Re: [CAD_CAM_EDM_DRO] Re: PWM vs Constant current

Jarrett & Heidi Johnson wrote:

>Our (K142C) Constant Current Source systems sense the drop in current and
>increase the voltage to the motor and thus the current and power is
>maintained with higher speeds. A common motor we tested gave similar torque
>at around 300 RPM as at 1 or 2 RPM (this is as FAST as we tested with a 200
>step motor).
>
>

Oh, so 300 RPM is fast? I demoed a stepper system at the NAMES show in
2002,
I think, using the Gecko 201A drive (a chopper or PWM design) where the
motor was shoving the table of a 150-Lb mini-mill around at 90 IPM. At
that speed, the motor was spinning at 1440 RPM! I would guess the
motor was delivering close to 50% of rated torque at 1440 RPM.
I was quite impressed by this performance, and I doubt anybody's
drives can do much better. I probably could have gotten even better
performance out of the same motors with with a higher power supply voltage,
but there was no need. These were not the latest high performance motors,
either, but some 30 year old ones salvaged from printers.

Jon