Test enamel insulation on torroid inductor - Page 1
Forum section: electronics / general

author: Faringdon
author_rank: Super Contributor
timestamp: December 20, 2023, 07:35:20 pm
content: Hi,Say you get some torroid inductor samples given to you, as an alternative to an inductor you have.Its for offline PSU input filter.1mm ECW.Goes in the live line.At startup, voltage across it will be mains peak.Turns at start are next to turns at end.So should you do a insulation test?, ie with two of them connected to a probe of hi-pot tester...and touch them together.Written Spec doesnt give insulation grade of the enamel. Just gives L and RDC.

author: coppercone2
author_rank: Super Contributor
timestamp: December 21, 2023, 08:01:34 pm
content: uh you can ask about what they use and the coating thickness to determine if its to your specificationit needs to be tested any way for safety reasons later? all I can see is a potential gamble on avoiding a measurement to qualify a component that can lead to a later failure

author: Kean
author_rank: Unknown
timestamp: December 22, 2023, 02:13:53 pm
content: Even if you did such a test and it passed, are you really comfortable using that part which isn't specified for mains voltage?The manufacturer can change their processes and material at any time that impacts your test result if there isn't a spec they need to meet.More importantly, isn't the end customer going to want safety approvals, and thus all parts used at mains voltage will need UL certificates?It is almost like you've never designed mains powered equipment before.

author: tooki
author_rank: Super Contributor
timestamp: December 23, 2023, 01:59:28 pm
content: Quote from: Kean on December 22, 2023, 02:13:53 pmIt’s quite remarkable, really. I mean, Ihaven’tdesigned mains-powered equipment for sale before, and it’s still obvious to me that one would use only certified components for the mains part at bare minimum…

author: BrokenYugo
author_rank: Super Contributor
timestamp: December 23, 2023, 02:23:29 pm
content: I was under the impression most professional PSU designers just buy/specify their chokes pre wound and characterized from reputable vendors, then they get done and get paid that much sooner.

author: Faringdon
author_rank: Super Contributor
timestamp: December 23, 2023, 06:38:34 pm
content: Thanks, to be honest, enamel for 1mm copper wire is always rated enough not to flash over with a mains filter inductor.And if it did, and say the inductor went short (which is extremely unlikley) ...then it still wouldnt make the product dangerous.....just would mean EMC may be failing.Off the shelf inductors used as filters dont have any voltage rating in their datasheet, to say that they are ok to be used as filter inductors with the nearness of either end of the coil to each other.In the following , you can see that even the lowest grade (grade 1) of enamelled copper wire at 0.5mm diameter has 2400V worth of insulation rating....so double that because each wire end is enamelled....so theres 4800v insulation straight off the bat......and thats for 0.5mm wire...so for 1mm wire...it gets even better...https://www.elektrisola.com/en/Products/Enamelled-Wire/Technical-Data#iec60317This is for an input filter inductor...no isolation requirement is even required by the regs.