Amal Souissi

MEC-Based Modeling and Sizing of a Tubular Linear PM Synchronous Machine

Linear machines are currently considered as viable candidates for direct-drive wave and free-piston energy converters. This paper is devoted to an approach based on a magnetic equivalent circuit (MEC), which is also called lumped circuit, dedicated to the modeling and sizing of a tubular linear permanent-magnet synchronous machine (T-LPMSM). The proposed approach considers, in a first step, the cancelation of the end-effect phenomenon. To do so, a dedicated design procedure, consisting in achieving a

Analytical Prediction of the No-Load Operation Features of Tubular-Linear Permanent Magnet Synchronous Machines

2\pi/3

An approach to reduce the cogging force in tubular linear PM synchronous machines

-shift between the armature phase flux linkages by selecting a fractional ratio of the stator pole pitch to the mover one and balancing the amplitudes of the phase flux linkages by extending the stator magnetic circuit with teeth of appropriate dimensions, is firmly applied on two basic T-LPMSM topologies using a dedicated MEC. Then, an investigation of the influent sizing parameters on the force production capability of the initial concept is carried out. The MEC-based prediction of the force requires the incorporation of the mover displacement, yielding the so-called “position varying MEC” on one hand and the armature magnetic reaction on the other hand. The finite-element analysis of the armature phase flux linkages and the developed force enable the validation of the results yielded by the established MECs.

Feature Investigation of a T-LPMSM Following the Selection of Its Slot-Pole Combination

This paper is aimed at an analytical approach to predict the no-load operation features of tubular-linear permanent magnet synchronous machines (T-LPMSMs). These are currently considered as viable candidates for wave energy conversion. The developed approach is based on the derivation of the air-gap flux density, considering both the first- and second-type modified Bessel functions of appropriate orders. Following its formulation, the air-gap flux density is applied for the prediction of the no-load operation features, with a focus on the cogging force, the phase flux linkages, and the back electromotive forces. A case study is treated considering three axial arrangements of a T-LPMSM, such as the case of an infinite length machine, the case of a finite length machine, and the case of a finite length machine enabling a quasi-cancellation of the end effect. A comparison between the analytically predicted features and those numerically computed by a 2-D finite-element analysis has led to good agreement.

A design approach to reduce the end effect in linear tubular PM machines

The paper is aimed at an approach to reduce the cogging force in tubular linear permanent magnet synchronous machines (T-LPMSMs). An analytic prediction of the air gap flux density distribution is developed in a first step, considering the case of slottless machine and the case where the slotting effect is taken into consideration. The established model enables, thanks to a simple formulation, the assessment of the cogging force assuming an “infinite” length machine. Then, the influence of the end effect on the cogging force is investigated in the case of the real machine. The study is extended to a cogging force reduction approach devoted to a quasi-cancellation of the end effect. It consists in a two-step procedure, such that: (i) achieving a 2π/3-shift between the armature winding flux linkages by arranging the ratio of the stator pole pitch to the mover one, and (ii) balancing the amplitudes of these flux linkages by extending the stator magnetic circuit with teeth of appropriate dimensions. The cogging force prediction of the T-LPMSM following the quasi-cancellation of its end effect highlights the effectiveness of the proposed approach.

On the design of fractional slot T-LPMSMs: effect of the slot-pole combination

This paper investigates the no-load and the on-load behavior of a fractional-slot tubular-linear permanent magnet synchronous machine (T-LPMSM). The study is initiated by the selection of the machine slot-pole combination. To do so, a formulation of the air gap flux density, based on the solution of the magnetic potential vector equation in the air gap and in the PM regions, is derived. The electromagnetic model allows the prediction of the phase back electromotive forces (EMFs) and of the cogging force. The effect of the slot-pole combination on these features is then considered to the aim of the optimal selection of the slot per pole and per phase. A case study considering the optimized slot per pole and per phase number is treated where the analytically predicted no-load features are validated by finite element analysis (FEA). The investigation is extended to the on-load characteristic which is predicted by FEA and is validated by experiments.

On the stator magnetic circuit design of tubular-linear PM synchronous machines: A comparison between three topologies

The paper is aimed at a design approach dedicated to the reduction of the longitudinal end effect in a linear tubular permanent magnet machine. The proposed approach consists in a two-step procedure, such that: (i) achieving a 2π/3-shift between the armature winding flux linkages by arranging the ratio of the stator pole pitch to the mover one, and (ii) balancing the amplitudes of these flux linkages by extending the stator magnetic circuit with teeth of appropriate dimensions. A magnetic equivalent circuit (MEC) of the linear PM machine is established taking into account the proposed approach. A FEA-based investigation of the flux linkage validates the MEC results.

Linear Machines: Electromagnetic Modelling and Analysis

The paper deals with an approach aimed at the design of fractional-slot tubular-linear permanent magnet synchronous machines (T-LPMSMs) with emphasis on the effect of the slot-pole combination. Following the description of the T-LPMSM concept under study, the developed approach is initiated by a formulation of the air gap flux density, based on the resolution of the magnetic potential vector equation in the air gap and PM regions which enables the prediction of the cogging force and the phase back-EMFs. The effects of the slot-pole combination on these features is considered in the second part of the study which is achieved by the selection of an optimized slot per pole and per phase number that yields a high phase back-EMF amplitude and a low cogging force peak-to-peak value. A case study considering the optimized slot per pole and per phase number is treated where the analytically predicted results are validated by finite element analysis.

Tubular-Linear Synchronous Machines: Application to Wave Energy Harvesting

This paper is aimed at the design of tabular-linear PM synchronous machines (T-LPMSMs) with emphasis on the stator magnetic circuit. Three topologies are investigated, such that: (i) an initial concept where the stator pole pitch is equal to the mover one, (ii) a modular concept where the stator is made up of magnetic units separated by a flux barrier, and (iii) a concept characterized by fractional slot per pole and per phase. A magnetic equivalent circuit (MEC) is build in order to select suitable geometrical parameters of the second topology that minimize the end effect; the ones of the first and third topologies have been treated in a previous work. The phase flux linkages and back-EMFs are investigated by FEA. It has been found that the second topology exhibits almost balanced back-EMFs. While, these have the lowest harmonic content in the third topology.

Linear Machines: State of the Art with Emphasis on Sustainable Applications

The second chapter is devoted to the analytical modelling of the electro-magnetic phenomena exhibited in linear machines. The study is initiated by an overview of electromagnetic basis. To do so, electric and magnetic material properties and specifications are firstly recalled. A formulation of magnetostatic and magnetodynamic models based on the main electromagnetic laws and the Maxwell equations is then carried out. Considering the case of conservative electromagnetic systems, a survey of the energy and the co-energy relations is provided. The prediction of the electromagnetic forces, related to the energy relations and based on the established models, is finally treated.