Your input line voltage doesn't have completely balanced for the FREQROL VFD to work. I have successfully run this spindle from 100 RPM to 6000 RPM using 220VAC Single Phase. This was done by simply faking out the since circuit on the VFD using a small cap and resister to create a phase shift on the since circuit, not on the power side. I would not recommend this for long term, but it proves the point.
The FREQROL, just like any other VFD, converts the input AC Voltage into DC. If you get a change to look at it, there is a large bank of caps and bus bars that stores this DC voltage. When I measured mine, it was 385-410VDC depending on the RPM. Then the inverter circuit will use large SCRs to switch on and off the DC voltage to create the precision AC 3 Phase and Target Frequency needed to drive the 3 Phase AC Spindle at the correct RPM. When the Spindle slows down, it acts like a generator and will drive up the DC bus voltages, thus you need to control how fast you decelerate the spindle or you will create a DC B bus voltage higher than the system can handle. Mine tripped out at 465VDC when decelerating to fast. Braking resisters circuits can help with this. They are simply switch onto the DC Bus when the voltage gets to high to absorb the voltage/energy allowing the system to decelerate the spindle faster, as the voltage is decreased the resisters are removed from the bus.
Since my shop only has single phase, short-term I am using my lathe (5 HP 3 Phase using a static converter) and its 3 leg for the 3 rd input into the FREQROL VFD. Long-term, because I don’t want the lathe running just to run the spindle, I plan to add a 5 HP Rotary just for the 3 rd leg needed to make the FREQROL VFD rectifier circuit happy.
Thanks
JH