and when I got the lathe it was set to a max frequency of 50Hz.I've read, re-read and re-re-read the VFD manual and changed the VFD to allow a max of 100Hz ... So, I go into Mach3 and say calibrate spindle and to go up to a max of 2000rpm .... and what happens is very odd! The motor does as it should, start slow and the Mach3 program records the speed, then steps up the frequency by a small amount to run the motor a little faster, and records that speed ... so far so good - it builds a nice calibration graph. But what I found at higher frequency's (can't remember exactly what the frequency range was - but beyond 65Hz+) there was a sudden noticeable drop in motor speed and a strange un-happy noise comes from the motor, almost as if it can't keep up with the frequency in the windings.
I've decided (for the moment) to set the max limit on the VFD to 60Hz which gives a spindle speed max of around 1000-1100rpm ...
Ideally I would love to be able to get this (what seems to me mythical) 2000rpm at the chuck. Does anyone have any hints as to what is going in in my motor, or have I overlooked something obvious? You mention in the posts that the VFD max frequency ought to be 87Hz - have I interpreted that correctly? Also any clues as to this weird motor slowing at certain frequencies would be gratefully recieved.