Contents I INTRODUCTION
Linear motors have been used in wide application in the transportation systems and factories as the there is no necessity for gearbox and rotary to linear converters [1–2]. Most of the linear motors are longitudinal with the flux flow is parallel to direction of movement. Some advantages of the linear motors are low noise, reduce operation cost, and increase flexibility (gearless feature), But the most important disadvantage of Linear Motor is low power density [3]. To overcome to this problem, the transfer flux structure with permanent magnet exciter is proposed in recent years. In transfer flux linear motors (TFLM) with permanent magnet exciter flux flow is three-dimensional (3-D) and perpendicular to direction of movement and permanent magnet increase the flux density in air gap [1]. The power density, efficiency and power factor are all greater than an conventional linear motor[4]. Most advantages of TFLMs are: direct linear motion with high power density, high force density per volume and high efficiency and also there is not rivalry between iron space and coil space [[1]–[2], [5][8], but the disadvantage of TFLMs are larger magnetic leakage flux in coils, larger inductance, which leads to a low power factor, complex structure with 3D magnetic circuit. High Density Linear Motor (HDLM) has a high density flux flow in the air gap with small magnets compared to TFLM [9].
