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The results of an investigation of glass formation on frit production by mans of induction heating are presented. According to x-ray phase analysis, the resulting frit is completely amorphous. The frit meets standard spreadability requirements — 45 mm and linear thermal expansion coefficient [LTEC] 120 × 10–7 K–1. The enamel coating has a high chemical resistance to acids and alkalis. A comparative analysis of frit synthesis in a laboratory electric furnace by means of induction heating demonstrated that the frit induction melting time is reduced by two-fold, energy consumption is reduced by 23%, and the process efficiency is increased on average by four-fold. [ABSTRACT FROM AUTHOR]

Fossil fuel firing heating systems will be substantially abandoned in the near future due to the zero-carbon goals. They will be replaced with heating systems that use renewable energy sources. Since the investment costs and area requirements of the renewable energy systems are high, the developments of highly efficient electric fluid heating systems have critical importance for a sustainable, environmentally friendly and clean heating. Among the electrical heating systems, induction heaters offer quite easy to use and better adaptability to most heating systems by allowing fluid heating without the necessity for contact. In this paper, a comprehensive review of the evolution of the induction fluid heaters is given by presenting the historical background. The most important milestones of induction fluid heating systems are presented. The development strategies suggested by the different papers including patents are investigated. The findings revealed that induction fluid heating systems, which reach approximately 100% thermal efficiency. These systems are introduced as follows: clean, non-emitting fluid heating system. Because of this, the study concludes that induction fluid heaters are one of the most promising alternatives to other electric heating systems in the long run. [ABSTRACT FROM AUTHOR]

This paper presents a method of measuring the temperature of water near a 1-mm-diameter magnetic sphere under induction heating. The method is based on the temperature dependence of the absorption coefficient of water at a wavelength of 1150 nm. In this study, two-dimensional images of the absorbance, which is the transverse projection of the absorption coefficient of water, were acquired by a near-infrared camera through a telecentric lens, and three-dimensional radial profiles of the temperature were then generated by applying inverse Abel transforms (IATs) to the absorbance profiles. To ensure the spherical symmetry of the temperature and the parallelity of the light rays, which are the conditions necessary to apply an IAT, the onset of free convection and the angles of deflection were evaluated. This paper also presents a method of estimating the heat generation rate in a sphere by fitting the numerical solutions of the thermal conduction equation to the measured temperatures. The temperatures and heat generation rates were observed to change consistently with the changes in the magnetic field intensity. [ABSTRACT FROM AUTHOR]

A closed-form solution is derived for the equivalent impedance of a planar winding with cylindrical symmetry placed between two half-spaces. This is basically the structure of a domestic induction heating appliance comprised of a planar winding, a metallic vessel, and a lossless magnetic substrate. The first matter addressed is the impedance of a sandwiched single-turn coil, obtained by using the vector potential Helmholtz equation solution, and the result is generalized to n-turn coils. The real part of this impedance represents power dissipated in the form of heat. The proposed model includes geometry dependence, frequency of excitation currents, and electromagnetic properties of both top and bottom media. Enhancement of power dissipation in the conducting media as a result of the inclusion of a magnetic substrate is also explored. Experimental results are presented in order to validate the theoretical model. [ABSTRACT FROM AUTHOR]

Interest on novel thermal technologies has been steadily increased in recent years because of the some undesirable changes in the quality characteristics of foods and the low energy efficiency during conventional heating. Novel methods that meet customer expectations for minimally processed and high-quality products and enable high energy efficiency production can be alternative to conventional methods. In this review, induction heating and ohmic heating processes, which are novel electrical heating methods, are explained, and working principles and the differences between their application areas are discussed. The studies on the continuous system pipe line and cooking applications designed for both heating methods are presented. Based on the food processing systems established for similar purposes, the applicability of both heating methods to foods is compared, and their potential application areas are suggested. [ABSTRACT FROM AUTHOR]

Flexible cooking surfaces represent the most innovative and high-performance induction heating appliances nowadays. This paper presents a multiple-output resonant inverter for multicoil systems featuring high efficiency and flexible output power control for modern induction heating appliances. By adopting a matrix structure, the number of controlled devices can be significantly reduced while high control versatility is ensured. The proposed converter is first analyzed and, in order to prove the feasibility of the proposal, a multiple-output prototype is designed and implemented. The experimental results prove the correct converter operation and output power control with multiple induction heating loads, validating the proposed approach. [ABSTRACT FROM AUTHOR]

