surge suppressor voltage limit

Hi Bud
Normally they do not indicate a failure after a failure has occurred, or they fail unsafe.
BillB
Leeds Lad in exile

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snipped-for-privacy@nospam.tesco.net wrote:

Is the standard is too tough?
At the risk of asking a dumb question, would the suppressors likely pass the US-UL tests?

Are you the entity formerly known as snipped-for-privacy@abc.net? (His posts were real interesting.) Still at TUV?

In exile?
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Hi Bud
Yes its a tough standard, in the UK I only know of one company that has had its products tested. The authorities responsible for enforcement only check products if someone gets injured, due to lack of funding.
Yes to both your other questions
I moved from Leeds about 35 years ago, to work in the West Midlands, hence I am in exile.
BillB
Leeds Lad in exile
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| On Sep 15, 11:44 pm, snipped-for-privacy@ipal.net wrote: |> In a previous thread a reference was made to an expert recommendation that |> surge suppressors have their clamping voltage doubled from 330V to 660V for |> 120VAC suppressors. | | Those voltages are ball park numbers. Actual voltage curve is not a | step function or 'knee voltage' as so many want to believe. A | protector rated at 330 volts will conduct current even at 130 V RMS. | How much current determines how quickly an MOV degrades. Yes, | degrades because MOVs inside protectors must fail only by degrading; a | change in its threshold voltage. A 10% change means the MOV has | failed. | | Typically, MOVs for 330 volts will also conduct at 180 volts AND | will increase voltage to greater than 800 volts as a surge current | increases. So what is its voltage? That would be the MOV inside a 330 | volt protector. 330 or 660 volt numbers are ballpark - arbitrary. | See MOV datasheets for the V-I charts. | | An MOV used in 120 volt operation must conduct less than acceptable | current at 185 volts. Idea is to select an MOV that conducts under a | minimum acceptable current constantly. How do we measure MOV | threshold voltage? One standard is to push a constant 1 milliamp | through the MOV and read its voltage. If that voltage changes by 10%, | then the MOV has degraded - failed. IOW that 1 milliamp voltage | should be sufficiently above 185 for 120 VAC operation and above 370 | for 240 VAC operation. These would also be 330 volt and 660 volt let- | through voltages.
So you think maybe I should fall back to the old plan of using Schuko power strips protectors?
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On Sep 17, 8:35 pm, snipped-for-privacy@ipal.net wrote:

I don't know what is inside that Schuko strip to suggest it is safe. Question is whether you are doing this to learn, or doing it to make a protector. Using (and modifying) a Schuko for North American power is not acceptable for normal operation and may even violate your fire insurance. But it might be educational if used as an experiment.

No. Same standards that also define what surges an appliance must withstand without damage also define how much voltage it must see constantly. That standard then defines the maximum constant voltage a protector must remain 'inert' for. For 120 VAC operation, that protector must remain 'inert' at voltages above 185 - not 170.
What happens when AC mains goes to a completely normal 125 volts? All part of a protector design.
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| On Sep 17, 8:35 pm, snipped-for-privacy@ipal.net wrote: |> So you think maybe I should fall back to the old plan of using Schuko power |> strips protectors? | | I don't know what is inside that Schuko strip to suggest it is | safe. Question is whether you are doing this to learn, or doing it to | make a protector. Using (and modifying) a Schuko for North American | power is not acceptable for normal operation and may even violate your | fire insurance. But it might be educational if used as an experiment.
Open one up and see. It's basically the same thing as used for 120V in USA, except it obviously has to be able to handle the 230V (+/- 10V) standard in Europe AND be able to handle being plugged in either way.
|> The PEAK voltage on 120VAC is 170V. | No. Same standards that also define what surges an appliance must | withstand without damage also define how much voltage it must see | constantly. That standard then defines the maximum constant voltage a | protector must remain 'inert' for. For 120 VAC operation, that | protector must remain 'inert' at voltages above 185 - not 170.
I was not saying the operative level was 170, only that the sinusoidal peak of a nominal 120VAC is 170V. Add 10% or more as needed.
| What happens when AC mains goes to a completely normal 125 volts? | All part of a protector design.
Of course. So the real level where the protector acts would be higher than 170V, such as the 330V figure I have read in a number of places.
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On Sep 19, 12:45 am, snipped-for-privacy@ipal.net wrote:

That 330 volt number is not a threshold voltage for MOVs. But again, MOVs do not have this knee voltage as so many want to believe. Too many think an MOV works like a zener diode. Same MOV rated for 170 volts is also rated by another standard at 330 volts and rated by another standard at 800 volts.
A varistor that does not conduct much at 185 volts and that conducts at 250 volts is the same varistor used in protectors with a "let- through voltage" of 330 volts. A 330 is a UL number which measures the same MOV differently than numbers in manufacturer datasheet. But again, get V-I charts from MOV manufacturers to appreciate why all these numbers are ballpark or arbitrary. Experience will make them more understandable.
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