JBee
Well-known member
- First Name
- JB
- Joined
- Nov 22, 2019
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- Australia
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- Cybertruck
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- . Professional Hobbyist
You need to include the final drive through a differential (if you have one) and realise that the limiting factor on many EVs is the traction of the tyres at any given speed. So adding more torque in any of the Tesla drivetrains just means it can spin the wheels easier, not that it would produce a meaningful increase in performance or efficiency.This must be what you are talking about, being able to produce lots of torque at low end.
So power is the product of torque and speed. At low speed the motor is delivering low power but full torque. Ok. At high speed the motor is still delivering full torque but it is now delivering more power.
I am saying that with a power split you can get MANY times the low end torque than the motor can deliver at that speed by itself. The motor is delivering more power at high speed. Torque is power divided by speed. Deliver a lot of power at low speed and you will have lots of torque. Again, many times more low end torque can be produced with the power split than with the motor alone.
Also, being able to extract all the energy, even at low speed even though there is not much power there, is a big deal. No need to tell me that it is not a big deal.
Using it as a power split device, like the Prius does, was done so that the Prius doesn't need a clutch and can be essentially "direct drive" but with a ICE attached, which is not normally possible. There one electric motor would spin in reverse at the same speed the ICE would spin forwards, meaning that the wheels would have 0rpm through the planetary gear. That is also why the Prius had a limited speed and power in reverse, in fact they won't reverse up a steep hill well because of this.
But in a electric only situation the variable gearing is not that beneficial if your motor already has full torque from 0rpm and has enough motor rpm to reach the vehicle top speed through a simple single gear ratio.
One idea I had ages ago was to use the powerspilt device and two motors as a flywheel storage for acceleration purposes on smaller EVs. There you could preload the motors by spinning them in reverse of eachother at the lights, then on launch they would both slow down putting both the power of the motors and the power of the decelerating motor mass/flywheels into the wheels for faster acceleration. In reverse you could do the same for regen to spin up the flywheel. But now I have a version of that idea that doesn't use a planetary gear at all and does it all electro-mechanically instead which also allows for higher flywheel rpm without the friction. The primary reason for it is to reduce peak power on smaller battery packs and to use it as a more "mechanical" voltage converter.
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