Manifestation of Partial Demagnetisation Fault Induced Unbalanced Magnetic Pull Effects in the Stator Current and Torque of Surface-Mounted PM Machines

This paper reports a study of rotor partial demagnetisation fault induced unbalanced magnetic pull (UMP) effects in the current and torque signals of a surface-mounted synchronous PM machine, with a view to evaluating their diagnostic application potential. A Finite Element Analysis (FEA) model of the test machine is first used to analyse the effects of rotor fault on the torque signal, and characterise the fault induced UMP effects. An experimental study is then performed on a purpose-built laboratory test rig for different demagnetisation fault severities in a number of operating points in the nominal operating range. The experimental results are used to explore the practical manifestation of the fault induced UMP related effects in the line current and rotor torque signals.