Re: MAGIC SMOKE Xylotex drives

--- In CAD_CAM_EDM_DRO@yahoogroups.com, R Rogers <rogersmach@y...> wrote:

>
> Bill,
>
> Are you switching the AC side or the DC side of the transformer to

energize the circuit? The DC side being switched through relay
contacts perhaps will definitely blow stepper drives. Capacitance
should be Current of all stepper motors cumulative X 80,000 / the DC
voltage. The voltage rating of the caps should be 20% higher than what
is present. You probably already know all this.

>
> If you have no Caps on the power supply. it's probably an current

inrush situation.

>
> Hope it helps, Ron
>

On a switcher the output caps are sized to take care of the ripple at
the swtiching frequency and normally consist of an LC circuit with an
inductor. Since the frequences are high all of the magnetic and
filter componets can be smaller in size and value.

One thing we know about the chips in the Xylotex is that they will not
tolerate an overvoltage condition and a short spike might do the
"trick".

If you hang a large filer cap capacitor (say 3300 mfd at 35VDC) across
the output it would act as a shock absorber for the spikes. You don't
need a huge cap like in the bulk supplies since you are filtering
higher frequency. Another approach is to hang the cap on the input of
the Xylotex.

I have had big power FETS blow because they were getting a 4ns 400V
spike (not visisble except with a high speed memory scope). Took us
weeks to determime the cause then the cure.