A series-connected two-motor six-phase drive with induction and permanent magnet machines

A novel concept for multimotor drives, based on utilization of multiphase machines, has been proposed recently. Independent vector control of all the machines of the group can be achieved while using a single multiphase inverter supply, provided that the stator windings are connected in series in an appropriate manner. One specific case of such a drive system is a two-motor drive, comprising a symmetrical six-phase machine connected in series with a three-phase machine. The group is supplied from a six-phase current-controlled voltage source inverter (VSI). The available considerations related to this two-motor drive system, consisting of two induction motors, are currently of purely theoretical nature, with the proof-of-concept provided by simulation only. This paper analyzes series-connected two-motor six-phase drive, comprising a six-phase symmetrical induction machine and a three-phase permanent magnet synchronous machine (PMSM) and provides, for the first time, detailed experimental verification of the possibility of independent control of the two motors. The operating principles of the drive system are at first reviewed and a brief description of the experimental system is then given. The emphasis is placed on an extensive presentation of experimental results, collected from a laboratory setup. It is shown that a truly independent and decoupled vector control of the two machines results, although a single supply source is used. The two-motor drive system of the proposed structure is seen as a potentially viable industrial solution for applications requiring one high-power and one low-power machine.