[thingstodo]

*WARNING * another long-winded post!

Originally Posted by cajunfj40

For aligning the two motors, I considered the rotors aligned by way of their built-in keys good enough, with the rest of the work being in aligning the two stators.

If you are using separate controllers, I don`t think you need any electrical alignment. If you are still looking to do one controller - I would be interested in your results.

As for possibility, AMR appears to sell "dual core" motors with single inverters, and IIRC those are IPM type REMY motor cores. No idea of the math needed, though! Sounds like trying to run two IPM or SPM or similar motors off the same drive may not be worth the hassle.

I didn`t know about AMR - thanks for the info.

I don`t know of any research on-going at the moment to drive multiple motors of any type in Field Oriented Control or sensorless vector. If the nerds are not arguing about it - there must be an obvious problem or two.

How much less critical is it to get two stator windings for induction machines equal in terms of resistance/inductance when running them in parallel off the same drive?

You can run the motors in parallel from one drive. I have 4 running in parallel on a machine that runs on rails. There is nothing critical about it - we ran one at a different horsepower for a month when we ran out of spares. But it is volts per hertz. You don`t maximize torque per motor, you waste a bit of power, the motors heat up more than they *REALLY* need to. It DOES give me 4 wheel drive, one motor and gearbox per wheel, with no need for limited slip or differentials. Each motor gets the same frequency, so if it has no traction .. even if it`s up in the air ... they spin the same speed and whichever wheels have traction take the available power. The others just spin the same speed .. or about the same speed. A motor under load spins slightly slower than a motor spinning unloaded.

You said it is possible to run two OEM AC motor/drive combos in master/slave mode on a common (or geared/belted together) shaft. Any ideas as to how to control those drives?

The throttle signal is sent to the first controller. I believe it is a Curtis controller. It outputs a torque signal to the second controller, which follows along.

With a modern dual-signal hall effect sensor, you could .. in theory .. send the same throttle signal to each controller. The controllers *COULD* fight if one of them saw the signal as slight regenerative braking while the other saw the signal as slight acceleration .. but the calibration curves for the throttle should take care of that. There`s always a bit of deadband around `coast`. That should take care of it.

Mostly thinking OEM EV drives here - for common junkyard availability. For the aftermarket Curtis controllers, and many common industrial VFD's, they have that feature built in - just connect them up and put in the right settings. Not sure that is the case for OEM EV drives - and it seems like it would be an extra-cost thing that wouldn't be worth it to the OEMs to implement.

The OEM EV drives (besides Tesla) appear to use CANbus to give them their throttle reference. Sending the same signal to multiple controllers should be quite easy to do.

Going back to a Jack Rickard (EVTV) video - you would need some sort of limited slip arbitration, or ABS maybe, so that you do not break loose one rear tire while accelerating through a turn.

Hmm. I guess I could send the throttle signal to a separate "controller controller" and have it divvy up the torque demand to the two OEM drives, possibly with a current sensor on a phase of each motor to have a feedback for how well balanced the setup is running, if needed.

EVTV has such a controller - they call it GEVCU - and it`s open source so you can see how they do it, or write it yourself.

Or just twin the throttle output and send it to both controllers at the same time, maybe monitor the current on/temperature of each motor for a while in early days to check the balance and see if it needs adjusting.

As I guess I did not really explain above - the throttle is a torque setpoint. If you lose traction, it still tries to drive the motor to the requested torque. That`s what the ABS is for. Or limited slip algorithmn.

I've got lots of time to plan this out as the budget builds all too slowly. I'll probably end up buying a used Leaf to replace my currently dissolving ICE car as a commuter (different budget - I need to commute, after all!) for my first EV, as my toy budget may get big enough to buy a running/driving FJ-40 before it gets big enough to buy enough good parts to build one plus the EV bits.

If I lived in the US, I would purchase leaf wrecks for the EV parts. $5K appears to be the going rate. You get the motor, the battery pack, the charger and the DC to DC converter. At least $10K in parts if you were to buy them. If someone figures out the CAN commands for the BMS and the controller - that`s an extra bonus. I think you have room in that beast for 3 leaf motors coupled end to end. You could keep the rest of the drive-train as is and twist drive shafts if that`s what you wanted to do ...

Making things work with OEM parts has some advantages:
- if you sell it eventually, the new owner can find parts and has confidence that he can
- you can go and buy a part off the shelf to get back running ... if you need to .. or you can get another wreck or buy something from a wrecker
- Comparatively little issues with `that company is out of business, or the part is obsolete so you can`t fix it`.

The alternative, for me, is Open Source. I`m not dedicated to building the boards, or soldering, or writing the program myself. But if you have the schematics you can troubleshoot it yourself. If you locate something that died - like an IGBT - you can buy a replacement and put it in, or get someone at a maker space to put it in. You have the power!

The software may not be as bullet-proof as an off-the-shelf product .. but it may be better .. depending on the guys doing the open source. If you see some new feature in a car in 2 years .. and you want it badly enough .. you can add it!

Boy - I do rant on, don`t I?

I will follow your build with interest!