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Thread: I Need a 400V, 3-pole, 25A circuit breaker.....what would you use?

  1. #51
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    Re: I Need a 400V, 3-pole, 25A circuit breaker.....what would you use?

    Quote Originally Posted by Oscar View Post
    The output of the RPC is already protected by a standard 240V/40A 3-pole breaker. I was looking for ideas/suggestions on actual breakers (and only breakers) that are rated to 400V (or even higher) for the output of the transformer. There is nothing to "tell", as I'm always pretty direct with my inquiries. I was looking for suggestions on suitable 400V 3-ph breakers, nothing more, nothing less.
    Well your definition of " tell" is hard to understand much less explain due in some cases to off the wall ideas. Either way the dinse rail mount breakers should certainly work to protect the circuitry coming off the transformer. Either way you would have to figure maximum amperage whether the welding machine, converter output or transformer output dictates maximum amperage draw and size according. Either way you have been given some good solutions and some off the wall ideas which would only complicate a relatively simple problem.

  2. #52
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    Re: I Need a 400V, 3-pole, 25A circuit breaker.....what would you use?

    Yes, I had already figured out the breaker size as 20-25A due to the machine only needing 21.5A I1max, and using 10ga conductors.
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  3. #53
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    Re: I Need a 400V, 3-pole, 25A circuit breaker.....what would you use?

    Out of curiosity, with that being a machine set up for the European market, does it run on our 60hz or the more common to Europe 50hz? If it is in fact 50hz, how would that play out using 60hz?

  4. #54
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    Re: I Need a 400V, 3-pole, 25A circuit breaker.....what would you use?

    The inverter power supply works with both 50 and 60 Hz. In the link that danielplace posted, I posted the electrical spec sticker indicating this.
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  5. #55
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    Re: I Need a 400V, 3-pole, 25A circuit breaker.....what would you use?

    Here it is,


    Quote Originally Posted by Oscar View Post

  6. #56
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    Re: I Need a 400V, 3-pole, 25A circuit breaker.....what would you use?

    Quote Originally Posted by Oscar View Post
    Yes, I had already figured out the breaker size as 20-25A due to the machine only needing 21.5A I1max, and using 10ga conductors.
    I believe the NEC language was based on transformer welders, it hasn't changed the rules in 50 years, but has rephrased to say the same thing. If an I1max rated breaker produces nuisance tripping, larger breakers up to 200% may be used, based on a formula factoring duty cycle.

    I size circuit conductors factoring voltage loss. It is seldom necessary to use the devaluation of load NEC allows. Conductor length usually negates. After sizing conductors, I begin with breaker size appropriate for the circuit conductor.

    Transformer welders are less common now, I seldom upsize the breaker from that. Code allows me to if it trips unnecessarily.

    Accumulated heat inside a welder is outside the capability of a circuit breaker. I'm not saying it can't work, I am saying there are other ways, likely more effective.
    An optimist is usually wrong, and when the unexpected happens is unprepared. A pessimist is usually right, when wrong, is delighted, and well prepared.

  7. #57
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    Re: I Need a 400V, 3-pole, 25A circuit breaker.....what would you use?

    Amperage aside, Any reason I could not use those 480V 3-pole breakers at 400V and 240V (3-ph of course)? What I know tells me the lower operating voltage (compared to the breaker voltage rating) should have no ill-effects, so long as they are sized properly to protect the wiring, etc. Thoughts?
    Willie eludes to this in a bit. The breaker is not there to provide thermal overload. I read a legend somewhere about sizing all that new max crap but I forget. But I bet this machine is legal 12 wire at that voltage and maybe even 14.

  8. #58
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    Re: I Need a 400V, 3-pole, 25A circuit breaker.....what would you use?

    The breaker in this type of circuit isnt sized to limit the heat but to allow enough current to pass without tripping. The machine itself is the current limiter and breaker there for service disconnect and sized for short circuit.

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    Re: I Need a 400V, 3-pole, 25A circuit breaker.....what would you use?

    I mean, here I am, a hobbyist, with a garage full of gear that likely no other hobbyist has
    That is likely true.
    it's just that I have a pretty good idea of where I don't have to spend a fortune, and can make do with less,
    Ok.
    But I like the fact you point out this is a hobby. You have some better tools than I do and I do this every day.
    Back to the original show though,,, it is sort of interesting and some of the other guys may be more qualified to answer tech questions about breakers,,,, I am kind of curious as to how the code would see the use of 240 breaker at substantially higher voltage? I think in a pure sense might be ok but would violate its listing.
    Last edited by Sberry; 10-07-2021 at 09:23 AM.

  11. #60
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    Re: I Need a 400V, 3-pole, 25A circuit breaker.....what would you use?

