Re: [CAD_CAM_EDM_DRO] pmi servo disk motor ok for cnc?

skykotech wrote:

>I saw an ebay ad for a pmi servo disk motor:
>
>http://cgi.ebay.com/ws/eBayISAPI.dll?
>ViewItem&item=2572523775&category=42920
>
>This reminded me of a box of these that I have gathering dust on a
>shelf. I think they are the exact model in the auction, 60V,
>something like 8.8 amps loaded current, 60 amps peak with some insane
>peak torque rating.
>
>I had never really considered using these for cnc (bought them for a
>battlebot back before you could buy battlebots at mcdonalds). Right
>now I use only gecko g320 (340) drives in my cnc mill, so I would
>want to control this motor with a g320. This would be the motor on
>my fourth axis project (converting a 10 inch phase II rotary table).
>Has anyone used this motor with a gecko drive? Does it perform well?
>
>

You will likely require a series inductor to use this motor with a Gecko
drive. The PMI (Printed Motors, Inc.) motors use a printed circuit
board as the armature. It has very low inertia, but also very low
inductance.
The PWM technique of the Gecko drives puts a 25 KHz square wave of
whatever DC supply voltage, across the motor's terminals. Very high
currents will be seen with the Gecko drives, as they have no output filter.

I think a 1 mH inductor would be a good value to start with, and the
DC power supply can be kept pretty low, maybe 30 - 40 V.

These motors are used primarily in cases where extremely fast starts and
stops are required, like line printer paper feeds and magnetic tape drives.
But, they should work in your application, if you use the inductor.

Jon