With the original Bosch drives, my 145v motors, etc, the mill was
capable of 200 IPM rapids. Right now I have a 70v power supply with
30A8 drives and the top speed is 60-70 IPM.

My question is how much am I losing, in reality, but having faster top
speed. My feeling is not much, but I want to know.

This is not an entirely idle question, as I could install drives that
match motor voltage (30A20AC or 25A20AC or some such). They would use
120 VAC as power source.

So, would I see any improvement in anything valuable with higher top
speed or no?

i