Jean-Claude Mipo

Combination of Finite-Element and Analytical Models in the Optimal Multidomain Design of Machines: Application to an Interior Permanent-Magnet Starter Generator

This paper proposes to apply optimal multiphysic models to the design of highly constrained electrical machines, such as interior permanent-magnet (IPM) machine intended for an automotive integrated starter generators. One of the main problems in the use of such optimal approaches remains the accuracy of the models used by the optimizer. In a recent study, we proposed a design model linked to three strong hypotheses: 1) Iron losses are calculated according to the flux density fundamental (sinusoidal approach); 2) flux densities are estimated with a saturated but decoupled d,q reluctant circuit model neglecting the cross saturation effect; and 3) thermal states are indirectly treated with a current density limit. This paper improves these models by using first the finite element method for the determination of flux and iron losses in the machine and then an equivalent thermal steady-state lumped-parameter network. These models are included in the optimization loop and so are evaluated at each iteration. The optimization method uses standard sequential quadratic programming algorithm and Sequential Simplex algorithm. A comparison between the design of an IPM machine with the previous model and the new one will be performed.

Influence of Magnetic Materials on Claw Pole Machines Behavior

This paper presents a study on magnetic materials for claw pole machines which are widely used nowadays in the automobile industry for their simple manufacturing and cost reasons. The finite element analysis with the loss surface model is used to evaluate the iron losses for three categories of material: M800-50A, M330-35A, and AFK502. Comparisons are made in terms of output current, efficiency, as well as iron loss as main characteristics of the machine. On the other hand, the experimental method of loss separation provides a clear idea of the loss distribution in the machines, from which the iron loss can be deduced. A qualitative comparison is made between the two methods, which proves to be coherent.

Design of a Brushless Rotor Supply for a Wound Rotor Synchronous Machine for Integrated Starter Generator

Wound rotor synchronous machines present interesting performances for integrated starter generator. Nevertheless, the lack of reliability of their gliding contacts remains their main drawback. The following paper proposes to replace the gliding contacts of such a wound rotor synchronous machine by an iron silicon axial rotary transformer operating as a contactless transmission power system. The design process is based on an accurate non-linear multidisciplinary analysis model divided into a magnetic, thermal and electrical part, optimized thanks to a sequential quadratic programming algorithm. The method is applied to a particular wound rotor synchronous machine and the electromagnetic and thermal performances are subsequently confirmed using the finite element method (FEM). The optimal result indicates that the rotary transformer is a good challenger to gliding contacts in term of compactness. Other advantages and limitations of the optimal rotary transformer are discussed.

Combination of Finite Element and Analytical Models in the Optimal Multi-Domain Design of Machines : Application to an Interior Permanent Magnet Starter Generator

This paper proposes to apply optimal multiphysics models to the design of highly constrained electrical machines, such as interior permanent magnet machine (IPM) intended for an automotive integrated starter generators (ISG). One of the main problems in the use of such optimal approaches remains the accuracy of the models used by the optimizer. In a previous paper, we proposed a design model linked to three strong hypotheses : (1) Iron losses are calculated according to the flux density fundamental (sinusoidal approach); (2) Flux densities are estimated with a saturated but decoupled d,q reluctant circuit model neglecting the cross saturation effect; (3) Thermal states are indirectly treated with a current density limit. The present paper improves theses models by using first the finite element method (FEM) for the determination of flux and iron losses in the machine and then an equivalent thermal steady state lumped parameter network. These models are included in the optimization loop and so are evaluated at each iteration. The optimization method uses standard sequential quadratic programming algorithm (SQP) and sequential simplex algorithm. A comparison between the design of an IPM machine with the previous model and the new one will be performed.

Comparison of Two Optimal Rotary Transformer Designs for Highly Constrained Applications

The lack of reliability of gliding contacts in highly constrained environments induces manufacturers to develop contactless transmission power systems such as rotary transformers. The following paper proposes an optimal design methodology for rotary transformers supplied from a low-voltage source at high temperatures. The method is based on an accurate multidisciplinary analysis model divided into magnetic, thermal and electrical parts, optimized thanks to a sequential quadratic programming method. The technique is used to discuss the design particularities of rotary transformers. Two optimally designed structures of rotary transformers : an iron silicon coaxial one and a ferrite pot core one, are compared.

