Teardown of a Eaton PowerWare 60kVA UPS system
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Tag: Full bridge
Kaizer DRSSTC III
Introduction
Having already built a medium and a small DRSSTC, I feel that I have the experience and want the challenge of building a large DRSSTC system.
Safety
WARNING!: Working with electricity is dangerous, all information found on my site is for educational purpose and I accept no responsibility for others actions using the information found on this site.
Read this document about safety! http://www.pupman.com/safety.htm
Considerations
I decided to design a high impedance system to run longer on times at a lower primary peak current. The average power flowing in the primary circuit will be the same as a low impedance system, but total cost of the system will be much lower. A MMC is typically much more expensive for a low impedance coil as a large capacitance is needed to work at a resonant frequency around 40 kHz. A high impedance primary coil also have a lot more surface area and will thus not require as much cooling.
When drawing power in the term of up to 10kW, power factor will become a problem.
Since this project have been running over a long period there have been many changes to the core design of the Tesla coil.
Secondary form went from 200 mm diameter to 300 mm diameter.
IGBTs went from CM300 to CM600.
MMC went from 400 nF at 12 kV made out of CDE942C capacitors to a 800 nF at 15 kV made from 5 heavy GTO snubber capacitors that is specified for over 5000 A peak currents.
Specifications
| Bridge | 2x CM600DU-24FA IGBTs in a full bridge configuration |
| Bridge supply | 4x 6000uF 350V filtering capacitors, two in series, two string in parallel for 6000uF at 700V. |
| Primary coil | Flat primary. Inner diameter 375 mm, Outer diameter 855 mm. 8 turns 10 mm copper tubing, turn spacing 20 mm tapped at 6.75 turns. |
| MMC | 0.8uF at 15kV. Made from GTO snubber capacitors. 5 in series. |
| Secondary coil | 315 mm diameter, 1500 mm long, 1800 windings, 0,75 mm enamelled copper wire. |
| Resonant frequency | Around 38 kHz. |
| Topload | 7 rings of 25 mm aluminium tubing forming a toroid. |
| Input power | 3x400VAC 16A / 11kW |
| Spark length | 3.6 meters |
Schematic
The driver is a variation of Steve Wards universal driver
Construction
24th December 2011
Work on the secondary coil began on Christmas day and lasted until the 6th January 2012 where is had its 7th layer of varnish. The first winding rig fell apart after the 4th layer of varnish and we had to build a better one.
The winding of the secondary coil was done on the first day, in about a total of three hours. The of the time was spent on varnishing. Took 16 hours for each layer to harden before a new layer could be applied.
With the frequency converter set at 70 Hz, the gear ratio and small to large diameter gear gave a winding speed of about 0,5 m/s.
29th December 2011
The primary supports was made from acrylic from the back light panel in computer monitors. It felt somewhat different to work with than new acrylic and it is our theory that the great tensions that it saw doing milling resulted in the catastrophic cracks that eventually led to the death of these supports.
On the 7th of January 2012, we gave up using these. Many hours of work was wasted here and we are now searching for a better material for the supports.
14th May 2012
When I first found these pieces of scrap PVC, my first thought was to use the already made holes to put the leads through and distance the capacitors that way. But recalling that Finn Hammer made a fish bone like skeleton for his MMC, I tried something like it and ended up using all the plastic, even the cut outs that is used for the backbone. The end terminals of 20×10 mm copper is overkill, but was what the scrapyard had at hand that day, they do however make a good connection in the sides for the capacitor strings.
The result is half of the MMC is completed. 0,2uF at 12kV. The completed MMC will be 0,4uF at 12kV.
Upgraded: This MMC will not be used, MMC is upgraded to heavy GTO snubber capacitors, scroll down for further information. This MMC will be used in a smaller Tesla coil.
17th and 18th May 2012
New primary supports was made from scrap PVC, I found some good pieces of 20 mm thick PVC to use for these.
