PMAC vs induction motor for model 3

[scaesare]

Make it closer to 2 hours in between stops then. Or throw in some cold weather. Or wind. Or snow. Or elevation. Or rain. Or...

I still don't think the general public wants to be forced stop every 2 hours for 20+ minutes. Spending 20% of your travel time budget charging is too much, IMO.

Thus my point is: faster recharge time is indeed a worthy goal. But it doesn't replace the need to also pursue larger batteries, for a variety of reasons. And this is even with your fantasy 5-10 minutes superchargers, which don't exist.. especially ones that would charge to 100% in that time.

People currently are touting the "we don't need bigger batteries, just more superchargers" idea, and that's with today's tech that requires 40 mins to get to 80% charge, which makes that travel-to-charge equation in the above-outlined scenarios much worse.

 

[R.S]

Make it closer to 2 hours in between stops then. Or throw in some cold weather. Or wind. Or snow. Or elevation. Or rain. Or...

I still don't think the general public wants to be forced stop every 2 hours for 20+ minutes. Spending 20% of your travel time budget charging is too much, IMO.

Thus my point is: faster recharge time is indeed a worthy goal. But it doesn't replace the need to also pursue larger batteries, for a variety of reasons. And this is even with your fantasy 5-10 minutes superchargers, which don't exist.. especially ones that would charge to 100% in that time.

People currently are touting the "we don't need bigger batteries, just more superchargers" idea, and that's with today's tech that requires 40 mins to get to 80% charge, which makes that travel-to-charge equation in the above-outlined scenarios much worse.

Look, if the car can go, say 350 km at appropriate Autobahn speeds, you only need two single stops to take a over 1000 km trip. Very few even do such distances in their cars. And with a petrol car it isn't even much different. Not every petrol car can go 500km at autobahn speeds.

And it isn't 20 minutes charging, people don't mind detours, it is 5-10 minutes waiting for something. But like you mentioned, todays charging speeds are just too slow.

So that you have to stop a bit more often wouldn't really be an issue for most people. It's the 40 minutes to 80%. Because most people probably don't want to stop for 40 minutes somewhere. Or rather they hear they might be stranded for 40 minutes and therefore don'T buy the car. If the charging is done in 5-15 minutes, most probably wouldn't care.

 

[scaesare]

Look, if the car can go, say 350 km at appropriate Autobahn speeds

You seem to be changing the discussion parameters. Previously you said:

The 3 gallons equivalent of fuel are enough to get 200 km even at rather high speeds.

200km != 350km

... you only need two single stops to take a over 1000 km trip. Very few even do such distances in their cars. And with a petrol car it isn't even much different. Not every petrol car can go 500km at autobahn speeds.

Well, your original assertion would have required 4 stops. Since you are changing up your argument, lets' go ahead and inject some real world experience. Your assertion suggests 225 mile range at autobahn speeds in order to make your 1000KM journey with only two stops.

Bjorn recorded some of his autobahn driving: Bjorn Autobahn the result is much more like the original 200km range for a 85KWh you mentioned at the speeds he was driving. Even if you aren't driving quite that fast and have a 100KWh pack, there's no way you are going to get 350KMh at the "rather high speeds" you mention.

And it isn't 20 minutes charging, people don't mind detours, it is 5-10 minutes waiting for something. But like you mentioned, todays charging speeds are just too slow.

They mind them if they are forced to take them every hour and a half regardless if they want to or not. And regardless of if the 20+ minute stop is charging versus navigating to the charger, it's time off your schedule either way.

So that you have to stop a bit more often wouldn't really be an issue for most people. It's the 40 minutes to 80%. Because most people probably don't want to stop for 40 minutes somewhere. Or rather they hear they might be stranded for 40 minutes and therefore don'T buy the car. If the charging is done in 5-15 minutes, most probably wouldn't care.

So now it's up to 15 minutes? Is that to 100%? So no taper or even higher charging rates for the first 80%?[/quote]

 

[R.S]

You seem to be changing the discussion parameters. Previously you said:
200km != 350km



Well, your original assertion would have required 4 stops. Since you are changing up your argument, lets' go ahead and inject some real world experience. Your assertion suggests 225 mile range at autobahn speeds in order to make your 1000KM journey with only two stops.

Bjorn recorded some of his autobahn driving: Bjorn Autobahn the result is much more like the original 200km range for a 85KWh you mentioned at the speeds he was driving. Even if you aren't driving quite that fast and have a 100KWh pack, there's no way you are going to get 350KMh at the "rather high speeds" you mention.



