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Messages - davekni

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81
Dual Resonant Solid State Tesla coils / Re: Problems with my first DRSSTC
« on: October 23, 2019, 04:33:46 AM »
Yes, I can imagine a switching supply being troubled by the nearby electromagnetic fields.  The cheap DMMs get completely confused by stray fields.  On the other hand, I have good luck with old Dell laptop 19V supplies, which are switching.

Sparks might be longer with longer pulse width and lower repeat frequency (to keep average power constant).  Other's likely have better intuition on that.

Looking forward to the video!  Glad I could assist - thank you for the mention.

82
Dual Resonant Solid State Tesla coils / Re: Phoenix's Large DRSSTC II
« on: October 23, 2019, 04:03:42 AM »
I'd agree that primary stray inductance isn't a "problem", but it is at least slightly undesirable.  Stray inductance reduces the coupling factor, by the ratio of primary_coil_inductance / total_primary_inductance.  The less stray inductance, the further the primary can be spaced from the secondary, reducing arcing problems (for a given coupling factor).

The effect of stray inductance is a bit more significant in designs with low primary voltage (few primary coil turns), as I've built.  With only 3 and 4 turns for my SRSGTC and DRSSTC primaries respectively, minimizing stray inductance was worthwhile.

83
Dual Resonant Solid State Tesla coils / Re: Problems with my first DRSSTC
« on: October 18, 2019, 06:30:06 AM »
Great!  Nice to see scope traces that look as expected.

The occasional startup issues at 24Vbus are reasonable for the UD2.7.  The 1.3A current of the first half-cycle fits calculations (15.7 ohms primary L and C at 149kHz on about 21V bridge output).  1.3A through 625:1 CT into 51 ohms gives 0.106V, barely enough to trigger the UD2.7.  This issue should completely disappear at higher Vbus.  (I'd previously suggested some UD2.7 patches if you want to get more reliable operation at low Vbus, but no need to change anything with Vbus above 24V.)

How are you scoping primary current on the blue channel?  (Cyan channel in my color-science world:)  Do you have a current probe, or a resistor in series?  I'm asking because the CT output appears to have 20-25 degrees of phase lead relative to that current.  Do you have L1 in the circuit now?  That would explain the phase lead of CT signal.  (The parasitic inductance of the CT would account for only 1 degree or so based on your N30 core and 25 turns for the second stage.)

Given that you have primary current scoped, primary voltage isn't necessary.  If you want to scope such in the future, inexpensive 100x scope probes are available, such as this P4060:
https://www.ebay.com/itm/P4060-1-100-High-Voltage-2KV-2000V-60MHz-Oscilloscope-Scope-Probe-100X/372463710732?hash=item56b891320c:g:eLIAAOSw8UZaLlMi

The occasional short positive spikes on the H-Bridge outputs might be due to not quite enough phase lead.  If the IGBTs switch after zero-current, the reverse diodes of a pair of parts are conducting.  The other pair then switches on, rapidly removing the diodes stored charge, then overshooting as the diodes snap-off.

The longer spikes when the drive pulse ends may be on the edge of problematic at 310Vbus.  This is caused by an L/C circuit ring, where C is the smaller Vbus capacitors at the H-Bridge and L is the wiring inductance back to the larger bulk Vbus capacitors.  That ring will grow in proportion to primary current at the turn-off point.  Over-current shutdown, by definition, occurs at high primary current, causing high voltage spike on Vbus at the IGBTs.  (This issue caused a rework in my Vbus wiring, as I'm using 600V IGBTs at 450Vbus.)  At your 310 Vbus, extrapolating the spikes, they should be a little below 600V, but without a lot of margin.

To reduce that Vbus spike at the end of high-current pulses, either increase the capacitance local to the IGBTs or reduce wiring inductance back to the bulk Vbus capacitors.  Using a few wire-ties to force the Vbus wires together will help.  Multiple pairs of Vbus wires, each pair twisted or tied to remain adjacent, will help even more.  That's what I did, as I had no room for more local-to-IGBT caps.

Have fun - nice progress!

84
Mads, Thank you so much for pointers to so much amazing information!  That's going to take a long time to study.  I did notice initially that some of the top current traces look somewhat like what I measure at the bottom of my secondary coil.

