VFD and vari speed pulleys

[HimyKabibble]

I used a Marathon Black Max inverter duty motor, max safe speed 5400 but I never needed to run it over 4500.
It runs at full rated HP down to 30 rpm, the lowest I have needed to run it so far.

"It runs at full rated HP down to 30 rpm" - You mean "...full rated *torque* down to 30 rpm...".  To achieve full rated power would mean the torque was actually *increasing* as you reduced RPM - which would be a good trick.

Regards,
Ray L.

[Overloaded]

Thanks for that correction Ray.
 
Russ

[bw]

I think I figured out what I would like to do but would like to run it buy here to see if I am missing something.

If  I go with a 6.75 pulley on the motor and 3.75 on the spindle, it will give me a 1:8 ratio with 3150 rpm at 60Hz and about 375 rpm in back gear.


At 120Hz I will have 6300 rpm
At the low end 10Hz, 525 rpm and 60 rpm in back gear.

Those numbers work or me as long as I am not missing something, also I can get a GS2 VFD from a friend who is no longer using it but it is not a sensorless vector unit and I am not sure if I should use it or just get a VFD that is sensorless vector.

Thoughts?

Thanks

[HimyKabibble]

Your numbers are correct.  I would hold out for a sensorless vector drive, otherwise you won't get useful torque at anywhere near 10 Hertz - more like 30-40Hz, before the torque  becomes too little to be of much use without switching to backgear.

Regards,
Ray L.

[bw]

Thanks,
From what I have been reading I figured the sensorless vector drive was the best choice, just wanted to be sure.

[bw]

I just wanted to thank everyone who helped me on this project.  I ended up replacing the spindle bearings as well as all the bearings that were left in the head after removing the vari speed pulleys.  I figured do it all when I had it apart.

The machine runs fantastic, sounds great and I now wish I did it a long time ago!  If I could just figure out how to get the auto zero to work with this Ajax system I would be done.  I posted on the Ajax forum but tech or anybody else has yet to answer and it's been several weeks.