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Old 27th Jun 2020, 2:32 pm   #1
Richard
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Default Olympic WT225 oil cooled welder.

Hi

Bought this, a spot welder and wheelbarrow full of rods a few weeks ago for £100, bargain!

It all works as it should, plugged into 240V 32A circuit in the workshop.

On the side there is a large capacitor, which measures as 70uF.
When the welder is on but not welding there is 415V AC across it.

Question is why, what is it doing?
I did wonder if its just phase correction to keep the supply company happy?

Richard.
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Old 27th Jun 2020, 4:01 pm   #2
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Default Re: Olympic WT225 oil cooled welder.

I'll think you'll find that's an arc or "stick" welder rather than a spot welder.

I have a similar one branded "Oxford", but it doesn't have the capacitor. PF correction seems the most likely function.
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Old 27th Jun 2020, 4:02 pm   #3
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Default Re: Olympic WT225 oil cooled welder.

That doesn't look like a spot welder.
I think it's a straight-forward arc welding transformer... looks like good quality. 225A will let you go up to 4mm electrodes.

Beware that the coating on electrodes has to be kept dry. Some even need preheating in ovens before use. (I keep mine in the airing cupboard!) You need to be sure any new electrodes you get are suitable for AC use (It won't do DC without a big add-on rectifier)

£100 is very good for an oil cooled 200A job.

Great for sticking structural stuff together, but you'll find it very limiting on light gauge stuff. 1/8 inch mild steel ought to be OK but anything lighter will be trouble.

The limiting factor is in the electrodes. You need to heat and melt a certain amount of the rutile coating to make enough CO2 to keep atmospheric oxygen away from the molten steel. That needs a minimum amount of heat from the arc, and that implies a minimum rate of melting the metal part of the electrode. This floor to the amount of heat forces a limit on how fine a gauge of metal you can weld and still have shielding gas.

To go finer you use the MIG or TIG processes and a bottle of shield gas, so you get shielding irrespective of the current you choose. Be careful they sell 'Gasless MIG' equipment, but these have shield gas generating chemicals in special wire - a bit like multicore solder, and you're back to limits on how thin you can go.

Spot welders are big heavy beasties like a machine gun with two large electrodes protruding at the business end. Squeezing the handle hard brings the electrodes together to clamp the two pieces you're welding together and then the current comes on for a moment. Then the current times out, you release your grip and the electrodes release the work. Think of footage of car assembly lines and you'll see robots weilding clamp shaped electrodes, clamping a flange overlap and a momentary shower of sparks before they move on to the next one.

Have fun.

Take great care to protect other people and animals from your flashes. Arc eye can be damned painful, feels like someone's rubbed fine sand in your eyes. Reflected flashes can do it too.

David
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Old 27th Jun 2020, 4:10 pm   #4
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Default Re: Olympic WT225 oil cooled welder.

At that size it likely has a transformer primary tapped for 240v or 415v input. If you're feeding it 240v and the power factor capacitor was left across the 415v terminals, that would explain what you've measured.

These things have been used with out the capacitors for over half a century, but they got a bit more insistent on power factor for high power loads.

I see you've got dual output voltages. Use the lower 40-50v for mild steel. The 80v output is for special nickel rods for welding cast iron. (Welding cast iron is much more specialised than it sounds. You have to pre-heat everything in an oven, and use the oven to bring it all down slowly after welding. The damned stuff cracks on cooling if you even look at it.

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Old 27th Jun 2020, 4:18 pm   #5
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Default Re: Olympic WT225 oil cooled welder.

Quote:
Originally Posted by Station X View Post
I'll think you'll find that's an arc or "stick" welder rather than a spot welder.

I have a similar one branded "Oxford", but it doesn't have the capacitor. PF correction seems the most likely function.
LOL

My fault, poor wording.

I bought this welder, and a spot welder, and a barrow full of rods, all for £100.

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Old 27th Jun 2020, 4:20 pm   #6
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Default Re: Olympic WT225 oil cooled welder.

doesnt the OP mean he bought a spot welder as well as this, as I understand it?
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Old 27th Jun 2020, 4:40 pm   #7
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Default Re: Olympic WT225 oil cooled welder.

Quote:
Originally Posted by Richard View Post
Quote:
Originally Posted by Station X View Post
I'll think you'll find that's an arc or "stick" welder rather than a spot welder.

I have a similar one branded "Oxford", but it doesn't have the capacitor. PF correction seems the most likely function.
LOL

My fault, poor wording.

I bought this welder, and a spot welder, and a barrow full of rods, all for £100.

Richard
What you said originally was absolutely correct, but I misread it.
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Old 27th Jun 2020, 5:08 pm   #8
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Default Re: Olympic WT225 oil cooled welder.

