Rabeb Rebhi

MEC-Based Sizing of a Hybrid-Excited Claw Pole Alternator

The paper is aimed at a magnetic equivalent circuit (MEC)-based sizing of a novel hybrid-excited claw pole alternator. It consists in a claw pole concept with a NdFeB permanent magnet (PM) excitation in the rotor and a dc one in the stator, with the homopolar flux eradicated owing to a magnetic barrier inserted between the stator yoke and lamination. The proposed MEC considers both linear and saturated magnetic circuit, with a focus on the modeling of the leakage fluxes. The developed model is applied for the prediction of the no-load characteristic which is validated by 3-D finite-element analysis (FEA). Then, a dual FEA-experimental validation is carried out considering the case of a dc excitation. Moreover, the proposed MEC makes the investigation of the influent sizing parameters on the machine back-electromotive force (EMF) production capability easy. This latter is enhanced owing to the integration of two ring ferrite PMs linked to the stator, along with a reduction of the volume of the NdFeB PM in the rotor. It has been found that the gained improvement is better than the benefit yielded by as many pole number ferrite PMs inserted between the claws.

Lumped Circuit Accounting for the Rotor Motion Dedicated to the Investigation of the Time-Varying Features of Claw Pole Topologies

This paper is aimed at the derivation and the resolution of a new lumped circuit-also called magnetic equivalent circuit (MEC)-based model of claw pole alternators (CPAs). Incorporating the rotor motion, the proposed MEC is intended to the investigation of the time-varying features of CPAs. Furthermore, it considers the saturation and the armature magnetic reaction. For the sake of simplicity, the MEC is derived assuming that the stator teeth and yoke are independent of the rotor position. Moreover, a specific hypothesis considering that the claws have the same shape along the axial direction with an opening equal to the one of the median plane is adopted. A dedicated numerical procedure based on the Newton-Raphson algorithm is developed in order to solve the proposed MEC. Hence, the prediction of selected time-varying features, considering both no-load and load operations, turns to be feasible. The comparison between the MEC results and those yielded by experiments carried out on a test bench, has led to good agreement.

On the Comparison Between the Stator- and Rotor-excited Claw Pole Alternators

Abstract This article compares the electromagnetic features of rotor-excited claw pole alternators and stator-excited claw pole alternators, which share the same rotor active length. Accounting for the 3D flux path characterizing both machines, the comparison study is based on a 3D finite-element analysis. Following a description of the flux linkage in these machines, special attention is paid to the investigation of their magnetic features, including the air gap spatial repartition of the flux density, torque-angle characteristics, and no-load characteristics. It has been found that the rotor-excited claw pole alternator exhibits a higher back-electromotive force production capability than the stator-excited claw pole alternator, which is penalized by (i) the additional lateral air gaps located in between the collectors and the magnetic rings, and (ii) the homopolar flux. The torque production capability of the stator-excited claw pole alternator is also affected by these drawbacks at low values of the field current. Increasing this leads to a saturation of the rotor-excited claw pole alternator, whose torque production is similar to that of the stator-excited claw pole alternator.

An attempt to improve the generating capabilities of an hybrid claw pole machine

Hybrid excited AC machines are presently given an increasing attention. Within this trend, the paper deals with a novel hybrid excited brushless claw pole machine. It consists in a claw pole machine excited by a PM in the rotor and by a field winding in the stator. In order to eradicate the claw-to-claw leakage flux and then improve the machine features, ferrite PMs are inserted in between the claws. An increase of the air gap flux density has been gained, so that the machine turns to be equipped by three excitation sources.

3D MEC modeling of a hybrid-excited claw pole alternator incorporating the rotor motion

The paper is devoted to the modeling of a hybrid-excited claw pole alternator (HECPA) by means of a variable position 3D magnetic equivalent circuit (MEC). The study is initiated by the derivation of a MEC with the rotor position kept at the maximum flux linkage between the rotor and stator, enabling the investigation of the steady-state features. The incorporation of the rotor position in the MEC is then considered. A dedicated numerical procedure based on the Newton-Raphson algorithm is developed for the resolution of the proposed variable position MEC. The obtained fluxes, for the different considered positions, allow the prediction of the HECPA time-varying features under no-load operation. A comparison between the results predicted by the variable position MEC and those computed by finite element analysis reveals a good agreement.

