Hello everyone,
We are e-gnition Hamburg, a Formula Student Team made up of over 100 Students, passionate about designing and building the fastest car possible.
However, before you can go fast, you must first be safe. And with a 600V tractive system, one of the most important safety functions is ensuring that the inverter DC Link capacitors get safely discharged every time the tractive system gets disabled. Otherwise, the residual voltage would present a potentially lethal danger to anyone working on the vehicle.
As our Inverters have a quite large capacitance, and given the safety importance of a timely discharge, we chose to go with a substantially overspecced PTC array. The PTCs protect themselves from overheating, and the large array ensures discharge times don’t increase substantially even after repeated use.
One area where we did save substantial area and weight vs the prior design was with the switching element: a bulky mechanical NC Relay was replaced with a photocoupler and power Mosfet.
Overall, this design worked very well and reliably, and we’re thankful to Aisler for supplying great PCBs for it!