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Electric motor characteristics and curves

Discussion in 'Technical' started by Jozeph, Mar 28, 2017.

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  1. Jozeph

    Jozeph New Member

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    Mar 28, 2017
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    Kazakhstan
    Hi! I've been looking for proper full-load curves for Tesla Model S and I've found that at the speed of 40 mph (approximately 64 km/h) car almost gains full power. This looks pretty strange to me, because speed continues to rise. As I know, there is no gearbox on Model S and the ratio in the gear unit is constant. So, why do we see increase of speed as the power and torque go down? As I see it, you can only do it by changing electric motor rpm. So, how does Tesla changes them? Do we have any curves (like rpm/power/torque) that describe it? e98Er.png
     
  2. arnis

    arnis Member

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    To reach gentleman agreement top speed 250kmh or 155mph vehicle like Model S and BMW 5-series need around 160kW of constant power. Vehicles with more drag need more - less drag need less. So some Teslas car reach gentlemen top speed agreement speed. At least for a short period as RWD model rotor will overheat. AWD should be able continue for longer.

    Motor RPM can be calculated as we know reduction gear ratios and tire diameters.
     
  3. jkn

    jkn Member

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    From 0 to 40 mph acceleration is limited by traction, so car cannot use full power. Above 40 mph acceleration is limited by available power. Above 73 mph (M SP above) acceleration is limited by available torque and power goes down. When power is low enough car cannot accelerate more.

    Motor RPM is almost 30* frequency of 3 phase AC into motor. (Almost, because there is some slip.)
     
  4. arnis

    arnis Member

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    Actually from 0-40mph it is not just the traction. People have used super sticky tires.
    Even though Tesla is magnificent, it is not limitless. There is a maximum torque value set to protect drivetrain.
    And also maximum amps battery can support. And also maximum amps inverter can invert.

    AFAIK OEM tires are near the maximum grip they need to have for maximum acceleration.
    With supersticky ones acceleration gets only marginally better from 0-30.
     

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