PMAC vs induction motor for model 3

[D-egg-O]

For a magnetic field ? The magnets

Induction motors do not have magnets, at least not in the current iterations of motor technology .

There are more disadvantages to PM motors than just worrying about the Chinese. I recommend that you read the blog posts at Tesla.com for great insight.

Seriously, watch this in its entirety.

Edit: And also this

I get the feeling you do not understand what AC induction implies. It is not to generate AC, it is to use AC to generate magnetic fields.

Edit 2: You do realize the the rotor in an AC induction motor mimics a permanent magnet in order to follow the rotating magnetic field generated by the stator, right? Instead of mimicking a permanent magnet, the PMACs already have this and don't waste energy generating one. An electric motor won't function with just one magnetic field. You have to have two.

 

[SageBrush]

All I was saying is that if you made a mistake in your title that a mod has the ability to correct it.

I know.

Nothing snippy directed your way.

 

[Thomas Edison]

I know.

Nothing snippy directed your way.

Oh, my mistake. No worries.

 

[samsamjr]

I think a few people mentioned these points but I feel I need to reaffirm them. It seems like a lot of people are citing a single article on the Tesla forum from 2007 with a lot of misleading terminology.
- The Tesla Model 3 uses a 3 phase permanent magnet motor (likely an IPM). Just like the induction motor from the Model S, it is powered by a variable frequency 3 phase inverter.
- Brushless DC is a really deceiving term when people apply it to an EV drive. What they are usually actually referring to is a 3 phase synchronous permanent magnet motor. This is the motor type used in almost every EV (with exception of the Model S induction motor).
- Modern IPM motors are more efficient than induction machines in almost every operating point. Back in the day, surface PMs had poor efficiency above base speed. Nowadays, well designed IPMs are smaller and more efficient than induction.
- Permanent magnet motors are more expensive than induction machines. However, EV system cost is driven by battery cost. If you can shave off 3-5% of a $15k battery with an IPM, you more than pay for the added cost of an IPM.
- Nikola Tesla also had inventions related to PM and synchronous reluctance machines. People only cite the induction machine because that was the most revolutionary back then. It was revolutionary because induction motor/generators don't require a variable frequency controller. It can start from fixed 60Hz. For this reason, it became part of the foundation of our AC power grid.
- I can only speculate why the Model S used an induction machine. It may be because the architecture started from AC Propulsion designs. There are a lot of good aspects to induction machines without magnets. It is possible that the industry will swing back to induction if battery cost drops significantly.

 

[hacer]

... You do realize the the rotor in an AC induction motor mimics a permanent magnet in order to follow the rotating magnetic field generated by the stator, right? Instead of mimicking a permanent magnet, the PMACs already have this and don't waste energy generating one. An electric motor won't function with just one magnetic field. You have to have two.

The word "induction" has multiple meanings. induction | Infoplease When anyone (knowledgeable) says "AC induction motor" the word "induction" refers to the induced EMF (electromagnetic induction!) in the (shorted) rotor. It does not refer to "magnetic induction," where a material (e.g. iron) is magnetized by an applied field. PMAC motors do not rely on the EMF induction (in fact you go to great pains to design the rotor to not respond to the induced EMF) when acting as a motor. When acting as a generator, they do use EMF induction in the stator, but nevertheless they are never called "induction motors" because that is a well-defined term in the world of motors referring to motors that use induced EMF in the rotor conductors to make the rotor field. These type of motors were originally invented by Nikola Tesla, who gave them that name, and they have had that unique name ever since.

 

[SageBrush]

At least I agree with you on this. Please revisit this subject using first principles.

ROFL !!

What first principle would you like to start with ?

 

[D-egg-O]

We're arguing semantics. I understand what you guys are saying. The "induction" portion is specific to inducing a magnetic field on the rotor.

I was implying the word "induction" also applies to generating the rotating magnetic field on the stator (regardless of the makeup of the rotor). If that's not typical, sorry for the confusion.

If Tesla is pursuing a PMAC for Model 3, they must have a reason. I believe the Bolt uses a PMAC. The drivability of the Bolt was very good, and the regen was especially impressive. The car came to a complete stop without touching the brake pedal. Would this be a benefit to a PMAC motor?

 

[Troy]

The opening message doesn't do a good job explaining what we are supposed to understand from the attached file. I assume the idea was to show that EPA documentation is not always accurate because it wasn't accurate in this instance. Therefore it might not be accurate in the Model 3 instance either. Is that the idea @SageBrush? Where is your data source to show the correct motor version? Where is the explanation what the thread is about? Where is the conclusion you wanted to draw? Why have you skipped all that in the opening message?

Also, if the Model 3 EPA document is inaccurate, in your version it would mean it is a complete coincidence that there were some news articles last year about Tesla making a deal with a Chinese rare earth elements supplier. Here is an example.

In addition, check out paragraph 10 in this article that starts with "Alternatively, in terms of ...". Here is the relevant section:

Although cheaper, the AC induction motor is larger, heavier, and less efficient resulting in more draw on the lithium ion battery pack, when compared to a permanent rare earth magnet motor. ... Tesla Motors likely chose the induction motor over the permanent magnet motor due to the existing REE [Rare Earth Elements] prices when their first electric vehicle was developed (Model S). As REE prices have fallen, the market fundamentals are now positioned for a long-term sustainable REE pricing environment where the benefits of rare earth permanent magnet motors far exceed the elevated cost compared to the AC induction motor currently relied upon.