This paper explores a model predictive control (MPC) strategy with constraints satisfaction for a high power induction heating load. The MPC predicts the state variables and future control sequence of the system in advance and achieves on-line-optimization with a reduced error. The state-space model of the system with a parallel resonant load is developed and then MPC is applied. The proposed approach controls the DC link current at the rectifier output and reactive component of the supply current. The DC current is used to regulate the power of the heating load and the reactive component of input current is kept at zero to attain the unity power factor. The results show that the proposed strategy regulates the power of the heating load, achieves unity power factor at input of the system and handles the variables within the defined constraints effectively. [ABSTRACT FROM AUTHOR]

The development of a rapid uniform heating process for blanks is needed to perform hot stamping processes. To solve the problem of inhomogeneous temperature distribution in conventional induction heating systems, a heating block has been added to an induction system and investigated to determine if it can achieve rapid and uniform blank heating. To characterize the effects of incorporating the heating block, the temperature distributions of various coil geometry have been experimentally analyzed. The results show that the proposed induction heating system makes it possible to achieve rapid and uniform blank heating, which is used to conduct stable hot stamping. The mechanical properties of a hot stamped part confirm that the proposed heating method is a feasible alternative method for hot stamping products, and that it yields excellent results. This system for the reduction of heating time requires less installation space compared to a conventional electric furnace and achieves uniform heating, which results in improved product quality and reduced manufacturing costs. [ABSTRACT FROM AUTHOR]

The aim of this study involved developing a temperature controller for magnetic induction hyperthermia (MIH). A closed-loop controller was applied to track a reference model to guarantee a desired temperature response. The MIH system generated an alternating magnetic field to heat a high magnetic permeability material. This wireless induction heating had few side effects when it was extensively applied to cancer treatment. The effects of hyperthermia strongly depend on the precise control of temperature. However, during the treatment process, the control performance is degraded due to severe perturbations and parameter variations. In this study, a modified self-learning fuzzy logic controller (SLFLC) with a gain tuning mechanism was implemented to obtain high control performance in a wide range of treatment situations. This implementation was performed by appropriately altering the output scaling factor of a fuzzy inverse model to adjust the control rules. In this study, the proposed SLFLC was compared to the classical self-tuning fuzzy logic controller and fuzzy model reference learning control. Additionally, the proposed SLFLC was verified by conducting in vitro experiments with porcine liver. The experimental results indicated that the proposed controller showed greater robustness and excellent adaptability with respect to the temperature control of the MIH system. [ABSTRACT FROM AUTHOR]

A novel hybrid approach for solving induction heating problems is presented. The electrothermal problem is discretized by the cell method (CM) and coupled to the boundary element method to avoid the air region meshing. The interface coupling is obtained by introducing a new topological framework for the CM, which is the augmented dual grid. The main advantage is that the electromagnetic hybrid formulation for computing time-harmonic eddy currents results in a partly dense indefinite linear system, which is solved by a fast TFQMR iterative method. The transient thermal problem, weakly coupled to the electrical one, is solved by the $\theta $ method under convection and radiation boundary conditions. The hybrid approach shows to be very accurate by comparison with third-order 2-D FEM on an axisymmetric test case. The applicability of the method then extends to full 3-D models with limited computing resources. [ABSTRACT FROM AUTHOR]

Induction heating (IH) converters operate just above resonant frequency, at near unity power factor (UPF), to supply power to the targeted work-piece. Some power electronic converter-fed IH systems use power control strategies based on dynamic tracking of the changing resonant frequency as the work-piece gets heated up (since inductance changes). Therefore, the correct in-process determination of the resonant frequency is essential. A method of dynamically detecting the resonant frequency is by calculating the phase-shift between current and voltage continuously during the process. In case of CSI- (and VSI-) fed IH, the phase-shift between voltage and current is zero at resonant frequency. Hence one way of identifying the resonant frequency is by varying the frequency until the phase-shift is zero. For controlling this phase-shift between current and voltage waveforms, most of the controllers use a phase-locked loop (PLL) IC. In this paper, a novel method for the dynamic tracking of resonant frequency is proposed and the practical implementation of the same, using a field-programmable gate array (FPGA) based digital-PLL, is presented. The scheme is first simulated with generated off-line signal samples and then implemented on a real-time model of a CSI-fed IH application. Finally, the digital-PLL logic is implemented on controller hardware and practically tested in a laboratory-made experimental set-up of 2 kW at a nominal frequency of 10 kHz. The switching frequency is auto-synchronising. This fact is practically verified both by varying (i) the geometric dimensions as also (ii) the initial temperature of the work-piece. It is practically observed in the oscillograms that the phase gets locked in few cycles (and hence ensures quick tracking of the dynamically changing resonant frequency for this set-up). [ABSTRACT FROM AUTHOR]

