A new design of permanent magnet machine for flux weakening operation

New design concepts for flux weakening operation of a PM (permanent magnet) machine are introduced and verified by field analysis using finite element analysis. The d-axis armature reaction inductance X _d, has been increased substantially with the new design concept. The increase of X_d does not necessitate the reduction of the thickness or width of PMs. Strong airgap flux weakening is accomplished without applying an excessive d-axis current to reduce the flux of the magnets. This significantly reduces the copper losses and prevents the PMs from being permanently demagnetized for operation in a wide range of speeds. Since the flux from the PMs is well preserved while in the flux weakening operation mode, the new design concept actually shows less PM materials to be used. As the result, a cost-effective high performance PM machine drive is made possible in a large power rating