Development of a New Stator Module Type Vernier Motor utilizing Amorphous Cut Core

Abstract

This paper presents a new stator module type vernier motor, which is applicable amorphous magnetic material effectively as a stator core material. The iron loss distribution in the stator module structure made of a Fe-based amorphous material is numerically investigated with the finite element method and compared with those made of oriented electrical steel sheets and non-oriented electrical steel sheets in the laminated core pattern. The results show that the proposed model is useful to improve significantly efficiency of the vernier motor model. Recently, industrial demands are increasing for electric machines with high torque density and high efficiency. Mechanical gears are usually used in order to realize high torque and low speed rotation as a speed reducer in a robot, an electric vehicle, an elevator and so on. However, the mechanical gears have difficulty in high precision control due to backlash and friction. Furthermore, there are mechanical contacts between gear teeth, so that maintenance is necessary. In order to solve these problems, vernier motors that utilize the magnetic gearing effects are getting attention due to their high torque capability and small pulsating torque. The vernier motor is a motor that obtains rotational force through the magnetic flux harmonic component modulated by the geometries of the stator cores. The magnetic flux harmonic component is proportional to the pole number of the rotor magnet and the modulated magnetic field generates the output torque on the rotor. Thus, in the vernier motors, it is important to analyze and design the armature magnetic field and the structure of the stator and rotor cores. The various kinds of vernier motor are still in the research stage, further improvement in efficiency and power factor is required for commercialization and mass production. In order to improve efficiency of the vernier motors, we try to apply the Fe-based amorphous magnetic material to the stator module. The Fe-based amorphous magnetic material has high permeability and low loss, and is extremely excellent as a core material. However, the amorphous magnetic material is difficult to process in the conventional laminated core structure. The proposed stator module type vernier motor is possible to use U-shaped amorphous cut cores annealed in a magnetic field. Thus this model has the following three advantages: the amorphous wound cores are applicable; the harmonic component of the magnetic flux increases in the divided core structure and it leads to improve the torque characteristic; the deterioration of the magnetic properties of the amorphous magnetic material after processing can be prevented by the magnetic annealing. Fig. 1 shows the model used in the analysis and its specifications. Because the fifth harmonic is used in the proposed vernier motor model, the number of the pole pairs of the rotor magnets is assumed to be 5. The analyses were conducted under the same conditions, and the stator core material was assumed to be the amorphous magnetic material (2605HB1M), the non-oriented electrical steel sheet (50H470), and the oriented electrical steel sheet (23JG120). Fig. 2 shows comparison of the output power, the iron loss, the copper loss and the efficiency of the each model when the load angle is 90 degrees. As shown in this figure, it is evident that the iron loss is the smallest and the efficiency is the largest in the model utilizing the amorphous magnetic material. Details of the stator module construction and its frequency dependency will be discussed at the presentation and in the full version of paper.