The enclosure have been put together with wheel mounted, the primary platform is raised from the enclosure to allow for taking the complete Tesla coil apart, make connections of cables and possible water cooling easier and to gain distance to metal objects in respect to the primary coil.
The enclosure and primary platform is entirely put together with only glue and wooden nails, nearest metal in the current construction is the wheels at the bottom.
6th October 2012
Copper bus bars for the bridge and spacers for capacitor mounting machined and milled. 260 mm² copper bars are used for the DC connection with the capacitors.
20th October 2012
Material for topload toroid construction was bought cheap from the scrap yard. 7 large rings of 25 mm diameter coaxial antenna cable, aluminium shield with PE foam filling and copper tubing core.
Started construction of full bridge
IGBTs mounted on heat sink, support for capacitors constructed and capacitors mounted on IGBTs. Construction of 3 phase rectifier bridge on heat sink and preparing mounting on the bridge supports.
3rd November 2012
Finished installation of wheels on the enclosure and secondary coil was sawn over in both ends to get the right secondary tube length.
10th November 2012
Winding of the two GDTs, etching of gate PCBs and soldering of the gate PCBs and the GDTs.
Mounted 3 phase bridge rectifier, DC cables, snubber capacitors and TVS strings.
24th December 2012
Installation of fan in the enclosure, installation of bridge module in the enclosure and finding a solution to keep the GTO snubber capacitors in place.
29th December 2012
Driver PCB almost completely populated, only a few components missing that are currently in the mail.
Winding of the two current transformers for feedback for frequency tracking and over current protection.
All the bus-bar work have been done, in 30×10 mm copper and brass.
The new MMC consists of five 4 uF capacitors at 3 kVDC in series for a 0,8 uF MMC at 15 kVDC, here it is installed with the bridge.
1st May 2013
Bench test of driver was carried out. This is Steve Wards universal driver 2.1 converted to single sided board for through hole components only. Still some bugs and misroutings that was worked out during the test. The pulse width limiting network was bridged over as it caused some oscillations that made the driver turn the output on despite no input from the interrupter.
21st August 2013
The primary lead and tap is constructed from three pieces of 35 mm² cable connected to a heavy distribution net clamp through home made cable lugs made from 10 mm copper tubing, all soldered together using a gas camping stove.
28th August 2013
Video of the driver behaving very odd. Very glitchy switching can occur but it can also run fine. As it can be heard in the video this is not a switching sound you want to hear in a feedback regulated circuit that should be stable. 225VDC on the bus and switching 400A in the primary circuit.
Steve Ward found out that the problem is residual charge in the tank capacitor in the primary circuit that, depending on it being positive or negative, can influence on the driver and give it a bad start that can last for several cycles before it gets back on track.
30th August 2013
At first I thought that the problem was to be found on the driver board and thus have tried several improvements to limit the amount of noise that could be inflicted on the driver from the switching of huge currents. 10uF Tantalum capacitors was added close to the 74HC08 AND gate IC and the MAX913 comparator IC in the feedback circuit. Ferrite beads was added to the positive and negative rails for the same ICs. Pull-up resistors was added to the outputs from the MAX913 comparator IC.
None of these improvements helped in regard to the glitches in the switching.
The solution to this problem is adding a large power resistor across the output of the inverter to burn off this small charge between bursts. A resistor in the range of 10K Ohm and a suitable wattage according to inverter output voltage is needed, normally a bleeder resistor for a capacitor would be placed directly across the capacitor terminals, but we would then need a high voltage resistor that can withstand the tens of kV that the tank capacitor sees.
This video shows a static load test with 225VDC on the bus and primary circuit switching 1000A.
20th April 2014
I installed a bleeder resistor across the inverter output to take care of the residual capacitor charge as described above. The resistor is made from three 2KΩ 75W resistors in series for a 6KΩ resistor.
DC bus voltage on multimeter to the left. Yellow trace on oscilloscope is primary current, blue trace is inverter output voltage.
