Kapanadze Cousin - DALLY FREE ENERGY

[Jeg]

Cross checking the 14MHz peak on the spectrum analyzer with the drain signal confirms that it is caused by the ringing of the MOSFETs.

Hi Itsu
I See two kinds of frequencies across your drains. The first 14Mhz oscillation happens when mosfet stops conducting, and a second lower freq. oscillation to the same drain, when the other mosfet starts conducting. Looks like that between the two oscillations we have a change to the values of paracitic capacitance and leakage inductance which determine the oscillation value. I hope Verpies will through some light to the shade.

One question guys.
Is there any way for someone to predict the capacity value of a diode when this works in combination with a coil? I see for example that the diode bridge at the output of grenade, gives specific resonant rise to a frequency value according diode's capacity and grenade's inductance. Can this be calculated from the begin?

[T-1000]

One question guys.
Is there any way for someone to predict the capacity value of a diode when this works in combination with a coil? I see for example that the diode bridge at the output of grenade, gives specific resonant rise to a frequency value according diode's capacity and grenade's inductance. Can this be calculated from the begin?

Each diode have capacitance in datasheet. It is easy to calculate parallel resonant ringing frequency with taking coil inductance and diode capacitance values. Just the aim is not for LC resonance in grenade coil. It should be more aimed for self inductance and self capacitance of the coil while sweeping wide range of frequencies if you do not know wire length which is best answer for resonant wavelengths.
On what frequency your grenade coil rings with largest current on wire when loaded with 10 Ohm resistor? The signal input from frequency generator is the inductor directly attached to it.

[Jeg]

Each diode have capacitance in datasheet.

Tnks T1000
I ask because except of the resonant rise frequencies which are related to the grenade length itself, there is always a high peak between 750KHz-900Khz which i suspect that relates to the diode capacity and it is always there in all of my grenade builds. I'll check again the datasheet as i can't find its capacity value.

[itsu]

As mentioned earlier, i build a new yoke consisting of a T-520 Toroid using the loss-less clamp design with the same number of turns on the primaries (2x 12) and secondaries (3 and 28),
see picture were i compare the new toroid with the first one (not loss-less) i had.

When firing up, the 24V battery stack hits its auto fuse of 10A and thats it.

It seems that this "toroid yoke" gives way less inductance to the primaries (5.8uH each compared to the 64uH on a "yoke yoke") so it presents itself as a short to the MOSFETs.

I had the same effect as when i by mistake had wound my present loss-less clamp design yoke as bucking primaries, also then the inductance was too low and the 10A auto fuse came out.


So how to remedy this?   Use more turns on the primaries, but that will influence the secondary turn ratios as well which could cause the toroid to run out of space for all those windings.

Or stick with the present "yoke yoke"?


Itsu

[verpies]

I measure the both primaries (only the C to B and the F to D part in your loss-less clamp diagram) to be resp. 62.5uH and 64,2uH.
For 14Mhz that comes to about 2pF on your above formula, so that can come from anywhere.

The drain to source capacitance is more that 2pF.  The additional inter-turn capacitance would make it even higher.
But it is not the ~60μH that is ringing with this capacitance.  It is the much smaller leakage inductance which forms an LC tank with this capacitance.  The leakage inductance should be measured with the secondaries shorted.

So with these numbers the LC resonance of the leakage inductance seems plausible.

Paralleling a 47pF capacitor to gate / source does not show any difference in this ringing, paralleling it to the drain / source shows a minor frequency decrease of about 200Khz.

Good. That confirms that the 14MHz ringing comes from the drain circuit.

However that does not explain the 35.25MHz peak and the 9.416MHz peak with its harmonics.
Please repeat this test with a 100pF capacitor and note whether these peaks are also affected.

In the test with the 4 stacked ceramic magnets, i noticed that when the magnets are attached to the yoke midway a primary, that that primary MOSFET gets hotter (due to the harmonic peaks production).
The other MOSFET stays the same in temperature.  When putting the magnets midway the other primary, then the other MOSFET gets hotter 

This means that the magnet forces the alternating magnetic flux out of the core, because the core forms a circular magnetic path and affecting any part of it would affect the inductance of both windings equally.