Re: Added a VFD to my CNC mill

--- In CAD_CAM_EDM_DRO@y..., Country Bubba <axtein@d...> wrote:

> Dan,
>
> I also have another file from a motor manufacturer that
> includes this information:
>
> "Maximum Safe Mechanical
> Speed Limits
> (does not imply constant
> horsepower capability)
> Motor @ 1800 rpm
> Frame Direct Belted*
> 56-184 5400 2250
> 213-256 4200 2250
> 284-286 3600 2250
> 324-326 3600 2250
> 364-365 2700 2250
> 404-449 2700 2250
> *Belted per NEMA MG1-14.41 (dated
> 1993)"
>
> nobody that I have talked with can tell me WHY the
> belted rate is lower than the direct drive rate???
>

I can't be sure, but I expect that the side load on the
shaft and bearings in belted duty is the reason for the
lower speed limit. I am most familiar with larger motors
(5HP and up, to 600-1000 HP). In the larger sizes, there
are different motor designs for belted vs. direct drive.
Bearings and shaft sizes, among other things, are adjusted
to handle the side loading.

John Kasunich