Would a delta or wye motor provide for better voltage stability in a rotory phase converter in the 25 hp. range? I realize an AC-DC-AC inverter would be best, but not cost effective.
I am not sure if the fact the motor is Star or Delta would actually makes any difference for its performance.
Motor internal electrical/magnetic losses will govern its performance.The internal connection should not make a meaningfull difference.
Suggestion: Generically, the delta connection cancells triplen harmonics no matter if it is within transformer or motor stator. This means that the harmonics will not propagate to the rotor via the iron magnetic circuits.