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Miller intelliweld blowing fuses

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  • #16
    Originally posted by Noel View Post
    I'm not sure what that was that went over my head, but it went over it. Yet I find it interesting just the same.
    Yeah, I was tired. probably not worth stating all that, just the late-night ramblings of a mind that's too old to be up that late. But I'm glad someone found it interesting. Thinking out loud does not always come across as necessarily useful to others. The key point is that just measuring D.C. resistance and applying Ohm's Law to a circuit wth AC or pulsating D.C. current will not give accurate answers for current flow. Tex's question is very legitimate, because at first glance it looks like the circuit would always blow the fuse, if you don't take the reactance into account. Figuring out the actual impedance of the circuit (the resistance to current flow, which includes both resistance and reactance) requires a little trigonometry and/or vector algebra depending on how you want to look at it.

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    • #17
      Ahhh that makes sense!!! I didn’t figure my over simplified ohms law was gonna be quite accurate, just using it for a ball park and got lucky it was close like you said and I’ll check for a mfn today to see if I can’t find any more info

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      • #18
        Something I could a little odd is in the parts list of the contactor the coil is labeled as a 120vac coil. Is it accurate on there part or a simplification ? But the good news is it looks like I’ll be able to get one without getting the whole contactor

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        • #19
          Interesting. I guess even though there is a series diode making the current through that coil a pulsating D.C., it will still work on an AC coil. I put both the coil and the whole relay part nos into the Miller4less parts site and got no hits. You may have to call Miller if you can't find a vendor number in the relay. If you're out of luck on a vendor number, You should be able to take the parts list and/or the old part to a local electrical distributor and find a generic part. Might be cheaper that way.

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          • #20
            I have a couple of random, Miller relays laying around, I can check and see the ratings on them. If they work, you can have them. Probably not much chance in them being what you need, but it’ll be worth a look anyway. I’ll check when I get done fixing the dog house on this dump truck and get back to the shop.

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            • #21
              Originally posted by Aeronca41 View Post

              Yeah, I was tired. probably not worth stating all that, just the late-night ramblings of a mind that's too old to be up that late. But I'm glad someone found it interesting. Thinking out loud does not always come across as necessarily useful to others. The key point is that just measuring D.C. resistance and applying Ohm's Law to a circuit wth AC or pulsating D.C. current will not give accurate answers for current flow. Tex's question is very legitimate, because at first glance it looks like the circuit would always blow the fuse, if you don't take the reactance into account. Figuring out the actual impedance of the circuit (the resistance to current flow, which includes both resistance and reactance) requires a little trigonometry and/or vector algebra depending on how you want to look at it.
              Tired or not, you did good!
              I just didn't want you to think you weren't making the rest of us a little bit smarter for those efforts...because you are.

              While I hope it helps Tex4580 put the spark back, the more I re-read it, the more I'm convinced that I'm learning something even if most flew past in my head in fully grasping it.
              But being new knowledge far from my comfort zone of understanding, I'm happy when a bit sticks to build on. Some did. I can build on that which did and fill in more blanks as time passes.

              I'm following along.

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              • #22
                For those who are interested and may want to go down a rabbit trail, here's a link to the math that describes why we use RMS (Root-Mean-Squared) voltage measurement for sinusoidal AC electricity. For everyone else, please just ignore this!

                https://www.electronics-tutorials.ws...s-voltage.html

                The section entitled "voltage analytical method" is the most succinct mathematical representation of the process.
                Last edited by Aeronca41; 08-26-2019, 11:10 AM.

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                • #23
                  Well not that you guys may care about this but I called my local welding distributor and they said the new direct replacement part number was 137901 and list for 466.38 Which is more than I have in the power source with a dual wire feeder and digital voltage control! However they also said it is the same contactor in a Deltaweld series welder so I may be able to get lucky and find a part out or such. And I will definitely be doing more reading on the math! I have an odd need when I come across something that I don’t understand completely I exhaust myself with finding all of the relevant information and absorbing as much as I can.

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                  • #24
                    Tex, that is just ridiculous. Take the old one to an electrical supply house and see what they can do for you. I would also spend some time just using the specs from the parts list looking on Ebay. I'd do it for you but due to a funeral for a close friend, I'm fully booked 24/7 through Friday this week now--not likely to be posting anything. There has to be an answer under $200, and maybe under $100 if you can happen on the right place. You will no doubt have to do some alternative mounting methods, but I'm pretty sure you can figure that out.

                    I just checked Miller4less; it's about $393 there. Still absolutely crazy.

                    OK, here comes the really cheap old guy part...we used to have to do this. Lots of the old timers did this for power supply chokes, which is exactly the same thing, just on a different core form.

                    If you have the mentality (patience/persistance) and the time for it, if it's just a bad coil, you could probably rewind it yourself for a few bucks worth of magnet wire. Problem would be if it's melted together inside, because you have to be able to count the turns as you unwind the old wire. Measure the wire with a micrometer, cross ref the diameter to the wire gauge (taking into account the varnish thickness), and buy a roll of magnet wire. After that, all you need to know is how to count turns. Depending on the construction of the coil supports, you may be able to even speed up the process quite a bit if you have access to a metal lathe.

                    And even if it's melted together, you could just carefully measure the outside diameter and length of the coil, and just keep winding until it's the same size.

                    But, you gotta have the patience and time to do it.

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                    • #25
                      Well I’ll be honest with you I’m not a very patience man .... and that all sounds very do able but I’m not sure I’ll be able to to sit there and count that high... none the less I don’t plan on spending that much on the part I’ve got a couple of contactor laying around that are higher amperage with 115vac coil but I worry that they will have two high of amp draw (since the magnet is also meant to pull it in ) through the control circuit and then we’re backing to blowing 1a fuses again. I’m also sorry to hear about your friend and try and good luck getting through the week... I know that stuff can be rough

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