Tesla motor’s had a challenge in front of them for model 3 car: making it economical. This new design of IPMsynRM seems like a weird choice over induction motors, as neodymium magnet costs reach higher levels. However not if you design them properly. Every automaker has their own unique design of the same motor IPM. Tesla had their own from scratch as well. Here is the reason how they saved cost:
Magnets placed within the rotor and designed to be thinner.
The IPM motor generates torque from the combined effect of Permanent magnets and reluctance effect of the rotor’s iron core. Due to the presence of this reluctance effect, they can reduce the magnet’s effect.
The advantage of these permanent magnets placing deep inside the rotor is that it saves the electronic inverter from back EMF from the motor. The magnets on the rotor interact with the stator windings. This interaction gives a back EMF to the stator. Due to which the inverter electronics face a voltage surge. To avoid this the controller of the motor reduces the permanent magnet strength or technically said “field weakening” of magnets.