2022 Lucid Air Powertrain Tech Deep Dive: Why It’s So Far Ahead of the Competition
Everybody is enthralled with the 2022 Lucid Air Dream Edition P’s big number of 1,111 horsepower. But there are smaller numbers that point the way forward toward mass electrification: 3.9 horsepower per pound and 4.6 miles per kilowatt-hour. The first represents the Dream P’s drive unit (motor, reduction gear, and integrated power inverter), which produces 670 peak hp and weighs 163 pounds, for roughly triple the power density Tesla achieves. The latter represents the range the Lucid Air Dream Edition R gets from its 113-kWh battery pack. These mass-reduction and efficiency measures are just the tip of Lucid’s (slower-melting) efficiency iceberg. Imagine how small and light a 200-hp version of this motor would be, and how many fewer kilowatt-hours of battery you’d need for a smaller, lighter, 300-mile family car that achieves 5 or 6 miles/kWh? That’s where this tech is headed.
Honey, I Shrunk the Drive Unit
By innovating a new type of square-bar winding that produces a denser magnetic field in the stator, and by minimizing the size and improving the placement of the permanent magnets in the rotor, the Lucid Air motor develops 20 percent more reluctance torque from the same magnetic mass as is used in the Tesla Model 3 (about 3.7 pounds). All of this allows the motor to generate more power in a package that’s 30 percent smaller than the Model 3’s. Utilizing planetary gears for the drive reduction saves a bit more space. The power inverter connects directly to the three phases of the stator to form an ultra-compact package.
Woven Winding for the Win
Stator power and efficiency is largely determined by how much copper can be squeezed into the stator. Tesla’s motors use thin, round-section wires wound tightly. The Chevy Bolt motor uses “hairpin” square-section copper that packs more copper into less space for greater efficiency, but the design requires hundreds of soldered connections of each of the myriad “hairpins.” Lucid conceived a design that “weaves” 24 long square-section wires on a kabob, and then presses them into the stator, leaving only the ends of these 24 wires that must be soldered to the connectors for the three electrical phases.
Better Oil Cooling
The ferromagnetic metal into which the copper windings are pressed is assembled of hundreds of thin, flat metal plates. Lucid engineers determined there were narrow magnetic “dead zones” between the windings, into which slim cooling channels could be cut without compromising the magnetic flux. These channels allow the cooling oil to carry away more heat from closer to where it’s created (in the copper). The oil flow exits these narrow channels via pinholes that spray oil onto the exposed copper windings. The system works so well, Lucid needs no internal temperature sensors—oil temperature monitoring and computer modeling does the job. Lucid holds eight patents covering the motor’s stator windings and cooling.
Simplified Battery Packaging/Cooling
The Lucid battery pack bears little resemblance to a Tesla pack. Both use cylindrical batteries, but Tesla cools them from the sides, requiring complex cooling passages and lots of heat-conducting glue. Lucid cools its cells from the bottom, claiming they radiate more heat axially than radially. Lucid’s battery-module case is a single injection molding that includes the sides and top of the box and encapsulates the power-conducting metal bus bars, which are all identical, whereas Tesla employs 17 different bus bars. (Lucid’s battery module box has won an award from the Society of Plastics Engineers.)
Once the cells are positioned in the pack, a thin schmeer of heat-conducting adhesive is applied on the cooling plate as it is installed, closing the module. Robots then solder the cells to the bus bars, using wire ribbon with lower resistance than the thin, round wires others use. Lower resistance means less heat, and Lucid reckons that if an Air Dream P used wires, thermally managing the heat generated during full-power runs could result in a reduction in output of 100 horsepower or more. Lucid claims its battery modules can be assembled robotically in a dark plant, and because they are not filled with glue, they weigh less and are far cheaper to produce.
Located just behind the front power unit and mounted to the firewall is the power controller, which is internally referred to as the Wunderbox. It incorporates a 19.2-kW bidirectional charger that can also accept DC fast-charging current. It uprates 400-volt power coming in from older DC fast chargers to the Air’s nominal 900-volt operating voltage. It also incorporates a DC-to-DC converter that steps down the battery pack’s 900 volts to 400 volts to efficiently operate the onboard heater (for cabin or battery conditioning) or to buddy-charge a fellow EV. And as a bonus, the box serves as an important load path to distribute frontal crash energy.
Put it all together, and the Lucid Air as a whole moves the state of the electric car art forward in impressive fashion—it’s no wonder we named it our 2022 Car of the Year.
Source: Read Full Article