The load in place instead of the secondary coil is a metal container with water in it, primary coil got hand warm from a total of 4-5 minutes run time at 1500W input power, IGBT and MMC stayed cold.
This test is limited by my mains supply available, it is only 230VAC at 6 Ampere.
In the first clip the primary current peaks at 1440 Ampere at 300 uS on time at 120BPS. 320 VDC on the bus and load on mains varies from 4 to 6 Ampere at 250VAC.
In the second clip a low 4BPS gives a peak current of 1640 Ampere at 300 uS on time. DC bus voltage is 370VDC.
12th July 2015
We built a quick solution for a motorized tubing roller, the coaxial antenna cable outer aluminium shell is very soft and can be bent easily with a moderate force. A few pictures of how it looked when picked up at the scrap yard.
After the first run all the circles are almost in a good enough shape to mount on the arms of the topload skeleton. Only a few of the rings was run through twice to get them round enough.
The rings are mounted with rivets from inside of the arm. Unfortunately the thin walled aluminium shell of the cable was not strong enough to resist a bit of handling and came loose at a few points. We had to use cable ties to secure all of the tubes at each point, by making a cross it does not look THAT terrible if a better solution is not found.
The ends of the secondary wire was secured at the bottom earth connection and to the topload insert mount. A nylon plug in the bottom is used to secure the secondary coil to the base of the primary coil with a simple knock in split for easy dis- / assembly.
The massive and towering look of the topload placed on top of the secondary coil. The driver and power electronics box and elevated primary platform will raise the coil even further so it will stand a total of 2,8 meters.
31st March 2016
The first time it was possible for us to make a test on full power from a 3×400 VAC / 16 A supply. To initially see if things would run smooth, a 3 phase 6 A variac stack was used to ramp up the voltage.
To our big surprise we were able to produce up to 3.6 meter sparks from a supply that we thought would be inferior to the coils power demands. We did however not trip any breakers or even have the OCD at 1500 A blink at all.
The reason why the OCD never tripped once when set for a modest 1500 A is because of the built in over-current protection in the IGBT bricks, a small RTC element shuts the gate off at 1200 A. I will have to open up the IGBT modules and cut the wires going from the RTC element to the gate in order to run these at much higher peak currents.
These ground strikes was achieved with a settting around 350 BPS at 200 uS on-time.
With the raised breakout point the total height of the coil is now up at 3 meters.
10th September 2016
After cutting out the bonding wires to the RTC circuit of the CM600DU-24FA IGBT bricks, which we thought could be one of the reasons that we were not able to trip the 1500 A OCD setting, we had a short test run to witness performance. I made a video with more details of the real-time current control removal.
While it might have limited the operation a little bit, it was nowhere near hindering performance, this coil is just so high impedance that it runs long on-times instead of high peak currents.
Fed with 3×400 VAC through a variac resulted in a 0.6 power factor. After roughly 8-10 test runs at up to 2 minutes, with peak power consumption hitting 14 kW at 500 BPS, 200uS, the total power consumption over all the tests was 0.281 kW/h, 0.331 kVAr/h and 0.438 kVA/h.
First video shows the coil running 120-500 BPS at somewhere around 200 uS on-time. Peak power consumption from the 3×400 VAC supply was around 14 kW. Sparks are 3 meters to ground and somewhat shorter to the ladder.
Second and third video show tests with a static load, peaking at about 10-14 kW depending on MIDI or interrupter is used.
and
Conclusion
With a time span of 4 years from first winding started rolling onto the secondary form till we have 3.5 meter sparks flying from it, it can easily be concluded that a project like this takes a long while to complete when having a normal family life on the side.
Initial results are highly satisfying as there are clearly room for improvement and still a lot of head room in power consumption.
Demonstration
31st March 2016
Video from the first full power test, but not yet properly fine tuned for maximum spark length.
Video of the first MIDI played on the coil. Portal – Still Alive was a appropriate choice for its lyrics.
“This was a triumph! I’m making a note here: Huge success!
It’s hard to overstate my satisfaction.”
