Q: Bridgeport Mill - Replacement motor like this?

OK, there are a few problems. The vari-speed driven pulley is still there. I suppose you could use it as a belt tensioner. But, I don't know if the flanges have the right angle for standard Vee belts.

2nd, the vari-speed drive, OR the 4-step pulleys, give a substantial torque increase at the low end of the speed range. With one fixed setting, you won't get that boost. On the other hand, I haven't really ever come close to using up the torque of a ONE Hp motor on my mill. A VFD will only give you rated torque below the nameplate speed, and the motor will overheat at low speeds.

Jon

I'm running an Index mill now with step pulleys and I have yet to do anything but switch the electrical hi/lo speed switch... so probably not a big issue.

As far as I can see the "Inverter Duty" motors do mainly two things; give even torque over a wide range of speeds (Baldor has some rated up to 4000rpm and some as high as 6000!), and not breakdown with the pulses from the controller...

As far as the latter, why not put some MOVs across the lines that shunt at something less than 1kv?? Thinking that 750-800vac would be about right to protect ur average motor...

It's not clear to me what makes the "Inverter Duty" motors different as far as maintaining torque... anyone know?

Setting the ratios on the pulleys right, ought to permit pretty good torque at low speeds... and yes I guess the variable pulley could be the "tensioner"... albiet for the fatter style belt.

And, I was wondering, why not set the motor on a spring loaded track or pivot that permitted a range of motion for the motor as the vari-speed flanges moved apart and closer? That would keep the belt tension in a manner similar to the spring loaded clamshell pulley arrangement??

I was looking at a nice 3hp motor C mount to put on top... extra built-in torque for margin...

ANYONE USING VFDs???

_-_-bear