Preventing irreversible demagnetization of linear oscillation actuator for compressor
                                                      ZHAO Ke1, TONG Shui guang2, LV Hong bing3, JIAO Lei4
（1.Changzhou Industrial Technology Research Institute, Zhejiang University, Changzhou 213022, China;2.College of Mechanical Engineering, Zhejiang University, Hangzhou 310027, China;3.College of Computer Science and Technology, Zhejiang University, Hangzhou 310027, China;4.Ocean College, Zhejiang University, Zhoushan 316021, China）

Abstract: Aiming at the problem of irreversible demagnetization of Nd Fe B permanent magnet material used in moving magnet type linear oscillatory actuator, the design of preventing irreversible demagnetization of Nd Fe B permanent magnet, which is under the condition of high temperature and alternating magnetic field was studied. The permanent magnet s traditional design criteria of optimum working point was corrected. The mathematical expression of maximal demagnetizing working point at working temperature was deduced by means of equivalent magnetic circuit method, and the influences of actuator s structural parameters on maximal demagnetizing working point were qualitatively analyzed. The position of knee point at working temperature was deduced from the magnetic parameters at normal temperature, and the discriminant formula of excitation loss was given, which is a necessary security constraint related to the structural optimization of linear oscillation actuator. Two grade of Nd Fe B permanent magnet 40 M and 40 UH were tested by experiment of excitation loss. The results indicate that the experimental results agree with the theoretical calculation, and this method can be used for the selection of Nd Fe B permanent magnet and preventing irreversible demagnetization of linear oscillatory actuator.

Key words: linear compressor; linear oscillation actuator; moving magnet; irreversible demagnetization