Originally Posted by
Rob Sack
The pulleys are coplanar, they have been checked with a precision straight edge. The belt tension has been adjusted to within 1/2". The belts were sized by Northfield when I did the motor swap. This had been going on since the belts were new, so I don't think the issue is worn or damaged belts. Northfield agrees. the reason for switching back to the 3 phase motor, and thus requiring the VFD, is that the 3 phase motor will not have the sudden drop in rpm's on shutdown, like the single phase motor. Again, this is according to Northfield.
I don't understand why the single phase motor would have a sudden drop in RPM's vs a three phase motor. After you stop supplying electricity to either motor don't they stop being the driver and become the driven? I would think that the three horse motor would have less mass than the five horse and would be easier to override with the cutter head.
When you put the new belts on did you loosen the motor and put the belts on or did you run the belts over the sheaves while the motor was bolted tight?
The problem could be badly worn sheave grooves. The sides of the grooves should be flat and not cupped.
I'll assume that the sheaves are coplaner in a parallel and angular plane.
Confidence: The feeling you experience before you fully understand the situation