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Will AC-rated solid state relay work for DC application?

Discussion in 'Electronic Basics' started by giuseppe, May 16, 2005.

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  1. giuseppe

    giuseppe Guest

    Assuming rated amperage is high enough? Also, will a 240v-rated AC SS
    relay work in a 120 application? Thanks!
  2. Chris

    Chris Guest

    Hi, Giuseppe. An AC SSR will turn on for a DC load, but it won't turn
    off. That's because the triac (or inverse parallel SCRs) at the output
    will only turn off at the zero voltage crossing of the AC line. That
    won't happen with DC, so you'll be stuck with a one time latch that
    will only turn off if you remove the power.

    Use a DC SSR for DC. Usual cautions about current and voltage ratings
    apply, of course.

    Good luck
  3. Chris

    Chris Guest

    Forgot to mention -- a 240VAC-rated SSR will always work for 120VAC.
    If you look at the data sheets, they will list a minimum as well as
    maximum load voltage. As I remember, that's usually around 24VAC for
    the 120VAC SSRs and 48VAC or so for the 240VAC SSRs.

    Good luck
  4. giuseppe

    giuseppe Guest

    Thanks very much for the info, Chris. Just what I needed to know. I
    really appreciate it!
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