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Sort of expanding a little on early adopter's response.
When you run an Induction motor off of a variable frequency drive (VFD). The motor is limited by the amount of current the coils can handle. This current is turned into torque. So you get a direct flat line for torque. As the motor increases speed the inverter/VFD will increase voltage. At the 7k inflection point the motor is running at maximum current and maximum voltage (and thus peaking in power). From that point downward the motor starts creating back emf, this is the motor producing voltage to counter the voltage supplied by the VFD, thus lowering the net voltage across the motor, and the current with it.
The second inflecting point is probably inherent in the ratings of the components in the inverter/VFD itslef. Or it could be programmed in the inverter/VFD to gracefully hit top speed.
Yes.Would anyone be shocked if Tesla announced an Autobahn model?
Yes.
- 125mph is enough even for Autobahn
- they won't sacrifice lowspeed acceleration
- multigear transmission is in the tesla's past not future
- KISS
Also, those torque/RPM charts should be tourqe/speed charts now that we have singespeed gearboxes.
Or even better: max acceleration/speed charts considering vehicle weight
So another way then to look at this graph, is to say your best efficiency is anything below 7k RPM, as after that you have some voltage not being directed to the propulsion of the car. Obviously Elon has posted the graph for speed vs range, but this dynamic comes in play, behind the scenes... correct?
So another way then to look at this graph, is to say your best efficiency is anything below 7k RPM, as after that you have some voltage not being directed to the propulsion of the car. Obviously Elon has posted the graph for speed vs range, but this dynamic comes in play, behind the scenes... correct?
Not necessarily, no.
Not really, electric motor is primarily limited by heat buildup and secondarily by maximum current surge it can take without burning the wires. The third limit is maximum voltage that is rarely a limiting factor i.e. insulation is usually strong enough.I think it's far more likely that the motor is simply limited in how much power it can handle
Not really, electric motor is primarily limited by heat buildup and secondarily by maximum current surge it can take without burning the wires. The third limit is maximum voltage that is rarely a limiting factor i.e. insulation is usually strong enough.
Electric motor is under maximum stress at 0 RPM, it acts almost like a short-circuit. After it manages to start turning it can take some maximum current all the way up to maximum power. After that back-EMF starts to eat away its power output. People doing DIY electric cars often found out that they can climb a hill faster in 4th gear than in third - motor would spin faster and output less power.
I transformed Torque/Rpm chart that EarlyAdopter posted above into a Power/Speed chart for MSP:
View attachment 22862
We can learn from this chart that:
- From 0 to 60 there is constant torque
- Model S has max power output at 60 mph
- From 60 up to 125 mph (15k rpm) power drops slightly but not much
- At 125 mph power drops sharply (at 16k rpm there is only ~ 60 Nm/100kW of torque/power left)
- Model S drivetrain (reduction gearbox) is optimized for 0 - 60 times
- At 125mph there is still ~250kW of power that should suffice for at least 150 mph with longer gear-ratio. 0-60 times would be worse/slower though.
Autobahn model S won't happen, but one could try "making one at home" - mount rear tires with bigger diameter like say 285/40R24. Such tires would move max speed from 125 up to ~150 mph.
Tires are torque-limited as well and most people wouldn't want their Model S to have big/wide drag slicks on the back of a 70mph-limited car, even it it could get to 70mph in a few seconds...Lastly, I strongly disagree with your conclusion that Model S gearing is optimized for 0-60 times. To achieve the best 0-60 times in a system only limited by a max torque, a max power, and a max RPM, you're going to do best when you gear the motor to hit its max RPM right around 60 mph. If you do that, you'll be putting out maximum power from like 20 - 60 mph. As the car currently is, you only put out the maximum power when you're above 50 mph.
No, it doesn't. It is a plot of preproduction version. I believe Tesla never released more up to date chart.Also, I'm not sure what the source for the plot was, but it doesn't necessarily match the specs of any production car:
I didn't say it would have been a good idea to change the gear ratio by 2.Tires are torque-limited as well and most people wouldn't want their Model S to have big/wide drag slicks on the back of a 70mph-limited car, even it it could get to 70mph in a few seconds...
Not that it matters, but 130mph is available.- 125mph is enough even for Autobahn
- 125mph is enough even for Autobahn
Then why should they enable even higher speeds and thus sacrifice low-speed performance? As I see it, you contradict yourself.And again, you wouldn't be able to drive the Model S at this speed for any extended period of time.
This problem, if it is a problem for you, can hardly be fixed by increasing the Model S' top speed (by whatever means).My normal cruising speed when I am in Germany is 100 MPH, something the Model S wouldn't handle well with any meaningful range.
That's very good range at high speeds! Many gas cars have similar ranges at those kinds of speeds. Heck, I had a Subaru which would only do about 230 miles before I had to fill up at US highway speeds, at Autobahn speeds I'd expect to do no better than 150 miles or so.Two German journalists already tried to bring down range as far as possible by racing the Autobahn, and they could still go 250 km (155 mi) on a single charge.
No, it doesn't. It is a plot of preproduction version. I believe Tesla never released more up to date chart.
MS60 | MS85 | MSP | |
Top speed | 120 mph | 125 mph | 130 mph |
Max torque | 0-5,000 rpm 317 lb-ft (430 Nm) | 0-5,800 rpm 325 lb-ft (440 Nm) | 0-5,100 rpm 443 lb-ft (600 Nm) |
Max power | 5,000-8,000 rpm 302 hp (225 kW) | 6,000-9,500 rpm 362 hp (270 kW) | 5,000-8,600 rpm 416 hp (310 kW) |
Speed mph | Power kW |
25 | 5 |
45 | 10 |
55 | 15 |
65 | 20 |
80 | 32 |
MS60 "redlines" at ~14.200 rpm, MS85 at ~14.800 and MSP at ~15.300 rpm.
These limits are set electronically, even MS60 has still enough power (~ 80kW) to climb to at least 130mph, but it would take same time to get there.
MS85 and MSP reach top speed when still having about 110kW of power.
Power in above plot is max motor output power but this is not the power that actually accelerates the vehicle as some of it is consumed to overcome the ever increasing air drag and rolling resistance.
We can deduce required power to maintain a constant speed from energy consumption chart here:
Raw max output power at 80 mph is ~280 kW for MS85/MSP and ~200 kW for MS60.
Speed mph
Power kW 25 5 45 10 55 15 65 20 80 32
MS85/MSP have ~40% more raw output power at this speed but almost half stronger acceleration.
Not that it matters, but 130mph is available.