Driving 3P Spindle Motor at Low RPM

I am looking to replace my Deckel FP5 Mill spindle motor. The original setup is an ABB/BBC thyristor driven DC motor. I intend to go to a 3phase driven via VFD. My concern is:
Can a VFD be setup to drive/jog it's motor as slow as 100rpm for short periods.
A number of the motors I've found spec operating ranges of 1000 to 1500rpm as the low end.
The FP5 includes a gearbox and the shifting is accomplished by jogging the spindle back and forth to get the dog clutches to engage the new gear. The jog process typically only requires 2-4 seconds each direction and usually only needs a forward then reverse jog to get the dogs to engage, now and then a third jog in the other direction is needed.

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The cheap VFDs I've used would do that no problem, but the issue is load dependent. If you set the VFD to drive a 1725 rpm motor at 100 rpm, once you fully load it you'll get 75 rpm of slip and it will only spin at 25 rpm. (full torque loading, and I'm not 100% sure it doesn't vary with speed). If you just need to jog forward and back to get into gear I would think that would be no issue.

Should have done my research before asking..... Looks like the concensus is that I should be able to run as low as 5% of rated speed with good cooling and the very low load required for jogging gear engagement. Now just need to find a nice cheap 7.5kw 4 pole spindle motor.

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Send your question to user "rklopp" or post in the Deckel forum. They might advise you to keep things they way they are.

I intend to keep the entire drivetrain and gearbox system in place. I will be able to replicate the signals my existing DC spindle driver outputs to the machine controller with the outputs from a replacement VFD.

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gernoff said:

I intend to keep the entire drivetrain and gearbox system in place. I will be able to replicate the signals my existing DC spindle driver outputs to the machine controller with the outputs from a replacement VFD.

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IF... one is going to replace BOTH the DC motor AND the "power / control" unit... why not make it a 3-way research project and also weigh pro's and con's of a servo vs VFD+3-P or restoral of DC drive?

What is the goal? Does the old system not work?