yes i will take some shortly, i think you are right, just stopping the phase converter with the stop start control Ie stop button, which is fine as long as you know to isolate before stopping.
i have always used vfd inverters where required but never rotary types, i was on the understanding that the rotary types were ok for non electronic machines, but too "coarse" for sensitive equipment, in saying that this m/c has run with this setup for many years so should it be considered ok?