The majority of electrical drive systems are three-phase systems. Recently some quasi-four-phase systems employing neutral leg also have been used for harmonic optimization and fault-tolerant drives. Three-phase drive systems have been widely used for years because of the availability of such machines, their inverters, modeling and control. However, polyphase schemes have been used in the past in drive systems where an induction machine with asymmetric windings has three-phase sets advanced by 30 degrees for twelve-step industrial applications. Such multiphase drives are likely to be limited to specialized applications where high perfor- mance and reliability are required (such as EV, HEV, aerospace, ship propulsion and high power applications) and when cost requirements are not so oppressive when compared to the overall environment.
The recent literature indicates several advantages for using a mul- tiphase multi-pole electrical machine in hub-wheel systems â€“ high-torque low-speed motors can directly drive systems, avoi- ding mechanical losses incurred by the clutch, reduction and differential gear during power transmission from the motor to the wheels. This work presents the design, analysis, simulation, modeling and control implementation of a high-torque, low- speed, multiphase, permanent magnet, brushless dc-machine. The paper focuses on issues regarding the high-level modeling, comprised of a transient model, in conjunction with correspond- ing experimental evaluation. Analyses were made to put together the modeling efforts with the expected behavior in order to have realistic simulation results verified by the experimental setup; comprehensive experimental results corroborate the work.