Michel Lajoie-Mazenc

Finite element torque calculation in electrical machines while considering the movement

Different methods are presented for the calculation of torque as a function of rotation angle in an electrical machine. These methods are integrated in a calculation code by using the finite element method. The movement is taken into account by means of the moving band technique, involving quadrilateral finite elements in the airgap. The torque is calculated during the displacement of the moving part by using the following methods: Maxwell stress tensor, coenergy derivation, Coulombs virtual work, A. Arkkios method (1988), and the magnetizing current method. The results obtained by the different methods are compared with experimental data and make it possible to obtain practical information concerning the advantages and limitations of each method. >

An inverse Jiles-Atherton model to take into account hysteresis in time-stepping finite-element calculations

A modified Jiles-Atherton model presenting the magnetic induction as an independent variable is proposed in order to be directly used in time-stepping finite-element calculations applied to the magnetic vector potential formulation. This model is implemented in the field calculation procedure by introducing a differential reluctivity. The calculated results are validated by experiences performed in an Epsteins frame.

Study and Implementation of Hysteresis Controlled Inverter on a Permanent Magnet Synchronous Machine

In order to set up brushless dc servomotors, a specially designed permanent magnet machine has been associated with a transistorized inverter. First, the different parts of the machine/inverter/control assembly are described. Then a numerical simulation of this assembly is presented. This simulation has been used to study different control strategies that have been implemented on the experimental device: the results obtained are presented and discussed.

Compensation of permanent magnet motors torque ripple by means of current supply waveshapes control determined by finite element method

A method for determining the supply current waveshapes for torque ripple compensation in permanent-magnet motors without saliency and damping bars, by means of a finite-element code, is presented. First, a theoretical analysis shows that current waveshapes producing constant torque can be determined. This analysis leads to an expression for the current as a function of the motor EMF (electromotive force) and cogging torque. Several methods, based on finite-element computation of the magnetic field, for computing the cogging torque and EMF are proposed and compared. A special experimental bench for motor torque measurement is used to validate the theoretical results. >

Finite element simulation of electrical motors fed by current inverters

This paper presents a methodology for coupling electrical machines represented by a Finite Element Model and power electronic devices. The technique, based on a time-stepping procedure for the simultaneous solution of the field and the electrical circuit equations, is applied to an inverter current fed permanent magnet motor.

Simulation of single-phase induction motor by a general method coupling field and circuit equations

A general method for coupling field and electrical circuit equations is presented in this work. The external electrical equations associated with the feeding circuit are represented in state space form. To illustrate the proposed methodology the dynamical operation of a single-phase induction motor is carried out. >

The effect of the stator-slot opening on the interbar currents of skewed cage induction motor

This work uses a method based on the two-dimensional (2-D) finite-element method (FEM) and on the circuits theory to model the interbar currents in a skewed cage induction motor. With this model, the effects of the stator-slot opening on interbar currents are analyzed. Two values of the stator-slot width are considered. The skewing effect is taken into account by the multislice technique.

Determination of synchronous motor vibrations due to electromagnetic force harmonics

A method for the computation of magnetically induced stator vibrations in synchronous motors is presented. The electromagnetic field in the motor is calculated, and the fluctuations of the magnetic forces applied to the teeth of the stator are evaluated. The harmonics of these magnetic forces are calculated by means of a mechanical finite-element analysis, leading to determination of the motor vibrations. The method is used to compare vibrations produced by two permanent-magnet synchronous motors of different magnetic structures, one with radially oriented magnets and one with tangentially oriented magnets. The results clarify the mechanism of generation of the vibrations. >

Design and Construction of a Brushless Permanent Magnet Servomotor for Direct-Drive Application

The feasibility and design of permanent magnet servomotors for direct-drive application at a power level near 10 kW at 270 r/min are investigated. Such applications imply low-speed machines with a great amount of iron and permanent magnet material. The compromise between the specific energy and the cost of magnets is one of the usual guides for designing such motors. The performance of an actual prototype shows that the use of low-cost ferrite material associated with a proper flux-concentration structure of a magnetic circuit is especially interesting at this power level. The design procedure is presented with a prediction of the performance based on field calculations, which can be compared with experimental results of generator operation. The motor can be used in several brushless configurations. An evaluation of the performance, in each case, according to the kind of static converter and control strategy is presented. Several improved models and computer simulations are used. The adaptation of the rotor damper circuits to the supply is also discussed.

Analysis of the effect of inter-bar currents on the performance of polyphase cage-induction motors

This work uses a methodology based on the two-dimensional finite-element method and on the circuits theory (independent currents method) to calculate the inter-bar currents and analyze their effect on the performance of the polyphase cage-induction motors. The circuit theory is used to couple the rotor circuit equations to the field equations. The multi-slice technique is used to consider the skew effect.