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Relay ratings

Discussion in 'Electronic Basics' started by Rylos, Sep 14, 2004.

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  1. Rylos

    Rylos Guest

    Hello All,

    I have a relay which has a rating of 1A at 24VDC. The current rating is
    pretty obvious but is the voltage rating the maximum open circuit voltage
    across it's terminals? Thanks.

  2. CFoley1064

    CFoley1064 Guest

    Subject: Relay ratings
    The relay is rated to switch a 24VDC resistive load at 1 amp for the
    manufacturer-specified number of times before failure. That number can be
    anywhere between 20,000 and millions, depending on the spec sheet. If you use
    a higher DC voltage, you will get excessive arcing at contact open/close, which
    will reduce life, pit the relay contacts and possibly cause them to spot weld
    together on make. Usually it's rated that way because of contact separation
    and contact separation speed.

    Good luck
  3. Rylos

    Rylos Guest

    Thanks Chris,

    If the load I'm switching is lower than 24VDC, actually it's 5 can you push
    more amperage through or is the 1A rating just 1A regardless?

  4. Relay contact ratings work just like switch ratings.

    In this case, the contacts can safely handle up to 1 amp, at up to 24
    volts DC.

    Peter Bennett, VE7CEI
    peterbb4 (at)
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  5. CFoley1064

    CFoley1064 Guest

    Subject: Re: Relay ratings
    You can't push 500% more than rated current through the relay and expect it to
    survive for long. A lower DC voltage won't help.

    There is one possibility of getting more, but I don't think it will be 5 times.
    Just like a switch, relays have a published rating for switching current, and
    another (almost always non-published) rating for holding current. If you're
    not going to use the relay to switch the load on and off, you could probably
    get more (say, 20% to 100% more, depending), but certainly not 5A. Guess you
    need another relay to do the job. They're not expensive, and that's what I'd

    Of course, you might just try it and see what happens. You might get anywhere
    from 1/2 (on, but no off -- contacts welded) to hundreds of uses out of the
    relay, particularly if it's a purely resistive load. No guarantees, though. A
    1A relay is pretty weak for a 5A load.

    Good luck
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