Research On Novel Semiconductor Converting Low Speed Reluctance Motor

This dissertation presents a type of low speed and high torque motor-semiconductor converting low speed reluctance motor (SCLRM) with novel structure and principle for the first time. In stead of any gearbox, SCLRM consists of a traditional VR low speed synchronous motor combined with a static converter composed only of six diodes. For this reason, SCLRM not only inherits the advantages of simple structure and techniques from the traditional VR low speed synchronous motor, but also overcomes its limitation of lower torque capability, which breaks a new approach to the research of low speed and high torque motors for direct drive applications. In this dissertation, systematic theoretical analysis and experimental study are carried out on the operation principle, design features, magnetic field distribution, steady-state performance characteristics and speed-adjustable controlling system, laying solid foundation of both theory and practice for this type of motor.On the basis of introducing the motor structure, the self-exciting converting principle of SCLRM under three-phase AC supply is described. By analyzing the perineance and magnetic field in the air gap of SCLRM, the conditions for constant torque to maintain when operated at synchronous low speed is deduced, from which the workable matching number of stator teeth with rotor teeth is determined. In addition, the mathematical models of SCLRM both in multiphase frame and in complex vector frame are established, as well as the linear magnetic network model from which the calculation of the inductance of the phase winding is derived. Besides this, the calculation of magnetic energy and electromagnetic torque of SCLRM is deduced by virtual displacement principle, and the physical essence of the electromagnetic torque is also analyzed in detail.The design features of SCLRM are analyzed comprehensively, based on which the engineering calculation methods of the performance are proposed. The comparison between the calculating and experimental results of the sample machine shows that the engineering calculation methods presented in this dissertation meet the accuracy demands of practical application.- II -The magnetic field distribution and the distribution of airgap flux density under one stator pole of SCLRM at different rotor positions are calculated in detail by two-dimensional FEM. The property and the distribution features of the magnetic field of the novel motor are analyzed, and the inductance characteristics of the sample machine are further calculated.According to the particular winding connection of SCLRM, an open-loopvariable frequency adjustable speed system with a novel inverter different from the&typical VSI is developed. The experimental results of the sample machine shows thatthere exists an approximately constant power speed adjustable characteristic in SCLRM. In addition, a project of speed control system with feedback is put forward in this thesis.The system simulation model is implemented in PSPICE. The steady-state simulation performance of SCLRM in both self-exciting operation mode and inverter feeding mode are studied, and the effect on the steady-state performance by the motor parameters and the driving mode are also simulated, verified by the experimental results. Further more, the main reason of the torque ripple is analyzed by simulation in the viewpoint of energy. The simulation and the experimental results are well coincided, which accounts for the sufficient accuracy of the simulation model proposed in this dissertation.