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.