Kaizer DRSSTC I
Published on: Nov 9, 2010. Updated on: Mar 17, 2020
Introduction
Building a Dual Resonant Solid State Tesla Coil have been the ultimate goal since I started experimenting with high voltage apparatuses 3 years ago.
A DRSSTC is the modern day topology of driving a Tesla coils taking advantage of IGBT technology, pulse rated capacitors and a very low inductance primary circuit layout.
Safety
WARNING!: Working with electricity is dangerous, all information found on my site is for educational purpose and I accept no responsibility for others actions using the information found on this site.
Read this document about safety! http://www.pupman.com/safety.htm
Considerations
Due to IGBT technology the resonant frequency have to be lower than what is normally acceptable in a regular solid state Tesla coil. The higher frequency the more demanding is the current delivering ability of the gate driving circuit and switching losses will stress the bridge more than good is.
Specifications
| Bridge | 4x IXGN60N60C2D1 IGBTs in a full bridge configuration |
| Bridge supply | 0 – 260VAC through a variac, 2x 35A rectifier bridges in parallel and 2x BHC 3300 uF 450 V filtering capacitors in parallel. (each: ESR 39mOhm@100Hz, Z 27 mOhm @ 10 kHz and 53 A Iripple @ 70 KHz @ 50 degrees Celcius) |
| Primary coil | 320 mm diameter, 10 mm diameter copper tubing ~ 28.27 mm², 9 windings. Tapped at 5.4 turns. |
| MMC | 6 strings in parallel of 2 in series Cornell Dubilier (CDE) 942C20P15K-F capacitors for 0.45 uF at 4000 VDC rating and 81 A Irms. |
| Secondary coil | 160 mm diameter, 605 mm long, 2200 windings, 0.25 mm enameled copper wire. |
| Resonant frequency | Around 65 – 70 kHz. |
| Topload | 127 x 620 mm aluminum flex tube with aluminium tape toroid. |
| Input power | 130 BPS, 9 cycles, 500 A limiter: 2500 W at 250 VAC at 10 A. |
| Spark length | Up to 1500 mm long sparks. |
Schematic
Bridge section
Driver section
Same as Steve Wards universal driver version 1.3. Just made on single sided PCB without SMD components.
The output MOSFETs are IRF540 and IRF9540.
Construction
20th March 2009
Bought 30x IXGN60N60C2D1 from Digikey USA, import taxes etc. almost killed me.
7th April 2009
Bought 60x 942C20P15K-F capacitors through Dr.spark, again hello import taxes.
15th May 2009
Bought heat sinks cheap from Germany.
19th May 2009
Started converting Wards latest DRSSTC driver to single sided board.
23rd July 2009
Started 3D designing the full bridge.
It is bulky, on 2 heat sinks with capacitors between them, its too big and needs to be overhauled.
23rd August 2009
Redesigned the full bridge
The two IGBTs in the middle are turned 180 degrees to have the supply at one side of the heat sink and output on the other, it got compact, neat and only one overlap with bus-bar, I am very happy with this design.
24th August 2009
Made a spreadsheet to ease experimenting with different DRSSTC settings, this was also a try to collect some of the different theory and put it side by side, it might not all make sense.
27th August 2009
Bought 50 meter of 10 mm copper tubing, two drain pipes 160 mm diameter x 1000 mm and a 200 mm x 300 mm copper sheet that is 1.5 mm thick. The copper tubing is for the primary coil, drain pipes for the secondary coil and the copper sheet is for busbar between IGBTs and capacitors.
Here is the collection of parts for the DRSSTC.
8th September 2009
Finished converting Wards latest drsstc driver to single sided board
12nd September 2009
Finished assembling the single side board ward DRSSTC driver. This layout has a few errors like mirrored connections for the optical input which you can see is turned 180 degrees and faces inwards on the board, there is too little space for some of the capacitors and the 78xx voltage regulators does not have room for a heat sink and they risk heating up the nearby electrolytic capacitors.
