Postfault Strategy for Dual Three-Phase Machines With Minimum Loss in the Full Torque Operation Range Under Two Open Phases

Dual three-phase machines (D3PMs) are particularly attractive due to their fault-tolerance capability. In general, under open-phase (OP) faults, the current references are adapted following a minimum-loss strategy (MLS) or a maximum-torque strategy (MTS). The MLS offers lower copper loss than the MTS for any given torque, but a smaller torque operation range (TOR). The full-range MLS (FRMLS) has recently been proposed, providing minimum copper loss, for each torque value, in the whole TOR (the MTS TOR); however, only one OP was considered. Furthermore, neither the TOR of the MLS nor the copper loss of the MLS or MTS have been assessed with two OPs. Consequently, it is difficult to infer a priori the relevance that the FRLMS may have for two OPs. This paper evaluates the extension of the FRMLS to D3PMs with two OPs. First, the procedure to carry out this extension is described. Then, the convenience of the FRMLS for two OPs is studied for different situations. It is concluded that for two OPs in most cases the FRMLS is substantially better than the MTS and MLS in terms of copper loss and TOR. Experimental results verify the theory.