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Model 3 electric motor design change.....thoughts?

Model 3 electric motor design change.....thoughts?

I wonder if this will have an affect on regenerative breaking in some way? Probably more efficient and easier on the battery, since AC induction motors use electricity stored in the battery.

https://www.edmunds.com/car-news/auto-industry/2017-tesla-model-3-has-un...

sp_tesla | 2017年8月17日

Wow, good to know, thanks for sharing.

Sound like it would be very suitable for vans trucks etc.

SUN 2 DRV | 2017年8月17日

If true, it might also allow regen to work better down at slower speeds...

Coastal Cruiser. | 2017年8月17日

rrobin36, there are several threads on this forum discussing this issue. You may wish to search the forum and read through them to see what people are saying (if you don't know how to search look at this post for instructions (https://forums.tesla.com/forum/forums/owners-manual-companion-omc-and-us...).

Having said that, I would offer that the edmunds article has some flaws, so don't take it as gospel. Although, yes, there is evidence that the Model 3 will have not have an induction motor, that has not been confirmed by Tesla.

The one item that the article got wrong is when they said:
"Not to oversimplify it too much, but AC induction motors have to use some of the electricity stored in the car's battery to generate the necessary magnetism within the motor. Permanent magnet motors have no need for this because they are made using, as the name suggests, permanently magnetic materials."

That is not only an oversimplification, it is not true. Even if the new motor in the 3 is a permanent magnet motor, you can be assured the motor still has "to use some of the electricity to generate the necessary magnetism within the motor". Perhaps less energy is drawn from the battery, but there is quite likely still an inverter to turn the battery's direct current into alternating current, which in turn creates magnetic fields in the stationary portion of the motor (stator). All that's different between the two designs is how the opposing magnetic field on the rotor is created; either by induction from the magnetic fields in the stator, or, by having magnets attached to the rotor.

Techno quibbling aside, I have read that an electro-magnet based motor has better regen capability. That may account for the superior in town efficiency.

As best I understand the Tesla Model S does not come to a full stop just with regen (owners?) but the Chevy Bolt, with a permanent magnet motor, does come to a full stop with pure regen. I drove one and can testify to that.

carlk | 2017年8月17日

Caostal_Cruiser Stronger regen and better stop and go efficiency could be the reason but do you know what was giving up with the permanent magnet motor? I thought I've heard AC induction motor has the advantage of power output but I'm not sure whether if that is true.

carlk | 2017年8月17日

BTW those speculations came from the EPA test form description which has no assurance of its accuracy and from a Chinese rare earth supplier that said Tesla has placed a rare earth magnet order. No one knows what those magnets will be used for it could be A/C, electric brake or any places that use the magnet. If this is true Tesla will have to put it in the 10K report since it has the potential of presenting a material risk from rare earth supply. We will soon find out.

jeffand | 2017年8月17日

A permanent magnet motor are more efficient than induction motor by about 2 to 4%. The 2004 Toyota Prius uses permanent magnet motor in it's hybrid drive system. So using a permanent magnet motor in vehicle is nothing new.

Coastal Cruiser. | 2017年8月17日

carlk "Caostal_Cruiser Stronger regen and better stop and go efficiency could be the reason but do you know what was giving up with the permanent magnet motor? I thought I've heard AC induction motor has the advantage of power output but I'm not sure whether if that is true."

If I understand your question carl, as best I understand from the research I did on the induction motor for an article I posted to clean technica (so wearing a pseudo journalism hat, not an electrical engineering hat), and as has been stated by many in the other motor threads... the induction motor is more flexible (you have control over, and can vary the electromagnetic fields), simpler design, fewer [maybe hard to source] parts, and better high speed performance.

Also, when I was interviewing a guy named "Ivan" (of Ivan's Garage) who winds his own motors for his car conversion projects, at one point he said to me "NOTHING IS GOING TO GIVE YOU TORQUE LIKE A DC MOTOR". He kind of underscored that remark.

