tšepe o fana ka bokhoni ba ho ipholisa: likhahla tse nyane li etsa mouoane oa metallization ho potoloha phoso, ho lumella capacitor hore e lule e sebetsa. Likarolo tsena li etsa hore li-capacitor tsa lifilimi tsa PP li be hantle bakeng sa li-circuits tsa motor run le EMI sefa.

2.3 Mekhahlelo ea Motlakase ea Bohlokoa

Li-capacitor tsa AC li sebelisa litekanyetso tsa motlakase oa RMS (VAC). Khatello e phahameng ea khatello e fihla Vpeak = VRMS × √2, kahoo karolo ea 250VAC e tlameha ho mamella tlhoro ea 350V. Ts'ebetso ea mocheso e laoloa ke tan δ, 'me lisebelisoa tsa X-class/Y-class li hloka UL, VDE, le Setifikeiti sa IEC bakeng sa lits'ebetso tsa mains EMI.

2.4 Lisebelisoa tse Tloaelehileng

Lisebelisoa tse tloaelehileng li kenyelletsa li-motor run/start capacitor (CBB60/CBB65), khatello ea X2/Y2 EMI, le ho sefa AC ho PFC le litsamaiso tsa phetolo ea matla, moo tahlehelo e tlase le ts'ebetso e tšepahalang ea libaesekele li bohlokoa.

3. DC Capacitors ke Eng? Moralo oa Unipolar Stress

3.1 Molao-motheo oa Ts'ebetso: Unidirectional Voltage

Li-capacitor tsa DC li sebetsa tlas'a motlakase o tsitsitseng, o le mong ntle le ho khutlela morao ha polarity. Bongata ba tsona li sebelisa meaho e nang le polarized, moo lera le lesesaane la oxide le sebetsang e le dielectric. Li-capacitor tsa electrolytic tsa aluminium ke mehlala e tloaelehileng 'me li hloka polarity e nepahetseng ho boloka botsitso ba dielectric.

3.2 Sebopeho le Lisebelisoa

Mefuta ea polarized e kenyelletsa aluminium electrolytic le tantalum capacitors. Likhetho tsa DC tse se nang polar-tse kang MLCCs le DC-rated film capacitor-li ka sebetsana le DC voltage ka ripple superimposed. Li-MLCC li fana ka ts'ebetso e ntle haholo ea maqhubu a holimo empa li na le tšekamelo ea DC, e ka fokotsang haholo bokhoni bo sebetsang.

3.3 Mekhahlelo ea Motlakase ea Bohlokoa

Tekanyetso ea VDC e hlalosa motlakase o phahameng ka ho fetisisa o tsoelang pele oa DC. ESR ke tekanyo ea mantlha ea ts'ebetso bakeng sa ho sefa DC, e susumetsang ts'ebetso ea ripple le tlhahiso ea mocheso. Li-MLCC hangata li bontša ho theoha ho hoholo ha capacitance tlas'a leeme la DC, 'me litekanyetso tsa hona joale tsa ripple li beha meeli ea mocheso bakeng sa lits'ebetso tsa SMPS.

3.4 Lisebelisoa tse Tloaelehileng

Li-capacitor tsa DC li sebelisoa bakeng sa polokelo ea matla a mangata, ho boreleli ka har'a li-circuits tsa SMPS, li-decoupling tsa lehae haufi le lithapo tsa motlakase tsa IC, le ho sefa tsamaiso ea betri. Li-electrolytics tsa aluminium li fana ka matla a phahameng, li-capacitor tsa polymer li fana ka ESR e tlase haholo, 'me li-MLCC li ipabola haholo ho hatellang lerata le phahameng.

