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.

Some wonderful people sent me a pair of Dolphins to repair. Someone before them
had been into both of them deeply and did some serious damage. Pins were not put
back into connectors properly. The fets on the charger board were not even
parallel to the base plate. Both main boards and chargers were toasted. Even the
GFI hardware was missing from both units. Parts were missing from one of the
dc-dc boards. So when these systems arrived they had one board out of 6 running.

The one charger was the very latest revision from USE as it had a new board and
revision I’d not seen before. Only one fet was shorted, the other was fine. My
standard rebuild is to replace both fets, both relays and the diode weather they
are bad or not. So that’s what it got. I was very happy to see that the T1
current transformer survived the onslaught of failure.

One main board had the standard shorted bridge rectifier that goes along with
the shorted charger fets. The fet driver pwm output was fine however. But it had
happily open circuited the traces that usually just get shorted to other things
and cause a whole other set of issues. So some jumpers were added to the new
bridge rectifier. The board made it through my long QC list of tests and runs
well in the truck. Both boards got the regen upgrade (I modify the Dolphin to
increase the regen output by 40%) and the Classic Dropout mods for vastly
improved reliability and a better driving experience.

Once the charger was supposedly rebuilt, and the main boards repaired, It was
time for a test run. The Dolphin booted fine. But as soon as the throttle was
pressed the Dolphin faulted with a sizable thunk and gave an IGBT fault. It
turned out that the large diode on the charger board, when shorted, ties the
motor’s neutral line to the pack negative. That’s essentially a short across the
output of the Dolphin. It was odd at the time that none of the Dolphins IGBT
fault circuitry was triggered. All of it was normal. Yet I got an IGBT fault. It
turns out that the software looks for a reasonable load at various throttle
positions. Since the load was nearly infinite at low throttle it protected
itself by disabling the IGBT’s by not energizing them rather than the IGBT
circuitry sending a fault.

Then there are the mice that got in these Dolphins. They love eating insulation
off of wiring. Especially teflon wire. Then of course they have to use the HV
section of the Dolphin board as the bathroom.

After all of the repair work, and the passing of the many bench tests, it was
time for a test drive. The first board had dropouts so badly, that it could not
even pull itself back into the garage. I would say a dropout every second. The
next board dropped out every 15-20 seconds. After much studying and testing over
4 years, this really bad board made it a little bit easier to diagnose what was
causing the classic dropouts. Thankfully I figured out the dropout issue as
these boards were destined for the scrap bin! I pulled a 3rd board out of
mothballs that had bad Classic Dropouts, and it too was cured of dropouts with
the mods I had made to the other two boards.

After performing the Classic Dropout mod, I took both Dolphin boards for another
ride in my truck. Zero dropouts at very high regen or very high acceleration.
Nice improvement! I went for a walk at the park to enjoy the rare sunshine. I
noticed a bad coolant leak as I walked back. The bottom plate on the Dolphin
chassis is just .125″ thick aluminum glued and screwed on. The glue is very
brittle. When I used my cooling system pressure tester on the radiator, the
Dolphin cooling plate squirted coolant all over. It’s almost impossible to get
the tiny red-loctited screws out. It takes quite a while to scrape all of the
adhesive off too. I’m about 60% done. Makes me think this is another ticking
time bomb. This is the second Dolphin I have had that has cooling plate leakage.

Time to get to it!

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