VVVF Inverter
Building my own variable voltage variable frequency (vvvf) inverter, just like the ones that power electric trains!
May 24th: Did research on how to build a VVVF inverter, and started with basic schematic
Recently, I stumbled upon a few youtube videos that made me really interested in the sounds that electric trains make. I discovered that many people made their own traction inverters to recreate these sounds, and I figured I wanted to try as well. Originally, I started this project a few months ago, but I hadn't made much progress.
I looked for ways I could aquire the needed 3 phase motor for cheap. Thinking of perhaps buying a cheap washing machine off Facebook marketplace.
Also looked at gate drivers, thought that the TI UCC21520ADW would be a good gate driver IC due to its various protections and being a complete half-bridge driver which makes it a lot simpler for me.
From this, I drew up a quick schematic using the above IC.
Total time spent: 3h
May 25th: Decided on a MOSFET, added current monitoring, brake chopper, and Raspberry Pi Pico MCU
So today I decided to use MOSFETS instead of IGBTs because they are a lot simpler. I chose IPDD60R037CM8XTMA1 MOSFETs because they were rated for the high voltage and they had a good exposed thermal pad that I could easily attack to a large heatsink.
I also added a hall-effect current sensor to one of the phases, and a Raspberry Pi Pico MCU. I drew up a good amount of schematic today.
Some parts I selected
Total time spent: 5h
May 26th: Looked at options for voltage monitoring, and started basic layout
It is pretty important for my inverter to know the voltage of the DC bus at all times, so I looked into what options I had to measure that voltage. I think I'll use a voltage divider with either the RP2040's inbuilt ADC, or an isolated ADC.
I also started laying out the MOSFETs and the gate drivers on the board. This is my first time working with a 4 layer board, which I mainly chose to do to keep things compact, and so I could have an uninterrupted ground plane and to have a larger thermal mass. I intentionally put the MOSFETs on the back because I was going to mount this board to a heatsink.
Total time spent: 5h
May 27th: A little layout work
Today I worked a bit more on the layout. Trying to keep gate drivers on the top side, and the MOSFETs on the bottom. Need to consider how I'll connect the power wires, through screw terminals or whatever.
Total time spent: 1.5h