Re: Bleeder resistor for power supply size?

Hi,

This is one of those "how many angels can dace on the end of a pin"
questions that come up again and again.

A capacitor stores a charge (voltage) for a long time if there is no
load on it.

That is not the way you are going to use your supply.

You will have various drives and other loads on it and you will turn
the supply on and off on the AC input to your supply.

With all these various drives and loads, your supply will very
quickly discharge (<< 1 sec) when you shut off the AC supply.

You never switch the loads on and off on the DC side. That is hard on
the switch and any electronics attached to it. You use the AC power
input for that.

You do that and there is no reason for a "bleeder resistor". It is a
pointless, sometimes expensive component that does precisely nothing
except get hot.

Long and short, turn your power on-off at the AC side and let your
drives be the "bleeders". They will do a better job than any resistor
and they will do it quicker and better for free.

Mariss

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Damon" <damonfg@y...> wrote:
>
> I found some amazing hang time in my system. When I was running
> only a transformer,bridge, and caps (no motors/drivers) I had
> 66VDC, shut down power and came back 48 hours later, it was only
> down to 35VDC. With a pair of geckos and 1050oz steppers, it
> bleeds down in about 10 seconds or so, entirely acceptable!
>
> -Damon