Concerning upper pole tuning (which I've tried in simulation only), what I see is significantly higher primary current and voltage needed to achieve a given secondary voltage, especially after the secondary frequency drops (capacitance increases).  I'll need to learn more about QCW drive circuits - there's probably something I'm not understanding yet.

Yes, the big TRIAC array for dynamic primary tuning is a huge project with a significant chance of cascading failure.  That is part of what makes it interesting.  (Like putting a scope on top of a Tesla coil - risky but rewarding.)  My hope is to extend arc length for my moderate-sized DRSSTC.  May not work, but I hope to find out.  Prabably 1.5-2 years out, as I have other improvements to make to my DRSSTC first, and other small projects etc.

In what way did the upper pole tuning did not preform well in simulation? The tuning relies on the fact that the capacitance from the discharge pulls the secondary into tune, so you need some sort of model relating power and spark length/capacitance. I recall there being some good posts on 4hv about the tuning method and models for arc impedance. The easiest model is assuming the arc has a capacitance equal to an equivalent length of wire, which is how I tuned my QCW coil.

One thing to note is that when the secondary is tuned above the primary the lower pole has higher gain, so a self oscillatory controller will lock onto the lower pole.

I am still unclear about what advantage the triac based system would have. It seems like a lot of work with a high potential to blow up if anything goes wrong.

85
Transformer (iron core) / Re: making a useable induction forge.
« on: October 17, 2019, 03:08:49 AM »
Counterpoint to a few previous comments:

The IGBT parts used in this design do not have internal diodes, so the external ones are critical.  If updating this design to use IGBT parts with anti-parallel diodes, then the external ones could be removed.

The TIL111 opto is used for over-current shut-down per the original article.  As long as the shutdown functions correctly, it will shut down before the opto LED current gets too high.  (I'd still add a small series resistor just for margin.)

Good point about snubber R/C pairs needing low inductance.  I'd hesitate to remove them, however, unless the rest of the layout is very clean.  The high-frequency ringing can couple to low-voltage logic even if it doesn't fry the high-power devices.  Such R/C snubbers are common in commercial switching power supplies to limit spikes and reduce EMI.

Yes, the 16V zeners won't survive a catastrophic failure.  However, they can help with ESD hits during construction and testing, and with over/undershoot if the gate wiring is long or sloppy.  I typically add such zeners to FETs and IGBTs at the start of construction just for insurance.

And a few other random comments:

Orange shunt is current sense for over-current shutdown.

The transformer is air-core per the original design.  Not something I'd recommend, but workable for demonstrating basic induction.  It's just a coil of two-conductor wire.  Same with L1 - air core in the original article, just a coil of wire.




86
Capacitor banks / Re: Mysterious Chinese HV capacitors
« on: October 16, 2019, 03:33:52 AM »
These look exactly like the polystyrene capacitors I purchased on EBay 3 or 4 years ago.  They are very-low leakage, great for voltage-multiplier use.  However, they are foil, and have random tiny bubbles included, which form corona discharges in AC or pulse (Marx) use.  For low-frequency Marx use, they work OK.  My Marx generator recharges up to 120 times per second (plays low-register tunes).  In that use, they last a few minutes at most.  Same for AC (Tesla coil) use.

87
Wonderful to have some AC flyback transformers!  I'd love to find a few.  Home-winding the HV side is difficult - to get low capacitance and high voltage w/o corona and arcing.  The HV potting info on this forum look interesting, but purchasing is easier.

A diode, capacitor, and your 40kV probe will work fine to measure peak voltage.  No concern about needing to guess.  (Of course, all the capacitors in the multiplier, except the first one, will see the peak-to-peak voltage, so twice the peak.)

If you have a scope available, measuring the secondary turn count would allow calculation of the primary turns needed to get 30kV peak-to-peak, so you can avoid needing to series-connect your caps.  Wrap 10 or 20 turns of scrap wire around the core.  If any source of kHz voltage is available (signal generator or other random project), connect that to the secondary.  If not, just charge a cap, then touch it to the secondary for a ring-down waveform.  Scope both the secondary (being used as a primary here) and your 10 or 20 turn coil to get the voltage ratio.  This is almost always the way I start with any unknown transformer.  (I prefer the ring-down, as it provides inductance also, from frequency and capacitance.  I use a TRIAC to connect the cap and coil for cases over 200V, as it makes a cleaner connection than just touching wires together.  Repeating with larger capacitance until the ring-down frequency isn't constant with voltage will provide saturation current.)

