Re: Power supply softstarts

Don,

In rush can blow your fuses and trip circuit breakers, not sure it
will in my case, I intend to breadboard it (safely of course).

The thunk is due to much higher primary currents than usual. This I
suspect is not so good for the transformer. There is also the fact
I am not building it for me so thunking is going to look a bit
unprofessional. I'd be disappointed if my welder didn't thunk but I
am not so sure about a high end scanning system with 1um resolution
and renishaw encoders etc :)

Alan,

I'll look into that. What happens if you turn it off then on again
I wonder?

Dave,

Probably can do some sort of bootstrap circuit to PWM the primary
but I don't have time to develope it. Looking for known solutions.


Graham

>
> /// I thought that was only an issue with some stepper drive

systems popping a drive on start-up. And aren't the Capacitors in
the system to tame the secondary side of the power supply? And we
put a cap at each drive to absorb any spikes? If the inrush is not
having any adverse effect on the system. I'd let it thunk. Welders
clunk every time they start for many years. It's not harming the
transformer. ////

>
> For the record I am in the UK on 240v
>
> Graham
>
>
>
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, R Rogers
> wrote:
> > How about a 110volt 10 amp variac on the primary? Strat the

power

> supply at a low setting then gradually increase it. They can be

had

> pretty inexpensively. With servos, I dont think this is an issue.
> >
> > Ron
> >
> > Graham Stabler wrote:
> >
> >
> >
> > I am building a 6 axis system with linear servo motors and have
> > bought a pair of 500VA transformers which should provide 50v and
> > sufficient amps for peak acceleration. I have also got a

100,000uF

> > capacitor for smoothing although I may increase this.
> >
> > On my previous homebrew power supply I added a softstart that
> > charged the output capacitors via a resister until they were up

to

> > voltage. The prevents a nasty thud on turning on the supply.
> > However I have a feeling that with the two transformers in this
> > supply in parallel I may have more of a problem with the
> transformer
> > inrush current which does more than make a thud!
> >
> > What is the "best" way to produce a soft start on the primary of
> my
> > powersupply. Should I just use a contactor, timer and power
> > resister to provide a current limited supply to the transformer

on

> > power up?
> >
> > Thanks in advance for any help
> >
> > Graham
> >
> >
> >
> >
> >
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