Detent force reduction in permanent-magnet linear synchronous motor utilizing auxiliary poles

Abstract

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

Linear generator design for concentrating solar power technologies: Optimization and prototype development

“…L p , primary length, is calculated with Equation (). To reduce the cogging force in the linear machine, ϑ can be calculated with external thickness in the end parts where $${b}_{tend} \approx 0.52{\tau }_p$$ [53, 58, 59]. $$$$\begin{equation}{L}_p = \ \vartheta + Xs\ {\tau }_s\end{equation}$$$$ $$$$\begin{equation}\vartheta \ = \ 2{b}_{tend}\end{equation}$$$$…”

“…L p , primary length, is calculated with Equation (11). To reduce the cogging force in the linear machine, 𝜗 can be calculated with external thickness in the end parts where b tend ≈ 0.52𝜏 p [53,58,59].…”

The Determination of Effects of Primary and Secondary Geometry of Tubular Linear Generator

“…Cogging force, output power change As known, it is desired that the cogging force as a result of attraction force between the primary core thread and secondary magnet shall be low without current at the coils. In order to decrease the cogging force, some techniques (hollow/pole combination [13], final thread width setting [14], hollow type [15], pole slip [16]) are applied. These methods significantly decrease the cogging force.…”