Interesting conversation. I recall '5 phase' suddenly being all the fashion because it allowed for better control in hardware at a very high expense and then two seasons later 5 phase had simply disappeared because the increased degree in control meant that the intractable problems of two phase resonance could be solved in software (effectively those drivers made it possible to draw energy out of the motor while speeding it up past those resonance points). The cost for a motor, wiring and controller dropped to a fraction of what it was before. Berger Lahr must have been seriously pissed, finally they had those resonance problems licked and then the software revolution simply overtook them.