A Leaf Chain Permanent magnet motor is a type of brushless electric motor that uses long lasting magnets instead of winding in the field.
This kind of motor is utilized in the Chevy Bolt[1], the Chevy Volt, and the Tesla Model 3.[2] Other Tesla versions use traditional induction motors motors.[3] Front motors in all-wheel drive Model 3 Teslas are also induction motors.
Permanent magnet motors are more efficient than induction motor or motors with field windings for certain high-efficiency applications such as electric vehicles. Tesla’s Chief Engine Designer was quoted discussing these advantages, saying: “It’s well known that permanent magnet machines have the benefit of pre-excitation from the magnets, and therefore you have some efficiency advantage for that. Induction machines have perfect flux regulation and for that reason you can improve your efficiency. Both make sense for variable-acceleration drive single-gear transmitting as the drive units of the cars. Therefore, as you know, our Model 3 includes a long lasting magnet machine now. It is because for the specification of the performance and efficiency, the permanent magnet machine better solved our cost minimization function, and it was optimal for the range and performance focus on. Quantitatively, the difference is usually what drives the continuing future of the device, and it’s a trade-off between motor price, 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 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 top of rotor core in a way that the magnetic field is usually radially directed over the surroundings gap. In other styles, the magnets are inset 
in to the rotor core surface or inserted in slot machines just below the surface. Another type of permanent-magnet engine has circumferentially directed magnets placed in radial slots that provide magnetic flux to iron poles, which set up a radial field in the air gap.
The main application for permanent-magnet motors is in variable-speed drives where the stator is supplied from a variable-frequency, variable-voltage, electronically controlled source. Such drives can handle precise speed and position control. Due to the lack of power losses in the rotor, as compared with induction engine drives, also, they are highly efficient.
Permanent-magnet motors can be designed to operate at synchronous acceleration from a way to obtain constant voltage and frequency. The magnets are embedded in the rotor iron, and a damper winding is definitely placed in slots in the rotor surface to supply starting capability. This kind of a motor will not, however, have means of controlling the stator power element.