4. AC vs DC Capacitors: Phapang ea Bohlokoa

Phapang ea mantlha lipakeng tsa li-capacitor tsa AC le DC li tsoa mefuteng e ikhethang ea khatello ea motlakase ea mofuta o mong le o mong o tlamehang ho mamella. Papiso e latelang e totobatsa lintlha tsa bohlokoa tse laolang khetho e nepahetseng:

5. Ke Hobane'ng ha Li-Capacitor tsa DC li sa khone ho sebelisoa Lipotolohong tsa AC

5.1 Kotsi ea Polarized Failure (Ho phatloha)

Reverse voltage nakong ea halofo ea potoloho e mpe ea ts'ebetso ea AC hang-hang e senya lera la oxide ho electrolytic le tantalum capacitors. Karohano ena ea dielectric e baka mocheso o potlakileng oa kahare, tlhahiso ea khase, le moea o ka bang teng oa ho phatloha. Mokhoa oa ho hloleha o etsahala ka har'a li-milliseconds tsa ts'ebeliso ea pele ea leeme, ho etsa hore sebaka sa DC capacitor lipotolohong tsa AC e be kotsi ea ts'ireletso hanghang.

5.2 Ho hloleha ha Dielectric

Li-dielectric tsa DC capacitor li ntlafalitsoe bakeng sa khatello ea motlakase e sa feleng, e bakang likarolo tse nyane tsa dielectric ho feta tse lekantsoeng ke AC. Ha li le tlas'a matla a AC peak voltage (Vpeak), li-dielectrics tse tlase haholo li ba le khatello ea maikutlo e fetang moeli oa tsona oa ho senyeha, e bakang arcing e ka hare, li-circuits tse khutšoane le tšenyo ea mocheso.

5.3 Thermal Runaway

Li-capacitor tsa DC li bonts'a lintlha tse phahameng haholo tsa ho qhalana ho maqhubu a AC ha li bapisoa le li-capacitor tsa AC tse entsoeng ka sepheo. Tan δ e phahameng e hlahisa mocheso o feteletseng oa kahare ho tsoa ho phallo ea hona joale ea AC, 'me butle-butle e theola dielectric le electrolyte. Loop ena e ntle ea maikutlo-mocheso o bakang ho senyeha o bakang mocheso o mongata-o lebisa ho baleha ha mocheso le ho hlōleha ho senya.

6. AC le DC Capacitors li ka Tšela Likopo Neng?

6.1 Li-Non-Polar DC Film Capacitors

Li-capacitor tse ling tseo e seng tsa polar tsa DC li ka sebetsa ka tšekamelo ea DC hammoho le motlakase o monyane oa AC ripple voltage, e tloaelehileng ho sefa se hlahisoang ke SMPS. Leha ho le joalo, boholo ba hona joale ba AC le ho itšehla thajana ho ntse ho le mabaka a fokolang. Lintlha tsa leqephe la data bakeng sa karabo ea ripple current le frequency li tlameha ho tataisa meeli ea ts'ebeliso.

6.2 Non-Polar MLCCs le Piezoelectric Trap

Li-MLCC li mamella maqhubu a manyane a AC empa li hlahisa phephetso e ikhethang: dielectric ea ceramic e bontša thepa ea piezoelectric. Matšoao a AC a maqhubu a phahameng a baka ho thothomela ha 'mele ha thepa ea ceramic, a hlahisa lerata le utloahalang la molumo o fapaneng oa 1-10kHz. Mosi ona oa acoustic o ama phihlelo ea mosebelisi lisebelisoa tsa elektroniki tsa bareki 'me o ka bontša khatello e feteletseng ea mechine.

6.3 Dual AC / DC Rated Capacitors

Ke li-capacitor tse khethehileng feela tsa filimi kapa pampiri tse nang le lintlha tse hlakileng tsa AC/DC. Likarolo tsena li etselitsoe maemo a thata a pulse ka sistimi ea dielectric e khonang ho mamella khatello ea libaesekele tsa AC le khatello ea leeme ea DC. Netefatsa lintlha tse peli ho database pele u sebelisa likopo tse fapaneng.

