Hi-Pot Testing in PCB circuit with MOV connected to gnd

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Anonymous Poster #1	Hi-Pot Testing in PCB circuit with MOV connected to gnd 08/08/2022 2:48 AM
	In a PCB circuit of EV charger / rectifier, containing MOV and GDT from phase to ground, can hi-pot be performed without disconnecting the MOVs? Will the MOV see the Hi-pot voltage as a transient noise and supress the Hipot test voltage? or is there some other ways of performing Hi-Pot on the PCB
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Rixter Guru Join Date: Apr 2010 Location: About 4000 miles from the center of the earth (+/-100 mi) Posts: 9910 Good Answers: 1141	#1 Re: Hi-Pot Testing in PCB circuit with MOV connected to gnd 08/08/2022 7:57 AM
	Will the MOV see the Hi-pot voltage as a transient noise and supress the Hipot test voltage? Most likely. You should contact the manufacturer.
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redfred Guru Join Date: Dec 2008 Location: Long Island NY Posts: 15600 Good Answers: 981	#2 Re: Hi-Pot Testing in PCB circuit with MOV connected to gnd 08/08/2022 9:02 AM
	Of course, one can perform a Hi-Pot test with MOV (Metal Oxide Varistor) and GDT (Gas Discharge Tube) attached. One can perform all sorts of useful, useless, and even damaging tests with a circuit board. Knowing the MOV and GDT will protect the circuit board would undoubtedly be helpful. Performing a Hi-Pot test without the high voltage protection devices attached should prove that the circuit board needs high voltage protection. It all depends on what you wish to be testing. If you do a Hi-Pot test with the high voltage protection missing then you shouldn't sell that circuit board regardless of the result. __________________ "Don't disturb my circles." translation of Archimedes last words
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SimpleMind Guru Join Date: Sep 2009 Posts: 1056 Good Answers: 88	#3 Re: Hi-Pot Testing in PCB circuit with MOV connected to gnd 08/08/2022 10:21 AM
	Why are MOVs connected to ground? Unless they're there to trip a fuse on lightning etc. If so they're rated just below bulk capacitors' max permitted voltage and of course located before main rectifier. So they are low voltage and no HiPot test to ground possible. Test voltage will latch to MOV voltage and results will be irelevant. It could very well be on specs for HiPot test after the internal fuse, with it being temporarily removed. Or HiPot is only applicable to output. S.M. __________________ Life is complex. It has a real part and an imaginary part.
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BruceFlorida Guru Join Date: Jul 2008 Posts: 1688 Good Answers: 145	#4 Re: Hi-Pot Testing in PCB circuit with MOV connected to gnd 08/09/2022 6:50 AM
	From my experience: HI POT TEST GOAL: Expose insulated items (wires, etc) to a high voltage for a specified length of time and expect (for safety) that leakage will be very, very small (possibly zero on your instruments). MOV GOAL: Pass (kind of like "leak") current when exposed to high voltage. This typically shunts current (high voltage) to ground to protect circuits. Think about it. We don't know what standards, test procedures, contract requirements, etc. you are dealing with. But, if you agree with the two goals I stated above then you agree that you don't Hi-Pot test a MOV circuit. How do you deal wth this conflict? Well, welcome to Engineering! __________________ Few things limit our potential as much as knowing answers and setting aside questions.
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PWSlack Guru Join Date: Jan 2007 Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on. Posts: 32175 Good Answers: 839	#5 Re: Hi-Pot Testing in PCB circuit with MOV connected to gnd 08/12/2022 6:28 PM
	The best thing to do is to pick up the phone to the manufacturer of the <...PCB circuit of EV charger / rectifier, containing MOV and GDT...> and ask its technical helpline. Why is this test being carried out if the procedure and the pass criterion is not known about beforehand? __________________ "Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
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