Yokeless radial electrodynamic bearing

Due to the presence of a ferromagnetic yoke in passive electrodynamic magnetic bearings, the stiffness associated with their radial centering force becomes negative under a critical speed. This leads to instability problems and to the necessity of using mechanical launch bearings at low speed. In this paper, an electrodynamic bearing without ferromagnetic yoke is proposed. An analytical 2D model of the bearing is presented and used to perform a first analysis of the bearing. The force predictions correspond to expectations: the stiffness never reaches negative values. It is also shown that for given geometrical dimensions, the performance of the studied bearing can be significantly improved by choosing the appropriate number of phases and number of pole pairs of the winding

Two time scale global dynamical modelling of power electronic systems

Global dynamical models of power electronic systems allow to compute their dynamics in a very easy way as they replace the switching behavior of the power electronic converter by a continuous process [F. Labrique, H. Buyse, G. Seguier, R. Bausiere, Les convertisseurs de l'electronique de puissance-Commande et comportement dynamique, vol. 5, Technique et Documentation, Lavoisier, Paris, France, 1998; H. Buyse, D. Grenier, F. Labrique, S. Gusia, Dynamic modelling of power electronic converters using a describing function like approach, in: Proceedings of the ELECTRIMACS'99 Conference, vol. 1, Lisbon, Portugal, 1999, pp. 7-14]. But they are unable to predict the ripples induced by the switching behavior of the power semiconductor switches. The aim of this paper is to show for power electronic systems using a power electronic converter working in a PWM mode, how it is possible to define a global dynamical model including a dynamical model of the ripple effects. (C) 2003 MACS. Published by Elsevier B.V. All rights reserved

Comparative study of a synchronous motor current control loop stability, implanted on mono and multiprocessor architectures

Classically, the control algorithms of high performance motor control systems using PMSM synchronous actuators are today implemented on DSP's. In previous papers, we have presented a multiprocessor architecture for such applications. The aim of this paper is to investigate how moving from a single processor to a multiprocessor architecture influences the stability of the motor current control loop. It is shown that, with a multi-processor architecture, higher loop gain can be used and that the damping of the response is much better

Study and Optimization of the Travelling Waves Generation in Finite-Length Beams

This paper presents a detailed study of the generation of traveling waves in finite-length beams. The method used is the mode superposition. It consists in exciting, with two actuators, two standing waves space shifted of a quarter wavelength and time shifted of a quarter period. Thanks to an analytical model giving the general solution of the flexural wave, we define the ideal conditions ensuring the best quality of this wave across the beam. Then, through an optimization process, we get the excitation parameters, position and frequency, that allow to approach at most these conditions

Analytical Prediction of Cogging Torque in Surface Mounted Permanent Magnet Motors

Cogging torque influences the control precision of permanent magnet motors used in actuation systems. This paper provides a rigorous analytical prediction method, easy to use in an optimization process. It relies on the fact that the magnetic energy variation due to one slot can be expressed by a coefficient k0 multiplying at the slot location the square of the airgap magnetic field generated by the magnets computed without taking the slotting effect into account

Optimal Design of Electromagnetic Devices : Development of an Efficient Optimization Tool Based on Smart Mutation Operations Implemented in a Genetic Algorithm

Topology optimization methods are aimed to produce optimal design. These tools implement optimization algorithms that modify the distribution of some materials within a predefined design space without a priori ideas about the topology or the geometry of the best solution. In this paper, we study a specific tool that combines a genetic algorithm, a material distribution formalism based on Voronoi cells and a commercial FEM evaluation tool. In particular, we show, through a simple but representative study case, that it is possible to improve the performance of the topology optimization tool during the local research phase, i. e. the geometry and dimensional optimization phase for which the topology optimization methods are generally not well-suited

Optimal Current Waveform for Permanent Magnet Synchronous Machine with any Open Faulted Number of Phases

Polyphase permanent magnet synchronous motors are well suited for developping electromechanical actuation system showing a high level of reliability as they are able to run with a reduced number of phases and therefore allow to make the actuation system they are driving tolerant to the loss of feeding of one or more than one phase. The paper focuses on the way to determine for motors with any number of phases greater than 3 the optimal values of the phase currents allowing the motor to develop the needed torque in healthy and fault tolerant mode operation. It also assesses the oversizing imposed to the motor and the power electronics for maintaining the performance unchanged in fault tolerant mode operation