Re: alternate idea for High Voltage servo power supply

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Ted Inoue" <ted@s...> wrote:

> Maybe this is a stupid idea, but I thought I'd field the question
> anyway...
>
> I'm looking to use some G320's to drive my servos. The motors I

have

> are actually rated 120v, but I'm fine running them at around the

80v

> limit of the G320. I've already built a pair of conventional 36v DC
> power supplies which run the servos fine when connected in series
> (giving around 72v), but I was wondering about a different approach.
>
> What if you use a solid state variable DC supply like:
> http://www.surpluscenter.com/item.asp?
> UID=2003111416550838&item=15-1074&catname=electric
>
> Perhaps putting on a big cap to handle surge load requirements. I

was

> thinking this would be a lightweight, compact high voltage supply.
> Just stick it in a box, dial in the voltage, and hide it away.
>
> What do you think?

The supply you are looking at is actually a form of PWM supply and
does not output pure DC (to a DC motor it looks that way). It might
work feeding a large capacitive load but most likely it will get
confused. The circuit is made to drive a large inductive load like a
DC motor. The other issue is isolation. I don't see any transformer
on the device so I have to assume the DC negative is not isolated
from the AC neutral. If you know what you are doing around non-
isolated high voltage then go ahead. If you don't know what I am
talking about DON'T DO IT. Make no mistake, 90VDC at any current
above a few mils across your chest will kill you isolated or not. The
circuit you are looking at is not much different than taking a light
dimmer across the AC line and running it through a rectifier. I would
rather see you find an isolation transformer (1:1) ratio and control
the primary with a dimmer circuit or one of the cheap router
controls.