Wpływ liczby par biegunów wzbudzenia na pracę bezszczotkowego silnika tarczowego ze strumieniem osiowym w stojanie

W pracy przedstawiono analizę wpływu liczby par biegunów wirnika na niektóre parametry statyczne bezszczotkowego silnika tarczowego ze strumieniem osiowym w stojanie. Obliczenia pola magnetycznego zostały wykonane przy użyciu trójwymiarowej metody elementów skończonych. Wyznaczono podstawowe parametry całkowe przetwornika jak: moment elektromagnetyczny, siła elektromotoryczna rotacji i moment zaczepowy.

In the paper a brushless disc-type motor with co-axial magnetic flux crossing the stator axially is considered. The motor structure is shown in Fig.1, while the motor parameters are summarized in Table 1. The static parameters i.e. the torque, the cogging torque and phase back EMF of an eight-pole motor, are compared with those for a sixteen-pole one of the same volume, in order to contrast the two potential candidates for variable-speed, Iow-cost drives. As a basis of the comparative analysis, three dimensional FEM magnetic field modeling is employed. An appropriate selection of the motor structure determines electromechanical properties of the machine. It is better for the brushless motor when the switching frequency is not high. Thus, the motors with N(S)/N(R) greater than unity are preferred for high speed drives. On the other hand, it is better for the motor with N(S)/N(R) less than unity to operate at Iower rotational speeds. Such two solutions of the magnetic circuit of the considered machine are anałyzed in this work. Due to the periodic motor configuration and axial anti-symmetry, the region of interest for the finite element analysis is an octant of the whole motor volume . In salient-pole permanent magnet machines, the cogging torque is one of the main components of torque fluctuations. The cogging torque can also be significantly reduced by appropriate permanent magnet width selection. Such a method can be used in axial-flux motors, without any loss of the average torque level. Five versions of the motor with different ratios of permanent magnet arc to pole pitch arc y/T are studied in the paper. In Figs 4 and 5, variations of the electromagnetic torque and the cogging torque for A and B constructions are shown. The cogging torque is about ten times smaller in B3 motor version as compared to A3 one with the same y/T ratio. Figure 6 shows angular variations if the phase back EMF. The calculations are partially verified by measurments.