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is my transformer bad?

Discussion in 'Troubleshooting and Repair' started by 1dumbquestion, Oct 12, 2011.

  1. 1dumbquestion

    1dumbquestion

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    Oct 8, 2011
    I have a Jefferson Electric transformer #631-1901-000. it is on a band saw that has not ran in a few years that I thought I'd get up and running again... anyway when I measure from either line to ground on the input I get about 230+volts. I cannot seem to get anything on the output posts. I replaced it with an identical model (used) I found on ebay and have the same results. before I shell out a few hundred bucks on a new one I'd like to know what people in the know think. Thanks in advance. 1
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,191
    2,693
    Jan 21, 2010
    What voltage is your mains there? 240? 220? 110?

    If you're getting mains voltage between either end and ground (and it's supposed to be connected across active/neutral) then it sounds like there's no connection to neutral.

    Another possibility is that you have some sort of ground fault.

    I presume these measurements are on the primary. Do you see any voltage on the secondary?

    Can you give us a little more information on this transformer (rated voltages and currents)

    Oh, and welcome to Electronics Point :)

    edit: no such thing as a dumb question...
     
  3. Resqueline

    Resqueline

    2,848
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    Jul 31, 2009
    What about the line-to-line figure? Does it hum or get warm? Are there other parts that could prevent power ffrom reaching the primary?
     
  4. 1dumbquestion

    1dumbquestion

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    Oct 8, 2011
    :rolleyes:
    give me a minute, I might prove you wrong on that last part.


    I don't even know how to answer your questions, but I'll try to give you some more info.

    I looked up the transformer on the JE website and it has a pic of the wire diagram. on mine the H1 is connected to one wire from the breaker and another wire goes to the H4. then there is a jumper between H1/H2 and H4/H3. just like the pic on the site shows. when I put my meter on H1 and ground to the machine I show 236V same with H4 to ground. nothing reads when I go from H1 to H4. on the output I only have 2 screws, when I check between them OR from one or the other to ground I get no reading at all. BTW the thing says 500va... whatever that means. Thanks agian. 1
     
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,191
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    Jan 21, 2010
    Any chance of you posting a link to that information?

    Are you in the US?

    Does this thing plug in to a regular household power outlet?
     
  6. 1dumbquestion

    1dumbquestion

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    Oct 8, 2011
    I didn't know if that was ok on the forum, here it is.

    http://www.jeffersonelectric.com/cg...y=636-1191&filtered=631-1901-000 631-1901-000

    The saw is a 3 phase and I had it running off of a static converter. It worked fine for a year or so and then stopped... its been sitting for a few years now. Hope this helps. 1
     
  7. Resqueline

    Resqueline

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    Jul 31, 2009
    Voltages relative to ground are not what's running the machine. It's the H1 to H4 that needs mains power. Measuring between H1 & H2 (and also from H3 to H4) would be relevant measurements too.
    Depending on what's your input terminals, you could then measure between X1 and X2 (and also from X2 to XF), but you seem to have no power going into the transformer.
    Ok, so you're in the US, running this on 230V (for 115V out?). And you have two jumpers, one from H1 to H3, and one from H2 to H4. Right?
    500VA means that you can carry/draw a maximum of 500VA / 115V = 4.35A on the 115V terminals (X1-X2).
     
    Last edited: Oct 13, 2011
  8. jackorocko

    jackorocko

    1,284
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    Apr 4, 2010
    Huh? Are you sure

    Also, if the saw runs off of 120V on the secondary and you live in a rural US location with 120, then why do you even need the transformer? As long as you fuse it properly... Resqueline has already given you enough information to do that in his last post.

    edit: I would like to see a picture of how it was originally wired up.
    edit edit: What is the present voltage as measured from H1 - H4 with the jumpers in place from H1/H3 and H2/H4. This voltage has to be 240V. I did this once with an old breaker box, I double tapped a single phase and even though I had 120V to ground on both legs, there was 0 Volts between the two phases. Just a thought.
     
    Last edited: Oct 13, 2011
  9. 1dumbquestion

    1dumbquestion

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    Oct 8, 2011
    thanks guys for trying to help me out, when I apperently have no idea what I'm doing.

