Philippe Viarouge

A frequency-domain maximum likelihood estimation of synchronous machine high-order models using SSFR test data

The authors propose a numerical scheme for processing noisy signals originating from standstill frequency response (SSFR) tests on synchronous machines. Instead of using a univariate nonlinear least-squares procedure to fit only the weighted sum of magnitude responses, they minimize a multivariate prediction error criterion based on the determinant of the residuals covariance matrix. The algorithm pertains to a large class of prediction error methods and results in a multiresponse nonlinear regression procedure related to the maximum likelihood viewpoint when the residuals distribution is Gaussian. To demonstrate the efficiency of the proposed scheme, the implementation was tested using noisy simulated data, based on the Rockport model 3.3. It is shown, using actual data from the Nanticoke turbogenerator, dating back to the EPRI-project RP-9997-2 (1980), that the frequency-domain maximum likelihood approach can be effective for direct estimation of generalized circuits with up to five equivalent windings per axis, providing satisfactory predictions of both magnitude and phase as far as the 16th harmonic. >

A new structure of universal motor using soft magnetic composites

The universal or AC commutator motor, widely used in hand tools or 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 (SMC) 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 classical universal motor structure with nearly identical performance.

Generalized transformations for polyphase phase-Modulation motors

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.

Characteristics and design of multilevel choppers

The aim of this paper is to determine the different characteristics of a new power converter topology especially suitable for high voltage applications, called imbricated cells multilevel choppers (ICMC) in order to design the reactive components of this power converter, such the capacitors and the output filter. The characteristics of this power converter are calculated, plotted, and compared to those of an elementary chopper (current and voltage ripple, RMS currents, harmonic spectrum etc.). These characteristics are then used to design a 600V-25A three-level MOSFET chopper.<<ETX>>

Analysis and implementation of a real-time predictive current controller for permanent-magnet synchronous servo drives

A real-time predictive current controller for PWM inverter feeding PM synchronous motor is presented in which the accuracy and the robustness of the control are improved by integral compensation. In the proposed control scheme, a parallel control loop is used to compensate for the inaccuracy of the model and the variations in the motor parameters and in the DC voltage source. The proposed current control scheme is described and analyzed. The performance is studied and evaluated by computer simulation. The implementation of a real-time EPROM-based predictive controller is considered and discussed. The performance of the controller is evaluated using a prototype 1 kW PM synchronous servo drive. Experimental results are given and discussed. >

Klystron modulator technology challenges for the Compact Linear Collider (CLIC)

This paper presents the research and development challenges foreseen for the klystron modulators design for a new accelerator complex, the Compact Linear Collider (CLIC). This huge electron-positron accelerator needs roughly 300MW of average power for feeding the 1638 required klystron modulators. The main challenges for designing theses new pulsed klystron modulators are described. Considering the state of the art in several domain such as converters topologies, voltage measurements precision, pulse-to-pulse reproducibility, AC power quality issues, efficiency maximization, accelerator reliability & availability, this paper illustrates the most challenging future developments directions and the need for an international and coordinated R&D program.

Design of PM brushless motors using iron-resin composites for automotive applications

New iron-resin soft magnetic materials are now commercially available for AC magnetic applications. These materials, often referred as dielectromagnetics, generally present relative low values of permeability and induction of saturation, but they possess a lot of advantages, if they are properly used during the design process of motors. The relatively low values of unsaturated permeability are not an important drawback in the case of brushless permanent magnet (PM) motors. In this case, the effective airgap of the magnetic structure is imposed by the length of the magnet which has practically a relative permeability equal to unity. An automotive electric fan composed of a conventional PM DC motor with a mechanical collector has been chosen to illustrate the performances of the motors using these new soft magnetic materials and to validate the authors design methods of brushless PM motors. Two prototypes of brushless PM motors using a dielectromagnetic material are presented, which can advantageously replace the conventional DC motor. These prototypes have concentrated windings rather than distributed windings in order to minimize the volume of copper. The magnetic structure of the first prototype is equipped with small teeth localized between the main poles. With this special arrangement, the experimental results show that the torque performances are the same as in the case of classical structures with distributed windings.

Thermal modeling of pot core magnetic components used in high frequency static converters

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.

Analytical Computation of the Full Load Magnetic Losses in the Soft Magnetic Composite Stator of High-Speed Slotless Permanent Magnet Machines

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.

Brush DC motors with concentrated windings and soft magnetic composites armatures

The armatures of conventional brush DC motors are using windings with interlocked coils elements. With this kind of distributed winding, the axial length of the end-windings is usually very important and their copper volume is large. In this paper, the authors present new structures of brush DC motor armature using a concentrated winding with a plurality of simple coils wound around the same tooth. The copper volume is about 60% lower than in the classical winding armature and the current commutation remains efficient. This kind of structure is well adapted to the use of soft magnetic composite materials for the realization of the magnetic circuit and can be used over a wide power range. The design method and a synthesis of these machines with concentrated winding armatures are presented. A prototype of concentrated winding brush DC motor is compared to a conventional motor used in a typical automotive application. The performance of the new structure in terms of torque to copper volume ratio is much higher than in the case of the classical structure.