Capacitor banks, when are they required?

[jzr75601]

Hello all , I've been tinkering with mig welders since the early 80's and have had many brand's over the years mainly



Airco's, Hobart 's Lincoln's and Miller's so through all that tinkering (and this is an electrical question for
some of us wanna be and real engineering geeks or just anyone who finds this stuff interesting--
I have found 2 machines that either don't use or only use a capacitor bank in the higher amperage ranges one machine in particular is the Airco DIP COR 300 this one switches out of the circuit in the higher amperage range the only thing I can see is capacitors are really only required in short circuit mode I have not had the opportunity to mess with three phase machines but I imagine a three phase machine's DC output is much smoother than single phase there fore not needed . Maybe I answered my own question. I don't know.Im more of an electrical guy than a real welder so go easy on me LOL Any thoughts???

[forhire]

On some older transformer machines capacitors are used to adjust the power factor on the AC input side of the transformer. On the DC side the capacitors are used to smooth the DC output of the rectifier. Typically capacitors are sized to ensure smooth DC power. The real question is if the machine used a full bridge rectifier or half bridge rectifier.

I personally feel three phase machines weld smooth than single phase machines. Like you, my theory is that the multiple phases create less ripple on the DC side. That said, I've been told the DC is the same regardless of the input phases. It very well may be the fact that three phase machines are generally bigger. I'm sure under heavy load the three phases would perform better.

On modern inverter machines everything is converted to DC so my understanding input power is less important.

[jzr75601]

Hey Forhire ,thank you for your reply appreciate it Well that must be at least one major factor in all this every machine I've come across has run least a full wave bridge a group of cap's and a choke (or a "stabilizer as Miller and others call it) the goal being to reduce ripple to a minimum. I'm sure we've often heard or read how this or that machine produces a harsh or smooth arc.
In all these years I've yet to get into inverter machines, seems they have somewhat overtaken the welder
market and I hear they
perform pretty well.
I still prefer the old transformer machines mostly for their simplicity and their bulletproof build quality.