Considerations on Thrust-to-Input Ratio of a Cylindrical Moving Coil Type Linear DC Motor

Abstract

Linear DC motors (LDMs) are widely used for servo-actuator, compressor and so on. High-efficiency LDMs are strongly desired for compressors. To realize the 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 that dimensions of the LDM influence 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 by 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.