Pascal Maussion

Induction Heating Technology and Its Applications: Past Developments, Current Technology, and Future Challenges

Induction heating (IH) technology is nowadays the heating technology of choice in many industrial, domestic, and medical applications due to its advantages regarding efficiency, fast heating, safety, cleanness, and accurate control. Advances in key technologies, i.e., power electronics, control techniques, and magnetic component design, have allowed the development of highly reliable and cost-effective systems, making this technology readily available and ubiquitous. This paper reviews IH technology summarizing the main milestones in its development and analyzing the current state of art of IH systems in industrial, domestic, and medical applications, paying special attention to the key enabling technologies involved. Finally, an overview of future research trends and challenges is given, highlighting the promising future of IH technology.

Electrical Aging of the Insulation of Low-Voltage Machines: Model Definition and Test With the Design of Experiments

The aim of this paper is to present a method for modeling the life span of insulation materials in a partial discharge regime. Based on the design of experiments, it has many advantages: It reduces the number of time-consuming experiments, increases the accuracy of the results, and allows life span modeling under various stress conditions, including coupling effects between the factors. Accelerated aging tests are carried out to determine the life span of these materials. The resulting model presents an original relationship between the logarithm of the insulation life span and that of electrically applied stress and an exponential form of the temperature. Results show that the most influential factors can be identified according to their effects on the insulation life span. Moreover, the life span model validity is tested either with additional points which have not been used for modeling or through statistical tests. Finally, it is shown that fractional plans are not suitable to reduce the number of experiments. This application of the experimental design is best used during the initial phase, before the final drive has been built and any online diagnosis.

Multiphase System for Metal Disc Induction Heating: Modeling and RMS Current Control

This paper presents a multiphase induction system modeling for a metal disc heating and further industrial applications such as hot strip mill. An original architecture, with three concentric inductors supplied by three resonant current inverters, leads to a reduced element system, without any coupling transformers, phase loop, mobile screens, or mobile magnetic cores as it could be found in classical solutions. A simulation model is built, based on simplified equivalent models of electric and thermal phenomena. It takes into account the data extracted from Flux2D finite-element software, concerning the energy transfer between the inductor currents and the piece to be heated. It is implemented in a versatile software PSIM, initially dedicated to power electronics. An optimization procedure calculates the optimal supply currents in the inverters in order to obtain a desired power density profile in the work piece. This paper deals with the simulated and experimental results which are compared in open loop and closed loop. This paper ends with a current control method which sets rms inductor currents in continuous and digital conditions.

Instantaneous feedback control of a single-phase PWM inverter with nonlinear loads by sine wave tracking

The authors propose a novel method for the instantaneous digital control of a PWM (pulse-width modulated) inverter used in an uninterruptible power supply. The output voltage is compared to a sinusoidal reference at each sampling instant to compute in real time through a digital controller the pulse width of the same interval. The closed-loop digital feedback eliminates the steady-state error of the output voltage with a very short computation time. This strategy is verified through computer simulations and provides a very fast compensation of disturbances caused by nonlinear loads, such as rectifiers and triac loads, with low total harmonic distortion and fundamental control.<<ETX>>

Optimization of the Settings of Multiphase Induction Heating System

This paper deals with the setting-parameter optimization procedure for a multiphase induction heating system considering transverse flux heating. This system is able to achieve uniform static heating of different thin/size metal pieces without movable inductor parts, yokes, or magnetic screens. The goal is reached by the predetermination of the induced power-density distribution using an optimization procedure that leads to the required inductor supplying currents. The purpose of the paper is to describe the optimization program with the different solution obtained and to show that some compromise must be done between the accuracy of the temperature profile and the energy consumption, with the calculation of the losses.

Characterization of Acoustic Resonance in a High-Pressure Sodium Lamp

In the last decades, the high-pressure sodium (HPS) lamp has been supplied in high frequency in order to increase the efficacy of the lamp/ballast system. However, at some given frequencies, standing acoustic waves, namely, acoustic resonance (AR), might develop in the burner and might cause lamp luminous fluctuation, extinction, and destruction in the most serious case. As we seek for a control method to detect and avoid the lamp AR, some main characteristics of ARs in a 150-W HPS lamp are presented in this paper. The first one is the characteristic of the lamp AR threshold power, and the second one is the differences between the forward and backward frequency scanning effects during lamp open-loop operation. Third, the lamp AR behavior in closed-loop operation with an LCC half-bridge inverter will be presented, and it leads to a new point of view and a change in the choice of the AR detection method. These characteristics allow us to further understand AR and to better control the lamp.

Current-Based Detection of Mechanical Unbalance in an Induction Machine Using Spectral Kurtosis With Reference

This paper explores the design, online, of an electrical machines healthy reference by means of statistical tools. The definition of a healthy reference enables the computation of normalized fault indicators whose value is independent of the systems characteristics. This is a great advantage when diagnosing a broad range of systems with different power, coupling, inertia, load, etc. In this paper, an original method called spectral kurtosis with reference is presented to design a systems healthy reference. Its principle is first explained on a synthetic signal. This approach is then evaluated for mechanical unbalance detection in an induction machine using the stator current instantaneous frequency. The normalized behavior of the proposed indicator is then confirmed for different operating conditions, and its robustness with respect to load variations is demonstrated. Finally, the advantages of using a statistical indicator based on a healthy reference compared with a raw fault signature are discussed.

Stator current based indicators for bearing fault detection in synchronous machine by statistical frequency selection

The aim of this paper is to present some indicators developed for efficient detection of bearing defaults in high speed synchronous machines using a stator current analysis. These actuators are used in an air conditioning fan for aeronautic applications. The signatures of the bearing defects appear through an increase in amplitude of specific current harmonics multiples of the rotation frequency. From an experimental comparison between a healthy fan and another with damaged bearings, an automatic frequency selection is performed to identify the frequency ranges for which the energy is the most sensitive to the considered faults. From these frequencies, several strategies are investigated to propose a suitable indicator for the bearing fault detection. A post-processing algorithm is then developed and tested for different measurements, different types of faults and different operating points, to ensure the robustness of the proposed method.

Optimization of the settings of multiphase induction heating system

This paper deals with the setting-parameter optimization procedure for a multiphase induction heating system considering transverse flux heating. This system is able to achieve uniform static heating of different thin/size metal pieces without movable inductor parts, yokes, or magnetic screens. The goal is reached by the predetermination of the induced power-density distribution using an optimization procedure that leads to the required inductor supplying currents. The purpose of the paper is to describe the optimization program with the different solution obtained and to show that some compromise must be done between the accuracy of the temperature profile and the energy consumption, with the calculation of the losses.

Robustness of a Resonant Controller for a Multiphase Induction Heating System

This paper presents a robustness study of the current control scheme for a multiphase induction heating system. Resonant control has been chosen in order to achieve a perfect current reference tracking in the inductors with different solutions from the literature. A simplified model of the system is given; it is based on data extracted from finite-element software, including a model of the energy transfer between the dc source and the currents. The metal sheet resistivity will change with temperature, inducing some modifications in the system parameters. These disturbances will be rejected by the resonant controllers whose pole and zero variations are investigated. In addition, the tuning method for the resonant controllers is detailed when the sampling frequency/switching frequency ratio is very low. Some specific stability zones are defined for the resonant controller gains. The application is currently developed on a test bench devoted to disc induction heating.