Spindles with 2 poles, which is typically for these types of spindles will have a minimum RPM of 6000 RPM or 100Hz; however, I would not run the spindle below 15000 RPM or 250Hz to give a safety factor and no damage will occur.
If you have a 4 pole spindle, then much lower RPMs can be achieved, and with higher torque than a 2 pole spindle. The 4 pole spindle will require more power than 2 pole spindles and will not be able to achieve as high maximum RPMs.
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What is the minimum RPM for the 2.2kW spindle?