It is going to be very interesting to see what the motor design team has come up with for the 3 because it is presumed they may have solved one or more of the downsides to the permanent magnet motor vs the induction motor. There is even a variant termed the "reluctance motor". Again, JB indicated last year a totally new motor for the 3.

Can you imagine enabling ludicrous mode on a reluctance motor? Might just break time/space barrier.

Here is a link to the reluctance engine:
en.wikipedia org/wiki/Reluctance_motor

And if you have not read the article on induction vs permanent magnet motors by former Tesla engineer Wally Rippel:
https://www.tesla.com/blog/induction-versus-dc-brushless-motors

And this is a less often linked article by Tesla co-founder Martin Eberhard:
https://www.tesla.com/blog/motor-city

And for anyone trying to understand the basics of the induction motor here is my attempt at explaining it:
https://cleantechnica.com/2016/05/30/nikola-teslas-19th-century-inductio...

Coastal Cruiser. | 2017年8月17日

To be clear, the reluctance motor mention is pure speculation on my part. I mention it only as a reminder for us to keep an open mind about what Tesla has come up with. There are many possibilities that we are unaware of.

milesbb | 2017年8月17日

Very sad to see them not use Nikola Tesla's greatest invention, the 3 phase induction motor IMO. Tesla Inc will now rely on China for rare earth magnets. China enacted a 2010 embargo on rare earth shipments to Japan for leverage in a territorial dispute. Good thing we have a president that knows the art of the deal. No chance of a dispute with China with Donald in charge. Or maybe time to sell Tesla stock before this all blows up.

Coastal Cruiser. | 2017年8月17日

"China enacted a 2010 embargo on rare earth shipments to Japan for leverage in a territorial dispute"

And they got bitchslapped for doing so. But again, we don't know what's in the new motor. Best to have a wait and see attitude.

PoweredBYsolar | 2017年8月17日

slightly disappointed by learning the motor in the model 3 is different than the model s and x. I hope this does not sacrifice the performance I am yearning for. I placed my reservation on 3/31/16 in Pasadena, CA, before the video release. As such I should be one of the first to receive the model 3. To date I have not been welcomed to design my model 3.

Remnant | 2017年8月18日

@Coastal_Cruiser (August 17, 2017)

<< There are many possibilities that we are unaware of. >>

Good point ... !

Open ended speculation can only lead to blurry pipe dreams.

Scuffers | 2017年8月18日

Not sure I would take any of this talk of Perm-Mag motors seriously unless Tesla specifically say so.

Seems to me everybody is jumping on the way a std form was filled in as a place-holder some time ago and may well be wrong.

I would be very surprised if they move away from induction motors, particularly when they have said they will be using the 3's motors on the Semi-truck.

Remnant | 2017年8月18日

@Scuffers (August 18, 2017)

<< I would be very surprised if they move away from induction motors, ... >>

If it has a PM design alternate already worked out, Tesla could offer it as an option, in order to probe the demand for it.

JustSaying | 2017年8月18日

If the document on file is incorrect/misleading who has the obligation to revise it?
Time frame?

carlk | 2017年8月18日

Too early to jump to conclusion until Tesla says so. There have to be overwhelming reasons to switch motor design not to mention to switch to one that uses the strategically less desirable material.

Just a fun fact Chinese obtained rare earth magnet technology when they bought, some say stole, the US Magnaquench plant from guess who, GM's Delco Remy division.

Bighorn | 2017年8月18日

If they call it Reluctant Mode, we'll know...

Coastal Cruiser. | 2017年8月18日

Maybe they will combine reluctant with ludicrous and have Ridiculous mode.

 
 
Then the Ridiculous car can race the Ludicrous for pink slips.

rrobin36 | 2017年8月18日

Appreciate the info Coasta_Cruiser and all the other input. I guess we'll wait and see what Tesla says about this, if anything.

msmith55 | 2017年8月18日

The advantage of PM motors is that they are a few percent higher efficiency than induction motors, the disadvantages are use of rare earth metals, and possibly demagitizing of the PM by exposure to higher than designed currents. Hopefully the peak current is carefully limited. And if the metals become to expensive, switch back to induction type is possible.

msmith55 | 2017年8月19日

This is why the performance of the PM motor is lower than the induction motor, to avoid demagitizing the PM magnets, The current must be carefully limited, to avoid long term loss in efficiency caused by these demagitizing currents. The limits are higher for an induction motor than a PM motor for the same size and weight!

