I went to the Alternative Car Expo in Santa Monica this weekend to check out some EVs and get away from home a bit.
EV in parking lot
I was assured we had arrived at the right place by the abundance of Priuses in the parking lot, a couple of EVs could be seen too.
I have been modeling some different configurations of the power stage in Solidworks.
First attempt The first attempt was an all bus bar based design that didn't come out very well. It became a little too tall for my liking and it doesn't use the available space effectively. I also modeled the capacitors the wrong size, the ones I have are a bit smaller.
The most basic form of switching DC motor controller is the DC chopper. It consists of a single silicon switch, a freewheeling diode, some capacitors for filtering out current spikes and electronics for controlling the switch.
Controller Diagram
Work on the motor is progressing slowly as I'm waiting for some parts to come in.
I've spent a lot of time lately contemplating what to do for the motor controller. The function of the motor controller is to regulate the current flowing from the batteries to the motor, based on input from the drivers lead foot.
There are a number of options for motor controllers, none of which seem very desirable to me at the moment. There's the king of motor controllers, the Zilla line made by Cafe Electric. The Zilla controllers are expensive but well worth the money, they're very reliable and dish out more power than I could possibly use. The problem is that they are back ordered for at least 6 months and there seems to be some production problems at the moment. You can read more at the Cafe Electric blog.
Quite some time ago I designed a quick and dirty prototyping board based on the AVR ATMega16 microcontrollers. I find it useful enough so I decided to share the design here.
BabyBlue
I've been busy painting the motor housing and some other parts. I used high temperature paint from McMaster for the housing and epoxy based high temperature electrical varnish (also from McMaster) for the field coil cores.
There were not a whole lot of colors to choose from and since I was ordering from a catalog I had no idea how the colors would come out. I picked blue and black since they seemed like fairly safe colors.
Czonka! I found a Kilovac Czonka II relay on eBay with a buy it now price of $75, they normally retail for around $400 so needless to say I bought it immediately.
The Czonka II/EV250 is a DC contactor capable of conducting 400A continous and can break up to 2500A. It also has a very nice economizer feature which reduces the power consuption of the main relay coil to a measly 4W.
Field Coils
After much scrubbing the coils are finally clean and the full extent of the damage can be seen. Varnish is missing in several places but it is not too bad.
The motor components are finally starting to get clean. I used a lot of different products but the most effective one was Easy-Off oven cleaner. I am in no way affiliated with them but if they want to send me a big check I will not turn them down :)
