Initial Test Results.
I finally found time to get all the bits and pieces together, and get the wind turbine up for a test run. For the first few days there was little to no wind. Typical..... After about a three day wait, I was rewarded with winds of around 9 mph. That was enough to get the wind turbine up to cut-in speed. I don't have any kind of tacho on the machine, so I'm not sure at what RPM, cut-in is achieved. I'd guess about 180 RPM.
So......How much power was it making?
Hmmmm...........Not a lot. I saw around 5 Watts on the first day that was windy enough to reach cut-in. I re-wired the stator to reach cut-in at a lower RPM, and although it started charging the battery sooner, there seemed to be more drag, preventing the wind turbine from reaching higher RPM's.
I knew the all wooden alternator was not going to produce much but I was expecting more than 5 Watts. It seems that one inefficiency in the design has a cascading effect on everything else. Firstly. The magnet rotors are made from wood. This is bad because it does not complete the magnetic flux path. A steel rotor would be a much much better choice. The wooden rotor makes the magnets inefficient, and so you need more turns on the coils to reach the required cut-in voltage. More turns means more electrical resistance in the coils and to get more turns you must use thinner wire, which increases the resistance even more. So one inefficiency leads to increasing losses all over the place.
I've deceided to leave this turbine as it is, rather than try to improve on it. So, it's lessons learned, and the Mk2 wind turbine is under way with bigger magnets, steel rotors and thicker wire. Maybe some bigger blades too. So Stay tuned......... The building of the Mk2 will be comming soon.
The Mk1 has been in the air for about 2 weeks. The highest output I've seen is around 20 Watts. It may have gone higher while I wasn't looking, but I think it's fair to say that the average output from this turbine is very poor and of little use. At least I have a very cool weather vane for my efforts. ;-) It's been fun and I've learnt some valuable lessons to help with the Mk2.....
Building of the Mk2 wind turbine has started.....Check it out here