Enjoyed the replies. I hope you enjoy mine!
This is in response to several post here so posted to the original question.
Generator efficiency is brought up frequently, it's important but not as important as system efficiency.
A good induction motor will be 88 - 92% efficient. Not bad. Heard of 96, not seen. Using 90%.
Bad motor may be 80% even worse. Something to watch out for. Sounds bad?
PMA – what percent is it? Nothing is 100%.
Everybody seems to think it's better so lets say 98% (Not likely).
The induction motor will require speedup gears, additional cost and efficiency cost 95%
People have a bad rap for gears, well your vehicle has many, work just fine when designed correctly.
On the web a 15HP with 16:1 gears for $300. surplus center.
The 15 HP induction motor operates at 220 or 460 vac, wind generator can be far away with acceptable power losses. PMA far away will need to be wound for the high voltage and require a transformer on the other end just like the induction motor will need, unless connected to the grid.
PMA can NOT be directly connected to the grid, no voltage or frequency control.
The induction generator can be connected directly to the grid. No grid, no problem several methods exist for excitation, capacitors are a favorite.
I used 90% motor * 90% gear and excitation = 80% generator efficiency.
The system: Wind turbine 24' dia blades, 10kw at 23mph with Cut in at 5 mph.
Low winds are often listed as reason for using PMA vs induction.
Since this is a large wind gen it needs a large battery 48 volts.
PMA system will have TSR = 7, induction will use TSR = 12 and speedup gears of 26:1
Note: PMA generator output voltage is directly proportional to RPM, which is wind speed.
Induction generator will not be using pitch, fixed, must be furled by 24mph when the wind can over power the generator.
Let's play with the numbers. Do you know what's going to happen?? I have a surprise for you.
Wind PMA I out Battery Efficiency Stator Induction
Vout Power Heat Generator
5 48 2.4 116 100 0 103.55
6 58 3.1 149 83 30 178.93
10 96 9.7 466 50 466 828.36
15 144 21.8 1048 33 2097 2795.73
We are cooking!
20 192 38.8 1864 25 5591 6626.91
Sizzling!
25 240 60.7 2912 20 11649 12943.19
Induction generator is more efficient except at cut in, after ten mph 2x to 4x the power generated!
Surprise!
PMA for the cost and simplify are hard to beat for a smaller less than 14'. The larger, the multitude of problems and lack of efficiency make the induction better for the cost. Add pitch control, the generator can continue to produce power to what ever wind speed you want. I target 70mph. Handles gust of wind better to.
Comments? Very dificult to post table here? tried html editors keeps getting errors.
Have fun,
Scott.