[mukanico]

This is not the best way to achieve the RPM required. Most certainly the motor can easily handle 120Hz, (check the MFG for max RPM it's probably 6kRPM.) By increasing motor pulley diameter you've reduced torque to the spindle. This will be troublesome if you work steel at 2" diameter.

Correct setup would give full motor torque to 60Hz, and as Hz increased to 120, available torque would drop but full HP would be available. As small diameter parts need less torque this is acceptable. This is how most spindle motors are configured. For my Emco I chose an ABB 2.2kW, 4 pole motor and run it to 6000RPM. This essentially matches the original motor exactly.

Hello,

Quick update to this build: I followed Diesel_Pilot's advice and went back to the original motor pulley. I had to increase the VFD max. frequency to 83Hz to reach the original 4000rpm max. spindle speed but the additional low end torque is quite useful. Thanks!

Attachment 415122

[Diesel_Pilot]

I had to increase the VFD max. frequency to 83Hz to reach the original 4000rpm max. spindle speed but the additional low end torque is quite useful. Thanks!

That's great. Must have 1:1 pulley ratio? Compact 6 is 80%.

[mukanico]

Hi,

I don't remember what are the pulley diameters, but the new motor is rated at 2845rpm@50Hz, so the pulley ratio should be around 85%.

Cheers

[MrMetric]

Nice job... I've been thinking of doing this same thing! I've had a 120 for a while, and I've been repairing driver boards for people for years. But, to be honest, it is a pain in the rear. I did it because I could help people out, but I think it may be time for me to start seriously considering a retrofit too.