Demagnetisation current due to short circuit effect on an inset permanent magnet motor

摘要

A permanent magnet machine with inset magnets has been evaluated during short circuit of the machine. The machine has been analysed with a FEM program ANSYS Maxwell and parallel to that a Simulink model of the machine has been developed. The latter model, has used a matrix of the inductances as a function of currents in d and q-direction. The Simulink model predicts the currents accurately during the short circuit if the analysis is made for a sufficient span of currents. With the Simulink model the case that produces the most negative i_d can be found.In order to analyse the actual flux density inside the magnet, a transient and static FEM-analysis is done and it is found that the corners of the magnets that is adjacent to the bridges that holds the rotor together is the most affected part of the magnet. Assuming that 1 mm's of the corners is anyway rounded off, the flux density is -0.1 T in the magnet material, in the investigated case which could be harmful for the magnet.