AlMc | 2017年8月19日

Yesterday I emailed a couple people in the Tesla IR department for comment. I would advise others to do so as well.

While trying to read the tea leaves and speculating is, I admit, fun, if we really want to know what is going on with the 3 motor best to try to get a Tesla comment/verification.

Coastal Cruiser. | 2017年8月19日

email address please...

weluvm3 | 2017年8月19日

@AlMc and what about all the other things people are endlessly speculating about? Should Tesla be made to clarify those issues as well?

Good luck with that. They did't even want to tell us how many KWhs the batteries had. :-)

TeslaTap.com | 2017年8月19日

PM or Induction - not sure it really matters. I'm sure Tesla has done extensive analysis of both and used what made the most sense for the vehicle it's used in.

PS. I really questioned Tesla using PM in another thread, but now I'm less sure. One advantage of Induction motor is it appears to be a better choice when you are looking for high performance and good efficiency. When going for good performance and better efficiency, PM wins out. So the Model 3 could well use a PM motor. There is nothing wrong with either choice - just a slight tradeoff.

Remnant | 2017年8月19日

@msmith55 (August 19, 2017)

<< This is why the performance of the PM motor is lower than the induction motor ... [To] avoid [demagnetizing] the PM magnets, [the] current must be carefully limited ... >>

PM motors are generally smaller and have higher power density, lower current and temperatures, and faster ramp-up times. These features suggest higher rather than lower performance when compared to the induction motors of the same power.

Incidentally, with PM motors, Teslas might not need a Ludicrous option in order to support the 30-60 acceleration, which is a known deficiency of the current models. Furthermore, manufacturers clearly prefer PM motors for their higher performance models (such as Rimac, Porsche, etc.).

jefjes | 2017年8月19日

My choice for the motor in my Model 3 is the one the experts at Tesla choose for me...case closed. Maybe I'm too trusting but I sleep better at night believing those with the most knowledge, experience, and education on such matters are making the best decisions.

weluvm3 | 2017年8月19日

I agree with jefjes. Anyway, We'll stress test our cars enough during the first few years that, if PM isn't up to it, Tesla will end up replacing them, anyway. Frankly, it's a bigger risk to Tesla to change technology than to their customers.

TeslaTap.com | 2017年8月19日

@jefjes +1

@Remnant - I'm just going off of what Tesla engineer Wally Rippel states that Inductive has better performance characteristics, which admittedly, could have a "Tesla" slant :)

The reasons for picking PM vs Inductive in any application can be very complex. Rimac uses four motors, so perhaps they could get the performance they needed, vs using one induction motor. Since Porsche is quite a ways from real production, I don't know what they will use in the final product.

For some cars, it may have more to do with what is available. Very few automotive companies make their own motors (Tesla is one exception). DC motors take a lot less engineering work to implement, so engineers may choose something off the shelf just to get a compliance car out the door - or it could be the best choice for that car or the most economical choice.

One area PM motors are poor at is coasting - they require power to "freewheel" due to the magnets, but has the advantage of slowing a car to a stop. Induction motors require zero power while coasting, but can't regen to a stop - only slow to about 3-5 mph. For Tesla's AWD S/X, at cruising, Tesla can shut down one motor (i.e. freewheel) and only power the the remaining motor. This wouldn't be possible with two PM motors - both would need to be powered all the time. PM cruising efficiency may be reduced in an AWD configuration unless some kind of mechanical disconnection is made.

I'm not sure any of us armchair engineers can say what all the constraints Tesla (or other manufacturers) have to deal with in the choice they make.

Carl Thompson | 2017年8月19日

@jefjes:
"My choice for the motor in my Model 3 is the one the experts at Tesla choose for me."