16th September 2009
Etched, assembled, tested and housed interrupter with burst mode.
19th September 2009
Cut out busbar from copper sheet and assembled the bridge with IGBTs, heat sink, capacitors and homemade 8 mm brass spacers are used. Wires to the primary are 16 mm² stranded 90 degree Celsius machine tool wire.
25th September 2009
Found a aluminium box and transformer for the driver, wound a GDT and started preparing decoupling capacitors, TVS and Zener diodes for the bridge.
With all the wonderful theory about GDTs in the wiki, it would be a shame not to check it out instead of just going for a high permeability core with 10 turns on CAT5 cable. So here goes
Its a Epcos ring core, material: N30, good up to 5 MHz, Aemm²: 95.89, AL: 5750 nH
Inductance with 10 turns: L = AL * N^2 = 5750 * 10^2 = 575 uH
Peak current: Ipeak = (Vin * t * D) / Lmag = (24 * (70000/1000000) * 0.5) / (575 * 10^-6) = 1460 mA
Irms = Ipeak * 0.577 = 842 mA
Minimum number of turns needed to avoid saturation
t, 50% duty cycle = (1 / 70000) / 2 = 7.3*10^-6
Nmin = ( V x t ) / ( B x Ae ) = (12 * (7.3*10^-6)) / (0.2 * (95.89*10^-6)) = 4.6 turns
Current needed to drive a single 60N60 IGBT gate
I = Qc / t = (146*10^-9) / (1/70000) = 10.22 mA, including magnetizing current, double this figure.
So it all seems to have overhead enough to drive a full bridge.
3rd October 2009
Started on construction of the MMC.
10th October 2009
Made the round platform plates for the coil to be built on, they were cut out from 19 mm MDF wood plates with a modified router, also shown in the picture, very neat for making circular cuts.
11th October 2009
Finished MMC construction, features a 80 mm fan that delivers 30 cubicmeters/hour of air.
5th November 2009
Debugged PCB design of the driver Forum thread link
Tested driver and interrupter on a small DRSSTC I put together just for testing purpose, blew the half bridge when I ran it in CW without feedback, I guess there is no way I could have treated that poor little coil any worse…
12th December 2009
Made primary form and winded the primary coil onto it, with a strike rail and mounted on the upper platform, took me 1½ hours just to wind the coil through the holes and also spend quite some WD40. I do not recommend anyone to make the same primary coil supports, trying to get the coil “screwed” in through all the holes, the supports only being mounted in on end made them lock up all the time and after a few turns had been put on, it was only possible to move the coil 1-2 cm at a time, before having to move it that much on each turn and then start all over.
The coil is a true helical coil with 4 mm steps between the supports.
27th March 2010
It is far from satisfying to wind half a secondary to learn that you have used a ruler with 2 scales and you started with a 100 mm offset in the wrong direction…
The second try on the secondary was winded in 2 hours using my new coil winder rig, its 2200 turns of 0.25 mm enamelled wire on a 160 mm diameter pipe, winding length is 605 mm, its currently hardening its second layer of varnish till I get time to visit my parents again as its staying at their garage while getting varnished.
Top end termination is a banana plug in a home made brass nut, fixed to the plexi top with nylon screws so no metal is inside the secondary coil. The bottom termination is made from a home made brass nut soldered to a strip of 1 mm copper where the secondary wire is also soldered to.
2nd August 2010
I made a brass fitting piece for holding the current transformers as the cable shoes on the wire to the primary coil were too wide to go through the CTs. There is also a nylon bobbin between the brass and the CTs to provide extra insulation and protection against mechanical wear of the thin CAT5 wire insulation.
7th August 2010
Today I assembled some of the parts on the platform, its beginning to look like a DRSSTC! Also I painted it black some weeks ago!
9th September 2010
The top-load is done, measuring 130 x 620 mm, made from aluminium ducting on a wooden form, smoothed with filler for metal and covered in aluminium tape.
