| The electronically commutated permanent magnet synchronous DC machine is such a DC machine without mechanical commutator, that its drive system successfully imitates the current commutation process occurred in the armature winding of the conventional DC machine, namely that the mechanical commutator is replaced by electronically commutator to realize current conversion of single coil so as to keep the current directions of the coils under the N or S pole unchanged, and then the directions of torque acting on the magnets mounted on the rotor would be changeless to make it rotate. Compared to the conventional DC one, the electronically commutated permanent magnet synchronous DC machine has an electronically commutation, while compared to the 3-phase brushless DC one, it brings in the conventional DC winding with more commutation-units to make up a DC armature winding circuit which is much closer to that of conventional DC one.However, the research progresses including motor theory and electromagnetic design methods are still in infancy.Against the background referred above, a deep and comprehensive study has been done for the development of electronically commutated permanent magnet synchronous DC machine. Four creative contributions have been proposed: the electronically commutated permanent magnet synchronous DC machine with frog-leg winding has been firstly proposed; a new preliminary design flow based on exact analytical method has been proposed; the relationship between mechanical commutation rule and power switches status has been united; a novel speed range extension method by conducting the power switches status in advance, based on reducing the effective number of coils, has been proposed to extend the speed range.Firstly, a familiar machine, electronically commutated frog-leg permanent magnet synchronous DC machine, which combines the frog-leg winding from the conventional DC machine and its concept, is presented. For the simplex lap winding and duplex wave winding from the frog-leg winding are equalizers for each other and they form a closed polygon winding with four layers, the proposed machine gets better performance in commutation and fault-tolerant.Secondly, a new preliminary design flow based on exact analytical method with the guiding concept of minimizing the cogging torque has been proposed to takeplace of the conventional magnetic circuit method. To verify its validity, both no load and load air-gap magnetic field, tooth-yoke flux density and cogging torque are calculated and compared with those of finite element method.Thirdly, inspired by the improvement measure for commutation process from conventional DC machine, a novel speed range extension by way of conducting in advance is presented to improve the delayed commutation process and current circulation caused by the inductance characteristics of commutation element group,and the power switching device would be damaged especially when the machine is operating under high speed or large current.Fourthly, to emphasize the essence just as a DC machine of the proposed machine, its mechanical, regulating, current-torque and efficiency characteristics are studied and compared with those of conventional DC one based on the experiment platform employing FPGA, and these characteristics under different speed range extension modes are also studied. The experiment results show that the proposed machine system successfully imitates the operation of conventional DC machine and it is convenient to extend speed range.Finally, as an offspring of the brushless DC machine, the electronically commutated permanent magnet synchronous DC machine provides a broader perspective to understand the historical mission of the higher performance brushless machine. Although there are few related research literatures on it, a series of research achievements in this thesis provide a valuable reference for the future work in prototype design expansion, electromagnetic field analysis and experiments. |
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