They mind them if they are forced to take them every hour and a half regardless if they want to or not. And regardless of if the 20+ minute stop is charging versus navigating to the charger, it's time off your schedule either way.



So now it's up to 15 minutes? Is that to 100%? So no taper or even higher charging rates for the first 80%?

[/QUOTE]

We assumed a 200km range at over 200 kmh constantly, but as I proved this is impossible, so 350 km should be reasonable for say a LR Model 3 at reasonable speeds. The Bjorn video doesn't really show much and the LR Model 3 has about 17% more range, than the P85.

Tesla has a post where they show range over speed, their assumption is about 225 miles at 80 mph, so about 200 at 90 mph and 175 at 100 mph, which is a reasonable average speed at the Autobahn. With the 3 LR 17% more range, I thought about 200 miles, or about 350km would also be reasonable. Maybe at 180 kmh it would only be 300km.

Now with my last diesel car, fuel consumption at those speeds 180 kmh was about 13l diesel and it had a 60l tank. Which is about 460km of range. I just looked up a 525i's consumption at 180 km/h and it is an impressive 16.7l, which with a 70l tank would only be a bit more than 400km. So even if we say the M3 LR only has 300km, would that really be much worse than the petrol car? In any case you will have to take two 20+ minute breaks for the 750km trip, since the cars without a battery usually don't start full.

My charging rates were examples. Of course in reality you would probably only take 5 minutes to 80% and use that for calculation, but my point was, that with high enough charging speed range becomes less and less of an issue, even on the German Autobahn. Of course you could solve that by putting in more and more kWh into the cars, but how often would you really use them? IMO quicker charging speeds are more important.

 

[SageBrush]

Aerodynamic drag is a force
Fd = 0.5*p*Cd*A*v^2
So at twice the speed, the Force is 4 times as high.

Power is Force times velocity
Pd = Fd * v = 0.5*p*Cd*A*v^3
So at twice the speed, the Power required to maintain speed is 8 times as high.

Energy consumption in cars is given as energy over distance. Since E = P * t, energy consumption is:
E/d = (P * t)/d = P/v = F
(interestingly energy consumption is the same as Force, the "right" unit would actually be Newton)

So if we say the power used to overcome drag at 60 mph is 7.5 kW, the Energy consumption just because of aerodynamic drag is 125 Wh/mile, or 279 N. At 120 mph the Power needed to overcome aerodynamic drag is 60 kW, Energy consumption is 500 Wh/mile, or 1116 N.

Right you are, thanks for the correction

 

[scaesare]

<BUNCH OF OTHER STUFF SNIPPED>

Tesla has a post where they show range over speed, their assumption is about 225 miles at 80 mph, so about 200 at 90 mph and 175 at 100 mph, which is a reasonable average speed at the Autobahn.

It's odd that you are suggested that each 10mph step in speed incurs a linear drop in range, when you yourself posted the formula earlier that demonstrates that aero resistance rises exponentially with speed.

And if you are talking about the graph on Tesla's blog post on the subject:

it indicates more like a ~40 mile range decrease from 70 to 80. So you expect 80 to 90 to be less than that, and the jump from 90 to 100 to be less as well?

Given the exponential nature of resistance at higher speeds, and the range decreases that graph demonstrates, I'd suggest between 100-125 at 100 is more likely.

Again this is before any other factors. Do that trip in 20 degree weather, and you might have a 75 mile range car.

So you can continue to be of the opinion we don't need larger battery capacities in these scenarios however the evidence you are using to refute that doesn't support your arguments very well IMO.

 

[Rashomon]

It's odd that you are suggested that each 10mph step in speed incurs a linear drop in range, when you yourself posted the formula earlier that demonstrates that aero resistance rises exponentially with speed.

And if you are talking about the graph on Tesla's blog post on the subject:

View attachment 247609

it indicates more like a ~40 mile range decrease from 70 to 80. So you expect 80 to 90 to be less than that, and the jump from 90 to 100 to be less as well?

Given the exponential nature of resistance at higher speeds, and the range decreases that graph demonstrates, I'd suggest between 100-125 at 100 is more likely.

Again this is before any other factors. Do that trip in 20 degree weather, and you might have a 75 mile range car.

So you can continue to be of the opinion we don't need larger battery capacities in these scenarios however the evidence you are using to refute that doesn't support your arguments very well IMO.