The procedure of semi-solid forming is composed of heating a billet, forming, compression holding and ejecting step. There are several methods to heat a billet during semi-solid forming process such as electric heating and induction heating. Usually in semi-solid forming process, induction heating has been adopted to achieve more uniform temperature of semi-solid material. Although induction heating is better method than any others, however, there is still difference of temperature between internal part and surface part of semi-solid material. Worse yet, in case of high liquid fraction of semi-solid material, liquid of the billet will flow down though solid of the billet still remains, which is very difficult to handle. In the present study, induction heating of the billet during thixoforging process with forced surface cooling has been performed to obtain more uniform distribution of temperature, microstructure and shape of the billet. Distribution of temperature of the billets was measured and compared with that of conventional distribution of temperature. Microscopic and macroscopic aspects of the billets were discussed according to location of the measuring points. By this new induction heating method, not only temperature distributions over the whole billet become uniform, but also control of temperature distribution between inside and outside part of the billet is possible as user's experimental intentions. [ABSTRACT FROM AUTHOR]

This paper describes a new method for the online parameter estimation of an induction heating system. Simulations and experiments are presented in order to measure its impedance matrix for more exact control in closed loop. In previous papers, various parameter identification methods including offline methods were introduced and compared for current inverters. It has been demonstrated that parameter identification is necessary to achieve good control of the inductor currents. A “pseudoenergy” method for a simple and fast implementation is compared to a classical “ $V/I$ with phase shift” method. They are experienced on a reduced-power three-phase coupled resonant system supplied with voltage inverters with satisfying results. [ABSTRACT FROM PUBLISHER]

The present study aims to develop a warm forming process for an aluminum alloy sheet to reduce weight of an electric housing part. Considering that the target product is produced through a series of metal forming processes using a progressive die, high frequency induction heating is proposed to heat a specific drawing punch locally and rapidly, out of a series performed using a progressive die. To validate the effect of the induction heating on the formability improvement of aluminum alloys, a fully coupled numerical simulation is proposed: (i) finite element (FE) analyses for the multi-stage deep drawing processes are performed to predict formability at each stage; (ii) electrostatic-thermal coupled FE analysis is performed to predict the temperature rise of the drawing punch; and (iii) thermo-mechanical coupled analysis is conducted to investigate the effect of induction heating on the formability change. Through the proposed coupled simulation, it is proven that the drawing punch can be efficiently heated without a significant increase in cycle time, and the corresponding drawing process using aluminum alloys can be successfully performed without forming failure. [ABSTRACT FROM AUTHOR]

The induction surface hardening of parts with nonuniform cylindrical shape requires a multifrequency process in order to obtain a uniform surface hardened depth. This paper presents an induction heating high power supply composed by a single inverter circuit and a specially designed output resonant circuit. The whole circuit supplies simultaneously both medium- and high-frequency power signals to the heating inductor. An initial study is made to select the most appropriated topology for this application. The resonant output circuit is analyzed, and a design procedure is presented. The selected inverter operation is described and simulated. Simulations are experimentally verified on a 10-kW dual-frequency resonant inverter operating at 10 and 100 kHz using MOSFETs of silicon (Si) and silicon carbide (SiC) technology. A comparative study is presented based on the measurements of power losses and the energy efficiency of the inverter using both types of MOSFETs. [ABSTRACT FROM PUBLISHER]

This paper presents a steady-state operation analysis of full-bridge series-resonant inverters focusing on the distorted load current due to low-quality-factor resonant circuits in induction heating and other applications. The regions of operation based on the zero-voltage switching (ZVS) and non-zero-voltage switching (NON-ZVS) operations of the asymmetrical voltage-cancellation control technique are identified. The effects of a distorted load current under a wide range of output powers are also analyzed for achieving a precise ZVS operating region. An experimental study is performed with a 1kW prototype. Simulation and experimental studies have confirmed the validity of the proposed method. An efficiency comparison between the variable frequency method and the conventional fixed-frequency method is provided. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM PUBLISHER]

Induction heating systems are the technology of choice in many industrial, domestic, and medical applications due to its high performance. The core component of such systems is the power supply, which is usually composed of a rectifier stage and a resonant inverter. In order to simplify and further optimize the performance of the power supply, a class-E direct ac–ac converter featuring multicycle modulations is proposed in this paper. The proposed converter is composed of two switching devices that enable the direct ac–ac conversion. Single- and multicycle operation modes have been analytically described to prove the benefits, in terms of peak voltage reduction and output power control capabilities. A prototype featuring SiC junction-gate field-effect transistor devices, which perfectly fit these applications, has been designed and built to prove the feasibility of the proposed converter. The experimental results match the analytical results and validate the benefits of this converter. [ABSTRACT FROM PUBLISHER]

