PaulT
Stainless
- Joined
- Mar 4, 2002
- Location
- Brisbane, CA, USA
I've got a Teco/Westinghouse FM100 3HP VFD on my Bridgeport clone CNC mill. The mill is a step pulley type with a switchable 2 pole/4 pole 3 phase motor.
Set to 2 pole on the fastest pulley it has a max spindle RPM of 5600.
The motor control works fine on the slower pulleys, but on this fastest pulley setting under cutting load I get a "surging" in the speed. The RPM will slow down under load and then overcompensate and go up over the targeted speed in a continuous cycle. Its not a little amount, I would estimate the speed change to be at least +/- 20% or so.
The period of the surging is around 2 to 3 seconds in the full surge cycle.
The motor/spindle combo definitely has a lot more rotational inertia in this high RPM pulley setting, it takes about 5 to 6 seconds for the spindle to hit full 5600 RPM under no load.
Does anybody know of a parameter on the FM100 that can be tweaked to eliminate or reduce this surging in this situation? It appears that the high inertia of this case is messing up the speed control somehow. I tried looking in the manual but its pretty cryptic.
Thanks,
Paul T.
Set to 2 pole on the fastest pulley it has a max spindle RPM of 5600.
The motor control works fine on the slower pulleys, but on this fastest pulley setting under cutting load I get a "surging" in the speed. The RPM will slow down under load and then overcompensate and go up over the targeted speed in a continuous cycle. Its not a little amount, I would estimate the speed change to be at least +/- 20% or so.
The period of the surging is around 2 to 3 seconds in the full surge cycle.
The motor/spindle combo definitely has a lot more rotational inertia in this high RPM pulley setting, it takes about 5 to 6 seconds for the spindle to hit full 5600 RPM under no load.
Does anybody know of a parameter on the FM100 that can be tweaked to eliminate or reduce this surging in this situation? It appears that the high inertia of this case is messing up the speed control somehow. I tried looking in the manual but its pretty cryptic.
Thanks,
Paul T.