In article , cas@w-
sherwood.ih.lucent.com says...


I am considering a 1.5HP to replace the exisiting 1HP motor. My logic is
that the lower speed motor will develop more starting torque and I can
still get the same spindle speed by increasing the freq on the VFD.
For example the 1140 RPM motor will develop 1HP at 900 RPM (900/1140x1.5)
where the existing motor will only develop 1/2 HP(900/1800) at the same
RPM (assuming constant torque). I think a 1.5HP 1140 RPM motor will
develop more low end torque that a 2HP 1740 RPM motor that I was
originally considering.

what do you think?


Unless you're actually experiencing problems operating the
lathe--not enough power on heavy cuts, for example--I
wouldn't bother. It's not unusual for the VFD to indicate
that the motor current is near nameplate current even when
lightly loaded. It's not necessarily an indication that the
motor is producing rated power, but rather is operating at
low power factor, which is typical of lightly loaded
motors.

I've tried without success to use a VFDs current sense as
an indication of overload on a conveyor. The difference
between normal load and gross overload, short of stalling
the motor, was not large enough to sense reliably.

Ned Simmons