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General Mach Discussion / Re: Bridgeport Knee Mill Conversion?
« on: May 21, 2016, 03:12:51 PM »
Ok the servo will have a continuous torque rating, 5Nm in the one you linked to, and 15Nm peak.
The Kw will only be at rated speed however, slow the rpm down and the Kw will drop.
It is exactly the same with an induction motor and a VFD when looking at the Kw but the Torque will also drop so the servo is better.
Now what you have at the moment is a VFD running an Induction motor but you are just using the VFD as a phase converter as you only vary the speed via the pulleys.
That means the motor is always running full speed so the Kw will always be the rated Kw. The torque however will vary as you adjust the pulleys, drop the spindle speed from 1440 to 720 and the torque has increased by two, Go the opposite was and run at 2880 and the torque will have halved.
I made a spreadsheet up a few years back to work out torque or Kw of a Servo when I only knew one or the other along with the rated RPM, I have attached it below.
Hood
The Kw will only be at rated speed however, slow the rpm down and the Kw will drop.
It is exactly the same with an induction motor and a VFD when looking at the Kw but the Torque will also drop so the servo is better.
Now what you have at the moment is a VFD running an Induction motor but you are just using the VFD as a phase converter as you only vary the speed via the pulleys.
That means the motor is always running full speed so the Kw will always be the rated Kw. The torque however will vary as you adjust the pulleys, drop the spindle speed from 1440 to 720 and the torque has increased by two, Go the opposite was and run at 2880 and the torque will have halved.
I made a spreadsheet up a few years back to work out torque or Kw of a Servo when I only knew one or the other along with the rated RPM, I have attached it below.
Hood