What is MG2's type and construction?

Hi all,

I'm having a bit of trouble finding some technical specs on the Prius electric motors, as in what type they are (induction, permanent magnet), how many phases, etc. The sort of thing you look for if you want to know whether they would be suitable for using in another project, unrelated to cars.

Does anyone have any detail about what type of motors they actually are?

I have only been able to find photos that show three or four connectors - so I'm guessing they might be three phase - and I'm presuming that they aren't induction motors as these seem like they'd be more difficult to reliably switch between using and generating power. Some people mention magnets when removing the rotor during replacement, so that makes me think they might be permanent magnet motors.

Since the Toyota manual mentions possible damage if the car is towed incorrectly, this also leads me to suspect a permanent magnet motor, which will generate electricity any time the shaft is rotated, potentially causing excessive heat build up in a towing scenario.

Am I on the right track? Has anyone used any of these motors in any other projects outside of EVs? If there's anywhere that lists the type of info I am after let me know as I haven't had much luck with Google.

Many thanks!

 

Many thanks for the helpful info! Through the other thread I was able to find a "Report on Toyota/Prius Motor Design and Manufacturing Assessment" which I would include a link to, but it tells me I don't have enough posts here yet. Here they broke the motor down into its components and I was able to ascertain that the Gen2 MG2 is:

• Three-phase permanent magnet synchronous motor
• 8-pole
• Operating voltage of 200-500 VDC
• 50 kW total power, when driven at 500 VDC (less overall power at lower voltages)

They didn't mention the windings so thanks @ChapmanF for letting me know they are delta-wound.

I haven't been able to ascertain whether the motors are driven on pulsed DC (e.g. PWM) such as from the output of three-phase VFD controllers, however given that they are AC three-phase but the power is always reported in volts DC, I am guessing that the Prius inverter may output PWM DC rather than sinusoidal AC. Please chime in if you know for sure.

My "project" hasn't started yet, but I am working towards moving to a rural property where there will be no mains power. So I am investigating some ideas for generating and storing electricity beyond just solar and batteries. I am thinking that the MG units could be a very inexpensive way of producing up to 50 kW of three-phase AC power, as buying second hand motors of this size are rather expensive, at least in my area. I don't talk much about my unconventional ideas in this respect because the first thing most people say is "oh why don't you do X instead, it would be much easier" completely missing the point that half the fun for me is in the challenge of getting it working!

 

Unfortunately they are very scarce in my area, as three-phase power outlets are not common here so they are all only small single-phase units for home use. I am looking for something that can produce a decent amount of power (at least 24 kW to match an on-grid service is the goal), and the Prius motors have been spot on in terms of power and price compared to everything else I have seen so far.

@TomB985: That PDF was quite interesting. More about how the transmission works and how to run the motor, but nonetheless some interesting detail there.

Very interesting. With that and the PDF, it does indeed look like the motor is controlled via PWM and then eventually just a low(er) frequency square wave at higher RPM. I presume it still generates a sine wave when run as a generator though?

Interesting note about the resolver, that could also make it much easier to calculate the rotor speed as opposed to measuring the output frequency separately.

@JimboPalmer: Thanks for the videos. I had seen one before but not the other, and they are quite interesting, although like most things I've found they are more focused on how the system works as a whole rather than the specifics of how the electric motors work. But it's still interesting to see all the same.

 

Ha, I hadn't even thought of taking sips from the generator as a way of boosting the voltage. I wonder what the maximum voltage the system has to deal with really is?

Any idea how much voltage the MGs might produce when used as a generator? I'm thinking that if they are run at 500 VDC PWM when used as motors, then running them as a generator might produce 340 VAC (which will hit +/- 500 V at the peaks) but that presumably means you can't get the full 50 kW out of them as a sine wave won't let them spend enough time at 500 V.

340 VAC is only a guess though, as this assumes a single phase and the MGs are three phase. I'm not exactly sure how to guess what AC voltage they might produce because I'm not sure entirely where the 500 VDC pulses are measured from - these must be phase-to-phase voltages as I don't think there is a neutral connection on them.