5 ms·

I'd like to point out this is not about increased range, for example, if the ECU already works at 95% efficiency, that's not a very high number for brushless EC

by Koiwai 5y ago

I'd like to point out this is not about increased range, for example, if the ECU already works at 95% efficiency, that's not a very high number for brushless ECU, just for example, so 5% of energy is wasted, if we can reduce that in half, the efficiency will only increase to 97.5%, that's a very small improvement on range. BUT, now the ECU only needs to dissipate half wasted heat, this could be a big net win. A more close to everyday life example would be chargers for notebooks, we now have smaller chargers thanks to GaN FETs, SiC is like GaN.

engie 5y ago
This is the key observation - hitting breakpoints in efficiency that let us remove active cooling, silicon area or heatsinks reduce weight, cost & complexity.
- taneq 5y ago
  Yep. High efficiency is also the key to the crazy high performance we see in high end EVs these days. Going from 96% to 98% drivetrain efficiency only gives you 2% more battery life but it doubles your power output.
londons_explore 5y ago
This isn't quite right... In a car which can accelerate up to speed and brake again every 30 seconds while going through a city with a lot of stop lines, the efficiency of the power components really matters. If you loose 5% in the motors, 5% in the power electronics and 5% in the battery in each direction, then each accelerate-brake cycle is losing you ~30% of the energy you started with. At town speeds, friction and air resistance losses are tiny, so that 30% is probably actually most of the energy you are using! Add that to the fact that certain motor control techniques such as field weakening involve every Amp of real power that comes from the battery passing many times though the inverter, since there is a higher circulating current between inverter and motor coils.
- Koiwai 5y ago
  > If you loose 5% in the motors, 5% in the power electronics and 5% in the battery You realize SiC is not the savior for all your problems right? I'm not saying efficiency doesn't matter, I'm saying this is not gonna improve range significantly, there is a difference.
  - marcosdumay 5y ago
    The GP's point is that this is not about maximum range, it's about increasing range in city transit that is normally much smaller. Both gains seem relevant to me.
    - sudosysgen 5y ago
      EVs typically have more range in city transit than on the highway.
- ianai 5y ago
  Totally! X^n with 0<X<1 quickly goes to zero as n increases. You get about 6 of those cycles if X=.9 before you lose 50% of what you started with initially.
- sudosysgen 5y ago
  You're going to lose a lot more than 5% in the motor. You will also lose more to rolling resistance, various hystereses, etc... Even assuming 100% inverter efficiency you will lose at least 20% in the regen part of the cycle alone.
  - londons_explore 5y ago
    Motors can get well above 95% efficiency, even at a wide range of speeds and torques. Eg. See https://cdn.motor1.com/images/mgl/y83JG/s3/tesla-motor-efficiency-slides.jpg https://cdn.motor1.com/images/mgl/y83JG/s3/tesla-motor-effic...
    - 5y ago
sudosysgen 5y ago
You mean ESC, not ECU. Generally cooling ESCs is not that big of an issue, just stick them in the same cooling system as the batteries.
- hwillis 5y ago
  arguably the same thing. If you want to get pedantic, "ESC" refers to a specific subset of drive topologies that are all fairly lossy on the D axis, meaning the efficiency drops at low speeds or under heavy acceleration. "Drive controller" or "motor controller" are common terms, and while I have seen acronyms like DCU, nothing really sticks. MCU is already taken as an acronym, which doesn't help.
  - sudosysgen 5y ago
    ESC doesn't have any connection to efficiency as a function of load. All circuits will be less efficient as you output more amps, ie, at low speeds where the voltage is low but the power stays the same, or under heavy acceleration. Nowadays ESC simply refers to any circuit you attach to motor and provide with a target speed/torque/power. In common practice yeah ESC/drive controller/motor controller are used interchangeably. ECU is specifically something else. It's "Engine Control Unit". It refers to the controller for a combustion engine, not a motor.
    - minetest2048 5y ago
      To make things more confusing, ECU can also stands for Electronic Control Unit
- Koiwai 5y ago
  I'm pretty sure Tesla refer to them as ECU. Trust me, I'm more customed to use the term ESC since I play RC models and I don't drive a electric car, or any car.
Gibbon1 5y ago
You are absolutely right there. I first read that in an article an EE wrote. He said what you care about with power inverters isn't the efficiency but the inefficiency. Small gains in efficiency you wouldn't care about translate in to large reductions in heat and smaller cheaper power devices. Power devices don't follow Moore's Law and aren't cheap.