    When I measure between H1 & H4 I have no reading...so not knowing what else to do I measured between H1 & ground and found a reading. The transformer is part of the original build of the saw so I don't want (have the ability) to bypass it. When I bought the saw if was in a shop with 3 phase, I don't have 3 phase so I put a static converter on it and it ran fine for quite some time. So now it has a 50A/220v plug just like my welder. 3 wires come out of the phase converter and 2 of them go to the transformer. Yes the saw runs on 115v except for the motor. So you guys are saying I SHOULD have a reading across H1 and H4? and not just to ground? I think I'm more confused than when I started. I have the factory schematic, but that doesn't seem to be helping. Jack/Res did I answer any of you questions? thanks, 1
     
  10. jackorocko

    jackorocko

    1,284
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    Apr 4, 2010
    I don't understand the 3 phase bit, That transformer isn't made for 3 phase AFAIK. And, yes from the link you showed us, you should have a voltage of 240V between h1 + h4 when h1/h3 and h2/h4 are jumpered(in other words with the power off there should be very low resistance between h1/h3 and h2/h4). I would start back tracking till you figure out where you lose the 240V between h1 + h4.

    can you draw a schematic of the wiring from the breaker box through the converter and then to the saw up till the motor?
     
    Last edited: Oct 13, 2011
  11. 1dumbquestion

    1dumbquestion

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    Oct 8, 2011
    I don't understand the 3 phase bit either. Well you've convinced me that I should have 240V between H1 & H4 so I guess I'll keep looking for it. So should I have 240v between H1 & ground and H4 & ground also? If I backtrack I'm going to run out of track pretty quick... the 2 wires go back to fuses (check out good) then back to the static converter then to the wall... if I have 240v between H1 and ground were is that coming from if something prior is not working properly? color me confused. 1
     
  12. jackorocko

    jackorocko

    1,284
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    Apr 4, 2010
    The only thing that makes sense to me is that if you have a 0V on the input of the transformer you will have 0V on the output. If you know for a fact that the transformer is jumpered h1/h3 and h2/h4 then there has to be a voltage between h1 and h4 for the transformer to work. So we figured out that much
     
  13. 1dumbquestion

    1dumbquestion

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    Oct 8, 2011
    I agree. I've also figured out that I know much less about much more than previously thought. I won't be able to get back to that machine until next week but will post my findings. Thanks all, 1
     
  14. Resqueline

    Resqueline

    2,848
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    Jul 31, 2009
    Please forget about the ground, it's irrelevant and it won't get you anywhere power-wise.. Backtrack from H1-H4 (or measure across the breaker or whatever there is).
    If you have the diagram it would be highly beneficial if you could scan it or take a picture of it and post it up here.
     
  15. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,191
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    Jan 21, 2010
    True.

    The original issue was that 240V were seen on both sides of the transformer.

    If you've got 240V mains, AND if your neutral is bonded to earth, then neutral should read zero volts (actually it will read a little higher). This is not particularly relevant unless you're measuring voltage with respect to earth instead of neutral.

    In the US, I believe 220V is achieved by using 2 anti-phase 110V rails (effectively 2-phase power). From ground (neutral) to either should be 110V.

    Seeing 220 (240V) from ground (the OP mentioned measuring from ground) on both ends of a transformer in 240V mains environment indicates that either active is connected, but not neutral, or that ground is floating and you're seeing 240 volts (or some other figure) to everything.

    I was trying to determine *exactly* what was being measured, not indicating that the measurement made any particular sense :)

    But we've moved on from there.
     
  16. 1dumbquestion

    1dumbquestion

    7
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    Oct 8, 2011
    update

    Hey Guys, well thanks to you telling me that I should have 240v between input terminals I tracked back and low and behold the phase converter had a wire that had come off. I put it back together and I now have a working transformer. The saw on the other hand still needs repair but I'm heading in the right direction. Thanks again for all the help. 1
     
  17. jackorocko

    jackorocko

    1,284
    1
    Apr 4, 2010
    Right on, glad you found the issue.
     
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