Re: [CAD_CAM_EDM_DRO] Re: Power Supply Caps and Xformer

Abby Katt wrote:

>Okay, so I lowered the specs a bit, here's what I'm thinking of
>putting in my power supply:
>
>Transformer, toroidal, 500VA, 0-230V pri, 50/60Hz, 2x0-35V sec
>
>Diode, Bridge Rectifier, SMT, GBPC2502
>
>Capacitor, electrolytic, aluminium, screw terminal, 105degC, 63V,
>33000uF
>
>I'll connect the two secondaries of the transformer together in
>parallel to give me the full amps. After rectification, this should
>be just slightly under the target 50V. So, with 500VA, will this be
>enough to run three of Dan's big,big servo motors then?
>
>

Yes, this should be quite sufficient for a mill system.

>And the cap, is 63V, 33000uf gonna be enough, or will it all end in
>tears, with me picking pieces of aluminum electrolytic out of my
>shins?
>
>

I think you should get away with it. I might opt for a 75 V cap, and maybe
45,000 to 66,000 uF of capacitance, but what you have should work.
Note than your line voltage is likely about 240 - 245 V in most of the US.

>Should I use fuses on the output, or input only, and what values
>would be appropriate? Slow/fast blow? Will it make a difference, can
>it save my geckos from cooking if the motor windings goes to ground?
>
>
>

Do not put fuses in the motor wires of the Gecko drives. You probably
would do
best to put slow-blow fuses in the input, and reduce the fuse value
until you find
them blowing, or getting warm during a run. A 2 - 5 A slow-blow fuse would
probably be good for a mill application. You want the fuse to blow during
abnormal conditions, such as a stalled motor when you aren't watching.
My local client had this happen. Presumably his encoder wire got a loose
connection, the axis rammed to the end of travel and kept driving until the
Gecko drive smoked. The motor still works, but it was badly cooked, too.

Jon