CAP's (once again) (was Re: another transformer question

--- In CAD_CAM_EDM_DRO@y..., "mariss92705" <mariss92705@y...> wrote:

> Dave,
>
> They still are aluminum electrolytics. Low ESR simply means
> low "equivalent series resistance". The bigger the cap (uF), the
> lower the ESR. One thing I forgot to ask; what is your power supply
> voltage and what was the voltage rating of the cap that blew?
>
> Mariss

Mariss: What have you seen in back EMF from motors under load? Is
it possible that voltage coming back might be charging the smaller
caps past their WVDC rating? What about negative spikes? Using a
low ESR cap will help absorb some of the higher frequencies but its
only as good as the ground you put on the ground lug. Most of the low
ESR caps I see now are three leads. Some of the controller
units/power supplies I have seen have intergal overvoltage protection
using the old voltage sensing power transistor to turn on a power
resistor to ground.

I diode isolated the last unit I did so that each motor had its own
isolated leg and could not shove voltage back into the main buss. I
put smaller caps on the anode side of the diodes to provide
additional isolation.