Re: [CAD_CAM_EDM_DRO] Sizing a power supply

"Carey L. Culpepper" wrote:

> Jon: There are no series(current limiting)resistors and I was
> running10
> volts supply.

Ahh, that's what you were doing. Well, it turns out that R control,
when the only R is the
resistance of the motor windings SERIOUSLY limits the speed performance
of the
motor. If you think that R limiting with an external resistor gives
poor performance,
with this low a voltage, the motor will be EXTREMELY sluggish. I doubt
you can
get more than a couple of IPM out of your machine before it starts
losing steps.

> The heat sinks were busy also. I put a fan on them. My
> goal is to get chopper drives. I got outbid on 3 of those OEM650x
> drivers on ebay 3-4 weeks ago. That wasn't you was it?

No, I don't have much interest in stepper systems.

> I will probably
> try to convert an oatley drive to chopper. I bought an extra for
> parts.
> I have one really big stepper that I will put on my knee feed that
> will
> use all of that 14A. For now I am just testing with one of the
> Compumotors on the knee.(Bridgeport J). It goes up and down but not
> very
> fast. I adjusted the supply voltage up a couple of volts while running
>
> and the motor liked that a lot. A chopper would really wake it up.

Yes. But, if the Oatley is not designed for chopper type operation, the
transistors
may fry. When chopping, the circulating current in the motor windings
must be
permitted to continue flowing through 'freewheeling' diodes. If you
don't have these,
the transistors (and the motors, too) will be forced to start and stop
the current with
each chopping pulse, causing them to both heat excessively.

Jon