A permanent magnet electric motor is a type of brushless electric engine that uses long term magnets rather than winding in the field.

This kind of motor is used in the Chevy Bolt[1], the Chevy Volt, and the Tesla Model 3.[2] Various other Tesla versions use traditional induction motors motors.[3] Front motors in all-wheel drive Model 3 Teslas are also induction motors.

Long term magnet motors are more efficient than induction engine or motors with field windings for certain high-efficiency applications such as electrical vehicles. Tesla’s Chief Electric motor Designer was quoted discussing these advantages, saying: “It’s well known that permanent magnet devices have the benefit of pre-excitation from the magnets, and for that reason you have some efficiency benefit for that. Induction machines have perfect flux regulation and therefore you can optimize your efficiency. Both seem sensible for variable-rate drive single-gear tranny as the drive models of the cars. Therefore, you may already know, our Model 3 has a long term magnet machine now. The reason being for the specification of the performance and efficiency, the long lasting magnet machine better solved our cost minimization function, and it was optimal for the number and performance focus on. Quantitatively, the difference is certainly what drives the future of the machine, and it’s a trade-off between motor cost, range and battery price that is determining which technology will be used in the future.
The magnetic field for a synchronous machine could be provided by using permanent magnets made of neodymium-boron-iron, samarium-cobalt, or ferrite on the rotor. In a few motors, these magnets are mounted with adhesive on the top of rotor core in a way that the magnetic field can be radially directed over the air flow gap. In other designs, the magnets are inset into the rotor core surface or inserted in slots just below the surface. Another type of permanent-magnet engine provides circumferentially directed magnets positioned in Auto Chain radial slots that provide magnetic flux to iron poles, which in turn set up a radial field in the surroundings gap.

The primary application for permanent-magnet motors is in variable-speed drives where in fact the stator comes from a variable-frequency, variable-voltage, electronically managed source. Such drives can handle precise speed and placement control. Because of the absence of power losses in the rotor, in comparison with induction engine drives, they are also highly efficient.

Permanent-magnet motors could be designed to operate at synchronous speed from a way to obtain constant voltage and frequency. The magnets are embedded in the rotor iron, and a damper winding can be placed in slot machines in the rotor surface to supply starting capability. Such a motor will not, however, have method of managing the stator power aspect.