A bit off topic 
Just wondering if anyone could tell me if an oil cooled welder could be used as a power supply for my servos. I have an Oxford 140Amp Oil cooled welder that I never use, it has a 50V and 80V output terminals, I am needing 50V so that would just be perfect. However there must be somthing different in a welder compared to a normal transformer as the current is selectable on a welder.
Anyone have thoughts on this?

Hood

You sure are thinking Hood. Better be careful, might see some smoke from your head. I think it should work. Put your meter across the terminals and adjust until you get 50vdc. Then set you meter on ac and that will give you an idea of the ripple it is going to have. Not sure but it sounds like a good thing to test.

Brett

No chance of that, thats why I have no hair, its a form of air cooling
Not sure I follow what you are saying , mind you theres nothing unusual in that as its quite hard to follow a rednecks train of thought
The welder is AC and I will need to rectify it. The outputs are 80V and 50V both AC, the adjustment is for amperage.
Hood

Hood, If you can get the voltage you need and it is clean, it should work I would think. As long as you have enough amps. Their is no such thing as a power supply being too big unless it makes your power meter spin off of the wall or is supplying too much voltage. If you can get the right voltage and enough or more amps, I think it will work.

Brett

Edit,
I meant to say, you should be fluent in Red Neck by now.

Well these things weld at 140Amps all day long so that wont be a problem, I am just worried that it cant be like a normal transformer as the voltage varies as you go between different tappings on a transformer.
 Will eat my porridge tomorrow and go fetch it from the old workshop and see what its like, well I know what its like, its green and  its flippin' heavy
Hood

I would check it with a scope just to be sure its clean DC. Otherwise I think it should work.

Thanks, the DC should be OK once I rectify/smooth  it but will make sure I check before I hook things up to it, dont want to let any more magic smoke out

Hood

Once rectified and smoothed, the AC voltage of 50 Volts will become 70 Volts DC.
This is caused by the full wave rectification. I assume you know this ?
You multiply the AC voltage by 1.4 to establish the DC voltage.

EDIT : When AC voltage is measured, because it has waves with peaks, the peaks are not measured, but an average is measured. (RMS) (Root Means Squared) one you are converting both sine waves to one side and you then smooth between the peaks, the average Voltage becomes a constant voltage. Hence a little higher than AC

I did this a few years ago and always look for an excuse to replublish old works 

Ha ha, thanks Benny, yes I did know but it does no harm to post it.
I am looking for 80v dc so 55V ac would be better for me but 50 will have to do My mains is about 440 across phases so I might get nearer the 80V that I am seeking.
 
Hood