Just for giggles this is a current table I compiled today. My system is 150mm on the main duct and to my mitre saw and two ducts which are not are 125mm and 100mm because the machines cannot be altered to accept 150mm without huge internal changes or in one case (the overhead hood) the machine simply won't work with anything else which is a pain.
Attachment 413001
It can be seen that the current draw does not appear to have peaked at 70hz but I am not pushing it any further. I am not qualified in VFD's or electrical matters and cannot comment on whether there are any differences between a single phase and three phase supply and what that may do to the results above but mine is three phase in and out.