This. I don't want to design and build a car myself so I trust the engineers at Tesla to have considered the pros and cons of the available options and pick what's best for the company (and by extension for the consumers who they need to buy what they sell). I'm sure it will be reliable and perform well because it is, after all, Tesla.

Carl

Carl Thompson | 2017年8月19日

@TeslaTap.com:
"DC motors take a lot less engineering work to implement..."

I though that while the Model 3 purportedly uses a PM motor that it was still an AC motor and not DC? But I don't know much about motors so maybe there's something I'm missing?

Carl

AlMc | 2017年8月19日

@Fiddlesticks:

you said >>@AlMc and what about all the other things people are endlessly speculating about? Should Tesla be made to clarify those issues as well?

Good luck with that. They did't even want to tell us how many KWhs the batteries had. :-). >>

Not saying Tesla needs to share anything with us. The point was/is: We can all speculate till we are 'blue in the face' but we will only know when Tesla decided to tell us. I am OK with that but if you want to know something about what type of motor the model 3 has: ask Tesla or wait until Jason (wk057) decides to tale one apart. Until then it is a fun discussion but gets us no closer to 'knowing'.

AlMc | 2017年8月19日

BTW: Tesla's IR department does respond to email at times (not every time) for information or clarification. But if you don't ask I am 100% certain they won't respond. :)

Coastal Cruiser. | 2017年8月19日

Carl Thompson "I though that while the Model 3 purportedly uses a PM motor that it was still an AC motor and not DC? But I don't know much about motors so maybe there's something I'm missing?"

Good question Carl. The Permanent Magnet motor is referred to as a "DC" motor, but in my view that is some rather sloppy terminology that took hold. Although in the often referred to Wally Rippel article he does make a side reference to a magnet creating a DC current, in fact most permanent magnet motors designed for automobiles are definitely AC motors, usually a 3-phase design.

The "AC" part for both designs is the magnetic field created in the stator (the outer stationary part of the motor). DC voltage from the battery is inverted to 3-phase AC (3 fat wires coming out of the inverter) that create 3 staggered magnetic fields around the stator in an oscillating fashion. It is actually the oscillating of the alternating current that creates the electromagnetic field).

The only difference between the induction motor and the PM motor is how the OPPOSING magnetic field is created on the rotor (it is the interaction of the two magnetic fields that forces the rotor to spin). With the PM motor the magnets attached to the rotor provide that opposing field. The induction motor creates the field on the rotor by "inducing" a current to flow on the rotor. The stator electromagnetic fields are what induces current to flow on the rotor, and it is the current flowing on the rotor that induces an additional electromagnetic field in opposition to the stator fields.

That last part was the genius of Nikola Tesla figuring out that there was a relationship, and a cause and effect between electricity and magnetic fields! :>

------------------
TeslaTap.com "One area PM motors are poor at is coasting - they require power to "freewheel" due to the magnets, but has the advantage of slowing a car to a stop."

TT, are you sure about that?

Coastal Cruiser. | 2017年8月19日

This is an old Tesla blog from co-founder Martin Eberhard talking about PM vs induction motors. There is this somewhat humorous (to me) passage where Martin is talking about "DC" motors and injects that "JB" just reminded him him that even so-called DC motors use AC (as described in prior comment).

https://www.tesla.com/blog/motor-city

This is why for our purposes here, it seems to make more sense to do as Tesla Tap and others do, and refer to the non-induction design as a permanent magnet design. There are such things as pure DC motors (no inverter, no AC) but that is not what's being used in electric cars such as the Bolt, the Volt, etc. ;>

Carl Thompson | 2017年8月19日

@CC

Thank you for the detailed answer!

georgehawley.fl.us | 2017年8月19日

I didn't do well in the DC and AC motors course back in the Stone Age but it was fun revving those things up in the lab.

It appears that Tesla is going the PM motor route for the M3. The regen performance may be a little different. As is is, I like to coast up to a stoplight using regen to try to time the light. If I miss the timing, then I have to tap the brake pedal to stop. It seems like the PM motor regen will actually stop the car. This will take a little getting used to in order to have it come to a halt at just the right spot.