| | | Lucid is attempting to build the most efficient EV on the market.
spectrum.ieee.org
“The main loss in the battery is from impedance in the battery pack,” Rawlinson says. “Now in an [U.S. Environmental Protection Agency] test, the actual currents drawn are so small that those losses are tiny, so efficiency of the pack doesn’t really come to play. But in high-performance driving it matters: Double the current, you get 4 times the losses.”
So he designed the Lucid around a 900-volt architecture. “It’s the only one I’m aware of,” he says. “Tesla’s round about 400 V. Porsche, they upped the ante last year to 800 V.”
Rawlinson says the auto media have wrongly explained this push toward higher voltages as being chiefly about faster charging. “Our real reason for having a high-voltage system is the greater efficiency of the inverter and the electronics that control the motor,” he says. “The inverter is a high-frequency switch that converts direct current to alternating current; the frequency of that AC determines the frequency of spin of the motor.”
Lucid’s inverter—which he boasts was built completely in-house—uses a silicon carbide MOSFET chip, which he says “really thrives” on high voltage. He lambastes Porsche for using a high-voltage IGBT (insulated-gate bipolar transistor), which is “probably the worst way to do it—nowhere near as efficient at high voltage as silicon carbide.” |
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