https://www.fieldlines.com/index.php/topic,147259.msg1015975.html#msg1015975with regard to this claim in the above post:
This below photo is for a single stator ferrite generator, designed for MPPT, that produces 3.0 kW @ 1,200 rpm and peak 4.2 kW @ 1,500 rpm. It is right on 90% power efficient at 3.0 kW output. It is 13.8" in diameter and also weighs 22 lbs.
I'm assuming there are two magnet disks, for a total of 44 pounds, plus the single stator coil.
modern hvac fan motors are getting 1hp at 1250 rpm, out of 6 cubic inches of ferrite magnets in a 56 frame motor. my last experiment with such a motor as a generator produced around 200 watts output at 800 rpm with a significant voltage drop. my guess is the inverter drive send a lot of leading power factor current into the motor, to get the required torque. the coils are 4 ohms, 2.5 amps at 50 volts 3 phase, 80 volts open circuit.
In any case, you can do the mental math yourself. 1hp out of a 56c frame.. vs 4-5hp out of something with 16x2x2 (times 2 stators) cubic inches of magnets.