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Old 03-19-2019, 10:34 PM
gyula gyula is offline
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Join Date: Apr 2007
Posts: 820
Originally Posted by bistander View Post
Hi all,

I happened across this video which I think is an excellent demonstration and explanation of generator speed up under load.



Hi bi,

Unfortunately, Conrad used a steel bolt for his coil core and back then this was not taken into account. Such bolts can introduce eddy current losses and this manifests in heat while the rotor magnet spins in front of it. And this eddy loss does get reduced the moment you attach a load to the generator coil so this inherently built-in drag does get reduced and so does the earlier draw of the motor. I am not saying that the capacitor tuning has no any beneficial effect here, just that the effect of the bolt can be decisive.

The correct test in this respect would have been to replace the bolt by say a ferrite or metglas or finemet (or other low loss) core, these types have the least amount of eddy current loss, at least by 1 or 2 order of magnitude less than a bolt has. Of course, this replacement should have provided nearly the same L inductance for the coil the bolt did, to be able to make correct comparisons between the two cores.

One more notice: A suggestion made by other builders for a fair test to demonstrate the 'generator speed up under load' effect would be first to measure the unloaded power draw for the prime mover motor, i.e. no generator shaft attached.
Then attach the generator shaft to that of the motor with no load across the generator output and check the prime mover power draw again.
Then load the generator as best you think and here it is also assumed your motor RPM is chosen in advance as best as you think it should be for your setup and check power draw for the prime mover for the 3rd time.

Only then could conclusions correctly be made on the 'effect'.
I also believe all builders should follow such measuring principle for a correct evaluation of their motor-generator setups.
Notice that I do not question this effect, only wish to draw attention for a correct evaluation like mentioned above.

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