Thought on a Variac Power Supply

Discussion in 'The Projects Forum' started by Andrew Leigh, Oct 21, 2008.

  1. Andrew Leigh

    Thread Starter Well-Known Member

    Sep 8, 2008

    conceptually what would you guys do?

    I have recently acquired a three phase variac for free that I wish to turn into a variable bench power supply. The phases are mechanically coupled and cannot be uncoupled. Each winding is capable of 240V @ 2A. The power here is 220V.

    I was looking at options like to switch in as many phases as required in order to increase the output current. Or perhaps to use each phase with independent circuits.

    I don't make many circuits and they are mostly low voltage low current applications. The pain is always to find a suitable power source when required. As the variac is free it would be nice to make full use of it and to put it to good use.

    Any thoughts or am I beating a dead horse pursuing this one.

  2. beenthere

    Retired Moderator

    Apr 20, 2004
    Variacs do not provide any galvanic isolation from the mains. They always carry the danger of lethal shock hazard. One could obtain some isolation transformers to give that protection, but it's expensive.

    Having a Variac is good for testing equipment because you can reduce the input voltage to the power supply and do checks on repairs at less than full load. hey are not suitable for anything more than that because of that lack of isolation.
  3. vetterick

    Active Member

    Aug 11, 2008
    Yes, beenthere raises a good point, the only way to safely use a varaic is with an isolation transformer first.
  4. Andrew Leigh

    Thread Starter Well-Known Member

    Sep 8, 2008
    Thnaks will do