The first full power light sparks have been flown and the results was more than satisfying!
The first full power light sparks have been flown and the results was more than satisfying!
I have finished the first steps that included mapping the circuit boards, getting the unit to run and test it with a few simple test and finding out which input and outputs the module have.
Schematics and further experiments with f.ex. scintillation crystals are set for the near future and will be announced when they are added.
I had the chance to take this Eaton Powerware 30 kVA / 27 kW (9355-30-N-7-2x9Ah) uninterrupted power supply apart to look for parts worth salvaging for future reuse in other projects.
Looking up the type on the Eaton website we learn that it is a UPS using double conversion topology that provides isolation from all input anomalies on the output side. Double conversion means that there is AC to DC converter that is connected to the battery pack and the DC to AC converter, a total of two power conversions.
The use of 432 VDC battery pack makes the whole construction smaller and more light weight, the higher voltage avoids the use of step-down or step-up transformers, large switches to handle high current at low voltages but it also adds another danger element as a high voltage battery is not as easy to service and failures can be more catastrophic. This design is called transformer free design, but apparently they do not count in the large choke transformers in the inverters.
The following schematic shows the block diagram of a double conversion UPS.
Viewed from the side we can see the four compartments for batteries, with this rather small battery stack this unit is only able to keep up for 7 minutes at its rated load of 27 kW.
In the close up picture of the circuit board, we can basically see the complete controls of this unit. Out to the far right is the CPU board, top of it connects out to the inverter modules and at the bottom its outputs for relays / switch timing on the large main circuit board.
All wiring was unfortunately cut off when I got to the unit, but looking at the amount of cable shoes still sitting in the bolts, I can safely assume that the PFC connects our to the left side terminals, one inverter module connects at the top terminals and at the bottom near the three black current transformers two inverter modules have been connected in parallel.
Four 230 VAC 15 Watt fans ensure the cooling of the IGBT switches and chokes.
Below the fans we can see the three identical inverter modules, they were easily pulled out when the copper busbars was disconnected. The copper busbars is the battery rails between the the input conversion and output conversion.
At the following pictures of one of the modules it can be seen that they are very generic, not meant for a very specific task, but is merely a dumb inverter module that is connected to a control bus for input signals.
The IGBT modules Semikron Skiip 25AC125V10 are ultra fast NPT IGBTs, rated for 1200 V and 100 A pulsed, combined switching time is a mere 600 ns. Each of the IGBT switches has its own output choke.
The circuit board contains a few ICs at the data bus connector, three isolated power supplies for the six gate drive circuits. From the number of drive circuits and tracks to the IGBT gates it is clear that these 3 phased bridge IGBTs are driven with the three upper dies in parallel as the same for the 3 lower dies of the brick. The four electrolytic capacitors are connected two in series and two of those strings in parallel for 3000 uF at 900 VDC rating.
The PFC circuit board has three SKKT 122/16E thyristor half-bridge modules, rated at 1700 V and 130 A. In the lower left of the close up picture we can see PFC controls which consists of normal logic ICs and a PIC processor that is connected to the CPU on the main circuit board through the RJ22 connector.
On the upper left side of the circuit board is the various house keeping power supplies for all of the control circuitry and networking interfaces of the UPS unit.
A very modular design that was easy to take apart, but unfortunately not that great on collecting useful parts. The lack of large IGBT bricks and capacitors is the worst let down of this unit.
I picked up two of there 5.5kW frequency inverters from a scrap yard. Both assumed to be thrown out due to malfunction. I took them home to dismantle them for parts to use in other projects.
First we have the front and two stickers, one with specifications and the other with end of life information. These are fairly new units from 2013.
Removing the front metal plate and display unit, in the upper left corner we can see the house keeping power supply part of the main board, just below we can see the input filter PCB and upper right corner in the beige plastic we have connector and terminals for input/output control signals. A close-up of the input filter show that we have a varistor between phases and two 1 uF capacitors in parallel for each phase to ground.
The main board has the low voltage power supply for logic and gate drive in upper left corner. All control is done in the upper right corner, at first is the 3 phase PFC with output wires to the 3 SCRs for the input rectification, to the far right is brake chopper part. Below that there is resistor chains used for some kind of voltage feedback from the brake chopper and at the bottom of the board is the three gate drivers with each their connector with coloured cables red, yellow and blue that goes to the gates of the main IGBT brick.
