Wiring up the Oxford RT 300

  1. zardoz

    zardoz Old school Socialist

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    2,219
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    Chetser, UK
    When we had to manhandle the beast out of the back of my hatchback, I took off all the cables, as these must have weighed 40lb themselves. Anyway, i unscrewed th connections in the wiring box, without looking what went where. Now of course i cant recall what went where. Anyway there are 5 connections, An 'E' in the centre, top right '440' top left '415' bottom left '400' bottom right '0'

    I have an ordinary 240Volt outlet, so i cant use to the full potential, but then i rarely weld bridge girders anyway. Can someone please tell me which to wire to, and what the others are for?
     
    • oxford wire layout copy.jpg
  2. hmmm very strange, the rt300 is supposed to run on 240v, but i dont see a 240v connection
     
  3. zardoz

    zardoz Old school Socialist

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    Chetser, UK
    Indeed thats what is puzzling me. Now someone with more experience that me has confirmed it, im worried now?! Dont say i cant use it, sob!:vsad:

    I certainly cant afford a phase converter either.

    thinks... "Hm? fleabay will help me"

    Hey maybe ill build me one with this snazzy set of plans for only £19,99 plus 3.50 p&p {rip off}

    Item number: 270193160224
    BUILD YOUR OWN SINGLE PHASE TO 415V 3 PHASE CONVERTER

    Anyone know any factories closing down, where i might acquire a 3 phase converter :eyepatch:
     
    Last edited: Dec 5, 2007
  4. Welderpaul

    Welderpaul Moderator Staff Member

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    Yorkshire
    A phase converter is fine for running a motor - lathe etc, but not a three phase welder. The phase converter will glow bright orange then burst into flames!

    Earth goes on the centre E pin, Neutral on 0 pin, and put live onto one of the terminals - 400, 415, 440. You wont get full power - it will work. I think!. Thats what i did with mine. There is a thread kicking about somewhere with my welder on.

    PS I am a welder, not an electrician.
     
    metalmelt likes this.
  5. zardoz

    zardoz Old school Socialist

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    thats what i was going to do, so im glad someone else has mooted it. Can anyone else confirm ?
    I dont think this is a three phase welder. er is it ? now im really confused. I was only joking anyway.(Note to self: must use more smilies) Anywho the only phase i know about is a phaser off Star Trek and i think they only had 2 settings, Stun and Kill (originally anyway. I think they tinkered with them for Next Generation) :)
     
    Last edited: Dec 5, 2007
  6. Drains

    Drains Yeah, nah.

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    Yon lump is a one/two phase welder (depending on your point of view)- so only twin and earth. Normally that would be two phases for 415v. But you could get a transformer to go from 240 to 415 and wire that into the set.

    What you may find (but I really don't know) is that your open circuit voltage is a bit low (even on the 80 volt setting), if you just put 240 over it. But it should still squeak at you a bit.

    Otherwise, for fun, you could just try different combinations on the different posts (but not the earth). Then again, you might die :laughing:
    Go on, go on, live on the edge :p

    Si
     
  7. Welderpaul

    Welderpaul Moderator Staff Member

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    Go for it. You'll never kill it.
    First job when an Oxford was delivered to the workshop was for the apprentice to make a trolley and set of wheels for it. Not all came with wheels. No doubt many a bird-poo-welded-together trolley sat under Oxfords around the country.
     
  8. Bung them terminals on, I think one of mines wired with two phases across 240 and 0 even tho its getting 3 phase into it, It doesnt seem to make any diffrence to it.
     
  9. peterd51

    peterd51 happy to be here!

    Messages:
    1,593
    Scunthorpe UK
    Hi,

    I'd try with an ohm meter across the various combinations of contacts first though.

    Double check that the earth lead is also connected to the case.

    Then I'd put the mains between '0' and the highest resistance pole first to try it, moving it down to lower resistance poles later.

    When taking things apart I usually take digital pictures of the various stages to assist in re-assembly. It also means that I can write it up as a project later if I want to.

    Regards
    Peter
     
  10. piman Member

    Messages:
    1,755
    Location:
    Oswestry Shropshire
    Hello Zardoz,

    that welder needs two phases of a three phase supply. The terminals 400, 415, 440 are for slightly different supply voltages. What ever you do do not connect 240 between any combination of those three terminal,the welder will not work and unless your supply has not got adequate protection will just blow a fuse\trip a breaker. Simply the voltage difference between terminals 400 and 440 (the maximum span) is 40 volts so 240 volts will do it no good.

