Chris Olsen’s latest project involves a Classic 150 controller connected to an alternator that is gear driven from 3.2m diameter blades. The gear ratio is 1:2.5 up ratio.
It’s a single-stator with 3-phase star connected windings this time. The ferrite magnets (16 of them at 50 x 50 mm) are crammed close together. This reduces the moment of inertia and also allows short turns on the coils which reduces overall resistance. Chris could have put a lot more copper into the stator but actually the loading to max out the Classic is only 30 amps (at 100 volts) so he decided that it was efficient enough already.
The big advantage of the Classic controller is that it allow the alternator to work at variable voltage while charging a battery at relatively constant ’24 volts’. By programming the Classic, Chris can keep the tip speed ratio at 6 over a wide range of windspeeds. At the same time the alternator voltage rises in stronger winds, reducing the current in the coils which makes the alternator more efficient. It’s a win/win situation with an MPPT controller (so long as it doesn’t blow up 🙂 ).
The stator ended up 10.5 mm thick wound with 45 turns of 13 AWG wire. It produces 119.1 volts @ 1,000 rpm with an 18.5 mm air gap. The voltage is about 80% of what I would normally see with a larger hole in the coils, and more widely spaced magnets, but the compact style of construction has potential for much reduced resistance.
Resistance of the star-connected stator is .55 ohm. Losses at 30 amps should therefore be around 500 watts for a 3 kW output. That’s a hot stator but safe with good cooling. I calculate the power dissipation on the surface of the coils to be around 0.5 watts/sqcm (6W/sqinch).
Gear ratio is .4 to 1 (or 2.5 times up-ratio) so it can produce battery voltage at about 100 rpm on the blades – nice for low windspeed cut-in.
here is a video of the turbine mechanical stuff part assembled
The whole story is here.
this is really a great invention i hope u send me the steps on how to make it for my latest invention
interesting, btw magnets are 50x50mm x 25mm thickness? if you place Y25 grade magnets will this yield this much, i guess somewhere he stated it is equivalent to Y35 grade’s
Hi Sanjeev,
I believe the magnets I am using would be equivalent to a Y30 grade. But I am not sure as I am not too familiar with the Chinese grades of ferrite magnets.
I would like to get these in wedge shape. But ferrites are very hard and can only be cut with diamond tools. The cost of getting wedges custom machined was not worth it when I can buy these magnets “off the shelf” at a very good price.
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Chris
Thanks for the nice blog entry on my turbine project!
I hope other folks will see it and it will inspire them to try ferrite magnets in their own wind turbine. I have never had so much fun (and challenge) building turbines until I got interested in using ferrite magnets in them. It takes a bit different approach in some cases, as trying to apply the usual neo designs to a ferrite generator is hard to do. The main reason I decided to try this project is because the cost of a Classic 150 controller is not really much more than a set of neo magnets these days. So I wanted to do a sort of proof of concept project to show that an efficient 2.5 kW turbine can built with ferrite magnets in it. And my testing indicates it will perform better in the long run than a direct-to-battery connected conventional neo machine.
This machine has required more testing, research and experimenting than any I have built so far. But it has also been a lot of fun!
Thanks!
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Chris