Shark - a new concept in electric motors

Increasing awareness of the finite global resources requires a more efficient approach to their use. In this context, many government regulations impose new standards for more efficient energy conversion in industrial applications. Electric motors are the main consumers of electric energy, with applications ranging from large power plant to domestic appliances. In industry, about 70% of total energy consumption is by motor driven systems. Therefore, any solution allowing for improvement of the torque production, and hence the efficiency, without using more material, and without increasing the manufacturing cost is valuable. The solution proposed in this project is to modify the cylindrical air gap of an electric motor by applying a non-linear axial profile (called Shark profile). Various shapes were studied, such as saw-toothed, square-wave, sinusoidal or trapezoidal. These increase the air gap area and therefore, it is claimed that the energy conversion process is improved. The benefit of this solution is that a torque improvement might be obtained without using more material. The required air gap shape is obtained by redistributing the iron material. This means that a certain amount of material is removed from the stator in order to shape the Shark profile of the stator body. The same amount of material is added to the rotor to form the Shark profile of the rotor body. The theoretical study of the various Shark profiles was performed on a basic configuration of a cylindrical air gap Switched Reluctance Motor (CSRM) because it presents the advantage of a simple structure. The initial study, of the influence of the various Shark profiles on the magnetic performance of the SRM, was performed by using Finite Element Analysis (FEA). Subsequent optimisation of the SRM, with the Shark air gap determined the optimum shape (a saw-toothed profile) and dimensions of the Shark profile, which were applied in a demonstration prototype machine. Additionally, an analytical model of Shark structures was developed and verified by using the data provided by FEA and those measured on the demonstration machine. Finally, the performance of the Shark SRM was compared with that of other motors of other types, having identical size. These motors were: cylindrical air gap SRM, standard Induction Motor (IM), Brushless Permanent Magnet -DC motor (BDCM). The results indicated that the Shark air gap provides the predicted improvement. For the Shark SRM, an efficiency 2 % higher than that measured on the CSRM, was measured at the rated working point. It was also determined that the efficiency improvement is greater at reduced load, where the iron regions are not saturated. In this work, the force components produce in the Shark SRM were also studied because they are important factors in regard to the mechanical assembly or the noise and vibration produced by the machine. The proposed solution exhibited considerable assembly difficulties, due to the special air gap configuration. Therefore, alternative solutions for simple assembly methods applicable to the Shark SRM were suggested