Axial Flux Alternator Size

I hate to be the one to tell you this but for what you spent developing and building your big VAWT only to get a few tens of watts you could have built a very effective and reliable thermoelectric generator that puts out a few hundred watts just by scavenging heat from your stove and converting it directly into DC electric power.

It appears that you're trying to use the generator as a brake...and simultaneously discovering why that it's a bad idea. Since you're using the short circuit to slow the turbine, all the energy from the turbine is being dissipated in the windings. That's why your stator warped. Normally braking resistors are located away from the motor because of all the heat that needs to be removed.

In high winds your goal is remove power input to the generator; i.e., reduce the mechanical input from the turbine. The best way to do that is mechanically, by feathering the turbine, braking it, then locking it.

VAWTs are to my mind, the best for us amateurs to play with, just as you have done.

They have a number of good points, one of which you appear to have missed in that electrical braking, though good to have for the short term, can prove to b a problem, as you have found out!

In an emergency, a method of slowing the rotor down (electrical can be good here) and then basically throwing a sack over the rotor, or dropping a big tube to cover it, will actually prove a safer method.....

The tube could even be automatically released when over speed is detected in some manner....so that it is safe even when you are not at home.....

It will need some vertical guidance, guy wires for example, to make sure it sits down and cannot tilt and catch the wind....etc etc etc..

The fine details you need to work out for yourself......

I wish you well in your experiments and a few photos of your VAWT would be appreciated by us all here, especially myself.

Further thoughts:-

Some VAWTs need to have the rotor covered up on the side where it opposes the wind to improve efficiency. This can be increased to a point where doors open only for the side in use and can all be closed if the wind/weather is to strong, or even just maintenance is required.

Building any windmill without a safe and 100% working method of stopping it and holding it stopped can be very, very dangerous to life and limb. That is where you need to start any design, not think about it afterwards....

Think safe.

Electrical breaking, understood, thanks! I guess I was not clear. While the 18 AWG stator does break very weakly as opposed to the 16 AWG stator that breaks very strongly, breaking is really not my issue at this time. I posted it as an observation hoping others would have it as a guide to helping predict an optimal size motor. Just as I noted about not reaching a stalling state is an observation to help in that manner. I am increasing the size of the motor by 1.5 times. I began work on it yesterday and have finished 5 of the 9 additional coils I need. I will continue in 0.5X increments.

Thanks for the feedback! Now the question is, optimized for what? Output current, voltage, losses, braking power, weight, cost, etc... More details = better responses.

OK, first will doubling the size of the 18AWG AFA double the breaking power when shorted out making it harder to turn. Twice as many coils twice as many magnets.