For aerodynamic forces alone, power goes with V-cubed, and range with V-squared. So doubling speed (very roughly, as we're ignoring rolling friction) from 60 mph to 120 mph cuts range by a factor of 4, to 25 percent of what you get at the lower speed. When you get up 150 mph, it's more like a factor of 6, or about 15 percent of the range at 60 -- say from 300 miles to 45. It strongly argues that only the most aerodynamic of EVs are suitable for the autobahn. See the figure below of effective frontal areas, which has a slightly high value for the i3, which should be about 0.72 m2. The Tesla M3 is the best current production sedan around, with a lower effective area than most motorcycles. The VW XL1 wouldn't be horrible on the 'bahn as a pure electric, and the Peraves Monotracer better yet. I was once in one of those at 250kph crossing Germany, but it wasn't the e version. The ICE version had a 50-liter tank, and a German car magazine published a test that demonstrated it was the fastest vehicle for autobahn travel, because it had high-top-speed, quick acceleration, and an exceptionally long range at speed, something neither the Suzuki Hayabusa or the Porsche 911 Turbo they compared it to could match. Both spent too much time in fuel stations to beat the Monotracer on a Munich to Berlin run.

Oh, and ICE vehicles don't scale as neatly as EVs, because their engine efficiency generally increases at speed and increased load. Their range won't drop as quickly as the above formulas predict.

 

[alloverx]

Motortrend lists PM for M3 here
2018 Nissan Leaf First Drive Review - Motor Trend

 

[stopcrazypp]

Motortrend lists PM for M3 here
2018 Nissan Leaf First Drive Review - Motor Trend

They also list AC induction for the Leaf.

 

[scaesare]

For aerodynamic forces alone, power goes with V-cubed, and range with V-squared.

Correct. Hence the reason I pointed out that the assertion @R.S made of linear range drop at increasing speed didn't make sense.

 

[insaneoctane]

Anyone else amazed by how inefficient their ICE car(s) are by comparing them to the estimated energy content of your gas tank (easily found on the EV monroney sticker) ? My current ICE Nissan Altima has a 20 gallon tank. 20 X 33.7 kWh/gal = 674 kWh. Granted, I get 500 miles per tank, but at the cost of 674 kWh? Wow, not impressed. Think if I had to fill that up at a non-free supercharger! 674 kWh X $0.20 = $134.80 to fill up. Oh, and at the M3's advertised charge rate of 86 kW that's 7.8 hours to charge without tapper. Sure glad EVs are efficient!

 

[rabar10]

Mod note: 30 posts moved to exponential vs polynomial

 

[SageBrush]

Mod note: 30 posts moved to exponential vs polynomial

I object !

This is a Tesla forum, not a math forum.
"Exponential Vs Power Functions" is acceptable

 

[Trek12]

Seriously, watch this in its entirety.

Edit: And also this

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.

No.

The stator in the ac asynchronous motor does not "mimick" a permanent magnet. The stator is made of steel so it interacts with the rotating magnetic field. And you don't have to have two fields. You can rotate a simple piece of steel with a rotating magnetic field. Steel laminations and squirrel cage design help magnetic field "pull" and rotate the steel rotor. The stator not mimicking a magnet is the exact reason why it is called asynchronous. Because the magnetic field ALWAYS has to rotate at higher frequency than the rotator. If it turns at the same speed, no force will be applied on the rotator and it will slow down. If it was a magnet with poles, being asynchronous would create huge problems, like motor not working at all and design being in trash can.

On PMAC's however, rotor you have magnetic poles on the stator which are "locked" onto the opposing poles of the rotating field. That is synchronous ac motor. Here as rotor is a magnet, your motor turns exactly at the frequency of the rotating magnetic field. And you can make the rotor out of steel as well, then you induce a current to make it act as a permanent magnet. That extra current causes it to be little less efficient than a DC motor.

 

[R.S]

S

No.

The stator in the ac asynchronous motor does not "mimick" a permanent magnet. The stator is made of steel so it interacts with the rotating magnetic field. And you don't have to have two fields. You can rotate a simple piece of steel with a rotating magnetic field. Steel laminations and squirrel cage design help magnetic field "pull" and rotate the steel rotor. The stator not mimicking a magnet is the exact reason why it is called asynchronous. Because the magnetic field ALWAYS has to rotate at higher frequency than the rotator. If it turns at the same speed, no force will be applied on the rotator and it will slow down. If it was a magnet with poles, being asynchronous would create huge problems, like motor not working at all and design being in trash can.

