Effects Of Unbalanced Magnetic Force And Torque Ripple On The Performance Of A Double Stator Permanent Magnet Machine

Abstract

he effect of unbalanced magnetic force and torque ripple of on the output performance of a double stator switched-flux permanent magnet machine would be investigated and compared, with particular reference to the machine’s varying rotor pole number. The finite element analysis (FEA) predicted machine parameters are: unbalanced magnetic force (UMF), total harmonic distortion (THD), torque ripple (Tr), cogging torque and static torque. The considered machine types hav- ing 10-, 11-, 13- and 14-rotor pole numbers are desig- nated as: 6S/10P, 6S/11P, 6S/13P and 6S/14P, re- spectively; 6S represents six (6) stator slot or teeth number. It is revealed that the machine types that have odd number of rotor poles would have lower machine output characteristics such as: low cogging torque, low torque ripple and low total harmonic distortion of the voltage, compared to the ones that have even number of rotor poles; though, with higher amount of unbalanced magnetic force on the rotor. Further, the sensitivity of the machine’s output performances due to electric loadings is higher than its corresponding response as a result of machine’s varying rotational speed. More so, the machine types having odd number of rotor poles would have higher air gap flux density magnitudes; and would also exhibit better average torque per magnet us- age, which is desirable for reduced cost implications.