Possible student research project

Adriaan Kragten has been kind enough to notify me of his latest design work which is documented in his free pdf reports available for download here.  Most of his wind turbines have been based on converting induction motors to pm alternators in the past  Now he is designing axial flux ones with similar geometry to mine.  But the designs are largely untested.

Here is a drawing from report KD571 which is about an alternator for a 1.36 m diameter turbine.  Maximum output would be about 80 watts at 670 rpm with alternator efficiency below 40%:

This is a single-rotor machine with a steel disk behind the coils that has rather high iron losses due to eddy currents.  My personal view is that although this is easier to construct the loss of efficiency is unacceptable.  There are also rather high loads on the bearings.  I would prefer a spinning steel disk behind the coils (as in my 1800 mm diameter design in the Recipe Book).  But in principle this design will work and deliver useful output.

Adriaan has gone on the design a larger version in KD596, using 12 magnets (but at lower rpm) to achieve 50% higher power output with similar efficiency.  He speculates that it might be worth overlapping the coils to obtain better usage of the space.  I have seen this down a couple of times with axial flux alternators using specially designed presses etc and it can offer slight improvements in efficiency.

So Adriaan is looking for somebody to test this idea and others, most likely as an electrical engineering project.  I suspect that he would be a helpful mentor, and much would be learned.

Finally I’d like to say mention a couple of pitfalls that engineering students tend to fall into.  One is that you do not want to test this with a resistive load.  Test it with a rectifier and a battery for realistic results.  Second is do not worry about Hz or try to obtain a 50 Hz sine wave output.  That is not relevant for small systems where the output is going to be converted to DC.  Finally please do not use a vertical axis blade design for the turbine.  For some reason everyone wants to do this, and it is a huge mistake.