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35Volt MOV testing

Hi,

I tested some MOV's, part#: ROV10-560K-S

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These are called 35Volt MOV's, and I tested 20 of them with my bench supply set to 61VDC, and the minimum current was about 10mA, and the max current was about 50mA, with the vast majority in the 10mA to 20mA range. With 57VDC across them, none of the MOV's had any noticeable current through them (less than 1mA indicated on the bench supply).

I would like to use MOV's to protect my electronics, these ones seem perfect to protect a max 60VDC cap bank. Why are these MOV's rated 35V? I guess this is an AC rating, so 1.7*35VAC=59.5VDC peak, makes sense I guess :) Is it acceptable (for UL certification) to use these 35V MOV's to protect a 60VDC cap bank in a battery charger/inverter application?

I was under the impression that MOV's weren't very accurate but these ones all seem to be pretty close in tolerances.

cheers, Jamie

Reply to
Jamie Morken
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that part has a 110Volt clamping voltage, this makes it pretty useless to protect the 60VDC cap bank I think, is there an "active clamp" circuit that is used to replace MOV's?

cheers, Jamie

Reply to
Jamie Morken

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Whats wrong with a TVS zener .Heres a 600W one with a breakdown at

56.7V max leakage 5uA.0.18 CENTS.

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Reply to
Hammy

What are you protecting the caps from? Why does UL care?

-- bud--

Reply to
bud--

MOVs are crap. You should use Transzorbs. I know this from experience because I worked at a place that had a lot of HV electronics, and there were MOVs all over the place - when Transzorbs came out, they were SO much better that the PHB ordered an EO to rip out all of the MOVs and replace them with Transzorbs.

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I don't have any kind of affiliation with Vishay - in fact, they weren't even the ones who initially introduced them (I think it was General Instruments or some such); I'm just a satisfied customer.

Cheers! Rich

Reply to
Rich Grise

In UL1741, section 53, "a) Ten applications of a 6 kV surge impulse at 60 second intervals."

This is applied to a the output of a grid inverter, but I think similar surges are applied to battery terminals. UL is a huge pain that they don't have publicly available documents!!! I am trying to access the UL943 which shows the surge generator circuit that is used to apply these 6kV pulses..

cheers, Jamie

Reply to
Jamie Morken

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Your test at 61 volts is meaningless. Read up on MOV ratings & how they are tested. All your 57 volt, no current test shows is that the MOVs are not shorted. MOV is not a good choice to protect against overvoltage, which appears to be what you have in mind. Think transient protection, not overvoltage.

Ed

Reply to
ehsjr

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