Update by Onno
Hello, it’s me. I was wondering if after all these weeks you would like to hear from me-, wait that is a song isn’t it. Sorry anyway Onno here to give you all another blog post.
So last time I focused on my experience from working on the formula student team. Today I will be talking more about the actual part I am designing: the AMS master. Don’t know what that is? Good, because I am about to tell you. The AMS (Accumulator Management System) is the electrical system that makes sure that the accumulator stays healthy and happy and isolates it from the rest of the car when required. If the AMS was not present, formula student would probably experience a lot more explosions and electrocutions. However, I am told that this is in fact a bad thing, so we need it anyway.
The AMS itself is a multi-board system, meaning that the system is so complicated and/or so big that it would be very impractical to put the whole system on one board. The system we use utilizes a so-called master-slave structure, meaning that there is one ‘brain’ PCB that controls the less complicated ‘slave’ PCB’s. As said before the master PCB is my design this year. Besides controlling the slaves the master also has a lot of other functions, that are required for safe use of the accumulator. A big one is that it must control the relays that isolate the batteries from the outside of the accumulator when the car is not turned on or when the accumulator is taken out for maintenance. As you may know a relay is essentially an electromagnet that pushes two contacts together when current is flowing through the coil. In the first year of the electrical engineering bachelor you learn that a coil in a circuit eventually becomes like a short circuit. For those unfamiliar with electronics, short circuit => high current => high power consumption. Since we have a limited amount of charge in our battery, this is not exactly something we liked. Our solution is to essentially switch the voltage over the relay on and of so fast that the average voltage is a lot lower, while still enough to keep the relay closed. This resulted in the system drawing one tenth of the power that it did before, so it works damn perfect.
I hope you enjoyed this little insight into our engineering process. For more blog posts you can look at what my colleagues have written or wait until I am forced to write another one of these.
See you next time!