EPA Certification Data

MelindaV

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#61
I'm trying to better understand these documents. I managed to track down what UDDS stands for - Urban Dynamometer Driving Schedule (aka "the city test").
https://www.epa.gov/vehicle-and-fuel-emissions-testing/dynamometer-drive-schedules

For electric cars, the test procedure is to run each of the highway & city tests in succession until the battery completely runs out. The results are then multiplied by 0.7 to come up with the numbers on the sticker.
https://www.fueleconomy.gov/feg/pdfs/EPA test procedure for EVs-PHEVs-7-5-2012.pdf

So, given the certification report for the Long Range Model 3, I would expect to see:
City Range = 495.04 * .7 = 347 miles
Highway Range =
454.64 * .7 = 318 miles

Holy Crap!!! The Standard Battery might end up beating the Bolt's EPA range after all! :)
so is the .7 for air resistance that would not be an issue on a dyno?
 

garsh

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#62
so is the .7 for air resistance that would not be an issue on a dyno?
That could be part of the reason. And given that the testing is performed on a dyno, low Cd values don't help with the mileage estimates. I guess that's why the EPA allows some other options besides the 0.7 "fudge factor":

Electric Vehicle - Adjustment Procedure used to Derive FE Label (Window Sticker) Estimates -
EPA regulations require fuel economy, energy consumption, CO2 and driving range values listed on the FE Label (window sticker) to be adjusted to more accurately reflect the values that customers can expect to achieve in the real world. EPA currently allows fuel economy, energy consumption, CO2 values, and range values listed on the FE Label (window sticker) for electric vehicles to be adjusted using one of the following methods:
  • by multiplying city/highway fuel economy and range values by 0.7 and dividing city/highway energy consumption and CO2 values by 0.7;
  • using the vehicle specific 5-cycle method described in 40 CFR 600.210-12(a)(1);
  • using a method which is equivalent to the vehicle specific 5-cycle method described in 40 CFR 600.210-12(a)(1) (with prior EPA approval);
  • using adjustment factors which are based on in-use data (with prior EPA approval).
Currently, most EVs use the first method (the 0.7 factor).​
 

garsh

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#63
In the Model S document that @MelindaV posted, I found the values for the 100D. When I apply the same 0.7 fudge factor to those values, I get:
City Range = 414.45 * .7 = 290 miles
Highway Range =
469.99 * .7 = 329 miles

That doesn't match the official EPA values of 331 city / 337 highway. But it's interesting that the official EPA results are even *better* than what I calculated from the certification document. :)
 

Model34mePlease

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#64
We may be setting ourselves up for disappointment again, but I think we are going to find the real-world range of the M3 to be really good.

On the one hand, we are seeing dynamometer range numbers that are pretty over-the-top, especially for simulated city driving (495 miles). On the other hand, there is this:

upload_2017-8-8_7-44-45-png.2798

These curves are based on the EPA ramp test that derives parameters that model friction and air resistance. As you can see, the M3 is only ok at the very bottom, but becomes one of the best above 20 or 30 mph, so should be really good on the highway, where the dyanamometer test was 'only' 455 miles. It should be noted that the ONLY Teslas that equal or exceed the dynamometer milage of the M3 are the S 100D and S P100D, and then only on the highway (and only by a little - 470 miles).

Time will tell....:)
 

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#65
Anyone else a little disappointed that the motor is only rated 258hp vs 375-400hp of the S/X?

I was surprised to see permanent magnet at first, but I think it does make sense. The material might be slightly rarer, but cost of copper is very high, so it is probably still cheaper than the cost of the copper windings they replace in the rotor. Furthermore it makes a significantly simpler motor to assemble, replacing lots of windings with chunks of magnets. @John 's article above also states they are more efficient as well due to less efficiency loss from windings.
Also, the inverter electronics would also be much simpler, as they only need 3 phase AC for the stator and not an additional 3 phases for the rotor.
Down side is that you can't control and vary the magnetic charge of the rotor, which allows for some 3D torque curve maps and electromagnetic trickery.
The biggest point is that the permanent magnet is simpler and that's what everything needs to be to make the Model 3 mass producible.
In an induction motor, the rotor does not have copper windings, they are instead aluminum, cast into the rotor stack.
The permanent magnet AC motor replaces the aluminum windings with magnets.

