Welcome to Tesla Motors Club
Discuss Tesla's Model S, Model 3, Model X, Model Y, Cybertruck, Roadster and More.
Register

motor efficiency

This site may earn commission on affiliate links.
I will be amazed if this microsleep theory turns out to be true.

When i originally posted the idea back in the original tweet thread it was an idealistic theory for pulsing. Any time you can cut power to something you obviously make gains in energy efficiency unless it wastes energy in the switching process. Couple that with higher efficiency at higher load it made sense to me.

I simply thought what could they do across the range and as Jerome had mentioned firmware too i started to think about changes to the control hardware. I thought maybe not all cars have nav or supercharger so it can't be map based or route through superchargers. Why would it be 3rd party charging waypoints when the tesla experience is much better. It can't be dual motor based, so it's either got to be motor efficiency (logical progression - they released torque sleep) or it has to be battery mapping based.

Trouble is, once you spend time theorising, your favourite starts to lead you down a certain path and you look for facts to convince yourself the theory is the right one. Stepping back, i actually posted saying its probably a pigs can fly theory but it seems other people had similar ideas.

It does make sense but without being an engineer on electric motors who knows. If anyone can make it work it will be the tesla engineers. The automotive world are slowly acknowledging tesla as the the lead on this and the germans have already thrown ego ahead and said they are now going to do it better. Porsche.

The reason why you haven't seen motor efficiency in industrial application is because they size the motors to run at peak efficiency and set load for the application install.
 
Suppose the motor is turning at 7000 rpm. Due to friction, unless you provide electricity to power the motor it will slow down. Assume that it takes 1 kW of electricity just to maintain 7000 rpm. Then the mechanical power output of the motor is 0 kW and it is consuming 1 kW of electricity. Efficiency is 0%. If you want to go 10 mph, you need the motor to provide 1 kW of power. That means you need 1 kW of electricity just to counteract friction and another 1 kW of electricity to provide the mechanical power needed to propel the car. In this case you get 1 kW of mechanical power output from the motor by feeding it 2 kW of electricity, i.e. efficiency is 50%. If instead you drive on the freeway, you might need 14 kW of power to maintain speed. Friction will increase with higher RPMs. In this case, you might need 2 kW of power to counteract friction and 14 kW to provide the output power for the motor to propel the car, i.e. efficiency is now 14/(2+14) = 88%.

Note that regen is 95% efficient over most of the regen range. I'm not sure why the motor is so much more efficient at regen versus propelling the car.
 
You can see a plot of mechanical power vs. electrical power for my EV at 6750 rpm at the following link and in subsequent posts. The power measurements from the battery and the motor are not perfectly synchronized so the measurements are a bit noisy and less reliable at high power output levels (during acceleration when things are changing rapidly).

OBD II Data for HVB - Page 5 - Batteries & Charging - Ford Fusion Energi Forum