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Low voltage cut-off at Mains level

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tribat:
My load is a 230VAC 28kohm (8.2mA) relay that on its own has a must drop-out voltage of 0.2Un which makes the relay open when voltage goes under 50VAC. But I need the relay to open much sooner, say when voltage goes below 200VAC. Is there a simple circuit I could use to achieve this?

Kiriakos-GR:

--- Quote from: tribat on January 25, 2011, 02:31:34 pm ---My load is a 230VAC 28kohm (8.2mA) relay that on its own has a must drop-out voltage of 0.2Un which makes the relay open when voltage goes under 50VAC. But I need the relay to open much sooner, say when voltage goes below 200VAC. Is there a simple circuit I could use to achieve this?

--- End quote ---

Please define the word " simple " .  :)

FreeThinker:
You could try wiring a resistor across a nc contact in series with the coil and playing with the spring tension of the moving contact block. When switched on the full 230v is applied via the nc contact which then opens and holds the coil just above the desired dropout voltage, may work never tried it but the theory is sound.Some experimentation will be required and current capacity could (almost certainly will) be reduced.Also no two coils will be the same so some variation in the operating point is to be expected.

Zero999:
The easiest way is to buy a low voltage protection relay which will do what you want.

JohnS_AZ:
You might get some ideas from here ...

http://www.brighthub.com/engineering/electrical/articles/68396.aspx

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