On PMAC's however, rotor you have magnetic poles on the stator which are "locked" onto the opposing poles of the rotating field. That is synchronous ac motor. Here as rotor is a magnet, your motor turns exactly at the frequency of the rotating magnetic field. And you can make the rotor out of steel as well, then you induce a current to make it act as a permanent magnet. That extra current causes it to be little less efficient than a DC motor.

It isn’t the “steel” that makes an induction motor.

a) it’s iron
b) you don’t need it
c) Most PMAC Motors also have iron stators and rotors.
d) the squirrel cage is usually aluminum, or sometimes copper, if it’s a fancy induction machine. And that’s the only thing needed to make the induction machine work.

But in general it’s true that the induction motor doesn’t mimic a synchronous motor.

 

[Trek12]

S


It isn’t the “steel” that makes an induction motor.

a) it’s iron
b) you don’t need it
c) Most PMAC Motors also have iron stators and rotors.
d) the squirrel cage is usually aluminum, or sometimes copper, if it’s a fancy induction machine. And that’s the only thing needed to make the induction machine work.

But in general it’s true that the induction motor doesn’t mimic a synchronous motor.

I dont get why you are splitting hairs and making lists as if I said something fundamentally wrong.

"It isn’t the “steel” that makes an induction motor." = Never said that.

a) Steel is 90% iron.
b) I am not sure what you are trying to say.
c) Already pointed it out. " And you can make the rotor out of steel as well, then you induce a current to make it act as a permanent magnet."
d) 90% of squirrel cage is steel. Aluminum is really the outer part. If aluminum was anything significant the rotor wouldn't turn. Mind you aluminum has a very very weak interaction with magnetic forces. That's why your magnet does not stick to an aluminum bike.

 

[R.S]

I dont get why you are splitting hairs and making lists as if I said something fundamentally wrong.

"It isn’t the “steel” that makes an induction motor." = Never said that.

a) Steel is 90% iron.
b) I am not sure what you are trying to say.
c) Already pointed it out. " And you can make the rotor out of steel as well, then you induce a current to make it act as a permanent magnet."
d) 90% of squirrel cage is steel. Aluminum is really the outer part. If aluminum was anything significant the rotor wouldn't turn. Mind you aluminum has a very very weak interaction with magnetic forces. That's why your magnet does not stick to an aluminum bike.

The aluminum doesn't need to interact with magnetic forces, the magnetic field through the aluminum winding needs to change. You can build an inductor motor with no ferromagnetic material, but not without conductive material in the rotor. The iron works as an amplifier for the magnetic field, but it is the current induced into the conductor, mostly aluminum, that makes the rotor turn.

 

[Trek12]

The aluminum doesn't need to interact with magnetic forces, the magnetic field through the aluminum winding needs to change. You can build an inductor motor with no ferromagnetic material, but not without conductive material in the rotor. The iron works as an amplifier for the magnetic field, but it is the current induced into the conductor, mostly aluminum, that makes the rotor turn.

you are saying the same things as I did with different sentences again.

Aluminum or copper winding are used for the same reasons in an induction motor. To create a rotating magnetic field by connecting them to an ac current.

You cannot make the rotor out of aluminum, as it will not interact with the rotating magnetic field. The Rotor of a motor is the rotating part. Rest of it is called stator. Copper or aluminum parts in an induction motor does not rotate.

You are probably mixing rotor and stator, windings are not in the rotor.

 

[JRP3]

Copper or aluminum parts in an induction motor does not rotate.

The new wave of copper rotor applications | Copper Rotor Motor

Copper rotors are now being used in different branches of industry, especially for applications where high efficiency is required.

 

[R.S]

you are saying the same things as I did with different sentences again.

Aluminum or copper winding are used for the same reasons in an induction motor. To create a rotating magnetic field by connecting them to an ac current.

You cannot make the rotor out of aluminum, as it will not interact with the rotating magnetic field. The Rotor of a motor is the rotating part. Rest of it is called stator. Copper or aluminum parts in an induction motor does not rotate.

You are probably mixing rotor and stator, windings are not in the rotor.

Where do you think the induction part comes from? Of course the rotor needs conduction parts, otherwise it wouldn't be an induction motor.

The squirrel cage is made of aluminum, or copper and it generates the rotor field by having a current induced by the stator field. The iron is only used to enhance the magnetic field.

But an induction motor with no iron at all will also rotate. Without any conductor in the rotor it's impossible, because then there is nothing where the rotor current can be induced into.

If you want a motor w/o any conductor in the rotor you need one with permanent magnets. Or one that works with reluctance torque. Maybe you are confusing a reluctance machine, with an induction motor?