    I don't believe that it will work if you connect 240 to 0 and 400 (the best option) and as Simon says you need a transformer.

    However you connect it do make sure there is an adequate earth connected to E terminal.

    Alec
     
  11. zardoz

    zardoz Old school Socialist

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    okay so now the advice is NOT to wire it up to 0, 400, and earth ? What sort of transformer would i need ? I assume its a 240V to 440v step up transformer ? (I can wire a plug and thats about it)
    I have a Gunsons pocketmeter I 4141, but lost the instructions, so can only do the most basic things on it.

    However did not Paul say he has done his like that and all is well ?
     
    Last edited: Dec 6, 2007
  12. dcocks

    dcocks Member

    Messages:
    349
    Location:
    Leicestershire
    Hi
    we have a old Oxford wired up on 2 phase it will not work on 240 very well it has no power will not swing a 2.5mm stick.
    Best thing to do is call pickhill 01845 567234 and ask them the girl is very helpfull nothing to much trouble
    Regards David
     
  13. piman Member

    Messages:
    1,755
    Location:
    Oswestry Shropshire
    Hello Zardoz,

    you would need, ideally something like a 240 to 415 single phase transformer, bear in mind that transformers are rated for power so you will need to size it to the welder. Normally rated in volt amps (not watts), e.g if the welder primary (input) is rated at say, 15 amps then it's power rating is 415 x 15 = 6225 volt amps (6.225Kva). due to losses you would need a larger transformer to use full power of the welder.

    Alec
     
  14. Drains

    Drains Yeah, nah.

    Messages:
    7,716
    Location:
    Sefton, South Island, NZ
    I think the advice was not to wire it up to 400, 440 and earth, (or 400, 415, or 415, 440), as you will get a short.

    But 0,400 and E should be fine, not very good, but worth a try.
     
  15. dcocks

    dcocks Member

    Messages:
    349
    Location:
    Leicestershire
    I have got a CYTRINGAN 180 same as a OXFORD when i got it was sposed to be 240 volt as was Zardos,s all they had done was put a 13amp plug on it. Rubbish you can weld better with a zippo we do have 3 phase in our unit so we stuck a 4 pin plug on it we use the earth the n and 1 positive now it will burn 4mm sticks all day
    as i said before talk to pickhill very much same sort of guys as weldiquip tell you how it is.
    Regards David
    PS i would say buyer beware on fleebay cus it only use 3 wires they say its 240v some are but most are 415 volt
     
  16. zardoz

    zardoz Old school Socialist

    Messages:
    2,219
    Location:
    Chetser, UK
    Cheers for the good advice. I think i will ring pickhill.
     
  17. Weldingartisan Aiming for retirement

    Messages:
    533
    Kent, UK
    I believe those 300amp Oxfords were available with different primary windings at the time of purchase. But the loading on 240v was high (63amp) so most were purchased with 400/415/440 primaries. You'll be lucky to even strike an arc with 240v on the 400v terminal W/A
     
  18. mishka

    mishka Is it me?

    Messages:
    247
    Cambridge, UK
    As its only a large oil-cooled transformer the output voltages will be lower if you connect 240V to the 400V terminal. Running through the sums you will get 30V on the "50V" terminal, and 48V on the "80V" terminal. So on the "80V" terminal will have just enough volts to strike and hold an arc (comparable to cheapo SIP arc welders).

    Also, the primary won't be wound to deal with the higher currents for comparable ratings, so I wouldn't operate it above, say, 2/3 max.power (say, 200A).
     
  19. wiring up the Oxford

    Hello, connect the mains as follows-: Neutral=0, Live=any of the terminals marked 400+volts (preferably the lowest number), Earth as shown on welder. Use a seperate 25 Amp mcb (circuit breaker) for the mains supply, and wire it to the elcb side of the fusebox if one is fitted (presuming you have a modern fusebox). If not then you should not use the oxford on a rewirable fusebox, it may get a little smokey when hard pressed. I do have an Oxford myself, and despite the newer equipment around nowadays they are more robust and forgiving when used by novices, I have never ever seen one burn out. Lift the lid and check that the internal connections are still tight and the oil level is correct and you will not go wrong, you may have to check them again in 10 to 20 years or so. If you try to run it on high current using a 13 amp ring main plug then I would suggest you stock up on fuses, it will eat them quite rapidly. I use a cooker cicuit for mine with a 25 amp breaker and 32 amp plug /socket combination. I hope this helps you out, Bob.
     
  20. zardoz

    zardoz Old school Socialist

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    2,219
    Location:
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    thanks for the advice bob
     
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