88
Sounds like fun! Since you will be driving the flyback transformer with a sine-wave, either full-wave bridge or the single diode into capacitor will work fine, giving the same result.  BTW: I'm presuming you're using an existing high-voltage winding and don't know its turn count, so need to measure?  Or, is it just to get more precision than a theoretical value?

Center-tapping the primary winding is great for Royer oscillators - single smaller inductor for power feed.

This is surprisingly related to my current project.  I've recently become intrigued with driving inverters with ZVS (Royer) oscillators.  A lot of simulation and some test results for small Jacob's ladder driving.  Is your flyback transformer already glued together, or do you have the ability to adjust the gap (inductance)?  If not adjustable, can you add a little extra primary series inductance to adjust net coupling factor?

The key issue is keeping the Royer oscillator running over the full range of load, including the initial short-circuit condition at startup when the load capacitors are discharged (or when the arc first strikes in my case), then remain running as the load voltage increases.  In simulation (and roughly verified experimentally), a transformer with <86% coupling factor works, and >86% doesn't.  I've adjusted my core gaps for 83% coupling - a bit of margin from 86%, but still good energy transfer.

With shorted load (ie. initial startup), the Royer oscillator frequency is set by the leakage inductance.  At light load, it is set by the normal transformer inductance. Between, where maximum power is transferred, it is between those two frequencies, and a bit distorted.  With coupling above 86%, it will function shorted (at high frequency), but drop out as the load voltage increases.  The Q becomes too low to sustain oscillation.

Have fun!  I'm anxious to hear how your project goes!

89
I purposely selected TRIACs with high dV/dT rating, 1000V/us (BTB16-800BW from ST).  That's well beyond the 400V/us they'll see.  Each TRIAC will be shorting one MMC section, which will have 800V peak at 80kHz, thus 400V/us.

The TRIAC specification that is most risky is "critical rate of rise of on-state current".  These parts, as with almost all similar parts I could find, are specified at 50A/us maximum.  In my particular odd application, the rate-of-rise is controlled primarily by how fast the TRIAC manages to turn on.  (Ideally, it would instantly conduct all the capacitor current at the voltage zero-crossing.)  I made a small 3-cap MMC in a resonant circuit with one TRIAC shorting one stage.  It ended up with ~100A/us, about twice spec.  I've done some other single-shot tests running these to 250A/us, but not repeatedly nor with high die temperature.  It's been fun learning about "critical rate of rise of on-state current", as I had no idea previously what that spec. meant or why that would be limited.  (Turns out that TRIAC gates are in one corner of the die.  It takes time for the primary current to spread across the die.  It starts in the gate corner and spreads.  Too high current immediately overheats the gate corner of the die.  I can see this in the forward drop voltage/time behavior.  Starts at ~20V forward drop, which goes down to normal ~1V over 1-2us.)

90
Spark gap Tesla coils / Re: so far video
« on: October 14, 2019, 05:40:27 AM »
I'll second that 7.2kV RMS should be plenty.  My RSG coil uses two MOTs in series with resonant charging, so gets to about 9kV peak, which works well (with close gap spacing).

Did you say 27nF primary capacitance at 32kV?  I have no familiarity with pole-pig transformers.  Is there some resonant-charging effect that will get you much above 10kV?  If not, 27nF will be rather low energy per spark.  For my two-MOT coil, I used 680nF with a 3-turn primary coil to get reasonable energy per spark.

91
Dual Resonant Solid State Tesla coils / Re: Drsstc 4 (new direction)
« on: October 14, 2019, 05:23:48 AM »
What is the pipe material?  It doesn't look like anything I've seen before.

PFC refers to "Power Factor Correction".  Most DC power supplies start with a PFC circuit, taking the line main in and generating a non-isolated bus supply, often around 400VDC.  The main switching-regulator circuitry runs on this bus voltage, generating whatever outputs are needed (ie. 12V or ...) with an isolated forward converter or whatever topology is used.  The PFC stage attempts to draw current from the line that is sine-wave shaped and in phase with the line voltage (close to 100% power factor).  Most PFC converters are boost topology, generating VBus at a voltage above the peak of rectified line voltage.

