Re: [CAD_CAM_EDM_DRO] Re: BP Power supply

rocketscientistnate wrote:

>"Keith Clark" <mail@t...> wrote:
>
>
>>Nathan, I used http://www.transformertechnology.com/ and just
>>bypassed all the Bridgeport power since it was dirty and burned
>>
>>
>two
>
>
>>motion board chips in a row. It is easier to control by the
>>computer using relays for emergency situations etc.
>>
>>
>
>Which transformer did you buy and how much did it cost? The
>installation info on the geckos says 24V - 80V, what seems to work
>the best on BP steppers? What Amperage does the supply need to put
>out? It says 67% of the motors rated phase current which should be
>a little under 6A, would that make it an 18A or higher power supply?
>I can't find anything on the size of my motors, except inside the
>back plate it gives some part numbers 025805 and 26744 (one is the
>alternate motor for the other) The power supply seemed to be pretty
>stable before my control died, so I'll try to reuse it for now and
>replace it as soon as I can.
>
>

18 A is probably overkill for a milling machine application. An
unregulated supply
with a 10A rating will almost certainly suffice. Unregulated power
supplies are
designed to deliver rated current continuously, or a bit less than the
rating with
occasional peak loads up to 2X the rating. I used about a 4-5 A power
supply on
3-axis Gecko 201 driver box for my mini-mill with NEMA 34 motors. It
was more
than sufficient! NEMA sizes are inch diameter of the motor X 10. So, a
NEMA
42 motor would be roughly 4.2" in diameter.

The Gecko 201 and 210 drivers are essentially swithcing power supplies,
so roughly
watts in = watts out. If the motors are 6 A at 2.5 V (random numbers but
representative) per winding, then you need 6 * 1.414 A for two windings, but
only at 2.5 V. That works out to 21 W. With a 50 V DC supply, the
Gecko would draw
about 0.42 A. When the motors are running at high speed, then the
applied voltage must
increase, and so the power input goes up. Only at the top speed, when
delivering torque
to the load will you ever see that maximum current rating of 67% being
drawn from
the power supply.

Jon