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

I don't think your response was to my post but to "caudlet"

I am using 4 diodes as a full bridge rectifier. Each is a D-05
package so that it bolts into an aluminum sheet for heat dissapation.
The D-O5 is a threaded end terminal that bolts onto a plate, making
that plate part of the circuit. the other end is a solder eye. A TO-
65 is similar in shape.

I'm using an old PC tower for the box, so the 68k cap is standing
upright behind the drive bays. I put the Gecko's on some 1/4
aluminum plate in 3.5" floppy drive holders that fit in 5.25 inch
bays. that way, I can pull what I call the sled out to access the
Gecko's.

The 470 caps are facing rearward, directly towards the 68k cap and
the diode/rectifyer/heatsinks.

I put some pics in the same 'Daves unit' folder in the photos section.

Dave



Those heat sinks are directly behind the

--- In CAD_CAM_EDM_DRO@y..., "mariss92705" <mariss92705@y...> wrote:
> Do not use a diode; that is asking for trouble! The returned energy
> is in the form of a current. It will happily charge the little
470uF
> cap way beyond the 80VDC limit. The diode prevents the much larger
> filter capacitor from helping, along with the other drives that
would
> act as a load to this current.
>
> Mariss
>
>
> --- In CAD_CAM_EDM_DRO@y..., "caudlet" <tom@t...> wrote:
> > --- 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.