Also, it seems unnecessary to create a new thread. Maybe this can be merged with an existing thread.

 

[chillaban]

I worked on high-power traction motor controllers for the government for almost 5 years. The term "AC Induction Motor" is absolutely specific to referring to a non-synchronous machine consisting of coils on the rotor and coils in the stator, and it's to contrast it from PMAC/PMSM (Permanent Magnet Synchronous Machine) motors. The control techniques are pretty significantly different, and I've never heard anyone in the field (no pun intended) referring to a PMSM as an "induction motor" of any kind.

Sure, both machines move through similar principles of EM induction, but that's a technicality nobody stops to think about. It's as nonsensical as someone not recognizing the difference between a microphone and a speaker because they're basically the same physical concept, or if you said "please pass the salt" and someone handed you a bag of water softener pellets… Sure technically some reading of the term could be ambiguous, but nobody who works on this stuff would use those words in that manner.

The OP's point still stands. In the EPA paperwork, the Prius Prime clearly has a synchronous permanent magnet motor, but is labeled as having an "AC Induction" motor. It calls doubt as to the accuracy of EPA documentation as a predictor of what underlying motor technology is involved.

 

[SageBrush]

The opening message doesn't do a good job explaining what we are supposed to understand from the attached file. I assume the idea was to show that EPA documentation is not always accurate because it wasn't accurate in this instance. Therefore it might not be accurate in the Model 3 instance either. Is that the idea @SageBrush?

You got it.

 

[D-egg-O]

I worked on high-power traction motor controllers for the government for almost 5 years. The term "AC Induction Motor" is absolutely specific to referring to a non-synchronous machine consisting of coils on the rotor and coils in the stator, and it's to contrast it from PMAC/PMSM (Permanent Magnet Synchronous Machine) motors. The control techniques are pretty significantly different, and I've never heard anyone in the field (no pun intended) referring to a PMSM as an "induction motor" of any kind.

Sure, both machines move through similar principles of EM induction, but that's a technicality nobody stops to think about. It's as nonsensical as someone not recognizing the difference between a microphone and a speaker because they're basically the same physical concept, or if you said "please pass the salt" and someone handed you a bag of water softener pellets… Sure technically some reading of the term could be ambiguous, but nobody who works on this stuff would use those words in that manner.

The OP's point still stands. In the EPA paperwork, the Prius Prime clearly has a synchronous permanent magnet motor, but is labeled as having an "AC Induction" motor. It calls doubt as to the accuracy of EPA documentation as a predictor of what underlying motor technology is involved.

Thanks for the laugh. And I wish I could click that helpful button many times. Sorry for rustling your feathers @SageBrush I got caught up in the details, I didn't take time to learn the general/industry terms.

@hacer you were very helpful too.

 

[chillaban]

Thanks for the laugh. And I wish I could click that helpful button many times. Sorry for rustling your feathers @SageBrush I got caught up in the details, I didn't take time to learn the general/industry terms.

@hacer you very helpful too.

No worries! I learn so many new things from here too. Man, I've been on a lot of car forums in my days of owning mostly German cars, but I've never seen a community so vibrant and passionate about the car/company/tech!

 

[D-egg-O]

No worries! I learn so many new things from here too. Man, I've been on a lot of car forums in my days of owning mostly German cars, but I've never seen a community so vibrant and passionate about the car/company/tech!

You're telling me. This is the only car forum I've even been a part of.

 

[Thomas Edison]

No worries! I learn so many new things from here too. Man, I've been on a lot of car forums in my days of owning mostly German cars, but I've never seen a community so vibrant and passionate about the car/company/tech!

TMC is home to the nerd, watch them in their natural habitat.

 

[gregincal]

Seems really silly to create a new thread to make a point that would have made a lot more sense in the original thread (or actually there are two threads that have discussed this). Not only silly, but counterproductive. Now we will have basically the same conversation happening in three threads.

 

[Thomas Edison]

Seems really silly to create a new thread to make a point that would have made a lot more sense in the original thread (or actually there are two threads that have discussed this). Not only silly, but counterproductive. Now we will have basically the same conversation happening in three threads.

I sent a request to the moderator.

 

[ohmman]

mod note: threads merged.

 

[omgwtfbyobbq]

I wonder if the Model 3 has some kind of hybrid motor/s setup.

My conclusion is that DC brushless drives will likely continue to dominate in the hybrid and coming plug-in hybrid markets, and that induction drives will likely maintain dominance for the high-performance pure electrics. The question is what will happen as hybrids become more electrically intensive and as their performance levels increase? The fact that so much of the hardware is common for both drives could mean that we will see induction and DC brushless live and work side by side during the coming golden era of hybrid and electric vehicles.

Induction Versus DC Brushless Motors

 

[SageBrush]

I wonder if the Model 3 has some kind of hybrid motor/s setup.
Induction Versus DC Brushless Motors

I'm more inclined to guess that either

• The EPA CSI report has an error
• The AWD Model will have one Induction and one PM motor.

 

[McRat]

They are probably going to have PMAC motors. They shaved a LOT of weight off that car over the original MS60 which was a car on a diet.
Weight reduction is like eating an elephant. One bite at a time. 10lb here, 1lb there, 3oz here, 5g here.

I'm guessing the inverter and charger went on a diet too, as did the axles, wheels, seats, insulation, stereo, and perhaps even glass thickness.