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

On Monday 22 March 2004 12:37 am, Jon Elson wrote:

> 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.
>
> You can connect a couple Ohm resistor between the bridge and the
> capacitors. Have a time-delay relay short the resistor after one second.
> This will reduce the power-on surge by a factor of 100 or so.

Yeah, but since power dissipation in the resistor is current-squared times
the resistance, putting it on the primary side is probably a *much* better
idea...