Oxford 300 16amp / 3 phase problem

[jim weston]

Hi all I have recently bought a Oxford 300 mig which I believe is a good 25 years old it welds lovely on 16 amp it has the function of 3 phase too I have put the 2 bars on the angle as marked 415v then I'm abit lost there are no instructions were to put the wires for 3 phase any ideas? I have contacted Oxford they said it only uses 2 phases not three but he couldn't remember were the wires went. Thanks jim

 

[piman]

Hello Jim,

aren't there markings on the terminal board, e.g. 0, 240, 415? Or can you post a picture of the terminal board?

Alec

 

[jim weston]

There are only markings for where to put the bars that I can see Alec I will take a picture later today.

Thanks jim

 

[wheresmejumper]

They are not 'three' phase really,but two phase 400v.just 2 live feeds

 

[jim weston]

I have had it running on 2 phases tonight but there must something Amis I put the settings to 1 course 1 fine earth in the minimum hole and it blows holes through 3mm plate were as on 240v you can weld 1mm tin fairly well

 

[Wedg1e]

Jim, does it look like mine (1987 model if I recall right)...?

If so then as Wheresmejumper says it is only single phase, i.e two conductors and earth but the links allow you to use either 240V or 400V input. If you're connecting the 'Live and Neutral' to two phases of a 3-phase supply that's correct (as long as the links are in the 400V positions, I imagine things would soon start smoking if they weren't ).
I've only ever run mine from a 32A 240V socket; it will go down to about 20A output on 0.8mm wire, it'd probably go lower on 0.6mm.

For the benefit of future thread-browsers here's the link PCB:

I have a copy of the owner's manual as well in case you need it.

 

[the snooper]

Jim, does it look like mine (1987 model if I recall right)...?

View attachment 63541

If so then as Wheresmejumper says it is only single phase, i.e two conductors

View attachment 63545

I have a copy of the owner's manual as well in case you need it.

but that doesn't make it single phase (2 conductors) using a single phase makes it single phase, 3 phase supplies are 120 degrees out of sync with each other so using 2 of the phases makes it 2 phase, no mains neutral used only live

 

[normspanners]

are you connecting the phases to the left studs as per the picture the ones marked 415- 480 ? I would say they need to be on the right two with the plates angled. because if you have put the phases to the studs on the left you are putting 415v across the 240v primary coils

 

[jim weston]

Firstly thanks for all of your replies I have been browsing the web looking for help phoned various companies including Oxford themselves and found nowt out! I have connected the blue to the right lower leg and the red to the upper right peg as you look at the board the welder works fine apart from having too much power on minimum there is a wire hanging down I'll take a picture later see what you all think.. Thanks again for your help

 

[normspanners]

Is it too high ------ only on the minimum setting ? ie does it go to a lower current on number two ? if so it could be the windings have shorted down causing the higher current on the lower setting

 

[jim weston]

It seems to be high in 1/2 settings I ve found a ring crimp floating about which goes to the coil not sure we're that ones home is!

 

[normspanners]

it could be the ring crimp is to tie one side of the primaries down there may have been a burnt section somewhere and it is finding another way through, ie energizing the higher voltage primaries.
one way round it could be to run an single throw 4pole extra switch and a 4 core and neutral plug and run a neutral in there, the switch would do the job of the swap bars then when you need low voltage the switch is one way running 240v then throw the switch and you are then feeding it with two phases 415v for the high end stuff.

 

[jim weston]

Wedge1e mine is exactly the same as yours if you have time could you look in your instructions and see if there is a procedure when switching to 415 v as I said in my last post there is a wire hanging so that's a bit odd! i think re wiring the switches is a tad advanced for me normspanners 12v is more my style 415 stuff is a bit scary for me especially as I'm colour blind with red brown and Orange! I'm goin down the 415v route because I have 3 phase in my workshop and to use it on16 amp I need to hardwire from the fuse board with an rcd etc and that adds up to a fair few quid I have tested the welder on my mates 16 amp it did weld well to be fair I think it must be a fair beast when she's got full power proper metal melter!

 

[jim weston]

 

[jim weston]

Don't know if this helps. Above is a picture of suspect wire

 

[normspanners]

But it is still set for 240V !!

 

[normspanners]

Ah but just spotted the single phase plug --------trying to fool us eh doesnt take alot

 

[normspanners]

that looks like it was on one of those studs looks the right size, my bet is it was on the stud that was left to hold down the primaries but cant be sure. DONT JUST CONNECT IT THOUGH

 

[the snooper]

so for this to work the transformer must have 2 coils that run parallel for 240v and in series for 400 so should be able to trace the circuit to see if is in series

 

[normspanners]

Thats my thought could be centre tapped and the coil has been burned on one side of centre