The purpose of most PFC circuits is to meet regulatory requirements.  But they are also useful to get the most from limited line power.  A simple bridge rectifier and large bulk cap can have power factor around 60%.  At the rated line RMS current, only 60% of the ideal power is available as DC.  Inductance on the input can improve the power factor some.

The PFC circuits I've built are very crude.  They draw something close to sine-wave current at full power.  At lower power, they just switch on and off to regulate output voltage.  Not friendly to the power line, but does get maximum power.  (Even a constant-current load achieves 90% power factor, much better than the current spikes drawn by direct line rectification into a large bulk cap.)

92
Thank you for the compliment.

That resistive divider works well at line frequency (50/60Hz).  It also allows the option of scoping the divider output w/o diodes to see the AC waveform.

At higher frequencies as in typical flyback transformers, stray capacitance across the HV resistors can give falsely-high readings.  Accurately handling that capacitance is why HV scope probes cost more than HV meter probes.  HV diode(s) directly on the flyback output avoid that stray-capacitance issue.  The resistive divider sees only DC, so stray capacitance is not an issue.

Also, I expect the desired information for the flyback output is peak voltage, not average or RMS.  Direct HV rectification with HV capacitor measures peak voltage.

93
Yes, that will work fine too.  Of course, you'll get only the peak voltage, no waveform shape information.
For a flyback, you could half-wave rectify using a single diode.  That way you can separately measure the positive and negative peak voltage.  Flyback transformers don't mind that bit of DC load.

Make sure the diode is fast enough and low enough capacitance to not affect results significantly.  I've had good luck with the little 5mA 20kV 100ns 2CL77 diodes from China:
    https://www.ebay.com/itm/20pcs-5mA-20kV-High-Voltage-Diode-HV-Rectifier-2CL77/290637855659?hash=item43ab5dbbab:g:PgYAAOxyLiJR1nm7
For low currents, they work fine in series to get higher voltage.  They need to be taped or potted (generic epoxy or silicon rubber caulk works fine) to reach 20kV w/o arcs along the package.  Tape is fine for short-term uses.

94
Dual Resonant Solid State Tesla coils / Re: My first DRSSTC on bricks
« on: October 13, 2019, 07:04:20 AM »
If you can find some, there's a part called IF-D92.  It's just a phototransistor in a housing for 1mm plastic fiber.  That's what my DRSSTC uses.  I've also used TOSLINK couplers with one end partially drilled out and a 3mm photodiode glued in the hole.

95
Before buying a used HV probe, for AC, I'd use a home-made capacitive divider.  Make a small linear HV capacitor, such as foil on the inside and outside bottoms of a small glass jar (ie. baby-food jar).  Place that from your HV AC source to a scope probe, with a larger value (say 1nF) cap from probe to ground.  Calibrate the setup with some lower-voltage AC source that you can measure directly and through this capacitive divider.  (Either adjust capacitors to get a nice ratio, or just do the math on the resulting waveforms.)

For DC, my solution is similar.  Soldered a string of 100 1meg resistors together, then fed that into a polyethylene tube for insulation.  Later I bought some 10kV rated resistors, so my string isn't as long.  I use 30 of those in a string on the output of my multiplier so that the multiplier's stored energy isn't a hazard to the public when they are making their hair stand on end or whatever.

My finished multiplier has too high an impedance to measure accurately even with a 100-resistor string.  Instead I use small aluminum disks of varying thickness on top of the 10" (254mm) ball.  When the disk just lifts from the ball, its weight/area and the ball diameter can be used to calculate voltage.  I have ran it to 250kV, but typically run around 100kV for public static-electricity activities.

BTW, I initially used a 20kHz transformer to feed my multiplier, but the cheap ceramic capacitors were too lossy (just feeding stray capacitance of the multiplier string), so some overheated and failed.  Changed to a spark-coil running at 700Hz.

