Re: [CAD_CAM_EDM_DRO] Re: welding machine as a power supply

On Sunday 21 March 2004 08:56 pm, ibewgypsie wrote:

> Probably, the best thing would be 3 smaller individual transformers. I
> got one large 2kva 220/24+24=48(dual tap) transformer and it weighs
> about 50 pounds. It cost about $200 Local. Problems with one large
> transformer is the bridge, you want to use a 35amp 600 volt cube for
> simplicity. I have lost 3 of them in a year. When the capacitors are
> discharged and you hit the go relay and throws power to the drives,
> charges the capcitors (looks like a short for a second) it fries the
> cube one time outa a hundred. I tried dual switches that would charge
> the capacitor bank half wave but quickly tired of it.

For a solution to that what you want is what's called a "soft start" circuit.
This basically consists of some big resistors in series with the primary side
of the transformer which are shorted out after the system has some voltage on
it, typically with a relay. Check http://sound.au.com/project39.htm (I
think) for a page that describes building these for audio amps. He gives all
of the formulas you need to figure this stuff...