Another DIY EV controller - Fuel Economy, Hypermiling, EcoModding News and Forum

NiHaoMike · 08-02-2009, 09:23 PM

Circuit Cellar - The Magazine for Computer Applications
The main advantage is that a common industrial 3 phase motor can be used.

MPaulHolmes · 08-03-2009, 02:44 AM

Those little buggers! They even did field oriented control! That has good behavior at low rpm and high rpm. It needs to do a few trig transformations, so you need something a little better than an ATMega8. I really want to try one of these.

bjn · 08-03-2009, 08:14 AM

Common industrial AC induction motors have a pretty bad power to weight ratio compared to commen DC motors, I think. However, if it's possible to drive them with a higher frequency than 50/60 Hz then maybe they can produce more power (if the torque doesn't decrease too much with RPM).

How high much can you overrev a typical 3-phase AC induction motor before it breaks apart? at which RPM does the power curve start to decrease due to the torque curve falling too fast?

NiHaoMike · 08-03-2009, 11:10 AM

Industrial motors are rated to operate continuously at their rating plus plenty of margin for overload. So in an EV, the motor would actually be much more powerful than its rating would indicate. As little as 7.5HP might be enough for an EV.

Maybe it's possible to make a small 2 phase version to allow the use of large appliance motors for something like power steering? Or to allow a common window A/C compressor be used for an EV heat pump?

MazdaMatt · 08-03-2009, 02:30 PM

He's still sayin 2500 dollars in components? Paul, what's your cost?

MPaulHolmes · 08-11-2009, 02:28 AM

Hey Matt! Well, for the DC controller, for 1 offs, it's about $300. In bulk about $230 or so.

MazdaMatt · 08-11-2009, 08:26 AM

Somebody ought to tell him he blew it. However, a 3-phase setup with IGBT's in the DIY realm is nice to see.

frodus · 08-27-2009, 11:58 AM

blew it? How so? because cost is $2500? He got a development kit, and had to pay full cost for parts.... you could cut that cost by 1/3-1/2 in bulk.

Its essentially 6 DC controllers (2 for each phase, one neg, one pos).... so its got 6 times the overhead on the microcontroller, 6 times the gate drive, 3 times the current control, 6 times the voltage sensing, vector or volts/hz control. 6 high power gate drivers, 3 IGBT dual packs....you get the idea). A DC controller is fairly easy to do, if you can get the FET's or IGBT's to gate at the same time. Its just pure PWM. An AC controller is PWM and PFM.

And not to mention, he can now use off the shelf AC motors, that don't have to be rewound, so that cuts cost quite a bit. Forklift motors are limited in voltage and RPM, induction motors can go quite a bit higher and are much more widely available. Just go look for an industrial 208V motor, they're everywhere.

NiHaoMike · 08-27-2009, 03:57 PM

Quote:

Originally Posted by frodus

And not to mention, he can now use off the shelf AC motors, that don't have to be rewound, so that cuts cost quite a bit. Forklift motors are limited in voltage and RPM, induction motors can go quite a bit higher and are much more widely available. Just go look for an industrial 240V motor, they're everywhere.

Actually, industrial motors in the sizes we are interested in are either 208v or 480v since those are the common 3 phase industrial voltages. (Some are designed so they can be used on either by rewiring.)

MazdaMatt · 08-27-2009, 04:04 PM

I didn't think that his cost was rolling in development kits, and since we're talking DIY then "bulk" is not really a factor. DIY mean batch or single... else you're not exactly D'ing IY.

I'd love to know his "second time around" production cost. One MAJOR savings area would be the IGBT drivers. Build them from scratch and save major coin. Those things are a niche market electronic device with high standards of reliability - read: expensive.