Here's my schematic. less the 30 x 10meg output isolation resistor string:


And a picture of the finished multiplier with ball at top:

96
The paralleled TO247 IGBTs were for fast switching, both because small IGBTs are rated faster, and the paralleling gives lower net lead inductance.  I would have had to parallel at least two sets of bricks to get 3500A peak.  Now that I'm reading what others are doing, it's clear that the bricks can be pushed to much higher frequencies in ZVS mode than I'd realized.  (The lower inductance does have an advantage still in peak voltage.  These 600V IGBTs still have sufficient headroom at 450Vbus, as there is very little overshoot during switching.  However, if I fry the H-Bridge, I may rebuild with bricks.  It was a lot of work to build a 40-IGBT bridge!

The thermal modeling seemed sensible for pushing devices to their limit.  The zener/resistor array at the bottom of the schematic page makes a current roughly proportional to the square of the primary current-sense transformer output, so proportional to forward-conduction power loss in the IGBTs.  That current charges C1 and C2, which are coupled with resistors modeling the transient thermal impedance from the IGBT data sheet.  I had no idea if anyone else was doing that - hadn't found much information before stumbling into this forum.  (Peak current causes all zeners to conduct, so behaves as infinite power, causing an immediate (next zero-current, rising or falling) end to that burst.  It also leaves the model in its hot state, delaying when the next burst is allowed.

The TRIAC switching will be a challenge!  I haven't found good modeling tools, so am relying mostly on testing individual TRIACs and gate-drive transformers etc.  Had to use NiZn ferrites for high electrical resistivity to avoid excess capacitive coupling.  MMC is split in half, one on each side of H-Bridge output to keep peak voltage to ground lower.  Finally, it's going to be inefficient in MMC capacitor use - many extra ones.  The plan is to build a huge MMC with extra voltage capability, then short out individual small groups of caps at the voltage zero-crossing.  Snubberless TRIACs have one quadrant where they won't turn on.  That allows the gate drive pulse to start early, before voltage zero-crossing, avoiding excessively-tight timing requirements.  Placing the TRIACs directly across capacitors prevents stray inductive spikes from triggering the TRIACs.  I did choose TRIACs with fast enough DVDT rating to handle the voltage slew rate of individual MMC sections.

I have some previous experience in failed TRIAC array switching.  My very first Tesla coil was an attempt to replace the spark gap with a TRIAC array.  Made three sparks before a failure cascaded through the array.  Turned that project into a rotary-gap coil.

I'll need to play with my basic coupled-resonator simulation some more.  (Anyone have a good SPICE model for a growing arc?  I've made a couple guesses, but not likely very accurate.)  In simulation, it seemed that starting on the upper pole didn't perform as well.  Does the ramped voltage make that upper pole work better?  I gather that most DRSSTC designs oscillate at the lower pole, as mine does.  Either way, I expect there's a limit to how far detuning can go, and I'm hoping to add to whatever that limit may be.

97
Should be a great primary with 4000-strand litz!  With such fine wire, the inner turn may not get much warmer than the outer turns.  Would be fun to see thermal images of your primary after a run.  Mine clearly shows higher temperature on the first turn.

Litz will have minimal affect on the secondary.  Typical secondary Q is already high, so relatively little power loss.  Even if you got infinite secondary Q (zero power loss), it's not that much savings.  No harm in using litz, though.

I'd love to see your coil once your up here.  Haven't been to Westercon, but I think Don Anderson was there with his coils.  He's the one who got me interested in Tesla coils.  We share demo space at Maker Faire here.

98
Thank you for the clarification about FET use.  I do see that clearly in your earlier posts now, but was confused at some point.

BTW, don't see anyone answering your "Kelvin connection" question, so:  One source lead is for the high-current connection (source-to-drain current).  The other is for gate-drive return.  That way the inductive and/or resistive voltage drop of the high-current connection isn't added to the gate drive signal.  The two source connections are identical in this part (not typical for other packages).  However, you should use only one for the high-current path, and the other only for gate-drive return.  (Connect gate drive to gate and that second source terminal.)

As long as there's a catch diode from the drain to the incoming supply V+, and a good capacitor from V+ to V-, I'd go ahead with fast switching.  (Inductance of the diode/cap/FET loop needs to be LOW.)  If you need to slow down the switching, the simple way is to add a resistor in series with the gate.  Another small diode and resistor are often added in parallel with the main gate resistor to make turn-off faster than turn on.  If you need a more uniform voltage ramp on the output, adding additional miller capacitance (gate-drain capacitance) can help.  I've personally had trouble with RF oscillation when adding external miller capacitance, I think due to gate and source lead inductances, but it can work.  Any additional miller capacitance is a second step after inserting gate resistance.