Modeling and control of a seven-phase claw-pole integrated starter alternator for micro-hybrid automotive applications

This paper deals with the modeling and the control of a new high power 12 V integrated starter alternator (ISA). This system is used to bring micro-hybrid functions to standard internal combustion engine (ICE) vehicles. The drive is composed of a seven-phase synchronous claw-pole machine with separate excitation, supplied with a seven-leg Voltage Source Inverter (VSI) designed for low voltage and high current. The system is modeled in a generalized Concordia frame and a graphical description is used to highlight energetic properties of such a complex system. A control scheme is then deduced from this graphical description. Two controls are achieved in generator mode and compared: one is using the VSI in a square-wave mode, the other in a pulse width modulation (PWM) mode. Experimental results are provided.

Some armature reaction compensation methods numerical design of experiments and optimization for a hybrid excitation machine

This paper presents a hybrid excitation synchronous machine which combines a permanent magnet excitation with a wound field one. With two sources of flux, this kind of machines is cited more and more frequently in vehicle application for easier control of flux. After a brief description of the structure, some methods will be presented to improve the performances of this machine. Simulation results have shown that the armature reaction has a magnetizing effect when it enters in a pole face and a demagnetizing effect when getting out from the same pole, which distorts the main field and to some extent deteriorates the performances of the machines. The methods we present here are based on the principle of armature reaction compensation which might be extended to many synchronous machines. And then, in the last section, a general optimization tool (numerical design of experiments and optimization) is used to maximize the impacts of these methods.

Hybrid-Excited Doubly Salient Synchronous Machine With Permanent Magnets Between Adjacent Salient Stator Poles

A novel stator hybrid-excited, parallel flux path, synchronous machine of doubly salient topology is proposed. It has the novel features of: 1) hybrid dc field and permanent magnet (PM) excitation in the stator; 2) magnets placed in the slots between adjacent salient stator poles; and 3) the magnetic poles of PMs arranged, such that the flux premagnetizes the stator, but it is in a direction to oppose the dc excitation flux. The electromagnetic characteristics of the machine are analyzed on open-circuit and load. Since the new machine topology is developed from the variable-flux machine (VFM), a comparison of their electromagnetic torque and machine losses is conducted. The average electromagnetic torque of the hybrid-excited machine can be increased by 18% for fixed copper loss in comparison with the VFM due to the reduction of magnetic saturation in the stator. It is also shown that at high temperatures some risk of PM demagnetization exists when excited with dc and armature currents due to fringing flux that exists between the stator and the rotor poles. However, this affects only a very small area of the PMs. The performance of the hybrid-excited machine is predicted by a 2-D finite-element analysis and experimentally validated.

Experimental Characterization of the Iron Losses Variability in Stators of Electrical Machines

Manufacturing processes may introduce a significant variability on the magnetic properties of claw pole generator stators. The present work deals with the analysis of two groups of stator samples. The first group is composed of 28 slinky stators (SS) and the second group is composed of 5 stators, manufactured using laser cut stacked laminations (SL). Both groups are made from the same lamination grade and with the same geometrical dimensions. Characterization was carried out for several levels of excitation field at 50 Hz. A noticeable variability has been observed on the iron losses for SS samples, whereas it appears to be not significant for SL samples. The loss separation technique has then been investigated for the SS samples. Results show that the variability of static losses is more important than the one of dynamic losses.

Design of synchronous reluctance and permanent magnet synchronous reluctance machines for electric vehicle application

This paper compares the relative merits of synchronous reluctance machine (SynRM) and permanent magnet assisted SynRM (PMA-SynRM), including ferrite-assisted SynRM, NdFeB-assisted SynRM and interior permanent magnet machine (IPM) for electric vehicle (EV) applications, in terms of electromagnetic performance and material cost. Firstly, the conditions imposed in the optimization process of SynRM or PMA-SynRM, which can minimize the number of optimization parameters, are discussed. Then, SynRM, ferrite-assisted SynRM and NdFeB-assisted SynRM are designed with the same stator outer diameter and stack length as Prius 2010 IPM. Finally, the results are compared and discussed.