Oxford 180A single phase

[Luggsey]

A lot of oils are hygroscopic, could this be partly responsible for the fuse popping

Bob

It's definitely a possibility, however the insulation resistance to earth is good and the windings are not short....
I will try again next weekend when its had more time to drip dry.
I saw a Yank vid of a guy who jet washed his and then turned it on to let it cook off!
I won't be trying that!

 

[Luggsey]

Things with a great big transformer like an oil cooled welder will often pop a fuse or MCB the first time you switch them on. 110-240v yellow transformer boxes do it as well. I had a Pickhill that did it every time but once I reset the MCB it would happily run all day without tripping again. Its something to do with inrush current when you switch it on. It can be helped by setting the welder to a low output setting before switching on.

I think it may well be the case here, my workshop is on the end of a 50m 1.5mm extension lead so that won't help!
I'm a sparks so I can sort that out sap.
If your breaker is dedicated to a welder it needs to be a type D which will withstand transformer startup currents.

 

[zzr1200]

Although the volt drop on your 1.5 mm2 cable will be excessive, it should not cause the fuse to blow when not under welding load.

I used to have an Oxford RT 180 it would throw a trip just by turning it on, plus that was only 15m from the fuse board...

50m of 1.5 no chance, 50m of 10mm (possibly 16mm) and your starting to get closer...

 

[Luggsey]

I used to have an Oxford RT 180 it would throw a trip just by turning it on, plus that was only 15m from the fuse board...

50m of 1.5 no chance, 50m of 10mm (possibly 16mm) and your starting to get closer...

I'm really hoping thats the case here TBH.
This is third time lucky to get an Oxford that I can fix!
I do however have plenty of spare parts now!
I do as it happens have a 16mm sub main that used to feed the barn where the new house and workshop are located, so I may try to resurrect that to allow me to test and hopefully use the Oxford.

 

[brightspark]

I think it may well be the case here, my workshop is on the end of a 50m 1.5mm extension lead so that won't help!
I'm a sparks so I can sort that out sap.
If your breaker is dedicated to a welder it needs to be a type D which will withstand transformer startup currents.

dont be using a d type breaker. a 32 amp c type is well adequate

 

[Luggsey]

dont be using a d type breaker. a 32 amp c type is well adequate

By all means use a C type if that works, I'm saying a deadicated MCB for a welder can be a D type to avoid nuisance tripping. If you run a welder at low current on a 32A ring circuit with a type b MCB its possibly less likley to cause problems for a welder as for example a radial fed socket on a 16 or 20A type B MCB.
Its horses for courses as it were.


I had a closer look at the primary windings from my other 180A Oxford when I got home from work today.
The top of the primary windings are 'cooked' and the insulation has flaked off.
That I suppose would indicate this one was run low on oil and overheated?
When this happens I think the windings show a good insulation to ground but present much to low an impedance and pull the fuse...
I will look into it more as I get the time but I doubt I can reserect any of the three I have which will be a shame.

 

[brightspark]

the 180 takes a 32 amp b type out on just turning it on. it will like a 20 amp even less .

 

[Luggsey]

the 180 takes a 32 amp b type out on just turning it on. it will like a 20 amp even less .

Exactly, thats why I suggested a dedicated welding MCB can be a D type of a lower rating and not nuisance trip.

 

[Turbo]

If your breaker is dedicated to a welder it needs to be a type D which will withstand transformer startup currents.

The breaker that was tripping was a type B, then I swapped to a 32a type c Hagar breaker & the welder has never tripped it.

The top of the primary windings are 'cooked' and the insulation has flaked off.

I've bought several pickhill/oxford type oil cooled welders, serviced them & sold them on in perfect working order. I've yet to get one that needed anything more than a good clean, new leads & the oil checked. I had one that had about an inch of emulsified oil in the base of the tank but once I separated that out there was still enough oil to cool the windings.

You must either be very unlucky or you're buying scrap welders to start with. They are incredibly reliable simple machines, able to withstand a full days welding in an industrial setting, day after day for many years with very little maintenance.

I would suggest you weigh in the ones you have for scrap & buy a good known working one. There's a good chance a member on here will have one for sale - try an ad in the wanted section. Given the current high scrap prices you'll likely make a profit!

 

[Luggsey]

The breaker that was tripping was a type B, then I swapped to a 32a type c Hagar breaker & the welder has never tripped it.




I've bought several pickhill/oxford type oil cooled welders, serviced them & sold them on in perfect working order. I've yet to get one that needed anything more than a good clean, new leads & the oil checked. I had one that had about an inch of emulsified oil in the base of the tank but once I separated that out there was still enough oil to cool the windings.

You must either be very unlucky or you're buying scrap welders to start with. They are incredibly reliable simple machines, able to withstand a full days welding in an industrial setting, day after day for many years with very little maintenance.

I would suggest you weigh in the ones you have for scrap & buy a good known working one. There's a good chance a member on here will have one for sale - try an ad in the wanted section. Given the current high scrap prices you'll likely make a profit!

Yes all three I have were in unknown or faulty condition when I got them.
The 180A had been used constantly I was told, by the look of them inside that was likley true!
I tested the winding resistance again yesterday on the one pulling fuses and its still under half an ohm. If I knew how long the winding was I could be sure it was correct. The winding wire looks to be at least 4mm possibly bigger, this gives only about 4 ohms per kilometre so that I would expect a low reading on say 100m of winding?
I am happy to keep tinkering these welders until I prove their condition conclusively, as you say they are worth a fair bit in scrap as specially stripped down.
Buying another one is a future option, I actually wanted one to repair my JCB buckets which need lots of welding! No hurry for that though.
On your welder a 32A supply is pretty big for single phase, is that your ring circuit or a dedicated supply for a welder?
If I was specifying a welder supply for say a 16A transformer welder current then I would likley choose a D type 20A that would trip on slow overload but not stay on too long if your welder started to slowly overload.
A 16A welder on a 32A MCB would have to draw much more current to disconnect unless you were using it on a 13A plugtop fuse?

