There is one circumstance that may have influenced the choice, it is about field weakening.
The "overdrive" (5th and 6th gear) that makes cruising at high speed economical is easier and safer - almost automatic (increase f and keep U so that V/Hz is reduced) when you use an induction motor.
If you have a PM motor, you need to reduce the flux by forcing it down with the stator flux. That is not only wasteful, it is also dangerous because the slightest irregularity in the control will let the PM flux grow back to base speed flux. Imagine then, what happens to motor voltage when motor is running at twice or three times base speed.
Yes, it gets very high and kills (explodes) the inverter.
Therefore, the induction motor is a better choice. And if you use a Cu cage, the slip can be kept at very low values, so that efficiency is maintained.
Gunnar Englund
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Half full - Half empty? I don't mind. It's what in it that counts.