AC overvoltage protection

Could some electronics guru please help ?

The certification standards for a wall- plug AC powered device in as Asian country states that :

"for use on DC supplies up to 250 V or on AC supplies up to 1 000 V at 50 Hz"

The normal AC line voltage is 230V @

50Hz, which means that the device under test (DUT) must remain intact if the applied testimg voltage is increased to 1000 V AC -- basically over voltage protection.

The two standard over voltage devices that we have used in the past in our designs have been (a) Zener diode -- e.g., a 200V Zener diode (b) Varactor -- e.g., a 275/20 rated device

Another scheme uses a relay powered by 2 - 3 transistors that trips when the AC line voltage exceeds a pre-set limit. We have never used it, but we are aware of it.

Are there any other schemes ? Of the the three above, which(or a combination) would be the best suited for this purpose ? We are inclined to (a) and (b), as they do not need any adjustment, and work on their own.

All hints/suggestions would be greatly appreciated. Thanks in advance for your help.

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Really need the standard this needs to be tested to.

It ~may~ be that this power supply may need to just not catch fire when 1000 volts is applied to it.

Or, it may mean that it needs to be "hi-potted" to 1000 volts from the

230 VAC connection to ground (if available) without arcing or breaking down its insulation.

It is difficult to protect to a contiuous high voltage that is virtually non-current limited. Can be done I suppose but... Next...

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I think you need a better translator.

umop apisdn
Reply to
Jasen Betts

I think you mean Varistor - varactor is taken to mean a variable capacitance diode.

It is not clear from your question how the apparatus is expected to deal with the 1000V : is it to continue normal operation or to survive the experience intact or just to fail gracefully without damaging people nearby. Is the 1000V exposure limited to 1ms, 1sec or continuous etc etc. More information is needed please.


Reply to

You may need multiple lines of defense:

  1. Spark gaps,
  2. Transient current limiting chokes,
  3. Varistors (VDR, voltage dependent resistor),
  4. Second set of current limiters,
  5. Semiconductor OVP, such as TransZorb

The overvoltages have to be transient, to match the nominal voltage spec.


Reply to
Tauno Voipio

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