The connection to the secondary coil is made with a small rounded brass piece where a regular 6 mm banana jack is screwed into, this fits directly down into its female counter part on top of the secondary coil.
17th October 2010
Final testing of driver features, got a 555 acting as a feedback at 70 kHz while my signal generator is used to simulate over current input signal.
FIRST LIGHT! YIPPEE! See further down for demonstration video.
22nd October 2010
The layout of the electronics have reached their final state
3rd November 2010
I made a new interrupter with selectable BPS, either from 3 to 15 or 130 to 500. On time from 1 to 20 cycles and burst mode.
5th November 2010
First test run, the coil is still slightly out of tune. Achieving sparks around 120 centimetres.
After a few adjustments of no more than 5 centimeters on the primary coil at a time, what seems to be the sweet spot have been found. Sparks will now fly out at 145 centimeters.
A run was made with the breakout point going straight up, beautiful sparks and some very heavy sparks directly between top-load and earth rail.
A final adjustment of the primary tap would be the end of the days testing, the variacs 10 A fuse blew after the coil had been running for 5 minutes.
150 centimeter long sparks! Running from 250 VAC in at 10 A, 9 cycles ~200-225 uS on-time, 500 A limiter.
Conclusion
A years work have come to an end with a result I am very satisfied with and still I did not make a spark longer than my own height, which was one of my goals.
The metal filler used for the top-load to smooth the surface is way too hard to sand down without damaging the aluminium tubing underneath. I will use ordinary wall filler if I use this method for top-load construction again.
A full bridge of IXGN60N60C2D1 SOT-227 package IGBTs is slightly too small for a Tesla coil this size, I will upgrade with some heavier silicon, preferably a Powerex CM300-24H brick.
Demonstration
17th October 2010: First light
5th November 2010: Stress test
5th November 2010: High BPS ground strikes
Kaizer SSTC II
Introduction
This is a modified version of the first SSTC I built, the Kaizer SSTC I. It uses the same secondary, topload and driver board. New things is a full bridge of IRFP460 MOSFETs, audio modulation, shielded drivers and a new casing.
Safety
WARNING!: Working with electricity is dangerous, all information found on my site is for educational purpose and I accept no responsibility for others actions using the information found on this site.
Read this document about safety! http://www.pupman.com/safety.htm
Considerations
In the quest for longer sparks I decided to use a full bridge to take advantage of the full voltage on the bridge.
The MOSFETs will be mounted on top of a heat sink so its easy to change them by only removing the secondary platform and solder them off.
The drivers will be shielded in order to avoid the EM field generated by the Tesla coil itself to inject noise into the drivers.
Specifications
| Bridge | 4x IRFP460 MOSFETs in a full bridge configuration. |
| Bridge supply | 0 – 260 VAC from a variac, 8 A rectifier bridge and 1500 uF smoothing capacitor.0 – 365 VDC on the bridge. |
| Primary coil | 115 mm diameter, 1.78 mm diameter isolated copper wire, 8 windings. |
| Secondary coil | 110 mm diameter, 275 mm long, 1000 windings, 0.25 mm enamelled copper wire. |
| Resonant frequency | Self tuning at around 250 kHz. |
| Topload | 100 mm small diameter, 240 mm large diameter, toroid. |
| Input power | Continues Wave mode: 2000 – 4000 Watt at 200 VAC input voltage. Interrupted mode: 100 – 2000 Watt at 260 VAC input voltage. Audio modulated mode: 300 – 400 Watt at 150 VAC input voltage. |
| Spark length | up to 475 mm long sparks. |
Schematic
The UCC3732X are MOSFET driver ICs, one non-inverted output and the other inverted, in order to get a push-pull drive of the gate drive transformer. A gate driver IC can deliver the high peak currents needed to drive MOSFETs efficiently.
The 74HC14 is a inverting hex schmitt trigger, it is used to get a proper solid 0-5V square wave signal from signals that are not perfectly square, the antenna feedback can vary a lot in waveform and amplitude, the 74HC14 converts this to a clean drive signal for the MOSFET drivers.
