far as I know, to get the most holding torque you need to short out these high pole count motors through a resistor equal to its internal impedance; otherwise they won't slow down the turbine.

my 30 pole motor had a 8.5 amp short circuit current, 97 volts at 440hz or about 1750 rpm, each phase was 1.1 ohm.

if i were to short out all three phases, 101 watts per phase would be dumped into the motor, about one half hp shaft power. this was at 1750 rpm. so the torque was about 1.5 foot pounds.

if i connected the motor through various resistors, i could stall a 1/2 hp induction motor at 800 rpm, or at least 3.3 foot pounds of torque, possibly as much as 5 foot pounds (the line current of the induction motor at stall was about 8 amps, full load amps was 6.6, so the torque at stall is unknown, but at least as much as 3.3 foot pounds)

I discovered this effect recently again, i found a 1/2 hp at 1250 rpm, 10 pole, 12 tooth concentrated pole motor (ferrite magnets) manufactured for the purpose of driving the fan in a relatively large heat pump. the motor had a built in inverter. If i shorted the motor phases out, the motor was difficult to turn of course, but once it was rotating above a few tens of rpm, the motor was effortless to turn.

As you propose making rather large high pole count motors, I suspect the torque cut off will be fairly sharp.

all this may not matter if you short the motor out after the rectifier.. i will have to try this again.