Paul and Sabrina's Cheap 3 Phase Inverter (AC Controller) with Field Oriented Control

[MPaulHolmes]

Thank you Cyril!!! Very informative indeed!

[nlc]

Your are welcome Paul ! I just looked your schematic rev 0.1 of the AC controller, and I see that you use a 30r Rgate, for switch ON and switch OFF of mosfets. I am almost sure you will have the autocommutation shoot throught condition. When we do not pay attention to this phenomenon, we don't see it because with the high mosfet derating mosfets will accept the peak current during the shoot through condition.

When you will do test of your AC controller, put the scope (channel 2) on Vgs of a low side mosfet for example, and trig on rising edge of channel 1, connected on the corresponding motor phase output. With 30r as Rgate and 144V bus (and even smaller bus voltage), I am almost sure you will see the Vgs signal rise up to the gate threshold voltage.

For comparison, last weeks I worked on a "small" BLDC controller, 72V/100A, based on 12 IRFB4110 mosfets (100V/120A), thus 2 mosfets in parallel on each half-leg. On the first version of the schematic my Rgates was based on 82r for switch ON and schottky + 10r for switch OFF.

Despite this I still was in limit of autocommutation under 84V (pack fully charged), because Vgs raised up to 3V when opposite mosfet switched ON. Thus to be sure, I passed the switch OFF Rgate to.....0r !!

Thus I let you imagine with 144V DC bus and 30r switch OFF Rgate !!
Regards
Cyril

[energymiser]

Hello all. Well, its been over a month since any one posted here. Is this project still on the go? I think there are people waiting with baited breath for some more input/progress. Has everyone gone home to their individual ventures? At this point I am not able to offer any technical assistance, so I (there must be others out there) am hoping to see some activity here which will give me some assurance that I am not waiting for nothing. All the best.

Nigel.

[rickheid]

Yes, I am waiting with baited breath.................wait I think that’s beer breath. Anyway great job so far!

[CollinK]

I'm really interested in this too. In fact, I'd like to build/test one ASAP. So, what's the status of things? Any updated schematics?

[DJBecker]

Originally Posted by rickheid

Yes, I am waiting with baited breath

The phrase is "bated breath", a shorted form of "abated breath" (in the sense of holding your breath, or forgetting to breathe because of the excitement).

[rickheid]

Hahaha, thanks, I stand corrected. Oh, and I still can't wait for more, and it is a great thread.

[nlc]

I also develop an AC FOC controller, but not open source, it's for a customer. I don't know which microcontroller you plan to use, but I decided to switch from dspic to STM32 (stm32f103 family), and it's a very very nice microcontroller !! And ST give a very complete and powerfull library to build a FOC controller very quickly.
The controller I developp is a "small one" (72V/100A), based on six IRF4468 mosfets, but will be a good base to more powerfull controller.

[CollinK]

I'm pretty sure that this project uses a dsPIC4011. However, I've done some STM32 coding before and I'm not opposed to that processor. It is, indeed, very nice. However, I'm not sure whether a change is in order or not. I suppose that one of the biggest problems would be expecting people to be able to solder 64 pin SMD chips. It's certainly not quite as easy or straight forward as 40 pin through hole microprocessors which is what the current controller uses. It seems to me like the current design is all through hole components.

[nlc]

Originally Posted by CollinK

I suppose that one of the biggest problems would be expecting people to be able to solder 64 pin SMD chips.

Humm, yes ! You are totally right !! I don't thought about this point because I have the habitude to solder these package with normal soldering iron. I will build the controller I talk about next week, I will try to post a video to explain how to solder easily a qfp package.
The other possibility is to provide the pcb with the microcontroller already soldered, or provide the microcontroller on a small piece of pcb to convert it to a "DIP" package.

But the FOC library provided by ST is really really nice, all the job is done, the application just have to use high level API to control the library and run the motor !