Added a VFD to my CNC mill

About a year ago I bought am Mitsubishi VFD for $238 on ebay. It
came with a 190 page installation, setup and operation manual. I took a
look at it and indeed it was a really nice inverter that would take
single or three phase supply and would run the three phase motor on my
enco mill. Most important was that it allowed for external manual
control with a speed pot, Parameter Unit, (a fancy keypad and LCD
display for programming the unit) and for setting various parameters)
and last and most importantly it took a +5 analog signal from an
external source for PC control. Well. I finally got around to connecting
it to my machine. Wow! I am impressed. So far I am just using the
parameter unit for changing speeds. It works like a dream and runs the 3
phase motor much better than the Phase-o-matic inverter that I use to
use.
Most impressive is that you can program the acceleration and
deceleration rates of the motor. Before my spindle would take for ever
to coast to a stop. I would have to use the brake. Now I have it
programmed to stop in 4 seconds.
I am going to figure out how to use the analog signal from DeskwinNC to
turn on and off my VFD and set the speed from computer via the G code. I
think that would really be a nice to automatically turn on the spindle
motor and set the speed via the program. So far I can heartily recommend
the Mitsubishi FR200E series inverters. BTW I have been told these
normally sell for around $800 but got mine New off ebay for a fraction
of that. It sure is nice not to have to change pulleys all the time.
Last I would like to know how to calculate the maximum safe speed that I
can run the spindle at. I would think that the 3500 RPM 50 Hz motor
would cause the spindle pulley to explode if run at 400 Hz.
Dan