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Help me with 3 phase supply monitor

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nuyi

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I have a refrence single phase voltage of 220VAC.
Now there are three (3) phase supply; a phase to neutral measure average of 220vac plus or minus
At any time I need a single phase output, out of this three phase supply with the nearest voltage value to my refrence voltage of 220VAC to be choosen to operate a 12VDC relay.
Kindly help me out with basic and simple circuit to achieve my aim

THANKS.
 
If I've understood you correctly any one of the phases should give you 220V AC from phase to neutral. Put that into a 220:9 step-down transformer and rectify and smooth the 9V AC output to give ~ 12V DC to power the relay.
 
Thanks Alec_t I ned a simple circuit to monitored the three phase and choose for me the phase that have the most colse value to my refrence voltage out of the three phase to supply my relay at any time.
 
It should make no difference which phase you pick as they should be all balanced anyway.

Any difference in meter readings from 1 phase to the next would likely be the meter used and not the phase.
 
i ned a simple circuit to monitored the three phase and choose for me the phase that have the most colse value to my refrence voltage out of the three phase
why??
 
Three phase power comes in both a Y (WYE) and Δ (Delta) configuration. Which do you have and what exactly are you trying to do?

Ron
 
Are you using the relay to power a 220V device?
Do you need to monitor both under-voltage and over-voltage?
 
Three phase power comes in both a Y (WYE) and Δ (Delta) configuration. Which do you have and what exactly are you trying to do?

Ron
He has a neutral.

Also I assume he want only one phase out, and then of course neither delta or y.

If this is going to be relay controlled, there is a couple of things that OP must decide:
  • Rule for how long time one phase must have higher voltage before action is taken
  • What kind of relay will be used?
  • The circuit have to be protected against relay shortcuts (short via two relays because the active relay doesn't open quickly enough)
  • Or will it be timed so relay close very near time of zeero voltage (won't work if control voltage is ac)

I must allow myself to guess why - he might be at a place where current supply isn't stable.
 
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