    I size circuit conductors factoring voltage loss. It is seldom necessary to use the devaluation of load NEC allows. Conductor length usually negates. After sizing conductors, I begin with breaker size appropriate for the circuit conductor.
    I size for this and length also but the breaker for a welder is sized by max,,,, or by short circuit for the circuit conductors if that kind of makes sense? Breaker is sized for the load not really the wire. Wire needs to be sufficient for the applied load.
    We can look at the instructions to 225. 12 wire, 50 breaker, machine comes 12 cord.
    I doubt anyone thinks 75 ft of 12 on a 50 is great but shorten it to 50 and up a size and its really good.
    This not aimed at Willie, he is above my level but others learning some fundamental circuit design. Look at electric range,,, yes, it comes 6 cord on a 6 wire circuit but the breakers isnt for thermal,,, all the combined loads limit that but the breaker needs to be large enough to pass the required current but small enough to provide short circuit for the internals of the machine. This is the fundamental principle that lets all the small fixtures and appliances be connected to common 20A, its why a 16 extension cord is allowed on a 20A.
    About the only place a breaker provides thermal is multiple recepts and why they add a thermal on power strips or other schemes with small wire feeding additional outlets. That little reset is not the sale as a breaker and doesnt replace it, its simply thermal overload and the breaker is still the fault protection and like many other outlets simply says,,, the wire is adequate,,, yes but it also means the outlet is fault current limited.
    The designer uses this to size controls, safety within the machine up to any additional protection doesnt fall within those parameters. The internals of lots of machine controls up sized to fall in there,,, while the transformer on my pressure washer,,, and the blower (which is the only piece in it with additional protection) uses 1/2 the current they do in a 120V machine the wire is upsized to meet fault protection.
    The MVP wrelders have come up with another scheme but single voltage machine ;like a 175 has a 12 cord and a new 210 a 14. The cord on the 175 is better than it needs to be and can actually be fed 14 if we limit the breaker,,, but its up a size simply to be able to be connected to 50A without adding additional protection. 6 ft of 12 wire vs 6 ft of 14 is cheaper than adding a bunch of fussy fuses.
    Last edited by Sberry; 10-07-2021 at 09:59 AM.

  12. #61
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    Re: I Need a 400V, 3-pole, 25A circuit breaker.....what would you use?

    I look at the chart again for the original machine in this thread, 14 wire probably not legal due to duty cycle. Also would be interesting to see if they have any controls after the switch and before the thermal in these type machines, seems a guy might be able to put the fan ahead provided the wire was heavy enough????

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    Re: I Need a 400V, 3-pole, 25A circuit breaker.....what would you use?

    Quote Originally Posted by Sberry View Post
    That is likely true. Ok.
    But I like the fact you point out this is a hobby. You have some better tools than I do and I do this every day.
    Back to the original show though,,, it is sort of interesting and some of the other guys may be more qualified to answer tech questions about breakers,,,, I am kind of curious as to how the code would see the use of 240 breaker at substantially higher voltage? I think in a pure sense might be ok but would violate its listing.
    I think this was mentioned earlier and was misunderstood because Smithdoor can be hard to understand but I agree, a 240 volt should be able to handle the load providing spacing between terminals is sufficient to prevent arcing between terminals. Higher voltage has more tendency to arc than lower voltage. Hi voltage wire is thicker to prevent arcing thru insulation. However, its a waste of time to offer advise. IMVHFO

  14. #63
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    Re: I Need a 400V, 3-pole, 25A circuit breaker.....what would you use?

    Yea sure use a 240 breaker. Should be fine. Wonder why they even bother to make ones for higher voltages. Lol.

    Imagine what the phase converter and step up transformer going to look like it if it happens to go phase to phase.

    If your over 400 volt I would not recommend a 240 breaker. It may work just fine but why. Too much at risk to try and save a few dollars when your invested thousands already.

  15. #64
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    Re: I Need a 400V, 3-pole, 25A circuit breaker.....what would you use?

    Just a carbon track in a plug cap is enough to cause an explosion at 480 v. Done it several times. Customer had live bottom trailers they hauled through a salty mess on winter roads. I did everything to persuade them to protect the cord while on the highway. Finally they converted the hydraulic power supply to stationary.
    An optimist is usually wrong, and when the unexpected happens is unprepared. A pessimist is usually right, when wrong, is delighted, and well prepared.

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    Re: I Need a 400V, 3-pole, 25A circuit breaker.....what would you use?

    Quote Originally Posted by Insaneride View Post
    However, its a waste of time to offer advise. IMVHFO
    Nah, I don't think so. I did take someone's advice. They advised 480V breakers from automationdirect.com. I liked that option, so I went with it. However, it simply wasn't the advice that you would've gone with, obviously. Not everyone is going to take the first piece of advice they are given, and not everyone will take your advice, since they have the right to decide and choose for themselves. That's life, right? No need to get all bent out of shape over it.
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  17. #66
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    Re: I Need a 400V, 3-pole, 25A circuit breaker.....what would you use?

    I'm sure I've missed the point about a 3 pole circuit breaker, so here goes, why not use 3 single pole and tie them together with a bar to make a 3 pole circuit breaker since a minimum of amps is being used. Guess I'll have to think about it some more.

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    Re: I Need a 400V, 3-pole, 25A circuit breaker.....what would you use?

    Quote Originally Posted by Bob-O View Post
    I'm sure I've missed the point about a 3 pole circuit breaker, so here goes, why not use 3 single pole and tie them together with a bar to make a 3 pole circuit breaker since a minimum of amps is being used. Guess I'll have to think about it some more.
    How are you going to feed them.

    Line load lugged single pole 277 volt breaker may not be plentiful but I haven't looked.

    3- 277 volt single poles and panel to feed them with would be expensive too.

    Think hehas found a 3 pole priced right already.
    Last edited by danielplace; 10-15-2021 at 07:22 PM.

  19. #68
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    Re: I Need a 400V, 3-pole, 25A circuit breaker.....what would you use?

    Thanks to everyone for their unwavering support! Took me this long since I been working long hours and only have like 20-30min free on the weekdays after I get home, and weekends are for traveling around Texas

    Receptacles from Left to Right:
    • 240A (just pass through, same 3-Φ coming from the rotary phase converter, not up/down converted)
    • up-converted 400V with a 25A B-curve breaker (right above, breaker on the left). They were out of stock on C-curve breakers, so I'm thinking it will be fine.
    • up-converted 480V on a 20A B-curve breaker (right above, breaker on the right).






    I still need to protect the wiring that comes out from the transformer, but for now it's no big deal as I don't work anywhere near there.
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