Renovating a Hardinge HLV-H

[aafradio]

It's a real pity that my VFD's 'catch spinning motor' routine doesn't seem to work 'as advertised'. If it is has to speed-up the motor (i.e. when changing from low to high speed) the motor complains loudly.

You might consider changing the sampling frequency as an experiment. If the motor is emitting higher frequency noises, it's often a function of mechanical resonance of the windings under load.

The Siemans VFDs are rated at full power while working on single phase (many [most?] that will run on single phase will not need to be derated - it's only losing two diodes in the bridge rectifier, if the remaining four will take the extra current there's no need to de-rate the VFD)

The size of the filter capacitor on the DC bus actually has more to do with derating than the size of the diodes, though of course the diode rating has to be considered for single phase feeding of a larger capacitor bank. Most of the VFD's I've seen suggest a 1/3 derating...e.g., use a 3hp rated unit for a 2hp motor. That's consistent with the energy under the power curve for three phase versus single phase rectifier designs. The VFDs that are rated for single phase simply have a larger capacitor bank in them. If the supplied voltage from a three phase input design VFD sinks under a heavy cutting load, it is usually fairly easy to add capacitance to the unit externally to solve the problem. The risk is exceeding the current rating of the internal diodes because they are charging a heavier peak load in each cycle. It's usually not a problem for reasonable (<50%) increases in capacitance, but needs to be checked.