Rolling Rotor Switched Reluctance Machines: Modelling and Design

Permanent magnet motors have been extensively adopted for years as power drives due to their attractive performances. However, the increasing cost of rare earth materials has led to the implementation of alternative motor technologies. In particular, the affordable electronics, the high robustness and low-cost manufacturing are appealing features of the Switched Reluctance Machine (SRM). The employment of a reduction mechanism is a common solution in drive systems when high torque at low speed is demanded. In such cases, the adoption of a gearing system involves further mechanical complexity and increased bulkiness. In this context, the Rolling Rotor Switched Reluctance Machine (RRSRM) is a reasonable solution, since it shares the main characteristics of a SRM while performing speed reduction due to the rolling motion of the rotor. Despite these advantages, the diffusion of such machine is hampered by the limited research results. The literature review reveals the lack of a generalised design procedure. These aspects motivate the work exposed in the present dissertation. In this fashion, a lumped parameter approach is used for the modelling of the motor. A design procedure is proposed and the validity of the results is enforced through Finite Element Analysis (FEA). Furthermore, the defined model is used to compute the torque-speed characteristic. Different analyses are accomplished aiming to the maximisation of the machine performance. Common control strategies used on the SRM for torque enhancement and control are extended to this case. Finally, a prototype is realised on the basis of the proposed methodology and used for validation purposes. The conduced experiments evidence the validity of the model and highlight the possibility of improvements.