Your not the only one! guilty as charged. I have a similar Cytringham Bantam. Its one or two phase depending on how it wired. Mine has a battery charger / engine starter incorporated.

The rods may benefit from a few hours drying in a oven if they have not been stored in perfect conditions.

The only trouble I had was the two most used settings the contacts got weak (An easy fix) these were swapped for first and second not used much position contacts only a small nut to undo (while trying to keep all the draining oil above the tank.

John.
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Old 27th Jun 2020, 5:15 pm   #9
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Default Re: Olympic WT225 oil cooled welder.

I read this thread with interest!
As being a Big Boys Toy buyer, I have three welders, even though I'm not that good of a welder. One is a Lincoln AC-DC stick welder, a Lincoln cored wire welder and a Chinese made wire welder that uses gas, instead of cored wire.
One thing that amazes me is the auto-darkening welder's helmet. It seems to work perfect and made for a person that doesn't have a lot of welding experience.
Best regards from Dave, USradcoll1
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Old 27th Jun 2020, 10:36 pm   #10
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Default Re: Olympic WT225 oil cooled welder.

Hi

I have also got 210A MIG welder, which is the main one I use.
Just couldn't resist it all for £100.
The rods included 3 packs of cast iron rods, which are expensive.

Years ago I borrowed a Oxford oil cooled welder when I built a big wood burning fire from 1/2" steel plate (total overkill, but the plate was free), after several hours of welding an Electricity board van turned up looking for a fault in the area, apparently they had detected the arc and thought it was a fault, they were not very happy ....

Not tried an auto welding helmet yet, may ask father Xmas for one

Richard
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Old 28th Jun 2020, 1:52 am   #11
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Default Re: Olympic WT225 oil cooled welder.

You wont regret it! When I was young, I waited for Xmas, so I could receive a special item that I longed for. Pleasant memories.
Dave, Usradcoll1:living in the past!
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Old 28th Jun 2020, 3:42 am   #12
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Default Re: Olympic WT225 oil cooled welder.

There's a similar welder in this place, it's an Oxford, model unknown but it has a handle on top to change the contact plates inside.
When it first turned up here, somewhat 20 plus years ago, one of the plates was knackered, my father accidentally dropped it in the oil! He fetched it out with a magnet.
It was originally bought to weld a 10 metre long yacht together (flatpack, from scratch), it worked faultlessly for thousands of hours, it's now long retired, still works but electronic units have taken it's place.
Whilst I like the Oxford, it's a bitch to strike up the arc, the stick has to be bashed into the metal before it works, modern machines use HF instead, tap & go!
No capacitor on this unit though, just red, black & green wires (mains), not sure nowadays if the wire has perished yet, it has a 60's look to it.
Miller make good welders but that was sold to a mate a few years ago, it worked fine but the HF had a habit of packing up, faffing the spark gap got it going for a short while.
BTW, he considered disposing the Oxford in recent times, I insisted on keeping it as a souvenir following the successful boat launch.
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Old 28th Jun 2020, 7:56 am   #13
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Default Re: Olympic WT225 oil cooled welder.

Yup, I too fell into the wrong interpretation of the first sentence and thought the OP didn't know the difference between a spot welder and a classic MMA stick welder.

I just run a 210A TIG with a water-cooled torch nowadays. It can run sticks, and with HF start which makes them a lot easier.

David
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Old 28th Jun 2020, 9:11 am   #14
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Default Re: Olympic WT225 oil cooled welder.

Hello,
If you look at the rating plate on the capacitor it shows its KVAr (Kilo-Volt-Ampere-reactive) rating but not its capacitance which indicates that it is designed as a power factor correction capacitor.
Yours, Richard
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Old 28th Jun 2020, 3:40 pm   #15
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Default Re: Olympic WT225 oil cooled welder.

A re badge Oxford Manual Metal Arc transformer.
Note Stick welding is done with P.V.A glue or hot melt glue. welding of wood with an arc is not permitted, FIRE HAZZARD.
The capacitor is often required when the welder is run from a mobile generator and evens the load. not necessary on mains unless the electricity suppler demands it.
However if you use the AC output to go to a DC converter it could well be necessary.
Remarkable what a course in the local Tech College teaches you I kept all the course work from 40 years back just looked it up..
All Oxfords suffered one design fault that is there is no lock on the terminal/post connections so if you do up the connections too tight the whole lead through connection moves and shorts to the frame.
This is found when you take off the lid/cover and prop it off the frame the welder works, put the cover back on and it blows a fuse. I wonder how many hundreds of welders have been scrapped for this reason?
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Old 28th Jun 2020, 5:06 pm   #16
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Default Re: Olympic WT225 oil cooled welder.

As the question has been answered, the cover can be closed.
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