Re: Yet another power supply question

Jay,

You're not doing bad at all, even for someone not "electrically
challanged"! The calculations are spot on.

(1) Step motors are current operated and have two windings. These
windings are called "phase windings".

(2) It makes no difference whether the transformer is torroidal
or "E,I" core (standard transformer). Use whatever gives the required
current at the voltage you need. A 24V (RMS) secondary is a good
choice.

(3) A 27,000uF cap is just fine. There is no point in using a larger
one.

(4) A 50VDC rated cap is the correct, most economical choice. The
capacitor is what is called an aluminum electrolytic. Use the kind
that have the two threaded (10-32) terminal posts. Be sure to mind
the polarity. One post will be marked with a "+" sign, make sure
the "+" output of your bridge rectifier goes there.

(5) Use a 25A 100V rated bridge. They cost just about the same and
will run a little cooler. Use a little heatsink compound underneath
it when you mount it to the chassis.

(6) Use as heavy or heavier wire guage as what your transformer leads
are. Stranded wire of course. Use two different wire colors to go to
the drives. Red for "+", black for "ground". If you can't, use a
lighter color for "+". This will avoid mixing the two up and
destroying the drives.

All in all, well done.

Mariss

--- In CAD_CAM_EDM_DRO@y..., "jbolt001" <js3mc@a...> wrote:
> Hi group,
>
> While the subject of power supplies is floating around right now
and
> I will be working on one soon I'll put my questions out as well. I
am
> very electrically "challenged" so be kind.
>
> My step motors are 8 wire PowerMax II double stacks. Connected in
> parallel they are rated at 4.6 amps/phase and 0.38 ohms/phase.
(This
> is where my ignorance starts to show.) What do they mean by phase
in
> a step motor?
>
> Using the formulas from the white papers on the Gecko site I came
up
> with the following:
>
> 3(motors) * 4.6 amps * .666 = 9.2 amps
> 4.6 amps * 0.38 ohms = 1.75 volts
> 1.75V * 25 = 43.75 VDC Max
> For Geckos I will need a Transformer with an output between 24 to
44
> VDC
>
> Transformer = single secondary 24VAC / 10amps (24*1.4=33.6VDC)
> Torodial? I could not make heads or tails of what would be a
> comparable torodial transformer.
>
> Filter Capacitor C=(80,000*I)/V or 80,000*10amps/ 33.6 = 23,810uf
> The closest CAPs look to be 27000uf 50V (more ignorance again)
What
> type of capacitor do I need? When I searched the electronics sites
> there must be a dozen or more types of caps.
>
> Bridge Rectifier, min 12A 50V max 25A 100V?
>
> What size, type wire should be used?
>
> So am I close?
>
> Thanks,
>
> Jay