Experimental performance evaluation of six-phase series-connected two-motor drive systems

It has been shown recently that it is possible to connect in series the stator windings of multi-phase machines in such a way that all the machines in the group can be controlled independently using field orientation principles, although the complete multi-motor drive system is supplied from a single voltage source inverter (VSI). This paper deals with one particular case, a series-connected two-motor six-phase drive system. Two configurations are tested experimentally. Both include a symmetrical six-phase induction machine, while the second machine is at first a three-phase induction machine and then a permanent magnet synchronous machine (PMSM). Additionally, experimental results obtained with a single six-phase motor drive are included as well, thus enabling a thorough discussion of the dynamic performance of the series-connected two-motor drive systems. The operating principles of the drive systems are at first reviewed and a brief description of the experimental rig is then given. The emphasis is placed on an extensive presentation of experimental results, collected from the rig in the already mentioned three different configurations. An ultimate proof that truly independent and decoupled vector control of the two machines is achieved, although a single supply source is used, is thus provided