1994 US Electricar Repair Blog by Mike

It occurred to me today that I could design a dropin replacement for the Dolphin’s filter caps, HV buss, and IGBT hardware under the main board. It would be put together a lot like the ACP cars. Separate igbt’s in parallel for each phase. Several filter caps too. This would make getting parts far easier. There is a a lot of volume to work with under the main board. I’ll have to draw it up in cad sometime to see how it will physically fit. I should dig up the ACP pics I have as well of their hardware.

Not only did I FINALLY get the cnc system debugged after blowing it all to hell last weekend (along with my truck), it looked like the main filter caps and the fets could simply just be upgraded in voltage. This would prevent that last disaster that blew everything up and the system would get a nice increase in feed speed. The parts upgrade works great!! Wow, it went from 75ipm to 125ipm. It’s been up to 160ipm. But it was a little too unstable. At that speed there was a little oscillation at high rpm. Can’t tell if it’s the hardware or the pc that is the limiting factor. Makes it tempting to upgrade this old 800mhz pc to an old 3ghz Pentium. The faster the pc the faster the parallel port speed.

While debugging the cnc system, the quill suddenly stopped going fully upwards. It was hitting something hard. I called Don and he said the sheetmetal quill cover had broken tabs and was floating around. So tonight I called him and he walked me through how to take the top of the Bridgeport head apart to get the quill cover out. It was just a little work. Don nailed the diagnosis. I’ll get over to his house in the next day or 2 and pick up a new one from him.

Later this year, I will have had the mill for 10 years. Don has a guy that might sell him a real Bridgeport CNC machine. He won’t jump on it unless I give him the ok. It’s not a bad price. I could sell my Bridgeport to get some of the expense back. Those original cnc’s have power oilers, chrome ways and very wide ways at that, along with ball screws on all 3 axis. The tables are not long and skinny. They are a lot deeper. They were made for flowing lots of coolant on them. Don says the drawbar is some kind of quick change set up not the standard BP stuff. I told him we’d have to make it a step pulley setup. But maybe not. As long as it fits in my garage it won’t matter. Besides if I have to sell it, having it original would be more appealing to a potential buyer.

After delivering several more Dolphin boards it was time to assemble my system. I turned the key and as soon as the ready light comes on there was a gun like pop! I had forgotten to connect the igbt driver cables. At least the main board was not affected. All 3 igbt’s are shorted. I am lucky that my last customer was willing to give me his 3 spare igbt’s.

The #2 and #3 main boards that have received the Classic Dropout mod shipped today. They work very well compared to when I first got them running. What a thrill to finally see such great success with a problem that plagued these vehicles for years.

Fritz put up his fet board for sale today. It’s a beauty! It’s made from 3 oz copper. It should handle the current spikes nicely. I have to decide to either have Shawn make me one of his chassis for the welder or just use a short PC tower that are super cheap but probably require some labor. Maybe a cool transparent case would look sweet. I am only waiting on the fets to arrive from Hong Kong and the board to arrive from Fritz. I still need to order the 4 farad capacitor too.

Today I wanted to see if I could devise a way to use my 3 axis cnc to wind 41ga wire onto the current transformers from the Dolphin charger. They tend to fail if the fets go up in smoke. So there are better grades of fets that have helped the chargers live well. But now I found that I don’t have a single spare charger. They all have open circuited secondary windings. After unwinding a bad one it looks like it holds about 407 feet of 41ga wire. But it is even more important that the secondary gets 3000 turns, I think.

Just as I was firing up the computer to see how to write the g-code for making my mill wind these coils, the hardware started popping fuses, and fets. When I installed the 60 volt 10 amp power supply in my rack cabinet, I must have rotated the knob on the variac to full output. Normally it’s set to about 55 volts ac. After rectification it ends up being about 75 volts. So at 120vac the rectified voltage had to have been much higher. That’s what killed the fets, fet drivers and the diodes.

I used some old 1407 fets to sub for the correct ones just to help me debug the system. The Z and Y channels worked out eventually. At first so did the X channel, but it then decided to smoke again. This time several of the fast recovery diodes were hit too. Now that I don’t have any diodes, I have to wait until I place a major order with Newark before I can get the parts. At least 2 of the 3 channels work.

I still need to figure out what code to find/make to wind the transformer. The idea is to mount the transformer to the vice. Then chuck the spool of wire with some tubing to the collet of the mill. The table will then move the transformer around in a circle to wind itself. It will be a very slow process, but I think simple to construct.

The second idea is to chuck the transformer into a collet and spin it to wind the wire up. Not that difficult as I think about it now. Just have to make the z axis go up and down to evenly distribute the wire onto the transformer. The Z axis is very slow and not too precise. I could move the wire up and down by hand. I’m trying to automate this as much as possible.

Either way I have to wait to get the cnc system restored to operation and installed back in it’s cabinet. That will take getting the parts. For now I can use 2 axis’ to just work on either of the 2 winding concepts.

Along with several others I’m on a spot welder project. This will be the tool I need to spot weld A123 cells together to make a nicad replacement module for my truck. I was in Merced a few weeks ago and got the chance to meet Fritz. Here is a video of the spot welder in action. It’s very sweet!!

The first main board with the Classic Dropout mod shipped today!! Two more have
been modified and are ready to ship as well.