Dynamic performance of linear electromagnetic actuators in a stray magnetic field: theoretical analysis and experimental verification

Linear electromagnetic actuators (LEAs) are widely used in tokamaks, but they are extremely sensitive to and are prone to fail in a high-strength stray magnetic field (SMF), which is usually a concomitant with tokamaks. In this paper, a multi-physics coupling analysis model of LEA, including magnetic field, electric circuit and mechanical motion, is proposed, and the dynamic characteristics of LEAs in SMFs are studied in detail based on the proposed model. The failure mechanism of LEAs in SMFs is revealed, and the influence of SMFs on the dynamic performance of LEAs is studied and quantified. It is shown that the failure threshold of the LEA selected in this work under the rated condition is 27 mT and 14 mT in the positive and negative direction, respectively. Under a typical SMF of 10 mT in the negative direction, the closing time of the LEA will be extended by 40%, while its opening time will be shortened by about 10%. Experimental tests are also conducted, which verify the validity of the proposed model and the analysis results. This paper provides a basis for the diamagnetic optimization design of LEA, and it is of great significance to ensure the reliable operation of the tokamak.