 

[Luggsey]

Well all three Oxfords are scrap!
The only way I could make one work is to swap windings as I 'apparently' have one primary and one secondary that work.
However swapping it all over and building up the transformer again will take more hours then I can spare sadly.
I will try and find a dark corner to let them hibernate in and maybe one day......

 

[8ob]

Well all three Oxfords are scrap!
The only way I could make one work is to swap windings as I 'apparently' have one primary and one secondary that work.
However swapping it all over and building up the transformer again will take more hours then I can spare sadly.
I will try and find a dark corner to let them hibernate in and maybe one day......

I have never heard of anyone killing off an oil cooled Oxford never mind three The only thing I have ever had to do to an Oxford is clean up the internal contacts.

Bob

 

[brightspark]

I have never heard of anyone killing off an oil cooled Oxford never mind three The only thing I have ever had to do to an Oxford is clean up the internal contacts.

Bob

ive seen one burnt out they took it to pickhill rewound it and filled it with new oil it cost £90 to repair 45 years ago my new one cost £115 at about the same time

 

[Barking Mat]

I have never heard of anyone killing off an oil cooled Oxford never mind three The only thing I have ever had to do to an Oxford is clean up the internal contacts.

Bob

me neither.

 

[Bornfree]

I've got a 1960s cytringan 250 amp it's never had anything done to it in 30years. Still welds brilliantly

 

[Barking Mat]

Most of my welding gear is 60, 70, 80's they don't make 'em like they used to.

All actually.

Doesn't have led panels , bells and whistles, and many of the modern fineities.

But it all works, day in day out, even if I've not used it for a year or two.

My plasma maybe be from the 90's not sure.

I've cleaned the contacts in my 60's Oxford arc, drained the oil, and refilled it.

Migs (Migatronic 320 Compact), never required intervention. 1980's ?

Miller Dialarc 300 amp ac/dc tig, (70's?), changed the on/off switch couple of weeks back, it has been broken since I bought it. Never really been an issue.

Plasma, the air solenoid relay briefly wouldn't play ball, recently, but fixed itself after I hurled abuse at it.

It will all pack up next week now I've written this.

 

[Turbo]

On your welder a 32A supply is pretty big for single phase, is that your ring circuit or a dedicated supply for a welder?
If I was specifying a welder supply for say a 16A transformer welder current then I would likley choose a D type 20A that would trip on slow overload but not stay on too long if your welder started to slowly overload.
A 16A welder on a 32A MCB would have to draw much more current to disconnect unless you were using it on a 13A plugtop fuse?

I have a dedicated ring for welders & plasma cutter all wired in 6mm T&E . You size the MCB according to your cable size so that will be 32a for 6mm2. On the circuit I have some 13a sockets & 16a commando sockets. All the tools I use on this circuit have 2.5mm2 flex so again the 32a will protect the cable. Ideally I should have used 32a sockets but I find them very unwieldy and a 16a one is more than adequate for the current draw. They never get even slightly warm even after a lot of welding.

The rule of thumb I was taught is you size your cable & sockets according to the equipment's max current draw then select a suitable MCB according to cable size & load type. The MCB is there to protect the cable, not the equipment, that's more the job of the RCD.

 

[Luggsey]

I have a dedicated ring for welders & plasma cutter all wired in 6mm T&E . You size the MCB according to your cable size so that will be 32a for 6mm2. On the circuit I have some 13a sockets & 16a commando sockets. All the tools I use on this circuit have 2.5mm2 flex so again the 32a will protect the cable. Ideally I should have used 32a sockets but I find them very unwieldy and a 16a one is more than adequate for the current draw. They never get even slightly warm even after a lot of welding.

The rule of thumb I was taught is you size your cable & sockets according to the equipment's max current draw then select a suitable MCB according to cable size & load type. The MCB is there to protect the cable, not the equipment, that's more the job of the RCD.

I see, so in fact you have 16A sockets on a 32A supply? The point I was making is that your equipment that 'should' run at no more then 16A can in fact overload a socket designed for 16A.
We normally add a 16A socket with an MCB locally in that situation.
Your installation is similar to a bus bar system in a factory, the supply is large but every 'tap' is fused at the tap box.
You would likley see smoke from your welder if it was drawing 30A though!

 

[Luggsey]

I have never heard of anyone killing off an oil cooled Oxford never mind three The only thing I have ever had to do to an Oxford is clean up the internal contacts.

Bob

They were all 'unknown or faulty' condition when I got them!
I think the one with shorted windings had been dropped, the primary windings had earthed out onto the transformer on an edge.
The other has burnt primary windings on top, looks like it was run low on oil and overheated.
The one I actually bought for £20 was full of water and shorted the primarys internally...
So not unlucky as such, just trying to get old broken stuff working again. But the time and effort to rewind them is just not feasible for me at present.

 

[nikos]

I'm a sparks so I can sort that out sap.

Can anyone shed any light on my transformer question?
Posting here in case you guys may not have seen it

Buzzbox tap wiring

Hi all, New user, first post here regarding wiring an old buzzbox gift. Came to me unwired, but rewound, and I want to wire it up w/ your help. The box has different taps on the primary, and is a core type, primaries on top of secondaries. 2mm copper primaries, 4mm coper secondaries, bout 30...

www.mig-welding.co.uk

regards,
nick