Sizing and detailed design procedure of external rotor synchronous reluctance machine

Abstract

Finding an optimally designed synchronous reluctance machine with desired performance among all possible combinations of the stator and rotor with different shapes of barriers requires long execution time, which is an overwhelming task. Selecting the number of flux barriers, for instance, in accordance with the pre-designed stator has a significant effect on the torque ripple. To tackle these issues, this study presents a comprehensive design procedure of an external rotor synchronous reluctance machine suitable for an electric bike application that includes considerations such as electromagnetic and mechanical aspects. Dimensions of the internal stator with tapered slots are calculated. Additionally, a global parameter, insulation ratio in the q-axis, is used to link the microscopic parameters. Seeking for the optimal design through the insulation ratio effectively reduced the number of geometric parameters involved in the rotor shape optimisation. The preliminary rotor design is used to run multi-objective optimisation to provide further improvement to the average torque and torque ripple. Utilising the finite-element method, thermal and structural analyses are conducted to guarantee the safe operation of the designed motor under a steady-state condition. Finally, measurement results of a 250 W-fabricated motor are compared with the predicted results, which validate the effectiveness of the proposed method.

Optimal rotor design of novel axial flux synchronous reluctance motor and validation

“…In AF‐SynRM double layer distributed windings are selected. Although concentrated windings are easy to manufacture and their copper losses are small, distributed windings are selected for high reluctance torque 11 . For these reasons, 48 slots and 8 pole structures are preferred.…”

“…The ratio of inner diameter to outer diameter is a value that varies directly proportional to the number of k d poles. This value is chosen between 0.72 to 0.74 in 8‐pole motor 11 . The initial values chosen for the design are given in Table 1.…”

“…The aim is to find the optimum design to maximize torque and minimize torque ripple. Studies have been conducted in the literature by taking k wq values such as 0.4, 0.6, 1, 1.2, and 1.5 for radial flux motors 11,14,15 …”

Modelling of axial‐flux eddy‐current couplers

“…The former, e.g. 2D and 3D finite‐element method (FEM) as employed for radial and axial‐flux machines [1–4], although precise, are very time‐consuming and not suitable for the preliminary designs, while analytical approaches provide fast, flexible and relatively accurate calculations, introducing a powerful tool for the design procedure. The second technique may be divided into two categories: first, subdomain methods which are on the basis of Laplace's and Poisson's equations as used for surface‐mounted PM machines [5, 6], switched reluctance machine [7], and flux switching machine [8]; second, flux‐tube models or magnetic equivalent circuit (MEC) approaches as used for salient pole [9], flux‐switching [10], Vernier [11], and switched reluctance [12] machines as well as magnetic bearings [13].…”

Modelling of switched reluctance machines

“…The finite element method (FEM) is a powerful numerical technique in the analysis of electric machines SRMs to PM machines [1][2][3][4]; however, FEM is expensive and time-consuming. On the other hand, analytical approaches are fast yet accurate alternative techniques that are very effective in preliminary designs.…”