very technical question AFPMG rpm with 5 meters rotor

[Anghel Parvu]

Hello all,
I want to buy an axial flux pmg and the manufacturer says they recommend 350 rpm rated at 3kw for hawt, but 350rpm must be very fast to achieve ( 15 inch diameter afpmg)
I am looking at a 22 inch afpmg 3kw 180 rpm or another 4kw 200 rpm.
Is there any chart to see what rpm pmg to be used with different blade sizes?
To have an idea what afpmg im asking I will post the link and scroll down the page at those specs and look at the inner rotor afpmg not outer.

Thank you so much guys!

[Rob Beckers]

Anghel, let's run a few numbers and see what's reasonable. A 3kW horizontal-axis wind turbine would be just about 4 meters in diameter to make that much at 11 m/s wind speed (assuming reasonable efficiencies). A reasonable TSR for such a turbine would be around 6 or 7. So those blade tips would be moving at 66 - 77 m/s at rated output.

Now we need to get from tip speed to RPM.
Each time the turbine spins around the tip travels pi x 4.0 = 12.6 meters. For 66 meters it needs to turn 66 / 12.6 = 5.24x around each second, for 77 meters that is 77 / 12.6 = 6.11x each second. For RPM we need to multiply that by 60 to get turns per minute:

RPM = 5.24 x 60 = 314 for a TSR of 6
RPM = 6.11 x 60 = 366 for a TSR of 7

So, yes, the recommendation you received is spot-on: For a 3kW alternator an RPM of 350 is very reasonable. That puts the TSR between 6 and 7 for such a turbine.

You can do the same calculations for a 4kW turbine (the diameter would be around 4.6 meters).

-RoB-

[Anghel Parvu]

Anghel, let's run a few numbers and see what's reasonable. A 3kW horizontal-axis wind turbine would be just about 4 meters in diameter to make that much at 11 m/s wind speed (assuming reasonable efficiencies). A reasonable TSR for such a turbine would be around 6 or 7. So those blade tips would be moving at 66 - 77 m/s at rated output.

Now we need to get from tip speed to RPM.
Each time the turbine spins around the tip travels pi x 4.0 = 12.6 meters. For 66 meters it needs to turn 66 / 12.6 = 5.24x around each second, for 77 meters that is 77 / 12.6 = 6.11x each second. For RPM we need to multiply that by 60 to get turns per minute:

RPM = 5.24 x 60 = 314 for a TSR of 6
RPM = 6.11 x 60 = 366 for a TSR of 7

So, yes, the recommendation you received is spot-on: For a 3kW alternator an RPM of 350 is very reasonable. That puts the TSR between 6 and 7 for such a turbine.

You can do the same calculations for a 4kW turbine (the diameter would be around 4.6 meters).

-RoB-

Hi Rob, thanks for your reply.
What do you think about these afpmg, are they better than Ginlong, and what is the difference between ginlong type and these coreless ones?

www.alibaba.com/product-detail/Axial-flux-permanent-magnet-generator-AFPMG380_1705401910.html

They are huge, scroll down the page and see the inner rotor ones that are desiged for hawt are up to 710mm diameter (28 inches)

Which one would you pick for a 3kw system? Big diameter orbsmall diameter? Low rpm /high rpm?
They said they can customize it the way I want?
Anyways, something that wont go above 550v .

This is the plan, to get this wind turbine www.hywindturbine.com/products/16.html

Its 3kw at 240 rpm rated at 9m/s because its pitch controlled, with 5 meter rotor, nowthe key question, which one of the axia flux inner rotor you recommend that will have rated rpm and wind speed for this wind turbine?
Something around 240 rpm since blade size doesnt change?
Like a 2.5 kw -3kw at 250 rpm