Orac Modernization Spindle Speed VFD
Posted: Fri 27 Jul , 2018 20:47 pm
Hello, first post on this forum.
I'd like to firstly say thank you very much to Denford for making ALL or at least HUGE amounts of information available via PDF. Without it I would have been reluctant to jump in blind to a lathe upgrade {update}. Looking for an old Denford cnc mill now
{I've an FB2 EMCO, which I keep thinking about converting to CNC, so looking for something similar capacity wise, suggestions would be most welcome on what to lookout for}
________________________________
Ok, the ORAC has a motor pulley OD of 35mm, and a spindle pulley OD of 63mm, so the drive ratio is ~1.8:1
The motor is 4 pole, and at UK 50hz, that would put motor speed at ~1400 rpm at ~7~6% slip.
The ORAC was advertised as "Spindle Speed (stepless) 0-2000rpm"
At 1.8:1 pulley ratio, this would put the motor rpm at ~3600 rpm (ok, I have not measured the pulley circular pitch, just the OD)
That implies that the motor would need to be run at ~120Hz minimum (allowing for 6~7 slip) bumps that up to ~128 hz
Question 1: Does anyone know what the original Orac VFD runs / ran at maximum frequency wise?
Question 2: Does anyone know what the original Orac VFD carrier wave runs / ran at?
I came across this post, but was not sure if the manual contained here was actually for the ORAC as it did not quite seem the same the the VFD board I removed viewtopic.php?f=43&t=1243
Thanks
Rob
I'd like to firstly say thank you very much to Denford for making ALL or at least HUGE amounts of information available via PDF. Without it I would have been reluctant to jump in blind to a lathe upgrade {update}. Looking for an old Denford cnc mill now
{I've an FB2 EMCO, which I keep thinking about converting to CNC, so looking for something similar capacity wise, suggestions would be most welcome on what to lookout for}________________________________
Ok, the ORAC has a motor pulley OD of 35mm, and a spindle pulley OD of 63mm, so the drive ratio is ~1.8:1
The motor is 4 pole, and at UK 50hz, that would put motor speed at ~1400 rpm at ~7~6% slip.
The ORAC was advertised as "Spindle Speed (stepless) 0-2000rpm"
At 1.8:1 pulley ratio, this would put the motor rpm at ~3600 rpm (ok, I have not measured the pulley circular pitch, just the OD)
That implies that the motor would need to be run at ~120Hz minimum (allowing for 6~7 slip) bumps that up to ~128 hz
Question 1: Does anyone know what the original Orac VFD runs / ran at maximum frequency wise?
Question 2: Does anyone know what the original Orac VFD carrier wave runs / ran at?
I came across this post, but was not sure if the manual contained here was actually for the ORAC as it did not quite seem the same the the VFD board I removed viewtopic.php?f=43&t=1243
Thanks
Rob