Mechanical Properties Analysis And Temperature Rise Calculation Of High Speed Permanent Magnet Claw Motor With Outer Rotor

A novel high speed motor has an extensive application prospect in areas like systems of high speed compressor and fan flywheel energy storage and high speed machine tool spindle motors. High speed permanent magnet claw-pole motor has advantages such as small size, high efficiency, high power density and high integration degree. The motor has become the hot spot in the field of international high-end equipment manufacturing. At present, most of the high speed permanent magnet motors often have internal structures. For the protection of permanent magnets to withstand enormous centrifugal forces,motors need protective covers and it leads to the increase of motor equivalent air gap and the amount of permanent magnets, decrease of air-gap flux density. The high speed permanent magnet claw-pole motor with outer rotor in this article can avoid these problems. Also, the calculation analysis of mechanical strength and dynamic characteristics are given in this article. For the temperature rise problem in high power density motors, two schemes of cooling system are designed and some comparative study are done. This paper deals with the work as follows:(1) Based on the study to structure and operation principle of the high speed permanent magnet claw-pole motor with outer rotor, the design of main dimensions are got in this paper. The properties of the soft magnetic composite materials for the high frequency conditions and complicated structure affect the nonlinearity of stator flux density. With the electromagnetic finite element calculation software, the analysis of steady state and transient field performance are given in the article and it provides theoretical basis for this kind of electromagnetic design and performance analysis.(2) A calculation model is set up which based on the FEA of high speed permanent magnet claw pole motor stress, and the strain field distribution of yoke and permanent magnet of outer rotor are calculated with great centrifugal force. The influence of rotor structure dimension on the strain field distribution is discussed as well as the method of decreasing the permanent magnet tensile strain. And then, the rotor dynamic analysis model is established in this paper. With the FEA, critical speeds and mode shapes of permanent magnet rotor are calculated, with analyzing the speed range of motor safely running, ensuring reliable operation for a long time.(3) After getting the loss of different parts of high speed permanent magnet claw pole motor, a fluid field temperature calculation model is built in this paper, and the temperature rise of the motor is calculated. Because of the high level of high speed permanent magnet motor power density, loss density and cooling problems as well. A definition of inside-axis cooling system and a stator cooling system are created, and the cooling effect of the motor is calculated with the two-phase flow method. This paper also analyzes the influence of water-loop cross sectional area and flow speed on the different parts’ temperature rise of the motor.