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Do not underestimate the power of the brick. V2

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Kizmo

Sun Sept 23 2012, 08:07PM

Registered Member #599 Joined: Thu Mar 22 2007, 07:40PM
Location: Northern Finland, Rovaniemi
Posts: 624

Just little bit something i wanted to share with you guys.

Inspired to by this thread:

My victim was Semikron SKM150GB128D which i got from German ebay for 20 euros.

Datasheet:

I wanted to see what kind of power levels and general abuse brick like that take. So far it has been very interesting.

Coil spec:

160x500mm secondary, about 1550 turns
100x490mm topload
flat pancake style primary, k=0.16
667nF tank capacitor
370VDC bus, 5600ÂµF bus capacitance
Single phase 32amp feed

Secondary unloaded resonant frequency was measured to be 115kHz, primary was tuned to around 104kHz.

First test setup looked like this. Later i added some more capacitors in series and made nice sealed metal box for driver. (Whole thing was put together from scrap parts in two days, it sort of shows in some places

)

First test at my student apartment, seriously limited by 10A breaker, room and noise.

2nd test later at other place where noise, room or power are not problems..

As video title said, i didnt have Over Current Detection in use. I did scope primary current and during air streamers it was around 1.5kApk and during heavy ground arcing it went way past 2kA. Coil seems to be making scariest sparks at around 300-400bps and 100-120Âµs on time.

Once i chose primary components i knew this thing would need serious amounts of primary current for impressive spark output. Low impedance primary (Zprim 2.22ohm), half bridge and relatively low input voltage made sure i was not wrong. (its hard to get any sparks out of that thing with less than 500Amps in primary!)

Coil ran just fine at 3-4kVA input power from wall for quite some time. Then primary cable that was leaning against bus capacitor mounting strap induction heated that steel strap to a point where cable insulation failed and it shorted primary lead to house ground. And it of course blew rectifier bridge and fuses from electrical panel.

Seems that everything else survived. Maybe next weekend we will see series-parallel bus capacitors for 3 phase power (565Vbus?) Maybe OCD will be added too..

Killa-X

Sun Sept 23 2012, 08:22PM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039

Nice job man, No need to build a fancy coil to get a fun toy :)

Hope to see more limit pushing! Maybe until utter destruction? How much will it take, hehe :D

dex

Mon Sept 24 2012, 09:07AM

Registered Member #2566 Joined: Wed Dec 23 2009, 05:52PM
Location:
Posts: 147

Kizmo wrote ...

I did scope primary current and during air streamers it was around 1.5kApk and during heavy ground arcing it went way past 2kA. Coil seems to be making scariest sparks at around 300-400bps and 100-120Âµs on time.

Does this mean that "heavy ground arcing" occurs before on time is over?

Steve Conner

Mon Sept 24 2012, 09:21AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

It certainly can depending on your coil setup. Classical Tesla coil theory assumes that the energy transfers quickly into the secondary, and the streamers and sparks appear after the energy transfer is complete, but the DRSSTC doesn't work like that. The streamers are being "fed" with energy from the DC bus by the inverter while they grow, and maybe develop into a ground arc. If the ground arc gets too heavy, the inverter may shut off (Steve Ward style) or go into a pulse skipping mode to limit current (my style) or ignore it and carry on (Kizmo's :) )

In fact I would argue that good performing classical coils didn't work like the classical theory either. Once you have a decent amount of bang energy, it's not possible to transfer it "quickly" without causing racing sparks.

Good luck Kizmo on your quest to burn up every part except the IGBT.

Kizmo

Mon Sept 24 2012, 10:16AM

Registered Member #599 Joined: Thu Mar 22 2007, 07:40PM
Location: Northern Finland, Rovaniemi
Posts: 624

Actually this style of driving is called Dalus mode (at least in chatroom..). Dalus has 20kVA low impedance liquid cooled dual h-bridge drsstc (can be found from projects board, search for drsstc named as "resonant rise").

I just find it cool how long on times and high peak currents produce fat and "hairy" ground strike sparks..

dex

Mon Sept 24 2012, 10:34AM

Registered Member #2566 Joined: Wed Dec 23 2009, 05:52PM
Location:
Posts: 147

Thx for the info.

Intra

Mon Sept 24 2012, 05:44PM

Registered Member #2694 Joined: Mon Feb 22 2010, 11:52PM
Location: Russia, Volgograd (Stalingrad).
Posts: 97

post please model number of this brown round caps for mmc?

Kizmo

Mon Sept 24 2012, 07:32PM

Registered Member #599 Joined: Thu Mar 22 2007, 07:40PM
Location: Northern Finland, Rovaniemi
Posts: 624

Caps im using are 4ÂµF 600VAC/1000VDC/1600Vpeak GTO snubber capacitors. 6 in series for 667nF. Rated RMS current is 70A and god knows how high the pulse rating is. I dont remember model number. I have to say they are awesome caps. I pushed that coil to a point where primary cable coatings softened and caps were stone cold :)

Intra

Tue Sept 25 2012, 04:52PM

Registered Member #2694 Joined: Mon Feb 22 2010, 11:52PM
Location: Russia, Volgograd (Stalingrad).
Posts: 97

Please. Could you cast a look on this caps or you very far from it? I'm really very important to know model number, because I'm looking for High RMS Caps for my Guitar Interrupter.

Kizmo

Wed Sept 26 2012, 03:14PM

Registered Member #599 Joined: Thu Mar 22 2007, 07:40PM
Location: Northern Finland, Rovaniemi
Posts: 624

Intra wrote ...

Please. Could you cast a look on this caps or you very far from it? I'm really very important to know model number, because I'm looking for High RMS Caps for my Guitar Interrupter.

PM sent

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