Thanks a lot for your response!
I think i had already posted the link to our german site where you can see pictures of the alternator. That one was tested in Belgium with loads. I do have a table which exactly indicates the efficiancy of the alternator at a number of voltages and with different loads. As a result I found out, that the results were estonishing close to what I calculated in advance.
Unfortunately that generator is not mine anymore :-(
A have now started to build another 2 pieces with slightly different parameters.
For the blades that I use I have a programm that gives me all nthe numbers I need.
for the 6 m prop with TSR 6 I have created a table of CP versus TSR shown below:
I first of all want to finish the grid tied project and later set up an independant battery system.
What I really wanted to get was confirmation on that kind of tables that I showed above. And as you say that you saw your prop spin with TSR 10 or more, this confirms me those numbers.
So what I plan to do now is:
1. make a new set of coils wound to fit the Aurora grid tie inverter making all the calculations using my excel tool that I once introduce here. It now has many new features and got prove several times that it now usually works on the spot :-)
2. I am planning to wind the coils for a cut in of designed TSR of 6 for 4m/s about 9 mph. I can then end up with a resistance of about 0.2 Ohms between the phases and thus have very low losses in high winds and no worry about glowing stators :-)
3. I know the losses of the bearing hub at various RPM and the losses that occour in the inverter and the alternator at various currents and loads. So in hand with that table on the picture, I am then able to make a good match of Alternator and prop and get a cot in about 5-6 mph considdering the loss of cp shown from the table.
From about 10 mph upwards, I will try to follow design TSR and thus get maximum efficiancy. If I trust that graph, TSR 10 or even 11 should still give me some power, at least it sould be possible to have the blades spin that fast to make those assumptions.
If everything works out fine, I want top use the same alternator to charge batteries and forget about gridn and hope to still have a good match if I set it to reach 50 Volts at design TSR for 9 mph in order to have real cut in about 7 mph or so and not to hit stall too early.
If there are problems occuring, I can still change design TSR in the range of 5-7 and make adjustments that way without having to play with the airgap.
According to my calculations, at an output of 6 KW to the grid, I would have less that 0.5 KW of losses in the stator which is like nothing for such a big stator as i think...
The pitch controll you mentioned has nothing to do with all of that. My prop is basically a fixed prop like the one you have. Angle off attack does not change with wind speed!
The mechanism only starts to release when the blade speed reaches a set RPM. I will adjust this to about 11-12 m/s
Only if that speed is reached (f.i. 250 RPM) the blades will start to turn and thus limit RPM. Below that, it is a normal "fixed prop".
I hope it is clear what goes through my mind these days... I basically want to increase efficiancy of the alternator using less wire by optimising it for a higher design cut in and live with less efficiancy at verry low winds.
Just what I didnt have experiance with was prove of how fast beyond design tsr blades can spin when no or only little load is applied.
Please comment :-)
Max