Proposal and Design of Primary-PM Transverse-Flux Linear Motor with Enhanced Secondary-PM Structure for High Power Density

Linear motor has shown its essentiality in industrial applications such as semiconductor manufacturing, high-grade CNC machine tools, rail transportation systems. Nowadays, the urgent demands for high power density linear direct drive system has been proposed. The traditional linear motors are subjected to serious competition between electric loading and magnetic loading. Further improvement of its power density seems uneasy to realize. The transverse-flux motors (TFM) have the peculiarity of decouple of electromagnetic loadings [1]–[3]. The TFMs are considered to be potential candidate for high power density systems. However, there are several common drawbacks need to be addressed before its practical applications. Leakage flux has led to poor utilization of permanent magnets. Owing to the structure peculiarity, TFMs experience more disadvantages from leakage flux. It was reported that the leakage flux would produce negative force in the operating process, led to poor power factor [4]. Up to now, several approaches have been brought forward to inhibit the leakage flux. One possible way is to use high permeability material to enclose the leakage flux, preventing it from interlinking the armature [5]. Another way is to use magnet shield technology. The magnets are placed in the leakage flux path in a direction against the leakage flux [6]. But they all increase the complexity of the motors, making it hard to manufacture and increasing the prime cost.