Re: CNC power supply question

Andy,
It's another form of protection for the driver chips.
Discharge the PS quickly so you can unplug motors without waiting
several minutes and the possibility of blowing the chips.
Also, a moderate load on the PS keeps back EMF from floating the
supply voltage up to max limits when all axis stop suddenly.
My experience has shown that for a ~30V PS, 1000 Ohms/5 watts is
a very workable value as a permanently attached bleeder.
My latest driver unit also has a relay to dump the cap with a 50 ohm
3 watt res when the AC is switched off.
I have never had a problem with blown chips since. (L-298 and A3977)
RichD

Andy Wander wrote:

>
> What is the advantage to the bleeder capacitor, aside form avoiding shocks
> while working on the circuit?
>
> Andy Wander
> Verrex Corporation

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