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The article doesn't pass the smell test for me. Claim 1. Smaller SiC inverters enabled Tesla to implement sports-car-like streamlined design. Traditional Si

by quanto 5y ago

The article doesn't pass the smell test for me. Claim 1. Smaller SiC inverters enabled Tesla to implement sports-car-like streamlined design. Traditional Si inverters are not that big. Certainly not big enough to single-handedly change the car design [1] Claim 2. Hyundai will use SiC chips to increase its typical EV range by 5%. The article claims that SiC will reduce wasted energy by half (or more). If we go by this figure, Hyundai's EVs need to waste 10% of its energy on Si chips. This seems quite high to me. No doubt there are losses in the motor, power electronics, and battery, but losing 10% of the EV's total energy on Si based chips seems incredibly inefficient to start with. [1] https://www.youtube.com/watch?v=mHVV52lPyIs&t=909s https://www.youtube.com/watch?v=mHVV52lPyIs&t=909s

tuatoru 5y ago
> If we go by this figure, Hyundai's EVs need to waste 10% of its energy on Si chips. Most of it is not lost in the silicon, but in the interconnects (wiring and connectors) and motor(s). SiC is better (more robust) than Si with high voltage, high current, and/or high temperature. Specifically, kilovolt-level, kiloamp-level, and temperatures above 150 celsius. If you double your battery voltage from 400V (current standard) to 800V, you halve your resistive losses in the "wires" for the same electrical power demanded. Silicon MOSFETS that can withstand a kilovolt and a kiloamp are very big and very expensive. You get more power delivered for the same power leaving the battery. Size: SiC's very high thermal conductivity means less of a margin of safety for secondary breakdown. SiC tolerates higher current density (amps/square mm) than Si, so smaller devices are possible, saving mass. Its temperature stability allows it to be sintered to the package heatsink--further improving heat removal. Tolerance for high temperatures means you need less mass and volume for heat dissipation structures. Other efficiencies: With very high currents (kiloamp) and medium frequency switching, SiC IGBTs provide more benefits, because rather than being directly proportional to current as with MOSFETs, losses are proportional to the log of current. Alternatively, doubling the battery voltage again to 1.5kV (and so halving the currents) might allow Hyundai to use more aluminium for the "wires", with a cost saving over copper.
- formerly_proven 5y ago
  Resistive losses are proportional to current squared, not linear.
- MertsA 5y ago
  >Alternatively, doubling the battery voltage again to 1.5kV (and so halving the currents) might allow Hyundai to use more aluminium for the "wires", with a cost saving over copper. This seems dubious, you're not going to be able to use aluminum for motor windings which is where the bulk of the copper in an EV is going to be. As for conductors between the battery, HV auxiliary devices, inverter, motor, charger, etc they could already use aluminum, it's not like they're space constrained on the gauge of cable between components. Aluminum is already more mass efficient than copper, you might need a thicker gauge to match the same resistance but that thicker aluminum is still lighter than copper and way cheaper. The problems with aluminum are oxidation and brittleness. Maybe eventually auto manufacturers will shift more towards aluminum bus bars between components with no relative movement but I don't see a big link here (haha, busbar puns) between ampacity and the choice between copper and aluminum.

by quanto 5y ago

tuatoru 5y ago

> If we go by this figure, Hyundai's EVs need to waste 10% of its energy on Si chips. Most of it is not lost in the silicon, but in the interconnects (wiring and connectors) and motor(s). SiC is better (more robust) than Si with high voltage, high current, and/or high temperature. Specifically, kilovolt-level, kiloamp-level, and temperatures above 150 celsius. If you double your battery voltage from 400V (current standard) to 800V, you halve your resistive losses in the "wires" for the same electrical power demanded. Silicon MOSFETS that can withstand a kilovolt and a kiloamp are very big and very expensive. You get more power delivered for the same power leaving the battery. Size: SiC's very high thermal conductivity means less of a margin of safety for secondary breakdown. SiC tolerates higher current density (amps/square mm) than Si, so smaller devices are possible, saving mass. Its temperature stability allows it to be sintered to the package heatsink--further improving heat removal. Tolerance for high temperatures means you need less mass and volume for heat dissipation structures. Other efficiencies: With very high currents (kiloamp) and medium frequency switching, SiC IGBTs provide more benefits, because rather than being directly proportional to current as with MOSFETs, losses are proportional to the log of current. Alternatively, doubling the battery voltage again to 1.5kV (and so halving the currents) might allow Hyundai to use more aluminium for the "wires", with a cost saving over copper.

formerly_proven 5y ago
Resistive losses are proportional to current squared, not linear.
MertsA 5y ago
>Alternatively, doubling the battery voltage again to 1.5kV (and so halving the currents) might allow Hyundai to use more aluminium for the "wires", with a cost saving over copper. This seems dubious, you're not going to be able to use aluminum for motor windings which is where the bulk of the copper in an EV is going to be. As for conductors between the battery, HV auxiliary devices, inverter, motor, charger, etc they could already use aluminum, it's not like they're space constrained on the gauge of cable between components. Aluminum is already more mass efficient than copper, you might need a thicker gauge to match the same resistance but that thicker aluminum is still lighter than copper and way cheaper. The problems with aluminum are oxidation and brittleness. Maybe eventually auto manufacturers will shift more towards aluminum bus bars between components with no relative movement but I don't see a big link here (haha, busbar puns) between ampacity and the choice between copper and aluminum.