Electrical Blog #5
Hi, I’m a second year electrical engineering student and I’ve been working as a part-time member at Forze Hydrogen Electric Racing for a while now. In this blog, I’m going to tell you something about the power distribution for the low voltage systems in the Forze VII. Examples of these systems are the waste water pump, the power steering, different cooling fans, but also less demanding equipment like the steering wheel display, the wipers or the headlights that must be powered.
PSU and PDU
Currently, I’ve been assigned to work on the PDU (Power Distribution Unit). The PDU is an important part of the car. It distributes power over different low voltage subsystems of the car. The PDU is connected to a power supply via the PSU (Power Supply Unit). The PSU converts DC voltage from the connected source to different DC voltage levels. The main source of a hydrogen electric car is of course the fuel cell, where hydrogen and oxygen are converted into water and electric energy. This is where the low voltage loads get their power from when the car is driving. However, the low voltage systems in the car must be able to start up before enabling the fuel cell. Therefore the PSU must also be able to convert supply power from an auxiliary supply and a startup battery.
The first thing that happens in the PSU is that the voltage from the supply is reduced to a fixed voltage level, this voltage must be the same, independent of the connected power supply. This voltage is then converted to a few different voltage levels with DC-DC converters. The outputs of these are connected to the PDU. Over there, the power is distributed over the loads. All low voltage loads in the car are connected to the PDU via load switches. The function of these load switches is to be able to remotely connect or disconnect the loads from the supply, to monitor the current and protect against overcurrent.
The first thing I learned when I started on this project is that you have to keep a lot of factors in mind. Not only are the components you choose not ideal, but you also need to account for your supply and load not being ideal and steady. For example, when you have an inductive load, you can’t just switch it off. In the worst case, your switch would break down, since an inductor doesn’t allow for a sudden change in current. Of course there are solutions for this relatively simple problem and for a lot of other problems, and that introduces you to a lot of concepts and techniques that are used in pcb design, that you don’t necessarily learn during the bachelor electrical engineering. This is one of the reasons that I think working in a DreamTeam is a valuable experience. It gains you a lot of insight in the practical applications of a lot of things that you learn during courses, but that you do not really get the chance to use.
– Maurice, electrical engineer at Forze