Influence of magnet layer number on electromagnetic performance of ferrite interior permanent magnet synchronous machine

This paper investigates the impacts of magnet layer number in the rotor on the electromagnetic performances of ferrite interior permanent magnet synchronous machines. Besides identical stator, the machines under study share the same key rotor parameters including rotor inner and outer diameters and especially ferrite magnet volume in order to hold the generality. The ferrite permanent magnets are specially arranged in the rotors of the machines with up to three magnet layers so that optimal torque characteristics could be accordingly achieved. The results from comprehensive two-dimensional finite element analysis have revealed that the magnet layer number would affect both the air-gap flux density distributions from permanent magnets and rotor saliency, and therefore torque characteristics such as average torque, torque pulsation, and optimal current phase angle for maximum torque output. Furthermore, its influence on the demagnetization of ferrite magnets has also been analyzed and exhibited. Overall, it has also been suggested that the machine with two-layer configuration strikes on the right balance between electromagnetic performance and rotor complexity.