Reactive power - Reactive Generator research from GotoLuc - discussion thread

[poynt99]

Please note these links are for brushed rotor gen heads and not like the ones TinMan and myself are using. We are using brushless exciter rotor gen heads.

Luc

How significant is the difference?

Is the principle not very similar?

[picowatt]

A good brief review of an AC generator.

http://www.auroragenerators.com/resources/articles/how-stuff-works/29-generator-fundamentals
http://armymunitions.tpub.com/Mm07047/Mm070470067.htm
Brad,

Not shown, but the caps in these generators you and Luc are using are for filtering a rectified AC (produced from a residual magnetic field) in order to produce a crude DC field coil supply?

.99,

The brushless cap regulated units Luc and Tinman are using are not covered in that doc.  The caps in their units actually regulate the voltage by resonating with and varying the phase angles of the exciter windings as load conditions vary.  Some units resonate the exciter at the fundamental, many newer units do so at the third harmonic.

I believe the cap regulated units draw a bit more from the prime mover under no load than required for a given output voltage because the exciter phase must be prepared for application of reactive loads, particularly for motor starting.  Severe loading or certain highly reactive loads applied to a cap regulated unit can cause the exciter phase angles to exceed a maximum and cause the exciter current to collapse with subsequent collapse of the field output . 

The reduction of this no load exciter "excess" is what I suspect is related to the reduction in prime mover loading observed with certain reactive loads applied.  Most reactive loads are inductive, so the gens are set under no load conditions to more ideally operate when inductively loaded. 

Please note that I am in no way an expert on induction motors or generators.  But there is a glimmer of an explanation in the above somewhere.

It would be interesting if the experimenters could find the schematics for their respective gen models.

PW.     

[poynt99]

Thanks PW. You posted while I was asking for an explanation from Luc.

I am not an expert in motors/generators either. Interesting modus operandi which no doubt must make analysis and the cause-effect relationship a tad more complicated.

[Cap-Z-ro]

How significant is the difference?

Is the principle not very similar?

Oh joy, a few more rabbit holes laid out before us to explore...wonder if there's anything relevant to find down there ?

[picowatt]

Thanks PW. You posted while I was asking for an explanation from Luc.

I am not an expert in motors/generators either. Interesting modus operandi which no doubt must make analysis and the cause-effect relationship a tad more complicated.

Way more complicated...

That is why I said earlier that this observed effect would likely be different when using a brushed unit with an EVR (electronic voltage regulator).  There are also brushless units that incorporate an EVR as well, wherein a fixed and rotor mounted pair of windings act more so as a rotary transformer to feed power to the main rotor winding.  I suspect that the units that use an EVR (or even a permanent magnet rotor) are all likely going to be less prone to exhibiting the observed behavior (i.e., reduction of PM loading with reactive load applied).

I hope the experimentation continues...

But everyone please be careful!!

PW