Hybrid excited claw pole alternators: Attempt to satisfy the increasing power need on board

This paper is devoted to the topological and functional descriptions as well as a 3D FEA-based optimization of a hybrid-excited claw pole alternator, with a focus on its back-EMF production capability. The proposed claw pole concept is equipped by PM excitations in both stator and rotor and a field one in the stator. A special attention is paid to the cancelation of the homopolar flux which represents a specific leakage one associated to the field excitation. To do so, the effects of two (complete and partial) Aluminium-made magnetic barriers, inserted in between the stator yoke and lamination along the active length, on the back-EMF production capability are investigated. It has been found that the partial magnetic barrier is a compromise regarding the homopolar flux cancelation and the 3D-flux enhancement. Compared to the complete magnetic barrier, the partial one allowed an increase of the amplitude of the fundamental back-EMF; those of its harmonics remain almost unchangeable.

An attempt to improve the sizing of a hybrid excited brushless claw pole alternator

Purpose – This paper aims at the improvement of the generating capability of a hybrid excited brushless claw pole alternator (HEBCPA).Design/methodology/approach – Following the identification of the HEBCPA influent sizing parameters, the investigation of their impact on the back‐EMF production capability is carried out considering a 3D‐finite element analysis (FEA).Findings – The HEBCPA Back‐EMF production capability is highly affected by the variation of the influent sizing parameters. A selected combination of these parameters has led to an optimized generating capability.Research limitations/implications – An experimental validation of the generating performance computed by 3D‐FEA shall be treated in the future.Practical implications – The optimized HEBCPA is of great interest for the automotive applications as well as for wind energy generating systems.Originality/value – The optimized HEBCPA is a new concept that has been proposed by the authors in a recent work.

Improvement of the back-EMF production capability of a hybrid-excited CPA

The paper is devoted to the improvement of the back-EMF production capability of a hybrid-excited claw pole alternator (HECPA) which has been introduced in a previous work. The concept was equipped by ferrite PMs in both stator and rotor. The improvement of the back-EMF production capability is gained thanks to the substitution of the ferrite PM linked to the rotor by a rare earth one. The study is initiated by the description of the HECPA concept and the analysis of the no-load flux paths generated by the rotor excitation and the stator ones. The investigation of the influence of the rotor PM substitution on the HECPA no-load features is carried out by a variable position magnetic equivalent circuit (MEC) whose results are validated by 3D finite element analysis (FEA).

On the modeling of a doubly-excited brushless claw pole alternator: Application to a solar-wind-wave hybrid energy conversion system

Within an FP7 project proposal, the paper deals with the MEC modeling of a doubly-excited brushless claw pole alternator (DEBCPA). It consists in a claw pole concept with two excitation sources: (i) a ferrite PM in the rotor and (ii) a field winding associated to two ferrite PMs in the stator. The proposed MEC considers both linear and saturated magnetic circuit, with a focus on the modeling of the leakage fluxes following a 3D finite element analysis (FEA)-based investigation of their paths. The derivation of the different reluctances as well as the MEC resolution procedure are detailed. The proposed MEC is applied for the prediction of the DEBCPA no-load characteristic, which is validated by FEA.

Magnetic equivalent circuit based modeling of claw pole machines: A survey

Optimizing the design of electromagnetic devices requires tools that enable one to calculate their magnetic and electric characteristics. The magnetic equivalent circuit (MEC), also called reluctance model, is regarded as a promising tool, providing short calculation time with adequate accuracy. Within this trend, the paper is aimed at the MEC modeling of four topologies of claw pole machines which differ by their excitation modes. Following the synthesis of the MEC of each topology, its resolution using a Newton-Raphson procedure is proposed. No-load and load characteristics are predicted by the proposed MECs. Experimental or 3D-FEA based validations of the results yielded by the MECs are provided.