Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: john larkin Newsgroups: sci.electronics.design Subject: Re: heating a cap Date: Sat, 05 Oct 2024 08:09:21 -0700 Organization: A noiseless patient Spider Lines: 26 Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Injection-Date: Sat, 05 Oct 2024 17:09:22 +0200 (CEST) Injection-Info: dont-email.me; posting-host="f434fdb690f0f26478851509569954f5"; logging-data="851659"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX19uNDskD3Tup/tPglWUAl+H" User-Agent: ForteAgent/8.00.32.1272 Cancel-Lock: sha1:vsdA/+j+3ODhmOYftW8Cg+dU5rU= Bytes: 1923 On Sat, 5 Oct 2024 13:20:51 +0100, Clive Arthur wrote: >On 04/10/2024 00:36, john larkin wrote: >> I got a small (under 1" long) aluminum electro cap, 220 uF 63v, and >> cranked up the voltage. It started drawing a bunch of current at 105 >> volts, got hot, and folded back to 80 mA at 87v. >> >> It got too hot to touch in a couple of minutes, after roughly 500 >> joules. Freeze spray let it go back up to 100 volts or so. >> >> None of that seemed to damage it, so an electrolytic cap sort of has a >> built-in MOV. >> > >If you need a high temperature cap, these work and they're not horribly >expensive... > >https://www.mouser.co.uk/datasheet/2/40/THJ-3165556.pdf I reall want to absorb joules when a power supply is back-driven by a load, like decelerating a motor for instance. So I want caps with a lot of mass, or MOVs that can get very hot before they die. The environment won't be very hot, but the cap (or MOV) will.