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

This type of motor can be used in the Chevy Bolt[1], the Chevy Volt, and the Tesla Model 3.[2] Additional 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 motor or motors with field windings for several high-efficiency applications such as electric vehicles. Tesla’s Chief Electric motor Designer was quoted discussing these advantages, saying: “It’s well known that permanent magnet machines have the advantage of pre-excitation from the magnets, and for that reason you have some efficiency advantage for that. Induction devices have perfect flux regulation and for that reason you can optimize your efficiency. Both seem sensible for variable-quickness drive Conveyor Chain single-gear tranny as the drive units of the cars. So, you may already know, our Model 3 has a permanent magnet machine now. The reason being for the specification of the performance and efficiency, the long term magnet machine better solved our price minimization function, and it had been optimal for the number and performance focus on. Quantitatively, the difference is what drives the continuing future of the device, and it’s a trade-off between motor price, range and battery cost that is identifying which technology will be used in the future.
The magnetic field for a synchronous machine could be provided by using permanent magnets manufactured from neodymium-boron-iron, samarium-cobalt, or ferrite on the rotor. In a few motors, these magnets are installed with adhesive on the top of rotor core such that the magnetic field is usually radially directed across the air flow gap. In other designs, the magnets are inset into the rotor core surface or inserted in slots just underneath the surface. Another kind of permanent-magnet electric motor has circumferentially directed magnets placed in radial slots that provide magnetic flux to iron poles, which in turn create a radial field in the air 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 controlled source. Such drives can handle precise speed and position 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 rate from a way to obtain continuous voltage and frequency. The magnets are embedded in the rotor iron, and a damper winding is usually placed in slots in the rotor surface to provide starting capability. Such a motor will not, however, have means of controlling the stator power factor.