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Thanks for the offer of books. A scan of the pages would be nice thank you (I have a nasty habit of not returning books but I also have an extensive library )
Scaling things up and down are useful exercises for me as I am at Engineering School so it helps to fill in blanks and make me think if a Scaled thing will actually
work. As I mentioned - I don't need the Quantum Mechanical Quirks just a good understanding about how it works and how to make it work, if I really need to know something in depth then I will research it.

A bunch of formulae and some data I can look up and an explanation of what it all means is plenty good enough for this exercise.

I am one of those people who know a lot of things about a lot of things but I don't know everything about anything. All that knowledge just gets filed and then
pops out later with something quite convoluted at times.

Cheers

Andrew

I think you are wanting to build your own - but just throwing this out there - stepper motors are really easy to convert. I work in i.t. so I get a lot of them off old printers, old sorting machines, postage machines etc so for me they are readily available and free. only real purchase would be some cheap diodes (I use 1n4005) to make a bridge recitifier or a single package bridge rectifier diode and some solder. I believe some old lawn mower and tiller engines have the rectifiers on them as well if they have battery starters. I have seen some really nice looking jobs done by machining a case that looks like an antique full size generator with the chain hoist hook on top and all that just surrounded the factor case of the stepper motor.

and I guess using a stepper would really be an alternator and not a generator - right?

Andres, I checked and both of my textbooks are available free on-line. Here is the info:

Design of Electrical Apparatus, John H. Kuhlmann - goes into detailed design criteria for both DC and AC machines. This one has the sample designs I mentioned in the earlier post. Keep in mind that these designs are for real practical machines for manufacture.

https://archive.org/details/in.ernet.dli.2015.19312/page/n5

Alternating-Current Machines; A>F> Puchstein, T.C. LLoyd, A.G. Conrad - goes into AC machine design. Much more basic than the above and quite a bit more theory than application.

https://archive.org/details/in.ernet.dli.2015.74862/page/n7

I don't have and didn't find anything on design of permanent magnet motors. What I have seen on-line is basic science project or research paper with nothing practical in between. There must be something somewhere if you are willing to do a more exhaustive search.

Just my two pennyworth

With small (less than about 20 Watt) machines many strange effects tend to occur that can be more or less neglected in larger sizes.

Friction is one thing that becomes increasingly important as does mechanical balance, there are many others.

I use small D.C. permag motors as generators in small Steam Turbo Generators and matching the load resistance to the motor characteristics is important

Brush bounce is also a problem at the high speeds these inevitably run at which tends to make the output a bit unstable at certain speeds. It can be overcome by use of capacitors and solid state regulators

I have a design for such a regulator which I can publish on the forum if anyone is interested

Werowance have a look at my Avatar is this the sort of thing you were talking about

yes it sure is.

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