by Koiwai 5y ago

engie 5y ago

This is the key observation - hitting breakpoints in efficiency that let us remove active cooling, silicon area or heatsinks reduce weight, cost & complexity.

taneq 5y ago
Yep. High efficiency is also the key to the crazy high performance we see in high end EVs these days. Going from 96% to 98% drivetrain efficiency only gives you 2% more battery life but it doubles your power output.

londons_explore 5y ago

This isn't quite right... In a car which can accelerate up to speed and brake again every 30 seconds while going through a city with a lot of stop lines, the efficiency of the power components really matters. If you loose 5% in the motors, 5% in the power electronics and 5% in the battery in each direction, then each accelerate-brake cycle is losing you ~30% of the energy you started with. At town speeds, friction and air resistance losses are tiny, so that 30% is probably actually most of the energy you are using! Add that to the fact that certain motor control techniques such as field weakening involve every Amp of real power that comes from the battery passing many times though the inverter, since there is a higher circulating current between inverter and motor coils.

Koiwai 5y ago
> If you loose 5% in the motors, 5% in the power electronics and 5% in the battery You realize SiC is not the savior for all your problems right? I'm not saying efficiency doesn't matter, I'm saying this is not gonna improve range significantly, there is a difference.
- marcosdumay 5y ago
  The GP's point is that this is not about maximum range, it's about increasing range in city transit that is normally much smaller. Both gains seem relevant to me.
  - sudosysgen 5y ago
    EVs typically have more range in city transit than on the highway.
ianai 5y ago
Totally! X^n with 0<X<1 quickly goes to zero as n increases. You get about 6 of those cycles if X=.9 before you lose 50% of what you started with initially.
sudosysgen 5y ago
You're going to lose a lot more than 5% in the motor. You will also lose more to rolling resistance, various hystereses, etc... Even assuming 100% inverter efficiency you will lose at least 20% in the regen part of the cycle alone.
- londons_explore 5y ago
  Motors can get well above 95% efficiency, even at a wide range of speeds and torques. Eg. See https://cdn.motor1.com/images/mgl/y83JG/s3/tesla-motor-efficiency-slides.jpg https://cdn.motor1.com/images/mgl/y83JG/s3/tesla-motor-effic...
  - 5y ago

sudosysgen 5y ago

You mean ESC, not ECU. Generally cooling ESCs is not that big of an issue, just stick them in the same cooling system as the batteries.

hwillis 5y ago
arguably the same thing. If you want to get pedantic, "ESC" refers to a specific subset of drive topologies that are all fairly lossy on the D axis, meaning the efficiency drops at low speeds or under heavy acceleration. "Drive controller" or "motor controller" are common terms, and while I have seen acronyms like DCU, nothing really sticks. MCU is already taken as an acronym, which doesn't help.
- sudosysgen 5y ago
  ESC doesn't have any connection to efficiency as a function of load. All circuits will be less efficient as you output more amps, ie, at low speeds where the voltage is low but the power stays the same, or under heavy acceleration. Nowadays ESC simply refers to any circuit you attach to motor and provide with a target speed/torque/power. In common practice yeah ESC/drive controller/motor controller are used interchangeably. ECU is specifically something else. It's "Engine Control Unit". It refers to the controller for a combustion engine, not a motor.
  - minetest2048 5y ago
    To make things more confusing, ECU can also stands for Electronic Control Unit
Koiwai 5y ago
I'm pretty sure Tesla refer to them as ECU. Trust me, I'm more customed to use the term ESC since I play RC models and I don't drive a electric car, or any car.

Gibbon1 5y ago

You are absolutely right there. I first read that in an article an EE wrote. He said what you care about with power inverters isn't the efficiency but the inefficiency. Small gains in efficiency you wouldn't care about translate in to large reductions in heat and smaller cheaper power devices. Power devices don't follow Moore's Law and aren't cheap.