Re: Sanity Check on Power Supply Capacitor Size

Luke,

I looked at your schematic, paralleling the primary is fine:

CAUTION !!!! for the secondary design:
1. DO NOT PARALLE THE SECONDARIES OF MULTIPLE TRANSFORMERS TOGETHER.
instead rectify each secondary independently then parallel the DC
output of the bridge rectifier. this also make it possible for you
not to care what the transformer phase connections of the secondary
are.
Reason: the method you use is fine with a single transformer with
dual/Multiple windings since the core is common. It is also
acceptable for matched transformers.
BUT!! when using separate Transformers the outputs voltage and load
Phase may easily Vary by 15% or more. the only thing you will do is
load one transformer with the other loosing power and possibly
Heating up and burning out the transformers.

The capacitance I typically use as a rule of thumb is to try to use
on a full bridge system is around 2000uF per amp at 60hz.


Regards...
BoonS, Principal EE


Moderators note : If you dispute this, please use engeinnering reasons why and please also offer solutions. Thanks

--- In CAD_CAM_EDM_DRO@yahoogroups.com, luke1027@p... wrote:
> Sanity Check
>
> Filter Capacitor Size for Power Supply based on:
> C==(80,000*I)/V
> Transformer (secondary tap) will be putting out (18V * 1.414=%.5V)
with
> 8.3A*2=.6A (since it is wired in parallel).
> With these specs I get C==(80,000 * 16.666)/25.452=R,386
Microfarads.
>
> So the filter capacitor size I need must be at least 52,386
Microfarads?
> Is this calculated correctly? Boy, that seem high � does it not?
>
> Back Ground info:
>
> I am building a Power Supply to drive my stepper motors out of two
Transformers
> (http://www.surpluscenter.com/item.asp?
UID= 05071308202974&catname==&qty==1&item=-1176)
> in wired in a Parallel circuit. My schematic is shown here:
> http://www.pennswoods.net/~luke1027/PS_Schematic.jpg