Study Of Hybrid Excitation Flux Switching Motor System

Hybrid excitation flux switching motor (HEFSM) is a flux switching motor (FSM), its excitation magnetic motive force (MMF) is established through field winding and permanent magnet. There is no permanent magnet or winding on the rotor of FSM, that means the motor is sturdy and durable. The FSM has a high winding utilization rate for the windings are powered in all time as the motor workinging. The excitation field is established by excitation current in the electrical excitation FSM, so the feild can be adjusted easily. The electrical excitation FSM brings more power consumption and loss. The permanent magnet FSM has a higher efficiency, but its air gap magnetic field is difficult to adjust. The HEFSM has the advantages of electric excitation FSM and permanent magnet FSM, both have higher utilization of the excitation current and the adjustment function of excitation feild, so it has great research value.The FSM can be divided into multi-phase and single-phase in structure and the multi-phase mainly refers to the three-phase form. The motor structure and external control circuit of single-phase FSM are simpler than three-phase FSM. The ratio of stator and rotor pole is an integer in the single-phase FSM, so the research method of single-phase FSM is different to three-phase FSM. Because there is no unified mathematical model can be refered to and the shortcomings of torque pulsation and existence of starting dead zone, the application range of single-phase FSM is limited. Whether the doubly salient motor is multi-phase or single-phase structure, increasing the pole number of stator and rotor can reduce the rotor stepping angle, which is beneficial to reduce the torque pulsation. At the same, it’s will lead to a higher switching frequencies, that means a higher controller capacity and more core loss. When the center lines of stator and rotor pole of single-phase FSM in parallel, magnetic circuit of the motor achieves stable state and the value of the motor’s electromagnetic torque is zero.Due to the inertia, friction and other factors, the motor can not work if the electromagnetic torque is less than a certain numerical. So there is a dead starting zone which center is the center line of stator and rotor pole while they are parallel. The dead starting zone is an inevitable question of single-phase FSM. The scholars have been made improvements on this issue, such as retrofitting auxiliary structure in stator or rotor, changing the rotor shape. The methods can improving the starting ability, but did not eliminate the dead starting zone.The existing researches about HEFSM mainly focus on three-phase structure. As a novel structure, single-phase HEFSM has different characteristics to the three-phase HEFSM, so it very worths to research. In this paper, the research works of single-phase HEFSM were carried out as follows:1. The HEFSM can adopt two kingds of strcture topology, one is hybrid excited in series, and the other is in parallel. The finite element analysis (FEA) simulation results proved that the excitation field setting effect and the regulating ability of the excitation field of the HEFSM in parallel is better than the HEFSM in series. Therefore, the HEFSM this paper researchs on adopt the parallel hybrid excitation structure. The working principle and the magnetic field distribution characteristics of the parallel HEFSM were analysed, the size of the permanent magnet and the excitation groove yoke were the largest factors to affect the motor’s electromagnetic properties. The impacts of these two points to the flux density of air gap and excitation groove yoke were shown out through the FEA simulations, the simulations results show that in order to obtain a better electromagnetic effect the two points should be considered both while designing the single-phase HEFSM.2. The researchs of modeling methods of the HEFSM werer carried out in this paper,A magnetic circuit model building method of the HEFSM was proposed, which can reflect the motor’s static characteristics under the different rotor position or current. The model provides a useful reference for the motor designe and analysis. This paper also established a nonlinear inductance model of the HEFSM. The inductance model is a higher-order function of the rotor position and dual continuously variable excitation current. It’s helpful to describe the motor’s dynamic characteristics, and to development and implementation the follow-up speed control strategies. A continuous permeance expression of air gap of single-phase FSM was established in this paper, it’s useful to determine the air gap permeance of single-phase FSM. The expression can be applied to building mathematical model for FSM in single-phase structure. Base the expression a simplified model of single-phase is established. The FSM and HEFSM prototypes were manufactured and the experiments were carried out. The experiment results prove that the model building motheds are ccrrect and the models are accurate.3. A novel rotor structure wase proposed to resolve the problem that the FSM in single-phase structure existing the starting dead zone. According to the analysis of the starting dead zone, two kinds dislocation assembly program of rotor laminations were proposed. Referencing the FEA results, the asymmetric rotor assemblied with different length laminations was adopted and its size parameters were defined. The 3D FEA results show that the asymmetric rotor can make the single-phase FSM put out positive torque continuously in a greater range than the pitch of one stator pole. It means that the asymmetric rotor can eliminate the starting dead zone of single:phase FSM. A simplified model of HEFSM with the asymmetric rotor was established using the model building motheds proposed in this paper. The 3D FEA and experiment results prove the simplified model is correct and accurate.4. The hardware design of HEFSM control system was given out in this paper, and the mechatronics simulation and experiments were carried out. The power circuit was realized with a three-phase inverter power module, it simplifies the power circuit design effectively. The function of control chip, the selection of the functional modules and their interface circuit were described detailedly in this paper. According to the characteristics of control circuit and position signal, current chopping control scheme was adopt to control the wingding current. The co-simulation analysis of HEFSM system was carried out by Ansoft Maxwell and Ansoft Simplorer. The co-simulation model can test the feasibility of current chopping control scheme and the parameter setting. A number of experimental tests were carried out, it including operation tests of conventional rotor HEFSM and start testing of asymmetric rotor FSM. The test proves the current chopping control scheme is feasibility, the controller and the prototype is matching well and operating satisfactorily. It also proves that the asymmetric rotor can eliminate the starting dead zone of single-phase structure FSM effectively as forward rotation, but not in reverse rotation.5. This paper have researched the speed control problem of the HEFSM system, and proposed practical speed control strategies. According to the features of hardware circuit and software design, the paper pointed out that it is feasible and reasonable to adopt the open-loop P-type iterative learning control (ILC) strategy. The iteration coefficient determining mothed was expound. Base on the strategy the experimental studys of conventional rotor HEFSM and asymmetric rotor HEFSM were carried out. The model iterative learning control strategy was proposed refered to the mathematical model established in this paper. Experiment results showed that the HEFSM system could achieve a good dynamic performance in the open-loop P-type ILC strategy. The dynamic performance of asymmetric rotor HEFSM is not well enough under the model iterative learning control strategy because of the accuracy decline of the mathematical model, but it still in the acceptable range.