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

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

Long term magnet motors are better than induction electric motor or motors with field windings for certain high-efficiency applications such as electric powered vehicles. Tesla’s Chief Electric motor Designer was quoted discussing these advantages, stating: “It’s popular that permanent magnet machines have the advantage of pre-excitation from the magnets, and therefore you have some efficiency benefit for that. Induction machines have perfect flux regulation and therefore you can optimize your efficiency. Both make sense for variable-swiftness drive single-gear transmission as the drive models of the cars. Therefore, as you know, our Model 3 has a permanent magnet machine now. The reason being for the Transmission Chain specification of the overall performance and efficiency, the long lasting magnet machine better solved our price minimization function, and it was optimal for the range and performance focus on. Quantitatively, the difference is definitely what drives the future of the device, and it’s a trade-off between motor price, range and battery cost that is determining which technology will be used in the future.
The magnetic field for a synchronous machine may be provided by using long lasting magnets manufactured from neodymium-boron-iron, samarium-cobalt, or ferrite on the rotor. In some motors, these magnets are installed with adhesive on the surface of the rotor core in a way that the magnetic field is radially directed across the atmosphere gap. In other designs, the magnets are inset into the rotor core surface or inserted in slot machines just underneath the surface. Another kind of permanent-magnet electric motor provides circumferentially directed magnets positioned in radial slots offering magnetic flux to iron poles, which in turn setup a radial field in the air flow gap.

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

Permanent-magnet motors can be made to operate at synchronous acceleration from a way to obtain continuous 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 provide starting capability. Such a motor will not, however, have means of managing the stator power element.