Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post - Paul and Sabrina's Cheap 3 Phase Inverter (AC Controller) with Field Oriented Control

tesla500 · 03-27-2011, 05:57 AM

Hi Guys,

I just found this project recently, really nice progress. I wish I'd found this project earlier, I've actually been doing similar work, unfortunately in complete isolation, for the last while. I had the inverter working nicely about a year ago, but sort of lost interest. Seeing there's lots of interest in such a project has rekindled my interest now. I've got a video showing what I've done so far:

Oops, I can't post a link. Go to youtube and search for "AC Drive System for EV", it's the first result.

We should compare notes and see if the work I've done could help on your project. I've done quite a bit of software work with the Microchip app note code, specifically with respect to setting the magnetizing current for optimal use of the power stage. I also have an autoranging encoder algorithm that uses a 50 pulse encoder that can easily be made DIY, as opposed to high count ones that are difficult to make.

I've also had a good go at getting the sensorless version of the code to work, with very limited success, unfortunately. I think I'll stick with sensored for now.

On the hardware front, I've done a lot of work on determining how far the IGBTs can be pushed safely, and it turns out that as a very rough estimate, the RMS output current you can run on most modules is about 1/2 of their DC rating. Eg, if you have a 600A module, you can get about 300A RMS (If you can keep the heatsink at about 50C). Also, the maximum inverter power throughput can be estimated as Pout = DC link voltage * RMS output current * 1.17. When you go through all the math, with the inverter at max duty cycle and unity power factor, the ratio of DC link current to RMS output current is exactly SQRT(2) * 5/6.

I've got lots of other little tidbits, probably too many to list. Ask away if you have any questions or want more details.

I think the next step for my project is to "productionize" it with everything on a PCB, and a proper power stage. The present power stage is cheap (about $300 for the IGBTs brand new for a 300A RMS output), but is too difficult to make, and has too many points of failure with so many parts. I'm currently compiling a spreadsheet of the various IGBT options, I'll post it when I have it filled in more. At the moment there's some Powerex and Microsemi modules that look pretty good.

Regards,
David

03-27-2011, 05:57 AM	#497 (permalink)
tesla500 EcoModding Lurker Join Date: Mar 2011 Location: Vancouver, BC Posts: 5 Thanks: 0 Thanked 4 Times in 2 Posts	Hi Guys, I just found this project recently, really nice progress. I wish I'd found this project earlier, I've actually been doing similar work, unfortunately in complete isolation, for the last while. I had the inverter working nicely about a year ago, but sort of lost interest. Seeing there's lots of interest in such a project has rekindled my interest now. I've got a video showing what I've done so far: Oops, I can't post a link. Go to youtube and search for "AC Drive System for EV", it's the first result. We should compare notes and see if the work I've done could help on your project. I've done quite a bit of software work with the Microchip app note code, specifically with respect to setting the magnetizing current for optimal use of the power stage. I also have an autoranging encoder algorithm that uses a 50 pulse encoder that can easily be made DIY, as opposed to high count ones that are difficult to make. I've also had a good go at getting the sensorless version of the code to work, with very limited success, unfortunately. I think I'll stick with sensored for now. On the hardware front, I've done a lot of work on determining how far the IGBTs can be pushed safely, and it turns out that as a very rough estimate, the RMS output current you can run on most modules is about 1/2 of their DC rating. Eg, if you have a 600A module, you can get about 300A RMS (If you can keep the heatsink at about 50C). Also, the maximum inverter power throughput can be estimated as Pout = DC link voltage * RMS output current * 1.17. When you go through all the math, with the inverter at max duty cycle and unity power factor, the ratio of DC link current to RMS output current is exactly SQRT(2) * 5/6. I've got lots of other little tidbits, probably too many to list. Ask away if you have any questions or want more details. I think the next step for my project is to "productionize" it with everything on a PCB, and a proper power stage. The present power stage is cheap (about $300 for the IGBTs brand new for a 300A RMS output), but is too difficult to make, and has too many points of failure with so many parts. I'm currently compiling a spreadsheet of the various IGBT options, I'll post it when I have it filled in more. At the moment there's some Powerex and Microsemi modules that look pretty good. Regards, David