Motor choice for VFD convertion?

[JimDawson]

Point is that Tesla does not need transmission.

I understand your disappointment. My mill has a 3 HP direct drive with a 1.5:1 overdrive. In order to run larger drill bits and for some other operations I have to put it into back gear (8:1 reduction) to have enough torque to handle the operation.

The motor that you have should handle 3600 RPM (120 Hz) with no problem. Which should give you a pretty good useful speed range of about 10 to 120 Hz, at a 2:1 reduction. But for excursions outside of that range I think you are going to have to change belt positions. The only other option is to increase the motor size, 3/4 HP just does not have a lot of torque.

Operation in SLV mode should give you near 100% torque from near 0 to 1800 RPM (constant torque) and the torque will fall off as the RPM increases above that (constant HP) up to 3600 RPM. There some torque adjustments that you can make in the VFD parameters that will improve the low speed torque, but that also increases the current (and heating) in the windings. The motor will take that for short periods, but should be used with caution.

 

[Mitch Alsup]

Point is that Tesla does not need transmission.

A tesla was designed and engineered to not need a transmission.
You lathe was designed and engineered to need a transmission.
See the difference.

Now, if you got a motor sized properly to drive large heavy slow RPM loads and was backed up by the electronics to properly spin that motor at high RPMs too, then yes, you can avoid the transmission. But as it is, you are only part way into the engineering, and thus, not done.

 

[Briney Eye]

I thought that after such upgrade I will be driving Tesla.

There are fundamental differences in the way Tesla motors are built that optimize the low-end torque (and make them much more expensive). I think we’ll see more choices in motor/inverter tech in the years to come. VFDs are just the first step.

 

[umnik]

I completely understand about limitations, just wanted to get a feel for the working range for some parameters.
BTW, there is Teknatool Nova Voyager drill press with so called DVR motor. It has Variable speed drive with range 50-5500 and no gear/pulley changes required, just direct drive. They say the lower the speed the better torque. You can buy such motor Directly from Striatech, though it is pretty expensive.