Aly Ferreira Flores Filho

Numerical model of electromagnetic stirring for continuous casting billets

This paper introduces a numerical model of an electromagnetic rotary stirrer based on the finite-element model. Such stirrers are used to improve the quality of continuously cast steel, particularly billets and blooms. The method determines the magnetic flux density profile and compares it to experimental measurements. In addition, it calculates the Lorentz force field as a function of the stirrer position, the current applied, and the frequency. The stirrer position at the end of the mold affects the profile symmetry of the force, creating a z component of the force. With this model, it will be possible to simulate the fluid dynamics effects in the molten steel.

Analysis of an induction planar actuator

The induction planar actuator, i.e. IPA, proposed in this study presents an electromagnetic structure formed by a static ferromagnetic core with an aluminium plate that corresponds to the secondary, and a mover also called primary; the latter comprehends two three-phase windings which are orthogonal to each other. When they are fed by a three-phase AC excitation, a moving magnetic field takes place, and can travel along the x-axis and the y-axis direction simultaneously. The travelling magnetic field induces electrical currents in the secondary material. The interaction between the magnetic field and the current produce a planar force, responsible for the car movement under the work area. The 3D flux density distribution of the actuator suggests the employment of a grain-insulated soft magnetic composite to reduce eddy currents and losses on the core of the primary. Flux magnetic density, induced current, traction and normal forces are studied.

Design Methodology of a Dual-Halbach Array Linear Actuator with Thermal-Electromagnetic Coupling

This paper proposes a design methodology for linear actuators, considering thermal and electromagnetic coupling with geometrical and temperature constraints, that maximizes force density and minimizes force ripple. The method allows defining an actuator for given specifications in a step-by-step way so that requirements are met and the temperature within the device is maintained under or equal to its maximum allowed for continuous operation. According to the proposed method, the electromagnetic and thermal models are built with quasi-static parametric finite element models. The methodology was successfully applied to the design of a linear cylindrical actuator with a dual quasi-Halbach array of permanent magnets and a moving-coil. The actuator can produce an axial force of 120 N and a stroke of 80 mm. The paper also presents a comparative analysis between results obtained considering only an electromagnetic model and the thermal-electromagnetic coupled model. This comparison shows that the final designs for both cases differ significantly, especially regarding its active volume and its electrical and magnetic loading. Although in this paper the methodology was employed to design a specific actuator, its structure can be used to design a wide range of linear devices if the parametric models are adjusted for each particular actuator.

An analysis on electric and magnetic behaviour on an induction planar actuator

The induction planar actuator, i.e. IPA, proposed in this study presents an electromagnetic structure formed by a static ferromagnetic core with an aluminium plate that corresponds to the secondary, and a mover, also called primary. The latter comprehends two three-phase windings, mounted in an armature core, which are orthogonal to each other. When they are fed by three-phase AC excitations, a moving magnetic field takes place, and can travel along the x-axis and the y-axis direction simultaneously. The travelling magnetic field induces electrical currents in the secondary. The interaction between the moving magnetic field from the primary and the magnetic field originated by the induced current in the secondary produces a planar force. That explains the primary movement over the working area defined by the secondary. The 3D flux density distribution of the actuator suggests the employment of a grain-insulated soft magnetic composite to reduce eddy currents and losses on the core of the primary armature core. Magnetic flux density, induced current and planar traction forces are studied.

A method to determine the capacitance required by the operation of a grid-connected induction generator

The induction machine operating as a grid-connected generator works under voltage and frequency imposed by that grid, and hence presents itself as an interesting approach to distributed generation systems. However, that is an inherently low power factor operation. The present work investigates that behavior of a 15-kW squirrel cage induction machine operating as a generator on such a system. Its equivalent lumped-parameter circuit is employed by the analysis and is based on actual parameters. As a result, a new formula to compute the capacitance that improves the power factor of that generator is proposed, and the theoretical results of reactive power are compared with experimental results.

Development of a New Electromagnetic Planar Actuator

Abstract This paper depicts a new electromagnetic planar actuator. It includes a slotless stationary plane annature, orthogonal windings and a wireless mover with two permanent magnets. The planar actuator develops movement over a plane surface as a result of the interaction between the air gap magnetic flux and current established through the orthogonal multiphase windings of the annature circuit The actuator was analysed by means of the finite element method The actuator can be used in mechatronic systems that require movement on a plane in two directions, e.g. semiconductor wafers and printed circuits movers, and pieces machined by nwnerically controlled (NC) machines.

A Study of the Influence of Quasi-Halbach Arrays on a Torus Machine

This paper aims to analyze the influence of quasi-Halbach arrays on the performance of an axial-flux machine with slotless toroidal core (Torus machine). The analysis was performed using a 3-D finite-element simulation of two machines, with one machine equipped with a quasi-Halbach array and a second with a conventional design with axially magnetized permanent magnets. These simulations were carried out in order to compare their performance. It was observed that the employment of quasi-Halbach arrays increases the torque density and the effective no-load terminal voltage.

Parameter extraction for three phase IPM machines through simple torque tests

This paper presents a method for obtaining the main parameters, such as the torque constant and the d- and q-axis inductances Ld and Lq, for a brushless internal permanent magnet motor by measuring the machine torque during testing. These tests are relatively simple to carry out compared to other test procedures described in the literature and do not require sophisticated equipment. The machine under test is supplied through a dc supply at different rotor positions. The shaft torque is measured through a torque sensor during the tests. The test current is varied to take care of the saturation effects. From the measured torque data and known rotor position, the required parameters can be obtained. Tests performed on two different internal permanent magnet machines confirm the validity and effectiveness of the proposed technique.

A Practical Method for the Characterization of Soft-Magnetic Materials

This paper presents a practical method for obtaining the constants that define the saturation and losses of soft-magnetic materials, making the separation of the magnetic field in four parts: 1) anhysteretic field; 2) static hysteresis field; 3) Foucault losses field; and 4) excess losses field. The proposed practical method for the characterization of soft-magnetic materials consists of the following steps: 1) an acquisition of the experimental data of voltage and current in a simple magnetic circuit (considering uniform field); 2) an assembly of tables with a period of the curve with the magnetic induction versus magnetic field; 3) a linear least square simulation to obtain the characteristic parameters of the material; and 4) error analysis. The ease of obtaining data, the objectivity of the algorithm, and root mean square error among the simulated and experimental hysteresis curves situated in the range of 6% are showing the efficacy of this methodology.

Influence of segmentation of ring-shaped NdFeB magnets with parallel magnetization on cylindrical actuators.

This work analyses the effects of segmentation followed by parallel magnetization of ring-shaped NdFeB permanent magnets used in slotless cylindrical linear actuators. The main purpose of the work is to evaluate the effects of that segmentation on the performance of the actuator and to present a general overview of the influence of parallel magnetization by varying the number of segments and comparing the results with ideal radially magnetized rings. The analysis is first performed by modelling mathematically the radial and circumferential components of magnetization for both radial and parallel magnetizations, followed by an analysis carried out by means of the 3D finite element method. Results obtained from the models are validated by measuring radial and tangential components of magnetic flux distribution in the air gap on a prototype which employs magnet rings with eight segments each with parallel magnetization. The axial force produced by the actuator was also measured and compared with the results obtained from numerical models. Although this analysis focused on a specific topology of cylindrical actuator, the observed effects on the topology could be extended to others in which surface-mounted permanent magnets are employed, including rotating electrical machines.