Considerations on the thrust-to-input ratio of a cylindrical moving-coil-type linear dc motor

Abstract

Linear dc motors (LDMs) are widely used for servo-actuators, compressors, and so on. High-efficiency LDMs are strongly desired for compressors. To realize LDMs with high-efficiency characteristics, decreasing the copper losses, namely, thrust-to-input ratio, F/P, must be increased. This paper describes an optimization method for the F/P of a moving-coil-type LDM. The following results are obtained: 1 Simplified expression for the F/P of the LDM is derived from the permeance analysis method. The effects of dimensions of the LDM on the F/P of the LDM are investigated through the simplified expression for the F/P. As a result, the optimum dimension of the LDM for maximizing the F/P exists. 2 When the static thrust is 100 N, the measured F/P of the initial LDM is 7.9 N/W, and the errors using the simplified expression for the F/P and the finite element method (FEM) are 33 and 8%, respectively. Derived simplified expression for the F/P is useful because the F/P can be calculated easily. 3 An improved LDM, which has 26% higher F/P than those of the initial LDM, is designed by using the permeance analysis method and the FEM. © 2000 Scripta Technica, Electr Eng Jpn, 131(1): 103–111, 2000