Hi all,

I've been out of the loop for some time and I'm trying to improve my understanding to add some incremental improvements to my current machine for a rebuild.

I'm trying to wrap my head around the limiting factor for stepper motor (and thus direct-coupled ballscrew) speeds and if anyone can help I'd be grateful - I've looked high and low online but I'm struggling with the last 10%!

I found this great link for calculating the maximum RPM different types of motors can run at based on the time it takes the field in the coil to build up and dissipate

The result is that for my current 3Nm motors (4.2A, 3.2mH, 68V, 200steps/rev, bipolar parallel wired) the max speed is 759RPM which checks out with my current max rapid speed of 700RPM (I had tried 800RPM in the early days but had some issues with stalling).

If I plug in values for the 3Nm NEMA 24 Leadshine Easy Servo [ES] (5A, 2mH, 48V, 200steps/rev, bipolar serial wired) the calculated max speed is 360RPM. - I had wondered whether the ES Motors might be wired internally as bipolar parallel to have such a low inductance - in which case the max speed should be 720RPM. These speed limits get much worse for the 4Nm ES motor, as well as the open loop 3.4Nm and 4.5Nm motors Zapp sells.


Can someone help me to understand how digital stepper motor drivers overcome these speed limitations please? I'd be most grateful! The graphs in the Leadshine literature would have me believe I can spin a motor at 1200RPM with maybe 1Nm of torque (in the case of this 3Nm motor)!

Regards,


Matthew