Re: [PSES] hipot test

Wed, 15 Aug 2018 12:44:12 -0700

Yes, it's more or less the same effect. Repeated surface discharges across contaminated thermosetting plastics also caused carbonization, often resulting in a fireworks display when the mains voltage was applied after testing. 

John Woodgate OOO-Own Opinions Only
J M Woodgate and Associates www.woodjohn.uk
Rayleigh, Essex UK

On 2018-08-15 20:29, Pete Perkins wrote:
John, your description sounds much like the failure mechanism seen is circuit boards which start in a small void and develop micro-arcing which feeds upon itself and eventually drives a large void that allows conductors to directly contribute current and destroy the board.  I’ve investigated some destructive fires in equipment from such a source. And the circuit boards don’t need full hipot voltages to do this, line operated units eat themselves up quite handily. 

No, I don’t mean to start anew thread here.

:>) br,      Pete

Peter E Perkins, PE

Principal Product Safety & Regulatory Affairs Consultant

PO Box 23427

Tigard, ORe  97281-3427

503/452-1201

IEEE Life Fellow

p.perk...@ieee.org <mailto:p.perk...@ieee.org>

*From:*John Woodgate <j...@woodjohn.uk>
*Sent:* Wednesday, August 15, 2018 12:17 PM
*To:* EMC-PSTC@LISTSERV.IEEE.ORG
*Subject:* Re: [PSES] hipot test
I think it's not quite like that. Modern insulating materials don't degrade, but old ones did, or at least appeared to. For instance, oiled paper had pinholes, and a discharge caused local carbonization, which prompted more discharges and more carbonization. 

John Woodgate OOO-Own Opinions Only
J M Woodgate and Associateswww.woodjohn.uk <http://www.woodjohn.uk>
Rayleigh, Essex UK

On 2018-08-15 18:07, Richard Nute wrote:

    Their claim is that the hipot can degrade some insulation and
    should be kept to a minimum.

    Conventional wisdom not supported by science.

    Best regards,

    Rich

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