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The methodology presented in this paper is using a modeling approach based on the observation of the real microscopic material structure to predict the global macroscopic magnetization curve of the soft magnetic composites (SMCs) materials. It can be used to investigate the influence of the variability of all parameters of the microstructure on the global macroscopic magnetization curve of the equivalent homogenous material that is essential to the optimal design of SMC electromagnetic devices. The proposed method includes several steps: acquisition of the microscopic structure by image processing, simulation by FE analysis, and identification of the global macroscopic magnetization curve. The results are validated by a comparative analysis with experimental hysteresigraph measurements and analyzed in order to investigate the influence of the microscopic structure on the global magnetic properties of the SMC material. Index Terms--Image analysis, magnetic material modeling, magnetization curve, soft magnetic composites (SMCs).

This paper presents an analytical model for predicting the stator full load magnetic losses in high-speed slotless permanent-magnet machines with surface-mounted magnets on the rotor and a stator core made of isotropic and conductive soft magnetic composite material (SMC). The losses are derived from the computation of the two-dimensional magnetic field distribution created by the rotor magnets, the currents in the stator windings and the eddy currents that circulate in the SMC stator core, according to the time and space harmonics. Both eddy currents and hysteresis losses are computed. The model is cross-validated by 2-D FE analysis in terms of magnetic field distribution and eddy currents losses. 3-D FE simulations are also carried out to quantify the end-effect on the stator no-load eddy current losses. The developed model is an efficient machine design tool, used here to quantify the variations of both the eddy currents and hysteresis losses under full load operation when the control angle is modified. Index Terms--Eddy currents, hysteresis losses, permanent magnet, soft magnetic materials, slotless machines, SMC.

Conventional modeling approach of brush de motor uses an equivalent electrical circuit with a variable switched-on resistance to model brush-collector contacts. Magnetic saturation and collector electric sparks are usually neglected despite their great influence on performance estimation and on current or voltage waveforms. In this paper, we compare several arc models that can be easily used for brush-collector contact modeling in finite-element simulation of brush motors with a direct coupling method. These models are validated by experimental measurements on a small brush dc motor. Index Terms--Arc discharges, brushes, dc machines, electromagnetic coupling.

This paper presents a factorization method for the generation and use of several kinds of transformation matrices in specific structures of phase modulation polyphase motors. The method can be applied to an arbitrary phase number. It avoids complex trigonometric manipulations. Several examples illustrate its application to a seven-phase machine. Index Terms--Brushless machines, permanent magnet machines, synchronous machines.

In this paper, we test a three-dimensional (3-D) magnetostatics model using Whitney's elements to study a permanent magnet machine made up of soft magnetic composite (SMC) material. Models based on both magnetostatic potential formulations are briefly presented. To evaluate the accuracy of these formulations, theoretical fluxes are compared with fluxes measured on permanent magnet machine. Computation resources of both formulations are also compared. Index Terms--FEM, permanent magnet machine, soft magnetic material.

The universal or ac commutator motor, widely used in hand tools and domestic appliances generally uses a two-pole stator with a concentrated winding and an armature with interlocked coils elements. The copper volume and the axial length of the end windings of such conventional structures are then usually very important. In this paper, the authors present a new universal motor structure based on an efficient use of the isotropic magnetic properties of the soft magnetic composites and on the concentrated winding technique. The stator core presents a claw-pole structure and the armature has a concentrated winding with several coils wound around the same tooth. With this new ac commutator motor structure, a reduction of the total volume by a ratio equal to 200% is obtained when compared to a classical universal motor structure with nearly identical performance. Index Terms--Brush ac machines, commutator ac motors, machine windings, powdered magnetic materials, universal motors.

New structures of motor magnetic circuits can be realized by use of the soft magnetic composites. This paper presents new claw-pole motors with a polyphase winding and a standard cylindrical rotor which use these isotropic materials. A division of the stator magnetic circuit into three parts and the use of a centralized-concentrated winding with a small number of coils simplify the production process, the mechanical assembly, and the winding realization. With these special stator geometries, the electromagnetic, mechanical and thermal functions are integrated into the same stator parts. This integration is much better than in a classical two-dimensional (2-D) structure using a laminated material. There is no end winding and the copper volume can be minimized. The size of the additional parts which are necessary for the bearing housings and the mechanical fixation of the rotor are reduced. These structures can be equipped with an integrated cooling system, with efficient air convection or water circulation. This paper describes the design approach of these original structures. It demonstrates that such three--dimensional (3-D) structures can be derived from their equivalent 2-D structures with a concentrated winding. The concept and the design approach are validated by the realization and the comparative experimental tests of two prototypes with a 3-D and its equivalent 2-D structure. Index Terms--Claw-pole motor, machine winding, motor design, permanent-magnet (PM) motor, polyphase stator, powdered magnetic material.

The windings concentrated around the teeth offer obvious advantages for the electrical machines with radial air-gap, because the volume of copper used in the end-windings can be reduced. The Joule losses are decreased, and the efficiency is improved. These machines are still limited to applications of sub-fractional power and they generally present a reduced number of phases. In the three-phase machines, the concentrated winding is too often restricted to a winding with a short pitch of 120 electrical degrees, i.e., to a winding with performances reduced compared to the traditional structures. But there is a significant number of three-phase structures which can support a concentrated winding if the number of poles is increased. In this article, the authors present a synthesis of the structures of three-phase machines with concentrated windings. 1) In the first part, the structures with a regular distribution of the slots are presented. A systematic method is proposed to determine the windings and the performances are discussed. 2) In the second part, the authors present original structures of three-phase machines with concentrated windings which use an irregular distribution of the slots. A specific method to identify these structures is described, and a comparative analysis of the performances of the original and traditional structures is performed by using a field calculation software. Index Terms--Brushless motors, concentrated windings, design of electrical machines, PM motors, windings.

This paper presents the essential aspects related to the thermal modeling of the magnetic components (power transformers and inductors) used in high frequency static converters. The main difficulties in the modeling of heat transfer mechanisms in such components are discussed and a thermal model for pot core magnetic components, represented by an equivalent circuit, is described.

A real-time current controller for PWM inverter-fed permanent-magnet synchronous motor drives is presented and analyzed. The proposed current control scheme is based on predictive control with a parallel integral loop added to compensate for the inaccuracy of the motor model and for the variations of motor parameters and dc voltage source. The proposed current control scheme is analyzed and its performance is evaluated by computer simulation. An EPROM-based implementation is presented in which calculations and pulsewidth modulation are executed by lookup tables resulting in high-speed operation. The controller performance is evaluated using a prototype 1-kW PM synchronous servo drive. Experimental results are given and discussed.