The rotors with buried magnets have circumferential magnetization and are installed in deep grooves. This setting is also referred to as “buried” or “spoke”. and in this configuration, a means must be used that prevents the flow from closing by means of the shaft. The use of a non-ferromagnetic material is essential.

With a ferromagnetic axis, much of the flow is located in a way to close without crossing the engine air gap and as a result this flow does not cause torque in the motor shaft.

With the principle of increasing the magnetic flux in the air gap, the axis must be non-ferromagnetic or a ring of non-ferromagnetic material should be applied between the magnets and the ferromagnetic axis. Because of this type of magnetization, the magnet height is in the tangential orientation and the effective arc coefficient is restricted by the groove.      Boston Gear SF-1 5/8

Thus, the synchronous reactance of the q-axis is greater than that of the d-axis and the thickness of the bridge between the axis and the adjacencies of the magnets must be meticulously chosen. This was the type of configuration that was selected for the design of this project.