7. Joang ho Khetha Right AC le DC Capacitors

7.1 Bakeng sa Lisebelisoa tsa AC (Mains/Motor)

Hlalosa di-capacitor tsa X2/Y2 tse netefaditsweng bakeng sa ditshebediso tsa ho sefa tsa EMI tse hlokang tumello ya setsi sa polokeho. Di-circuits tsa ho tsamaisa dienjene di hloka di-capacitor tsa filimi tsa PP (letoto la CBB) tse nang le ditekanyetso tse loketseng tsa mocheso. Sebedisa bonyane ntlha ya ho senya ya 1.2×—bakeng sa motlakase wa mola wa 230VAC, kgetha di-capacitor tse lekantsweng ho 275VAC kapa ho feta ho amohela di-transients tsa motlakase le ho netefatsa botshepehi ba nako e telele.

7.2 Bakeng sa Likopo tsa DC (SMPS/Digital)

Bakeng sa ho sefa ka bongata maqhubung a tlase a kHz, di-capacitor tsa aluminium electrolytic tse nang le ESR e tlase le ditekanyetso tse lekaneng tsa nako ya bophelo di fana ka tekanyo e ntle ya tshebetso ya ditjeo. Ditshebediso tsa maqhubu a hodimo (ho isa ho kHz ho isa ho MHz) di hloka di-capacitor tsa polymer kapa di-MLCC tse nang le ESL e tlase le ho bewa ka hloko haufi le mojaro. Sebedisa bonyane 1.5× voltage derating bakeng sa ditshebediso tsa DC. Bakeng sa di-MLCC, kamehla netefatsa bokgoni bo sebetsang ba motlakase o sebetsang, kaha leeme la DC le ka fokotsa bokgoni ba nnete ka 50-80% ho tloha boleng bo boletsweng.

8. Maikutlo a Tloaelehileng a Fosahetseng ka AC le DC Capacitors

8.1 Tšōmo ea 1: MLCCs e ka sebetsana le AC Mains

Bohata. Le hoja li-MLCC li se polar, ha li na tekanyo e lekaneng ea Vpeak le bokhoni ba ho sebetsana le AC bakeng sa lisebelisoa tsa motlakase oa motlakase. Litifikeiti tsa polokeho ha li eo, 'me botenya ba dielectric ha bo lekane bakeng sa khatello ea motlakase oa mohala.

8.2 Khopolo-taba ea 2: Li-Capacitor tsohle tsa Lifilimi li Lekanyelitsoe AC

Bohata. Li-capacitor tse ngata tsa lifilimi li entsoe ka ho khetheha e le DC link kapa high-voltage pulse capacitor, e ntlafalitsoeng bakeng sa mekhoa ea khatello ea maikutlo e sa tšoaneng. Kamehla netefatsa lintlha tsa AC ho database ho fapana le ho nka hore kaho ea lifilimi e bolela bokhoni ba AC.

8.3 Tšōmo ea 3: Li-Capacitor tse kholo tsa AC li Sebetsa bakeng sa DC Smoothing

E sa sebetseng hantle. Li-capacitor tsa AC li ntlafalitsoe bakeng sa tan e tlase δ, eseng tlase ESR. Ho li sebelisa bakeng sa phokotso ea maqhubu a DC ho fella ka ts'ebetso e mpe ea ho sefa ha li-switching frequency le litšenyehelo tse feteletseng ha li bapisoa le mefuta e meng e etselitsoeng morero oa electrolytic kapa polymer.

9. Kakaretso ea AC vs DC Capacitor

Molao oa mak'hadinale o lula o le teng: le ka mohla u se ke ua nkela sebaka sa DC capacitor bakeng sa kopo ea AC. Likotsi tsa ho senyeha ha polarity le ho senyeha ha dielectric li baka likotsi tsa ts'ireletso hanghang.

Li-capacitor tsa AC li hlalosoa ke bokhoni ba tsona ba ho sebetsana le Vpeak le ntho e tlase ea ho qhala (tan δ) ho fokotsa ho ichesa tlas'a metsi a feto-fetohang. Li-capacitor tsa DC li khetholloa ka litekanyetso tsa tsona tsa VDC le ESR e tlaase bakeng sa khatello e sebetsang ea ripple. Khetho e nepahetseng ea capacitor e ipapisitseng le liphapang tsena tsa mantlha e netefatsa ts'epo ea potoloho le polokeho ea ts'ebetso.