With the main control board removed we can see the three phases from input terminals that go to connect at the SCRs and their gate drive wires sticking out at the top. Below is the brake chopper with wires going back for voltage feedback. The beige box with the red wires looping through three times is the current transformer used for monitoring of the inverter output current to the motor terminals.
All capacitors needed for filtering and snubbering around the SCRs and brake chopper is mounted on the PCB that is turned upside down here. The SCRs are Semikron SKKH 57 / 22E H4, rated for 2200 Volt at 57 Ampere.
With all boards and wires out of place we can see the main power board. In the upper left corner is four connections to a choke that is placed underneath with the heat sink. Just below we can see the + and – marking on the PCB where the two electrolytic filter capacitors are mounted, also underneath with the heat sink. The choke and capacitors are down there to be cooled by the same air flow used for cooling of the heat sink.
The main IGBT module is a Semikron FZ100R17KE3 rated for 1700 Volt at a mere 200 Ampere repetitive pulsed current. The brake chopper is a Semikron SKM145GAL176D single IGBT rated for 1700 Volt at 100 Ampere.
The two electrolytic capacitors rated for 1100 uF at 550 VDC is connected in series to handle the DC bus voltage if the frequency inverter is supplied from 3x690VAC. Two 80 mm large 7.2 Watt Sunon fans run at 4900 RPM to move 75 CFM or 120 m3/h.
The 1500 uH choke is rated for 40 Ampere RMS or 30kW power. The long slim heat sink have all the SCR and IGBT modules mounted on it and run along side the choke and filter capacitors as mentioned earlier.
As an extra bonus in this teardown, I have taken some high resolution pictures of the FZ100R17KE3 IGBT dies, one from the IGBT that seemed fine and one that was exploded. This makes for a good comparison of the magnetic forces at play in the event of a short circuit inside the IGBT goo. The long and flat flower like black paths in the goo is actually the gasses from the exploded IGBT die, the gas expands out into the goo that blows a bubble and collapses as soon as the pressure is gone. Leaving a black trail of burned silicon, metal and goo. These are 3MB pictures.
Last two are die close-up photos, I tried to align them to show the exact same area of a good and a exploded IGBT. These are 9MB pictures.
I added a new online calculator that will help you do the calculations for IGBT gate drive. It is useful for continues wave operation and has a optional input and output for use with Tesla coils like DRSSTCs.
First light test and unfortunately under horrible conditions. We finished all the cabling and other small parts, bits and missing stuff in a days hectic work that lasted all night. So we missed the opportunity of testing in darkness.
There was no tuning performed, input was limited by a smaller 6A variac, it was broad day light, foggy and wet day, the coil was just pushed outside of the garage as no cables was long enough to get it away from the tree.
Sparks are about 60-70 cm and we killed the LED christmas light chain that was in the tree, it was unplugged before we started.
Read the whole article on this coil at: http://kaizerpowerelectronics.dk/tesla-coils/kaizer-drsstc-iii/
I would like to thank all the readers and commenters that use the information found on this site.
You are the fuel for me to add more content and hopefully I will finish some projects I have worked on in 2015 and get to write the documentation.
2015 was a year with over 200000 visits to the site and my YouTube channel soon reaches 1 million total video views.
Kind regards and happy new year
I found some old notes and a short video of a quick lash up vacuum tube tesla coil I made in a single day. I wrote the details down and drew a schematic for those interested in using small PL output tubes for similar VTTCs.
I found a little time to put together the pictures, measurements and results of a solar panel I built from broken solar cells for sale on ebay.
Not exactly a breakthrough in solar panel development, but more an eye opener on DIY solar panels, it might not always be a cheaper or better choice to build them yourself.
DRSSTC II article updated with 9 new pictures showing more details about the topload, secondary coil and construction from all sides.
DRSSTC I article updated with 2 new pictures showing secondary termination details.
SSTC III article updated with 3 new pictures showing some details about the secondary coil and primary coil.
SSTC II article updated with 7 new pictures showing some details about the secondary coil and topload.