Toyota Prius A/C Compressor Motorbike: The Bike of IPM Motor Science

[Grantmac]

What about driving an off the shelf IPM such as the QS mid-drives? Then you could perhaps run lower voltage.

 

[fpvdude]

What about driving an off the shelf IPM such as the QS mid-drives? Then you could perhaps run lower voltage.

IPMs are a bit annoying in that each IPM is different- the lookup table required to drive an IPM depends on: the bus voltage, the motor resistance, the inductances of the motor (which can even change substantially depending on operating current). Two Prius A/C motors are the same to drive, but definitely different than some other random motor. I'm sure this motor could be made to work, but it would take a lot of work.

This is why IPMs are pretty uncommon so far- really you need to dyno the motor and the controller together and tune everything as a system. Just hooking up a VESC to your random IPM motor will result in something that works, but probably with poor performance. Personally I am interested in building both the motor and the controller to go with it, and thinking of them as a system.

 

[Grantmac]

I was thinking about you offering a turn-key tuned controller for an off the shelf motor. Rather than focusing on a supply line that requires rebuilding surplus motors.

 

[macribs]

Sub'd for further reading and deep diving.

 

[Lebowski]

Perhaps the Lebowski controller can do this; or could be modified to do so. Similarly, Incememed's SFOC5 might, too.

I am not very familiar with either controller unfortunately. If they use FOC, they they probably could run this motor just fine. If they use block commutation, then the motor would still probably run, but you would be unable to really take advantage of what makes the IPM worth using.

There is a thread now explaining the main operation principles of my controller. The source code is also published so you can easily program a chip. I would be very interested in the results. For my controller no lookup table is necessary for IPMs or fieldweakening.

Here is the explanation thread with easy to burn hex or source code: https://endless-sphere.com/forums/viewtopic.php?f=30&t=104895

Here is my view on IPM : https://endless-sphere.com/forums/viewtopic.php?f=30&t=97880&p=1435404&hilit=IPM#p1435404

 

[sn0wchyld]

Have you been able to figure out a thermal limit? Looks like there's not much advantage to going with higher voltage due to the already high rpm's, just means more gearing. How long could it do double or even triple the current you're using now at, say, 30% duty?

Thermal limit: at 35 phase amps the motor got pretty toasty on the dyno stand, so I'd say this is a pretty solid limit. On the dyno stand we were only running about 30% duty cycle so I'd say 35 phase amps is a pretty hard max.

In regards to increasing the volts, your assumption that more volts = more RPM is not entirely correct. The motor only reaches 16,000 RPM due to the fact that I am doing a ton of field weakening. Without field weakening, the motor tops out at about 6500 RPM. After this, I use field weakening to keep the motor spinning, but this causes a huge dropoff in torque.
Here is a simulated torque surface running at 150 volts on a maximum of 35 phase amps, up to 50mph. Notice how torque is only high for the lower ~20% of the speed range, and afterwards torque drops off pretty quickly.

Here is the same torque curve but with a bus votlage of 250 volts instead of 150. Notice how the torque remains high for a little longer, and also how the torque at higher speeds is vastly improved.

We always think that volts = speed and current = torque, but this is not always true with regards to IPM motors. What is going on here is that to achieve high speed at a battery voltage of only 150 volts, the controller has to field weaken *really* hard to get to high speeds. This means that torque at high speed is exceedingly poor. When you increase the bus voltage, the controller has to field weaken less hard, and can therefore put more of the amps into producing torque.

it would be really interesting to see this same comparison between bus voltages with a fixed input power, to really highlight the impact of FW on output torque/power... great build btw.

 

[mxlemming]

This thread is amazing. Fpvdude you're the king of bodgers. And good work on FOC.

I need an ipm for my FOC project. Normally they're huge and expensive but if i can get one from an AC compressor...

Does this


have the motor you're talking about inside it? The pics show 2 wires but it's a prius ac compressor...i guess it has the inverter inside the can?

Would be ideal. Desk size 4kW inrunner i can practice field weakening and MTPA on.

 

[tylerwatts]

@fpvdude great thread thanks. How is the project going? May I ask you to share some more mechanical details of how you built a standalone housing etc to relocate the motor and your gear reduction please?

cheers
Tyler