Re: [CAD_CAM_EDM_DRO] stepper driver-transformer sizing question

On Wednesday 31 December 2003 16:24, Les Newell wrote:

> My Bridgeport has 3x steppers running at 65V,7A using Gecko G201
> drivers. Using the 2/3 rule my power supply should have been about
> 900VA. The power supply has a 500VA(not rectifier rated) toroidal
> transformer with 3x 10000uF smoothing caps.
> During testing I had the machine running really complicated 3D moves as
> fast as possible to find how fast I could run it without losing steps.

one question. Assuming these are fairly modern motors with a corners speed of
around 600RPM, (2khz) with gecko 201's thats 20Khz of pulses into the gecko
.. is your machine geared such that you where able to put AT LEAST 20Khz of
pulses into the drives, preferably twice that??

yes or no?

I suspect no, which is why you are only drawing minimal power from the
supply. Also, if the motors are already getting hot, you are probably using
too many volts ...

> The moves included lots of sudden changes of direction so the machine
> spent a lot of it's time at max acceleration.

regardless of the acceleration, the motors CANNOT provide maximum power (ie
draw the full &a at 65V from the power supply) below corner speed.

> After a day of testing the
> steppers were hot to the touch but the transformer and caps were only
> marginally above ambient.

That seems to verify that a) your gearing is worng, and b) your motor voltage
is too high.

--
Redpoint Consulting Limited

Real Solutions for a Virtual World
http://www.redpoint.org.uk