All unused input pins of a 74HC14 has to be tied to ground, floating inputs and a noisy environment is a recipe for trouble. The noise can couple between the gates internally and make the whole IC not work properly.
The music modulator works by amplifying the audio signal in the LM741 and at the BC547 transistors. The 555 timer ensures that the signal length of the generated square wave is much shorter than the audio signal, in order to not have too long on-time and thus damage the MOSFETs / IGBTs from over-current.
Construction
15th March 2009
I took apart a 19″ LCD monitor and a 24″ CRT monitor, from these respective computer parts I salvaged a good piece of acrylic from the LCD monitor and a fairly sized heat sink from the CRT. I cut the acrylic in half for a 2 level platform and the heat sink was cut in 4, its necessary to isolate the MOSFETs from each other as their housing is also a conductor.
19th March 2009
Driver electronics and audio modulator are installed under a metal casing from the CRT monitor to shield it from the heavy EM field surrounding the Tesla coil, this is to avoid problems with the driver being interrupted by its own EM field.
The bridge is made out of four IRFP460 MOSFETs, four MUR1560 diodes, four 5R resistors. The power supply is a 8 A rectifier bridge with a BHC 1500 uF/450 V smoothing capacitor, a 27K 7W bleeder resistor is added in the final build.
The audio in jack was later removed due to it making a short through its metal housing to the ground rail, I had overlooked that the audio in negative was not common with the ground rail, but there is a capacitor inbetween.
The secondary is held in place by a crate for ventilation on houses, its an easy and quick way of taking the coil apart for transport or storage, and it holds the secondary firm and tight.
A acrylic tube is added to support the antenna, in this way it is possible to adjust the coupling of the antenna to the secondary simply by pulling the wire.
The new shielding of the audio in signal is made from a piece of shielding from a industrial cable pulled over it and grounded.
The secondary with terminations. 110 mm diameter, 275 mm long, 1000 windings, 0.25 mm enamelled copper wire.
The complete coil looks, except maybe the electrical tape used to hold the topload together.
Sparks
Interrupted mode
At 250 VAC input voltage, 350 VDC on the bridge, it was possible to reach 475 mm long sparks, in interrupted mode, to a grounded object.
More pictures of sparks in interrupted mode, it is running at about 4 – 5 BPS.
3rd May 2009
Continues Wave mode
At 200 VAC input voltage, 280 VDC on the bridge and a power consumption around 10 A, peaking at 20 A, the coil was drawing somewhere in between 2000 to 4000 Watt. This resulted in very hot, thick white arcs punishing the dead iPod shuffle which remarkably left the player relatively unharmed considered what had just taken place.
These flame like sparks are 250 mm in length.
18th August 2009
I constructed a new topload from two cheap aluminium frying pans from Ikea. With handles cut off and screw from it grinded away it had a smooth surface and was fixed with a long screw through both of them.
6th September 2009
During a run of CW at full input voltage, the full bridge blew apart completely, with a loud bang.
Audio modulation
I use a audio modulator made by the user Reaching (Martin Ebbefeld) from 4hv.org.
For sound input I use a cheap children’s keyboard from a toy store, its far from perfect for the job, especially because its waveform is highly distorted and its not clean tones but seems to involve a lot of modulation inside it to simulate different instruments. But its cheap and expendable.
Watch the film and look at the schematics for more about the audio modulation.
Conclusion
Upgrading the SSTC I with a full bridge was a absolute must. It is small changes compared to the better performance and the driver have no problems at all driving four MOSFETs instead of just two.
Getting sparks at 475 mm length in interrupted mode and white power arcs at 250 mm length is truly satisfying for this little coil, the secondary winding itself is only 275 mm in height in comparison.
Enjoy the demonstration.
Demonstration
Demonstration of different modes.
New topload, running in interrupted mode.
New topload, running in CW mode.
New topload, running in interrupted mode and closeup of sparks.