The benefits of this setup are that fewer magnets are necessary, reducing cost, and it can make use of rotor reluctance, which improves torque across the power range, though efficiency suffers at high torque.
Regardless of which permanent magnet setup you go with, there are many benefits. The first is a higher efficiency across a wide range of speeds, especially low ones. The next is that its design allows it to be smaller, but the constant magnetic field of the rotor gives it greater power density, making it a popular option for high-performance EVs like the Lucid Air Sapphire or Pininfarina Battista.
The technology isn’t without its drawbacks, though. Since the magnets are always active they create a “back electromotive force” when not under load. This creates drag on the vehicle and can lead to heating issues. Additionally, the inclusion of permanent magnets results in higher production costs, and one can’t forget about the environmental and socioeconomic impacts of acquiring such things too.
