Re: [CAD_CAM_EDM_DRO] Re: Power supply softstarts

On Monday 04 April 2005 12:56, Graham Stabler wrote:

> It needs to be a box that just gets turned on. I don't want knobs
> to turn and the associated weight.
>
> The fact I am using servos has nothing to do with it, the softstart
> is for the inrush on the primary of the transformer.

Every switching computer power supply has exactly what you need, built right
in, an "inrush limiter" aka, a thermistor.

They are basically a resistor with a hot value and a different (higher) cold
value. They initially exhibit high resistance, limiting the inrush current.
Since there is (initially) a significant percentage of the supply voltage
across them they get hot, which causes their resistance to fall, eventually
stabilizing at some low value.

See

http://www.thermometrics.com/assets/images/cl.pdf

To test this out, you can just rob a bunch out of some old computer power
supplies, paralleling them (most likely) until you get what you want.


Alan

--
Alan Rothenbush
Academic Computing Services
Simon Fraser University
Burnaby, B.C., Canada


Before me things create were none, save things
Eternal, and eternal I endure.
All hope abandon ye who enter here.