Design And Controller Research Of High-speed PM Motor Based On The Soft Magnetic Ferrite

With high efficiency, high power density characteristics, more and more high-speed BLDC motor were applied in high-speed drive field. Because of huge harmonic content, serious core loss, difficult weakening magnetic of high-speed PM motor, high-speed PM motor was limited in some application. Core loss problem and weakening magnetic problem of high-speed PM motor always is the research focus of high-speed PM motor. Scholars both at home and abroad have carried through a large of research and obtained many achievements.In this paper, in order to solve the core loss problem of high-speed permanent magnet motor the soft magnetic ferrite which has high magnetic conductance, high resistivity, low loss characteristics was brought in to high-speed PM motor. and on this basis, this paper presents a new high speed of permanent magnet motor weakening magnetic structure. This paper mainly focus on field distribution characteristics, analysis model, weakening magnetic characteristics of high-speed PM motor, and the main conclusion has the following several aspects:Firstly, soft magnetic ferrite with high magnetic conductance, high resistance and low loss is used as the motor stator core, and the rotor adopts rare earth permanent magnet. Making use of the motor slotless structure, work points of the high energy product NdFeB and soft magnetic ferrite can be matched reasonablely, this can overcome the serious core loss of high-speed PM motor, at the same time this can guarantee the high speed permanent magnet motor high power density characteristics. Using finite element analysis software the characteristics of the magnetic field distribution in this motor was analyzed deeply. This paper expounds the air-gap magnetic field and the end of the magnetic field distribution and the influencing factors, which can provide theoretical reference of design optimization. Secondly, based on the above analysis a new type weakening magnetic structure of PM motor was proposed. Outside the stator a cylindrical bypass iron yoke is made by ferromagnetic materials and DC excitation winding is placed between the stator and bypass iron yoke. A axial field flux will be excited in the stator core. The magnetic saturation of the soft magnetic ferrite will be changed by regulating the DC exiting current. The equivalent magnetic resistance of PM magnetic circuit may be changed. Then the main flux is changed. In this paper the3D magnetic field distribution of this motor was deeply analyzed.At the sometime this thesis presents the weakening magnetic structure analytic calculation model, and through contrasting the finite element analysis and prototype test results, it can proved that the model is accurate and effective, which can be an effective tools of motor’s design and analysis.Lastly, based on the16-bit enhanced flash digital signal controller dsPIC30F2010, a square wave drive control system of Permanent-Magnet DC motor is designed. The experimental waveforms are comparatively ideal, and the motor speed and torque become relatively smooth so that the vibration is ameliorated. Through the3D finite element analysis and the prototype test results shows that the novel weakening magnetic structure of high-speed permanent magnet motor based on the soft magnetic ferrite is correct and feasible.