This paper proposes a novel technique to reduce the detent force in permanent magnet linear synchronous motor (PMLSM) using auxiliary poles. The detent force that is caused by the attraction between permanent magnet (PM) and the iron core without input current can be divided into two components: the slot effect and the end effect. To reduce these two effects, we analyze the characteristics of the detent force according to semi-closed slot clearance length and auxiliary poles position by using two-dimensional (2-D) finite element method (FEM). The numerical calculations and the experimental results prove that this proposed technique has a good effect on the reduction of the detent force. I. INTRODUCTION Permanent magnet linear synchronous motor (PMLSM)is extensively used in high performance drive systems and servo applications, because PMLSM has certain unusual features such as large air-gap, high force density, rapid dynamic response, low thermal losses, and simple structure. However, the detent force, which is the main disadvantage of PMLSM, results in a periodic force oscillation with respect to the mover position. Consequently, this periodic force oscillation causes mechanical vibration, acoustic noise, and velocity oscillation, which will deteriorate the performance of PMLSM [1].The detent force that is caused by the attraction between the permanent magnet (PM) and the iron core without input current can be divided into two components [2]. One is the slot effect caused by the attraction between the PM and the slotting of the iron core. It has a wavelength of one slot pitch. The slot effect of detent force is analogous to the cogging torque of rotary PM motors. There are many motor design techniques for the reduction of this effect [3]. In this paper the PMLSM is with a low number of slots per pole per phase, the fractional-slot pitch windings technique is much more suitable compared with the skewing technique. The other is the end effect caused by the finite iron core length of the mover, there is attraction between the PM and the iron core edges. It has a wavelength of one pole pitch [2]. The end effect of detent force is the inherent characteristic of PM linear motors, which is the difference from rotary motors. It is the reason that the detent force of PM linear motors is larger than that of PM rotary motors. Reference [1] and [2] provided the method of the modification of the end teeth length and shape, and the optimization of the iron core length. These methods have good effect on

This paper investigates an optimal design of a double-sided slotted iron core type permanent magnet linear synchronous motor (PMLSM) using for ropeless elevator system. To obtain the optimal structure, the combination of response surface methodology (RSM) and two dimensional (2D) finite element analysis (FEA), which can solve the problem effectively without much time consuming, is utilized to investigate the PMLSM characteristics. Moreover, the detent force is more detailed analyzed with the manufacturing consideration. In final some numerical calculation results are reported to validate the applicability of this double-sided slotted iron core type PMLSM in ropeless elevator system. Introduction

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This paper proposed a method to compensate the unbalanced magnetic force in 12/8 switched reluctance motor. Using two-dimensional transient finite element analysis coupled with external circuits, both motor and inverter could be modeled to study the performance of motor. Airgap nonuniformity caused by eccentricity between the stator and rotor axes was found to be the main source of unbalanced magnetic force. Several connecting methods of coils were studied and it was observed from the simulation results that the currents could be adjusted in certain parallel paths and unbalanced magnetic forces could be reduced. The effects were also verified by experiment results.

The detent force of the permanent-magnet linear synchronous motor (PMLSM) is caused by the interaction between the permanent magnet and the iron core of the mover without input current. It is a function of the mover position relative to the stator. This paper proposes a control based method to reduce the detent force for the PMLSM. This detent force that can be predicted by finite element method is compensated by injecting the instantaneous current using field-oriented control method. Both the simulated and the experimental results are reported to validate the effectiveness of this proposed method.