Formulas and calculators > Coil winding
How to determine the limits of a coil / magnet configuration
brandnewb:
As I am working on some test coils and test magnet holders. I thought it important to also be able to test for limits
I plan to test a variety of configurations.
The idea is to have a pure epoxy resin cast coil as a base line. And several other variations to see what the effects of those additives are.
And have several variations of magnet configurations spin over them while the coils are shorted.
Would it be ok for me to drive my alternator test bench with a 20KW AC variable speed motor? if at all affordable and required.
I can supply a continues power of 11 KW. spread over 3 phases. I am assuming this will enable me to supply the power needed to start seeking the limits of a coil magnet configuration. In case that is not enough I can temporary bypass the my circuit breakers in the part of the electrical breaker cabinet that is my responsibility and for short bursts supply a bit below 19.83 KW before the main breakers ( that are not part of my electrical breaker cabinet) trip.
I am hoping that this will enable enough power to start seeking limits.
I am asking for someone to tell me that this is a good way or how to do it even better.
Or I am kind of hoping I do not need to go that large to begin with. I mean if I can also reach conclusions that people would trust with much less power then I am all for that!
joestue:
The reason to do the test as I suggested is because it doesn't require you to measure the torque on the coil by the magnets. The torque is constant, by gravity. measuring rpm is easy, measuring torque isn't, especially if the torque is fluctuating due to the torque not being constant, because the rectifier either doesn't draw constant power, or its a single phase test coil.
you can do the tests with a single test coil, and the results will correlate well to 3 test coils connected in delta. but they won't when connected in Y. the reason being the third harmonic is canceled out and "missing".
so for example on my 3 phase generator, the phase to neutral voltage was 138 or maybe 142, but the phase to phase was 230. 10-16 volts went missing. however, it did produce a very nice sine wave.
basically all you need is a test coil, a scale to weigh it, then wind up the string around the generator shaft, short the coil, and measure the peak rpm of the rotor. then compare with thinner coils and closer magnet spacing, or wider coils, etc.. or coils with bigger or smaller ID or also the OD.
brandnewb:
ok brother.
I will first do as you suggest then!.
Thank you.
It will be soo much less hassle than getting out the big guns.
brandnewb:
Can you please elaborate a bit on what is OD and ID.
And what is it I am testing for again?
In my previous thread you mentioned we are looking for the sweet spot for how much mechanical resistance the coils can provide to the magnets to produce amperage or something to that extend.
Is this still related?
Bruce S:
ID= Inside dimension
OD= Outside dimension
When winding coils (even if it's only for a joule thief, though for a joule thief it's usually just a couple turns) I use the metric system, along with calipers with a digital readout.
Cheers
Bruce S
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