Julien Fontchastagner

New Model of Radial Force Determination in Bearingless Motor

This paper proposes to determine the radial forces in bearingless permanent magnet motor topology. We consider normal and tangential components of the magnetic field in the air gap. Their harmonic components and their evolution versus current and rotor position are considered. This allows establishing the semianalytical expressions of the radial forces considering different field sources. Their precision has been verified using a full finite element model and statistic analysis. The advantage of this semianalytical model lies in the swiftness of the different force components evaluation and consequently the reduction of CPU time.

A Fast Finite Element Model Taking Into Account 3-D Effects for the Optimal Design of Micro-Hybrid Starters

This paper presents a fast design method taking into account 3-D effects in a reinforced brushed dc motor used as starter in automotive application. Because of their low cost and simplicity, reinforced starters are used in micro-hybrid vehicles. The specific geometry of such devices induces an axial component of the flux which cannot be accounted for by 2-D models. 3-D finite element (FE) models are suitable for this purpose but their excessive need of CPU time complicates their use in an automatic optimization procedure. We propose to identify the overhang effects by using an adapted and corrected 2.5-D FE model which is validated by 3-D computations and experiments. Finally, the 2.5-D model is implemented in a multiobjective optimization procedure.

Torque modeling and optimization of DC machine based on reluctance network taking into account armature reaction magnetic field

In this paper, the main objective is to develop a fast analytical model to be used in optimization process or coupled with other fast analytical models. A reluctance network of DC series machine is developed and shows its accuracy and robustness thanks to the consideration of the armature magnetic reaction (AMR) which is an important phenomenon in high saturated DC motors. This model is validated by a statistical way and presents a fast computation time thanks to an equivalent symmetrical machine. The optimization is used with RN and FE models and shows the efficiency of the RN to find an optimum without needing the FE final step optimization.

Design optimization of an axial-field eddy-current magnetic coupling based on magneto-thermal analytical model

Abstract This paper presents a design optimization of an axial-flux eddy-current magnetic coupling. The design procedure is based on a torque formula derived from a 3D analytical model and a population algorithm method. The main objective of this paper is to determine the best design in terms of magnets volume in order to transmit a torque between two movers, while ensuring a low slip speed and a good efficiency. The torque formula is very accurate and computationally efficient, and is valid for any slip speed values. Nevertheless, in order to solve more realistic problems, and then, take into account the thermal effects on the torque value, a thermal model based on convection heat transfer coefficients is also established and used in the design optimization procedure. Results show the effectiveness of the proposed methodology.

Hybrid Analytical Model Coupling Laplace’s Equation and Reluctance Network for Electrical Machines

This paper presents a hybrid magnetic model combining reluctance network and Laplaces equation resolution using magnetic vector potential in the air gap. The coupling of the two models is performed by introducing fictive equivalent magnetomotive forces in the air gap. The model is applied to the study of dc machines used as a starter in automotive application. Good results are obtained compared with finite-element model and experimental measurements.

Optimization of DC Starters Based on Reluctance Network Accounting for Armature Reaction Magnetic Field

Abstract In the new generation of “Stop & Start” starters, a DC series motor with high power density is used. In this application, non-symmetrical machines are used due to the single wave winding in brushed motors. The saturation of the iron core in this application reaches a really high level. Moreover, armature reaction in DC machine with a large stator pole spans makes this phenomenon even more enhanced. All these criteria lead to model the whole machine in highly saturated conditions which is time consuming. In this paper, a fast reluctance network (RN) model for an equivalent machine is proposed. It takes into account the armature reaction in high saturation conditions. It also allows a good accuracy and permits us to show the relevance of taking into account this phenomenon in torque calculation. This model is validated by a finite element (FE) method in many operating points, and by a statistical approach. It shows high robustness and low computation time. Finally, an optimization procedure using this reluctance network model and FE is presented in order to show the accuracy of the RN compared to FE model.

Comparison of transient performances for synchronous and eddy-current torque couplers

In this paper, we compare the transient performances of synchronous and eddy-current magnetic couplings. Based on a two-dimensional approximation for the magnetic field distribution, closed-form expressions for the transmitted torque are first presented. The torque formulas are then used to study the transient responses during a start-up and for a sudden application of a load torque. Simulation results are compared with those obtained from tests. It is shown that overload torque condition leads to the loss of synchronism for the synchronous coupling. A discussion about the benefits and the disadvantages of each topology in terms of transient responses is given.

Hybrid analytical model coupling Laplace's equation and reluctance network for electrical machines

This paper presents a hybrid magnetic model combining reluctance network (RN) and Laplaces equation resolution using magnetic potential vector in the air gap. The coupling of the two models is done by introducing fictive equivalent magneto-motive forces (MMFs) in the air-gap. Good results are obtained compared to finite element model.

Hybrid model: Permeance network + 3D finite element for modeling claw-pole synchronous machines

An approach based on the hybridization of 3D finite element method and permeance networks is developed and applied for the modeling of a claw-pole synchronous machine. This model avoids the difficulties due to the movement and the complex geometry of the rotor and reduces the CPU time. A good agreement with experiments and full 3D models is obtained.