99
The IGBTs have a positive Vce-temperature coefficient, which helps with current sharing.  The only explicit step I took besides tight packing was to feed Vbus from one end of each half-bridge, and take the outputs from the other ends.  That way the Vbus voltage drop roughly matches the output voltage drop, keeping Vce roughly constant across the array.  I haven't attempted any specific measurements of current sharing.  Would like to check it before increasing max current from 2600A to 3500A, but not sure how.  (3500A still has some margin for sharing errors.  I tested one individual IGBT to 500A, both transistor and diode, at 90C initial temperature.  Rated peak current is 240A - the best I could find in a fast TO247 part.)

The reason for the discrete comparator (besides my habit of designing that way at times) is that it tolerates input voltages to 10V beyond supply rails.  That avoids diode-clamping the current-sense signal, which would make a non-linear load impedance on my phase-lead filter.

The phase-lead filter is a bit fancier than normal, designed for roughly constant time lead (not phase lead) from 50-80kHz.  That covers the range I'm planning with my eventual reverse-chirp primary resonant frequency.  The filter also has the advantage of not amplifying high-frequency noise as much as a single inductor or capacitor circuit.  (I'm currently running about 83kHz primary.  It works better with the arc-length constraint of the Faraday cage with the primary closer to the secondary's 92.2kHz resonance.)

Forgot to include a bit of basic information:
    Primary:  6.72uH (6.95uH including inductance of MMC and interconnect), 4 turns of 200 strands of 27AWG wire.
        222mm diameter of inner turn (diameter at center of wire).  308mm diameter at center of outside turn.
    Secondary:  68.0mH, 75 ohms DC, ~1800 turns of 24AWG wire, 157.5mm diameter, 1100mm high (not counting loose-wound ends).
    MMC:  10s16p of 330nF 1200VDC 630VAC Chinese induction cooker capacitors, 528nF total, half on each end of primary coil.
    Top Load:  194mm minor diameter, 632mm major diameter (826mm outside diameter).

Ignoring the comparator implementation, the circuitry around it is somewhat similar to the UD2.7 design.  A couple differences:  First, the bias point of the current-feedback is centered with no signal present, rather than a diode-drop low.  Second, I have positive capacitively-coupled feedback (as does UD2.7), but also weak resistive negative feedback.  That combination causes the circuit to oscillate with no current-sense present.  I've designed that oscillation frequency to roughly match the primary resonant frequency.  This allows synchronous oscillation to start even with very-low Vbus (5V works), independently of the initial state of the primary tank circuit.  No need for a resistor across the H-Bridge output.  (I do have bleed-down resistors with indicator LEDs across the MMC sections.)

100
Dual Resonant Solid State Tesla coils / Re: Problems with my first DRSSTC
« on: October 12, 2019, 04:41:19 AM »
I'm guessing there's another issue besides just the emitter wiring.  At 24V and ~26A, the emitter connections seem unlikely to cause the anomalous behavior (fast current reversal event and resulting short gate pulse).  The other things I'd suggested are in the minor-improvement category, not causes of the issue either.  Still suggest fixing the emitter wiring before any higher-power testing.

Is the current-limit circuit fully wired on your board?  If there were to be an open (no load) on the current-limit half of the current transformer, that core is likely to saturate, causing odd signals on the other half of the current sense transformer.  Not sure that could explain exactly what you are seeing, but worth a check.

Would it be possible to capture that anomalous event at 24Vbus and ~26A with the following four scope signals:
    Current sense voltage (as you had before)
    Both H-Bridge outputs
    High side of primary caps (connection to the primary coil).
If you have only two scope channels available, make three captures.  The current sense signal would be common to all three captures, with the other probe monitoring each of the three other signals sequentially.  At ~26A, the primary cap high-side should be ~400V, so within capability of normal scope probes.

This is interesting debugging remotely, where I can't just move a scope probe from one point to the next to see where an issue lies.  If my probing requests become too tedious, please feel free to say so.  If you don't mind continuing to capture signals, I'm confident it will be possible to find and fix the issue.  (If someone else manages to recognize the likely cause from the symptoms, that will be great.  If not, then walking through signals with your scope will get there.)

