Effects of perm. magnets on bifilar toroid transformer output

[exnihiloest]

...
It appears that simply adding the presence of a few neo magnets to this transformer DOUBLES its output without changing the input. 
...

Magnets change the permeability of the coil core therefore the inductance is also changed.
A coil has internal resonance frequencies due to LC effects, C being the resultant of the capacities between turns.
It follows that at some position of the magnet, the coil becomes resonant at the working frequency, increasing the voltage.

[gyulasun]

Hi exnihiloest,

What you propose could be possible but in this particular case we should see some sinusoid voltage waveform at the output instead of the still uggly pulse shape.  LC resonance always involves forming sinusoid or distorted sinusoid waves but not such straight lined pulse shapes.
I think void109 mentioned he swept the frequencies and it is like that everywhere as he showed in ScopeB.jpg if I recall correctly.

I agree that magnets change the core permeability, hence they can tune the coils just like a variable capacitor.

[void109]

I have a lot of work to do today (the kind that pays for my hobbies like this), but later today I'll do as you request Gyulasun.  I really appreciate the attention and insight.  After I posted those pictures I stripped down that setup (its easy to set up again and reproduce, I've done it a few times) for another test for which I'll start a separate thread - another interesting effect.

Thanks again!

[mscoffman]

@void109

I see from another thread you have seen the self-running coil thread.
Basically as you add neo's the coils inductance become much smaller
this allows your coil to become resonant with parasitic capacitance
of the driver device and coil self-capacitance. The core is very near
saturation as magnets have strong magnetic fields. This saturation
is why the inductance is reduced. The first screen shot is primarily
inductive back emf kicks from high inductance and the second is
nearer resonant. Your meter is happier nearer with the inductor nearer
resonance. Which is why it claims the voltage is higher. All of this goes
to show you *must* measure power as a DC level. Rectified and filtered
so that the voltage changes very little during the meters gating time of
about one second. You can't measure AC pulses voltage accurately and
you definitely can't measure current when the voltage is changing with
a DVM. AC voltage measurements of the DVM are sinewave RMS. AC
measurements are meant for 50/60Hz line voltage of sinewave shape.
Gotoluc's power supply and power reading set up was nearly perfect.

:S:MarkSCoffman

[void109]

Thanks for the feedback, I played with the setup further and I find I must agree, power measurements do seem like they should be made with stable, rectified DC signals - it started dawning on me how meaningless these readings must be when they are getting pounded with fast pulse streams.

Even the amperage drop I was showing - I was taking that using the 10A setting on the meter, I was just looking at the accuracy differences between the 200ma and 10A settings - I bet its just an aberration.