Eric Tischer Shows Off the Homemade 90kW Inverter Inside His Converted VW Passat EV
Having purchased a broken-down Passat for $1,800, Tischer converted it to an electric vehicle — including building a 90kW inverter.
Electric vehicle enthusiast Eric Tischer has published a video demonstrating a key step in his conversion of an internal combustion engine Volkswagen Passat to electric operation: the creation of a homebuilt 90kW EV drive inverter.
Tischer's journey into after-market electric vehicle conversion started with the acquisition of a 2001 Volkswagen Passat, purchased for just $1,800 on Craigslist owing to a seized cam. Tischer then picked up a Siemens 42 horsepower liquid-cooled three-phase motor, and set about putting one inside the other.
A year later, and the project had set Tischer back around $27,4000 — including the $1,800 for the Passat plus $1,638 for the motor, $12,334 in battery cells, $1,163 for the parts required for the inverter, and $2,450 for a battery charger, plus $1,450 in paintwork. Since then, Tischer has been improving the vehicle in stages — including the addition of an adapter to allow the Volkswagen tachometer to operate with the new engine, courtesy of an Arduino microcontroller and some clever tinkering.
Tischer's work is impressive enough just for the conversion of an ICE vehicle into an EV, but it's the amount of effort put in to designing solutions to problems rather than buying off-the-shelf parts that really impresses. In his recently-published update video, Tischer walks through the design and construction of the 90kW inverter that drives the Siemens electric motor.
"That grey box is an off-the-shelf one horsepower VFD [variable frequency drive], and I'm using that hardware/software platform as a firing circuit for a much larger IGBT [insulated gate bipolar transistor] stack," Tischer explains. "I wanted to keep the look of the VFD the same as it looks in the manual, so it would appear a little more legitimate when I had the car inspected.
"So everything in the black box below is what I built. Those two yellow cables are the battery leads, 300A at 330V DC, and the orange cables are the three-phase power cables going to the motor, and I have water cooling so those two black lines you see there are the coolant lines that go to the chill plate that keeps the IGBTs cool."
The full video goes into considerable detail on the inverter's design and operation, while more information can also be found on Tischer's ongoing project log.
