Paul & Sabrina's cheap DIY 144v motor controller

[duncan2]

Thanks Piotrsko

I have joined instructables and instagram - to search for Paul!

No joy so far!

I hope he is still OK - it feels weird thinking about the USA as a dangerous place

[mpgmike]

Took a week, but I read every post, opened several pics, downloaded several files, watched several videos (not nearly all), and learned a bunch. I'm seriously impressed with Paul's learning curve. It appears he went from ground zero to functional in a couple short months -- 5 months for him and he learned what it took me 5 years to learn!

Much work and sacrifice was portrayed as page after page unfolded. Many thanks to those that contributed to the community. Now on to the AC Controller thread!

[duncan2]

Hi mpgMike

If you have caught up with Paul's knowledge - does that mean that you could replicate his IBGT Motor controller?

I have one and it works superbly but I would love to have another one as a spare and another one for a friend (loony) who wants to build an electric drag bike

[mpgmike]

To answer, I could design the PCB using ExpressPCB; I work with PIC MCUs and could replicate the dsPIC software functionality on a newer dsPIC33EVxxGM (of course it'd be easier to copy/paste Paul's); I don't like the high-side switching concept and would prefer low-side switching, especially in light of the SiC N-MOSFETs that weren't available when Paul got started on the project. Overall, I'd probably make some of the same stupid mistakes Paul made getting to where he got it, but ... I'm confident.

I have other ideas. I have a toy brushed DC motor on my bench I've been playing with. I also have a small stepper motor, and a BLDC to learn with. Ultimately, I'd like to create a controller that allows an automotive alternator to be controlled as a motor. This would require removal of the diode bridge, and if applicable, the voltage regulator. The Field would be PWM controlled as its own entity, and the 3 windings would be controlled like an inductive AC motor.

Considering a Ford F-250 Diesel alternator is rated around 200 amps (at 12 volts), this could be a potent go-kart motivater!

[mpgmike]

I plowed through this thread over the course of about a week. I'm now swimming through the AC Controller thread. I have seen guestimations where you should only stress a MOSFET to about 1/2 it's amp rating. In fact, when you look at the data sheet for a MOSFET or IGBT, it includes a Watts rating! Watts = Volts X Amps. What I found is that you can only achieve the rated amps if the voltage drop is about 2-3 volts. Working with 144 volts (or higher in some cases), the watts blow MOSFETs rated for far more than the amp current being drawn.

Example: 144 volts, 100 amps -- 144 X 100 = 14400; 14.4 kW yes? The MOSFET/IGBT only sees that high energy flow for microseconds until things settle, but it still sees it. I went through a bunch of my MOSFET inventory, not having a clue why I was blowing them up one after another, with far lower amp flow than they were rated for.

The answer is -- Look at the Watts rating for the MOSFET/IGBT!

[Piotrsko]

Sure it's not ringing creating rather high voltages that destroy the junction? Big argument on the proper use of snubbers over in DIYELECTRICCARS

[mpgmike]

I'm fairly certain, I was driving a mostly resistive load.

[Piotrsko]

Not from anything carrying current which is a low henry inductor? Or how about the windings in the motor?

Put 200 amps at 300 vdc through your motor cables and watch them jump. I stopped using tiewraps on mine.

[duncan2]

Hi mpgmike

The Paul & Sabrina IGBT power "bit" uses a ring capacitor and the current carrying parts made from copper sheet

There are enough drawings of that to lead me to believe that I could replicate that part

Paul also had a very smart solution to the issue that IGBTs are not identical - each one had about a meter of power cable - this ensures that they will "share" the current

So the high power bit is not the problem (I think)

The problem (to me) is the other bit - the low power "brain board" and the drivers for the IGBTs - and it may be possible to simply buy some IGBT drivers

I believe that an electronics/software guy would be able to make new "brain boards" - I certainly can't!!

[mpgmike]

Duncan, I read your post right after it was posted. I've had it open in a window ever since, and have read it multiple times. I've been giving serious consideration to your request. Here is where I am:

1) I work with PIC processors -- 8-bit and 16-bit. I have never worked with Atmel (even though they are now part of the Microchip family). I certainly could start with Paul's dsPIC30F4011 code/design.

2) I don't work as part of a team of engineers, I work alone. This gives me the freedom to do things my way; both hardware and software. Since Paul's original design, SiC MOSFETs have hit the market big time. I would want to use these gems. Many other components used in his original work are now obsolete, and would have to be re-sourced. In other words, it's getting more difficult to follow the original recipe.

3) I don't have a suitable motor to use for testing & development. (Nuff said!)

4) Paul set a precedent of working his glutes off for free (at best, and it actually cost him money often). I am all for open source, but only when it's a project I get benefit from (which Paul did). Right now I'm chasing pay checks.

For me to commit to your request, it would require an investment of money and time. I have no real desire to go in that direction at this time, as I'm focused on other things. I am working on developing motor control, BMS, chargers, and other EV related technologies, but I'm not there yet. I'm bench-testing toy-sized motors just to get a handle on form/function/code/hardware/application/feedback..... Paul became the expert as he developed controls for his car. I have no car as yet to use for testing. I do have a 1984 Dodge Rampage slated for EV development, though.

With that said, I must regretfully say no to your request. Sorry.