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s18k150 MOV replacement

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    #1

    s18k150 MOV replacement

    I picked up an APC UPS (BK650) a while back that was was not providing any power output. I have done a few APCs before so I don't have a problem getting in there and looking for problems. I found a shorted out s18k150 MOV which appears to be a unit made by Siemens. I haven't been able to find a replacement and It's not a part of the circuit I have much experience with so I don't know what would be a suitable replacement. I know its an 18mm disc, and a 20mm would fit, but I don't know how this would affect it's protection capabilities. Any help would be appreciated. Thanks.
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    #2
    Re: s18k150 MOV replacement

    We, at the steel mill, if a MOV is blowing fuses, sometimes we run without the MOV. That will work in a pinch situation. So if you need the UPS asap, go without the MOV. Its not suggested to do so for long term or on a regular basis but it all depends on the situation.

    BY THE WAY: there is a lot of 10 of these on ebay for about $16
    Last edited by Dgtech; 04-06-2017, 11:53 AM.
    The strong-minded rise to the challenge of their goals,the weak-minded BECOME HATERS

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      #3
      Re: s18k150 MOV replacement

      Thanks Dgtech. I figured this would work as well but it's not needed at the moment, just keeping it as a working backup. Strange part was this MOV was on the protected backed up side so I think something took a surge from another point and came back into the UPS. Tested every other semiconductor for shorts and everything else seems fine, other than a small 1A fuse near one of the transformers showing as open, but no visible damage to any component.

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        #4
        Re: s18k150 MOV replacement

        yeah, you might be able to find a datasheet on the part and then either find a similar replacement or simply buy those from ebay.
        The strong-minded rise to the challenge of their goals,the weak-minded BECOME HATERS

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          #5
          Re: s18k150 MOV replacement

          Here's a datasheet. MOVs are a common part. You could use any available brand with matching or slightly better (max. surge current and power) specs.

          This sounds like it may have been a wear-out failure. If the unit is 5 or 10 years old and was in an area with lots of surges due to thunderstorms or industrial motors, it's probably wear-out. MOVs are very fast and can absorb a lot of energy. But every surge they absorb does a little damage. Over time and surges, the damage is cumulative, with the consequence being that the break-over voltage gets lower and lower until the MOV is conducting even with normal line voltage. The MOV soon self-destructs.

          This is the same reason it's wise to replace power strips with surge protection after every 5-10 years of continuous use, depending on your power environment.
          PeteS in CA

          Power Supplies should be boring: No loud noises, no bright flashes, and no bad smells.
          ****************************
          To kill personal responsibility, initiative or success, punish it by taxing it. To encourage irresponsibility, improvidence, dependence and failure, reward it by subsidizing it.
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            #6
            Re: s18k150 MOV replacement

            Thanks. Best match I have been able to find would be: https://www.digikey.com/product-deta...buynow&site=us

            That was a better datasheet than I was able to find, so that's much appreciated!

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