openinverter forum

For a long time this project has been rotting in my storage boxes and I thought I should just introduce it here and somebody might benefit.

So back in 2016 OEM power stages weren't really that abundant and I found the classic combination of IGBT module+snubber caps+bus caps+gate drivers too bulky and expensive.

So over many iterations I designed a two layer 70um board that would hold 4 TO-247 IGBTs and their gate drivers. Gate drive power and isolation was on a separate isolator board that plugged into mainboard. It featured a 6-channel digital isolator, a 5V and a 15V isolated DC-DC converter and an analog isolator for bus voltage sensing.

The high side gate drivers used the boot strap technique that just takes enough power to run with it by a 1uF film cap. Thereby the classical separate power supplies were made redundant.

Each board had its own bus cap of 100uF placed as close to the IGBTs as possible

The DC bus was put together with threaded rods surrounded by aluminium tubes. The phase terminals were brought out via 90° profiles which was also used to hold the module in place via isolated studs. They also ran past a Melexis chip for current sensing. The profiles could also be extended to connect a number of modules in parallel.

I actually tested this in Polo and drove around a bit but the problem was heat dissipation. I just never found a good way to electrically isolate the IGBTs from the cooling block while not thermally isolating it. With that problem solved this design would actually work.

I also sold a few boards for building an offgrid inverter, I think 10 kW peak. They only populated 2 of the 4 IGBTs per board and mounted them on a water cooled chill plate. They solved the isolation problem with TWO sheets of isolation foil.

If there is any interest I will collect the various design files and put them on github.

In the words of a wise sage...

"Make cool shit, put it on the internet."

Never know who might appreciate it.

In terms of having more projects than you have time to do them, it's interesting, but judge for yourself if it'd be more fun than whatever else you'd do with your time.

I'd pursue this if the OEM option wasn't around, or if I needed a power supply otherwise.

Greetings, the design seems interesting, I now came to the conclusion that the inverter can be broken into cells and scale them already for any current. IGBTs in my opinion are very hot, and why not replace them with mosfet transistors?

Yes exactly, it is well scalable.
The design also works with mosfets and they do indeed run cooler under partial load. Downside is they are more sensitive and they ring more. I needed RC snubber on the low side drain top keep ringing in check.

I agree with yaroslav, this is super interesting to me. The scalability especially.
Thank you for sharing, and look forward to seeing more.

Here are some files: https://github.com/jsphuebner/inverter- ... ase-module

You need a program called "FreePCB" to open the fpc design file.