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davekni
December 11, 2019, 05:01:31 AM
post Re: Using same winding on separate rails?
[Transformer (iron core)]
John123
December 11, 2019, 01:52:43 AM
post Re: Using same winding on separate rails?
[Transformer (iron core)]
klugesmith
December 11, 2019, 01:41:04 AM
post Re: Worlds Weirdest Microwave Oven, From A Weapons Factory - The Husqvarna Cupol
[Transformer (iron core)]
klugesmith
December 11, 2019, 01:37:13 AM
post Re: Using same winding on separate rails?
[Transformer (iron core)]
John123
December 11, 2019, 01:19:58 AM
post Re: SGTC MK1 - An Accomplishment in Progress
[Spark gap Tesla coils]
jturnerkc
December 11, 2019, 01:14:32 AM
post Re: Using same winding on separate rails?
[Transformer (iron core)]
klugesmith
December 11, 2019, 01:04:08 AM
post Re: SSTC low voltage at gate transformer and heating drivers
[Solid state Tesla coils]
babass
December 10, 2019, 11:24:50 PM
post Using same winding on separate rails?
[Transformer (iron core)]
John123
December 10, 2019, 10:52:50 PM
post Re: Duty cycle when driving a CRT TV flyback transformer
[Transformer (ferrite core)]
John123
December 10, 2019, 03:35:40 PM
post Re: Why did 4HV die??
[General chatting]
John123
December 10, 2019, 03:21:07 PM
post Re: Duty cycle when driving a CRT TV flyback transformer
[Transformer (ferrite core)]
Mads Barnkob
December 10, 2019, 03:04:28 PM
post Re: Duty cycle when driving a CRT TV flyback transformer
[Transformer (ferrite core)]
John123
December 10, 2019, 02:57:45 PM
post Re: Possible use for large inductor (laminated core)
[Transformer (iron core)]
kamelryttarn
December 10, 2019, 11:23:48 AM
post Re: SGTC MK1 - An Accomplishment in Progress
[Spark gap Tesla coils]
Mads Barnkob
December 10, 2019, 10:27:54 AM
post Re: Worlds Weirdest Microwave Oven, From A Weapons Factory - The Husqvarna Cupol
[Transformer (iron core)]
Mads Barnkob
December 10, 2019, 10:20:17 AM
post Re: Possible use for large inductor (laminated core)
[Transformer (iron core)]
Mads Barnkob
December 10, 2019, 10:16:32 AM
post Re: SGTC MK1 - An Accomplishment in Progress
[Spark gap Tesla coils]
davekni
December 10, 2019, 06:04:28 AM
post Re: Duty cycle when driving a CRT TV flyback transformer
[Transformer (ferrite core)]
davekni
December 10, 2019, 05:28:54 AM
post Re: Possible use for large inductor (laminated core)
[Transformer (iron core)]
davekni
December 10, 2019, 04:12:29 AM
post Duty cycle when driving a CRT TV flyback transformer
[Transformer (ferrite core)]
John123
December 09, 2019, 10:52:59 PM
post Replacement guide for Windows Media Center
[Computers, Microcontrollers, Programmable Logic, Interfaces and Displays]
MRMILSTAR
December 09, 2019, 08:29:16 PM
post Re: Sense coil fabrication?
[Induction launchers, coil guns and rails guns]
Uspring
December 09, 2019, 04:23:33 PM
post Re: Possible use for large inductor (laminated core)
[Transformer (iron core)]
MRMILSTAR
December 09, 2019, 03:59:02 PM
post Re: SGTC MK1 - An Accomplishment in Progress
[Spark gap Tesla coils]
jturnerkc
December 09, 2019, 03:41:42 PM
post Possible use for large inductor (laminated core)
[Transformer (iron core)]
kamelryttarn
December 09, 2019, 09:43:11 AM
post Re: SGTC MK1 - An Accomplishment in Progress
[Spark gap Tesla coils]
davekni
December 09, 2019, 12:53:57 AM
post Re: CW multiplier resistor string suggestions
[Voltage Multipliers]
davekni
December 08, 2019, 09:57:51 PM
post Re: CW multiplier resistor string suggestions
[Voltage Multipliers]
MRMILSTAR
December 08, 2019, 05:28:09 PM