Calculation of Eddy Current Loss in a Tubular Oscillatory LPMSM Using Computationally Efficient FEA

Abstract

In some special oscillatory applications, especially those operated at high speeds, the eddy current loss of a linear permanent-magnet (PM) synchronous machine (LPMSM) should be fully considered because the loss might be large and concentrated in PMs during the oscillation period. This paper presents a loss analysis method based on computationally efficient finite-element analysis (CE-FEA) for a 20-Hz oscillatory tubular LPMSM. Since the mover speed varies with time, an equally divided model in 1/4 period is introduced to calculate the average PM eddy current loss. The flux density curves in PMs are calculated at 18 intervals by the CE-FEA, through which the change rate of the magnetic flux density is analyzed, considering both the entering and leaving effects and coil end effects. The calculation results show that the eddy current loss is obviously concentrated in PMs near the two ends of coils. The calculation results at a speed of 3.6 m/s obtained by the CE-FEA and two-dimensional and three-dimensional time-stepping FEAs are compared to validate the accuracy. Finally, the proposed method is validated by the experimental test results on a prototype LPMSM.