Here is a very good video on the subject:


Here is a diagram:
upload_2017-8-8_10-2-14-jpeg.2799
 

garsh

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#68
there's comments also that the new magnet style motor is more efficient at the lower speed stop/start vs the induction better at highway speed travel (or did I flip the two? totally second guessing my memory now....)
It looks like, in general
  • permanent magnet motors are more efficient, at any speed
  • permanent magnet motors are smaller for a given power.
  • permanent magnet motors tend to be more expensive, due to the magnets.
http://empoweringpumps.com/ac-induction-motors-versus-permanent-magnet-synchronous-motors-fuji/
 

Topher

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#71
I have a feeling that as soon as Elon thinks M3 production is out of hell, the S & X are going to get a big battery pack upgrade based on the new cells he is using in the M3
Tesla has a contract with Panasonic to provide the cells for the Model S and X. They won't switch over to 2170s until that contract expires. Or until the savings exceed the early cancellation penalty (plus the conversion costs).

Thank you kindly.
 
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#73
There is no need to switch to 2170 on S/X.
2170 is optimized for best-bang-for-a-buck (best performance for any given price).
21850 is much more leaning towards performance. Cylinder is thinner, easier to keep chemistry temperature homogeneous.
Harry-Potter book sized slates Leaf/Bolt have lean toward best price, sacrificing everything else.

It's a misunderstanding that 2170 offers more performance per kWh of capacity. Including charge/discharge capability.


I don't smoke cigars. Are you calling me an idiot?
I have some hair left on my head. Therefore it's not me on the picture.
 

JRP3

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#75
It looks like, in general
  • permanent magnet motors are more efficient, at any speed
  • permanent magnet motors are smaller for a given power.
Tesla disagrees somewhat https://www.tesla.com/blog/induction-versus-dc-brushless-motors

Thus, the induction machine when operated with a smart inverter has an advantage over a DC brushless machine – magnetic and conduction losses can be traded such that efficiency is optimized. This advantage becomes increasingly important as performance is increased. With DC brushless, as machine size grows, the magnetic losses increase proportionately and part load efficiency drops. With induction, as machine size grows, losses do not necessarily grow. Thus, induction drives may be the favored approach where high-performance is desired; peak efficiency will be a little less than with DC brushless, but average efficiency may actually be better.
My guess is Tesla felt the lower powered Model 3 motor would be better using a PM design over induction.
 

JRP3

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#77
Not sure of your point. PMAC/BLDC motors are a different motor architecture than AC induction motors.
 

garsh

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#78
But the Model 3 uses permanent magnet with 3–phase AC.
Not sure of your point. PMAC/BLDC motors are a different motor architecture than AC induction motors.
My guess is that @Kizzy is wondering why you posted an article comparing AC induction motors to brushless DC motors, when the Model three has a permanent magnet AC motor.

The answer is that a Permanent Magnet AC motor is the same thing as a Brushless DC motor. :)

Mechanically, they are the same. The only difference is how they are run. Historically, brushless DC motors use a sensor to determine rotor position. The sensor then controls the waveform sent to the stator windings. And that waveform tends to be rectangular (well, trapezoidal).

Once high-power control electronics started being manufactured (late 80s), high-power variable-speed AC induction motors started to become more practical, since we could now send sinusoidal waveforms through the stator windings. Those same waveforms work perfectly well in a brushless DC motor - even better than the old trapezoidal waveforms. So at this point, brushless DC motors started to also be called Permanent Magnet AC motors when they were being driven similarly to AC induction motors.

Ah, it feels good to make use of that EE degree I earned so long ago. :D
 
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MelindaV

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#80
not sure how this article may relate to Tesla's induction vs PM motors, but lays out the basic differences between the two types of motors.
My big takeaways from this article is the PM is smaller and lighter than the IM, the magnets are more expensive than the copper that would go into a IM, 2x as efficient at low speed, equally efficient at mid and highway speed. Maybe one of you that have that EE degree can take a look and give your opinion ;) (since I'm still wrapping my head around @garsh's last comment that a brushless DC is the same as an AC PM motor...)

induction


permanent magnet