difference between positive and negative back emf

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difference between positive and negative back emf
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I've been wanting to show/understand the difference between positive and negative back emf.

First I made a small spark from a 900V negative back emf. It looked different, white and gasous, and was very loud.


https://youtu.be/zQNKQWFCFCs

Then I realized the voltage was simply to low. I needed to step it up.
I ordered a step up transformer from china, but realized, I havr a xar bobine/ignition coil.

I hooked it up to my 12V battery and a lowside igbt switch (creating "regular" positive back emf).

I put a 0.1uF plus 10k parallel over the primary, to restrict the back emf (I first used a diode but then there is no spark as all energy is shorted via the diode).

tuned in a 400Hz square wave and turned it on.

Spark works. blue lightning as expected.

but also a loud noise out of my speakers, and led lights turning off
lol :P

the emp is rather intense :emperor:

but it works...
need to tune the snubber cap/resistor so a 500V back emf on the primary is possible.

after filming it, I want to use a high side switch, and show the negative spark. and the difference between them.

I hope the neighbors will not get mad with all the emf noise this will produce, and, I need to make sure I dont nuke my electronics with those EMPs...

 talking about longitudinal pressure... EMP is such a bad name...
its should be MDP
Magneto Dielectric Pulse.

 20190628_002423.jpg - 1615.82 kB, 2560x1440, viewed 7 times.

Re: difference between positive and negative back emf
« Reply #1,  »
did the same test, with the high side switch, spark looked the same, also purple, not gaseous (slightly but not like before).
I wonder if it is due to a not proper grounded primary (need to test this)
Or if it is due to the secondary of the ignition coil, It could be I have connected it the wrong way round.
I feel it has to do with the counter rotation of the coil (and the Aether) when the magnetic field collapses.

also I'm not happy with my snubber cap resistor. I want to reverse it, place the cap on the back emf (switcheded) side, so the cap gets charged, and slowly discharges through the resistor.

pulsing at 400Hz works best