Some years ago i was asked to provide a regulator for PM alternators the application
was for small wind turbines. I had been making a couple of different units for bikes for
awhile and word gets around etc. The stator winding for these devices was really nicely
wound and had an air gap of around 2.5 thou, these were very efficient devices, they
would give around 25a @ 48v for large battery charging. When i first agreed to take on
the project i didn't realise the overall complexity of what was required and the job grew
considerably. The use of shunt style unit on these was not really so straightforward as
when the unit was shunted to control output the coupling on the stator was so good that
the braking effect would shear the drive gear system. The original unit ended up with
several stages of control and worked out at around 3 times the predicted price, consequently
i only ever built a few.
It's a digression i know, sorry. I also worked with a guy who repaired and rebuilt alternators
here, he wanted to reproduce a package to replace the Lucas rm 19-21-23-24 with his new
setup. He had a great reputation for mag/dyn/alternator winding and had done a lot of work
on the project already. He had heaps of test notes regarding windings wire gauge etc on
Lucas and his version of stators. The project was never pursued as the higher output of his
upgrade forced the use of a regulator and many customers would not want to pay the extra.
This was around 18 years ago now and since then the chap has died. Shame, but at that
time we had a very good setup that would provide a comfortable 15a @ 3500 RPM. We just
needed orders for 200 at a time for it to be worth while.