The use of Internal Permanent Magnet Synchronous Reluctance Motor improves efficiency by a few percent compared to an induction motor.
Originally, Tesla was using induction (or asynchronous) electric motors (by the way, invented by Nikola Tesla).
In the Model 3, the company used IPM-SynRM motor (Internal Permanent Magnet - Synchronous Reluctance Motor), known also as PMa-SynRM Permanent Magnet Assisted Synchronous Reluctance Motor.
In general, it's a type that combines Internal Permanent Magnet motor type with Synchronous Reluctance Motor rotor type to achieve a more desired characteristic in EV application - high efficiency at low and high speeds.
Tesla is not the first to use this type of motor, but its version is considered as one of the best (simply because of the high efficiency and range of Tesla cars).
Tesla's specific innovation is the segmented magnets (four parts instead of the more typical single solid magnet). According to Learn Engineering, it helps to reduce the eddy currents and lowers the risk of magnets overheating.
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