Design of a High Torque Density Interior Permanent Magnet Synchronous Machine with improved Efficiency using Amorphous Magnetic Material

Abstract

Several novel designs and techniques are available in the literature for achieving higher torque density in electrical machines. This higher torque density usually comes at the cost of lowered efficiency or power factor of the machine. In this paper, an interior permanent magnet synchronous machine with an additional inner stator is proposed for achieving higher torque density. There are certain issues that arise with the employment of an additional stator. Firstly, the problem of temperature rise is dealt with by using a cup-shaped rotor for exhausting heat from the inner stator core. The current density of the inner stator is also kept lower, for the same reason. Hence, two separate inverters of different current ratings are used to feed current to the windings of the inner and outer stator. Secondly, the problem of increased iron losses (thereby lowered efficiency) that arises due to an additional stator is resolved by using an amorphous material as a stator core instead of silicon steel sheets. The conventional single stator machine and proposed dual stator machines with silicon steel and amorphous material are analyzed and compared using 2D-FE Analysis. The back emf, output torque, losses, and efficiency of all three machines are compared. It is showed that the proposed dual stator machine with an amorphous material core significantly improves the torque density of the machine without lowering its efficiency.