Non-Linear Space-Dependency of Main and Differential Inductances of Permanent Magnet Electric Machines

In this paper a 4.5 kW 6 pole permanent magnet motor with buried magnets is reviewed. The design and the control process of such permanent magnet motors depend on the parameter of the machine especially of its direction-dependent inductances. In order to get robust rotor position detection by a test signal the inductance of the d-axis and the inductance of the q-axis must be have a remarkable great difference. Besides the control of the permanent magnet motor, such a rotor design increases the torque of the machine remarkable by the additional produced reluctance torque. Therefore a new oriented stator current vector is used for the control because the load angle changes. A robust machine behavior with an increased torque mainly depends on the design of the flux barriers between the rotor magnets and the rotor surface.