Hello mitcamp,
This is certainly addictive,and fun.
Yes it is.
My view is not to use PM gen on the larger machines.
Due to the problems outlined above and others.
Remember anything can be made to work.
Look around here you will see some of the things people have done to get better efficiency out of the PM gen. They add complexity, reliability issues and cost.
PM gen is great for the smaller wind generators. Not sure where the cross over is, depends on your goals.
Web link showing how to calculate the power in the wind:
http://www.windmission.dk/workshop/BasicBladeDesign/bladedesignleft.html
I made a spread sheet with the calculations, reports power in watts and HP in 1 mph increments.
Work sheet shows the RPM of TSR 1-15, so is big.
I can change any number... I use open office.
The power in the wind is NOT the power you get from the generator.
The RPM of a wind gen is directly proportional to wind speed over a good range.
Voltage output from PM gen is directly proportional to RPM.
If the PM gen is generating 24v at 5mph, then at 10mph it is outputting 48vdc.
The batteries impedance is so low it yanks the voltage down to what it needs. The impedance in the gen is higher so the power is dissipated in the stator. At 10mph, half the power is output into the battery, the other half is heat in the stator. You can see why low cut in is not good for PM gen.
Larger PM gen people have fried their stators, sometimes not even in huge winds.
Good air cooling can help. I want as much of the power as I can get, not satisfied with just getting a little more in higher winds, I want it all. (if free:-)
I am working on a 10kw design. Considerations:
Grid connected. Too large to store this much power in a battery.
Not interested in power in the winds above 20MPH, storm, costly.
Design LOW cost. 5 year payoff. 10 cents KwHr.
Use as many off the shelf parts as possible.
Recover all the power 5-20MPH. Helps with payoff.
3 ph power at 240vac.
If your needs are not the same then reconsider.
Generator is an unmodified 4 pole 1800rpm 20HP 3ph 240v induction motor.
24' Blades spin at 80RPM, using speedup gears to spin motor at 1855RPM full power.
To use induction motor as generator you need to spin it as fast as it slows for full motor load.
Gears are from a vehicle power train. Nice quiet gears, junk yard stuff. 97% efficient.
The downer, why this solution is not used more often:
Requires active pitch control, must keep RPM nearly fixed, Needs high T/D blades.
Pitch changes TSR from 14 down to zero. Challenging.
Furling is done by pitch control.
Normal looking Unusual Tail allowing yaw rate change control.
If interested, click on my user name look at my post, most of this is covered in them.
For the slight cost and increase in complexity I expect to recover 3 times the power vs simple PM gen.
Looking at the cost of the complex PM gen with equal performance, $12k. Induction $6k.
Which fits in your wallet?
For me the grid tie was the deciding factor, induction gen connects directly to it. Huge inverter would be needed for PM gen. Became simple decision to select induction.
Questions email me. Or post.
Have fun,
Scott.