Re: G201 modifications/update (P.S.)

Hi,

This subject got my interest so I just did an experiment, which had
very interesting results.

I picked a drive (G201 of course), hooked up a size 34 motor rated at
4 Amps per phase, set the power supply to 40VDC and accelerated the
motor to 10,000 full steps per second (3,000 RPM). I placed a scope
probe on the supply voltage at the drive. While running:

1) I disconnected the supply wire at the drive. The voltage peaked at
91 VDC at the drive.

2) I gated the STEP pulses off. The voltage peaked at 94 VDC at the
drive.

Conclusion (1): Don't do that! The drive survived with no damage but
doing that is hard on it. Lower voltage rated drives would have died
on the spot at that speed. The G201 would have died if the speed had
been higher.

Conclusion (2): Power a drive down by powering down the power supply.

Conclusion (3): Don't shut off step pulses at high speed, decelerate
them.

I then coupled a servomotor to the step motor and spun it up to 3,000
RPM and scoped the step motor leads. The back EMF was, wonder of
wonders, 200 volts peak-to-peak. Subtract IR losses in the motor and
2 MOSFET diode drops and there is the 94 VDC measured!

Mariss