Regarding margins on S Plaid, unless I'm misinterpreting, the car uses three AC induction motors, none of the Model 3 style PMSR. Depending on CapEx of the winding machine and per unit cost, these may be cheaper than the PMSR version.
Quick rundown (further tech discussion deserves a thread)
Key clues from Tweet:
Copper rotor
Coaxial cooling
Supporting data:
High power
High RPM
Quiet (no torque cogging)
Efficency (due to torque sleep)
AC induction makes the dual rear motor packaging simpler by removing the tail shaft mounted encoders. Other cost savings are elimination of the magnets and stacked laminates.
It will be interesting to find our how they eliminated the rotor heating issue. Could be a design change, or it could be the up sized radiator Elon called out along with new heat pump (still running in AC mode) loop design lets then send cold enough coolant into the motor to offset the heat generated.
This would also allow more aux heat generation from the motor, if needed for cold weather operation.
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