Paul & Sabrina's cheap DIY 144v motor controller

[TheSGC]

Originally Posted by MPaulHolmes

Actually, I'm very confident that the mosfets were breaking because of a floating gate. I added a resistor from gate to source, and now it's fine. Turning on the power section before the control section creates a high voltage difference between drain and source. The mosfet was turned on because the floating gate was above 4v relative to source. Basically the mosfets got shorted, and the current limit was exceeded, causing them to fail in a shorted state.

Those 200v 60 amp diodes have a very fast response time (20 ns). I'm getting voltage spikes of only about 4 volts when I run the controller at 72v. I have been using freewheel diodes. I'll use about 10 or 12 of them in the car's version. That will allow for a current of 500 or 600 amps, and a voltage of around 144v, with voltage spikes of around 5v or so. The EVTech list has suggested the components I'm using, including filter caps, mosfets, diodes, etc..., and there are working 144v 600amp controllers made by people on that list that are using those parts.

I find that pretty worrisome. I guess I would like to see some of the working controllers in EVs. Everything that I have tested, and was confirmed by others, is that the reverse diode has to be at least 4x your voltage, 8x to be safe. It's one of the reasons why you don't see many controllers past 144 volts because of all the spikes associated with that those voltages. I doubt you will see any real spikes in bench testing any controller. And I would limit the paralleling of the diodes to no more than 12.

[MPaulHolmes]

One of them is Ian Hooper's. He's very accessible, and is very friendly about answering questions.

ian@zeva.com.au

Check out his website, too.
Ian's Controller Information


He is running his controller with current and temperature limiting, etc... with the parts I listed. He has a worst case scenario motor setup for a controller. It's an 11 inch WarP (I think) with no transmission (direct drive!). He blew up a 144v 500amp Curtis, so built his own to handle it. It also uses Lithium Iron Phosphate batteries I think.

[bennelson]

Happy birthday Paul.

Something's coming your way.

http://www.youtube.com/watch?v=iO1n_SDvT1k

[rgathright]

Originally Posted by MPaulHolmes

He is running his controller with current and temperature limiting, etc... with the parts I listed. He has a worst case scenario motor setup for a controller. It's an 11 inch WarP (I think) with no transmission (direct drive!). He blew up a 144v 500amp Curtis, so built his own to handle it. It also uses Lithium Iron Phosphate batteries I think.

Direct drive! Yes!
The motor's are great because they can operate above 11,000 RPM. Which means your motor requires little power to rebuild its EM field above 5,000RPM after a restart (acceleration). A direct drive motor is also very easy to install in trucks because you can use the bed to hold the batteries and controll/charging equipment with the motor beneath. With all equipment on hand and good instructions you could convert a Dodge Dakota pickup over the course of two weekend with two people.

[MPaulHolmes]

Originally Posted by bennelson

Happy birthday Paul.

Something's coming your way.

Happy Birthday to me! Happy Birthday to me! Happy Birthday, Dear Pauuuuullll.... Happy birthday to me!!! Yahoo! Thank you, Ben!
Want to see a cool note? One of the bigwigs on the EVTech list wrote it to me. I needed some isolating material for the mosfet backs. (note: it wasn't a private email, but sent to the EVTech list)


Paul,
If you need isolation material I can probably send some
for free. Let me know what you're looking for and I can send it your
way.
Something like this,
sil-pad, gap pad, hi-flow thermal interface materials/home
I admire your homebrew efforts and I'm willing to support them.
I've sent free stuff to Lee Hart, Morgan LaMoore and many others.
I'm in a position to get free stuff since my designs sell millions of dollars worth of electronics at Ametek. Sometimes I ask for free stuff for other peoples projects and pass it along :-)
Rod

[MazdaMatt]

TheSGC, Thanks for your explanation of freewheel diodes. I find it funny that you say "that's what i learned from majoring in Computer Engineering" because I also am a computer engineer and my knowledge of analog and power electronics is pathetic. Digital controls, architecture and communication are what I got out of my computer engineering degree - i know nothing about things >24 volts and >10 amps. Mosfets and IGBTs are foreign to me.

[MPaulHolmes]

Rod Hower mailed me a whole 10.5"x8.5" sheet of the the isolating material. He also sent me a free small brushless DC motor that he designed, and a fan for cooling the controller! Isn't that awesome? If you haven't checked out the EVTech list, I highly recommend it. You get to talk to experts. Throw out a question, and you get 10 different, thoughtful answers that are all based on real world experience. I love it!

I've been working on the layout for the capacitor side of the power board, and the mosfet/diode side. I'm doing it with ExpressSCH. I have it set to a 0.5 mm grid spacing. That's good enough to get as much detail as I need. Since I think I'm getting a mill soon, and I have almost all the measurements done, it will be pretty easy to etch with great accuracy with a mill. The one I'm looking at can move around with 0.05 mm accuracy. I'm excited. There's not much room in the garage, but I'll make it fit. Also, It can be done without a band saw if you have M- come out the back, and B+ and B- come out the front. It's cheaper and easier for a regular person to manufacture if it is done that way. I even heard that there are advantages as far as the internal electronics go. Path lengths for various currents (coming through different mosfets) are the same. It is non-standard, though. I guess it could still be done without a band saw, but B+, B-, and M- would be pretty close together. There could always be a non-conductive barrier between each of them. That's no big deal, I guess.

[Daveedo]

If ya need to use a band saw just let me know.

[MPaulHolmes]

Thanks, Dave! I might, but I'll try it this way without one first I think.

[bennelson]

Here's a photo of Ian Cooper's controller mentioned above.



As you can see, the buss-bars coming out the right are all very close to each other and are cut to a nice shape to have enough room to bolt the power cables to them.

I like the idea of one of the connections coming out the other end, to save space, make it easier to use plain/straight buss bars, and maybe save an accidental short!