An alternative way of induction heating of nonmagnetic cylindrical billets is modeled. The billet rotates in static magnetic field generated by permanent magnets. The mathematical model of the process consisting of two second-order partial differential equations describing the distributions of magnetic and temperature fields is solved numerically in the quasi-coupled formulation. The computations are carried out by a fully adaptive higher order finite-element method that is implemented in own codes Agros2D and library Hermes. The most important results are verified experimentally on a prototype device built in our laboratory. [ABSTRACT FROM PUBLISHER]

The wide variability of the load is the main problem of domestic induction-heating technology. The considered power control strategy should guarantee stability and regulation with a suitable response time and no overshoot independently of any perturbation or load variation. In addition to this, it has to ensure the operation under safety conditions. This paper is focused on the power control applied to one heating unit by means of continuous modulations. An inverse-based power controller is proposed for dealing with load uncertainties. The proposed power control combines different variable frequency pulsewidth modulation strategies (constant duty cycle, constant on-time, and constant off-time modulations) for reaching the target power level while minimizing the switching frequency. Finally, simulation and experimental results compared with other techniques in a prototype of an induction-heating system are presented in order to validate the proposed control strategy. [ABSTRACT FROM PUBLISHER]

A novel soft-switching high-frequency (HF) resonant (HF-R) inverter for induction heating (IH) applications is presented in this paper. By adopting the current phasor control of changing a phase shift (PS) angle between two half-bridge inverter units, the IH load resonant current can be regulated continuously under the condition of wide-range soft-switching operations. In addition to this, the dual-mode power regulation scheme-based PS angle control and asymmetrical pulsewidth modulation in one inverter unit is proposed for improving the efficiency in low output power settings. The essential performances on the output power regulation and soft-switching operations are demonstrated in an experiment using its 1-kW 60-kHz HF-R inverter prototype, and then, the topological validity is evaluated from a practical point of view. [ABSTRACT FROM PUBLISHER]

Domestic induction-heating technology requires specific features such as high output power levels in a reduced enclosure, elevated operating temperature, large load variation, and reduced cost. To fulfill these requirements, classical solutions are based on the combination of a rectifier and a dc-link inverter. This is a well-balanced solution, but there is still room for efficiency and cost improvements. Unlike previous proposals, this paper proposes a direct ac–ac converter to reduce the component count, reduce cost, improve reliability, and increase efficiency. The proposed converter is a voltage-source series-resonant converter that achieves linear output power control, reducing control complexity. Moreover, the proposed converter achieves soft switching during both turn-on and turn-off transitions, further improving the efficiency and enabling the selection of low-speed devices with improved conduction properties. A 3.6-kW converter has been designed and implemented, verifying the feasibility of the proposal and the expected performance. [ABSTRACT FROM PUBLISHER]

The wide variety of models for analysis of processes in the inductor-detail systems makes it necessary to summarize them. This is a difficult task because of the variety of inductor-detail system configurations. This paper aims to present a multi physics mathematical model for complex analysis of electromagnetic and thermal fields in axial symmetric systems inductor-detail. [ABSTRACT FROM AUTHOR]

Highlights: [•] Microwave and induction heating were compared with respect to their abilities to stabilize monosaccharides. [•] Monosaccharides were more stable under microwave heating than under induction heating. [•] The internal heating property of microwave might reduce the decomposition of monosaccharides. [Copyright &y& Elsevier]

Induction heating (IH) technology is nowadays widely present in domestic appliances because of its cleanness, high efficiency, and faster heating process. All of these advantages are due to its heating process, where the pot is directly heated by the induced currents generated with a varying magnetic field. As a result, the glass where the pot is supported is not directly heated and, consequently, efficiency and heating times are improved. IH systems are based on dc-link inverters to generate the required alternating current to feed the inductor. Usually, resonant converters are used to achieve higher efficiencies and power densities. In such systems, the maximum output power and efficiency are achieved at the resonant frequency, and the switching frequency is increased to reduce the output power. As a consequence, in these converters, the efficiency is also reduced in the low-medium output power range. This paper proposes the use of the half-bridge inverter in two operating modes to achieve higher efficiency in a wide output power range. The power converter topology can be reconfigured by changing the resonant capacitors through electromechanical relays. As a consequence, the entire efficiency of the cooking process is improved with a cost-effective procedure. [ABSTRACT FROM AUTHOR]

Abstract: Induction heating of nonmagnetic cylindrical billets by rotation in uniform magnetic field produced by static permanent magnets is modeled. Numerical analysis of the process providing the distributions of magnetic and temperature fields is carried out in the monolithic formulation, using our own code based on higher-order finite element method. The methodology is illustrated by a typical example and the most important results are validated experimentally. [Copyright &y& Elsevier]

In this paper, a hot embossing heating roll with induction heater inside the roll is proposed. The induction heating coil is installed inside a roll that is used as a heating roll of a roll-to-roll (R2R) hot embossing apparatus. Using an inside installed heating coil gives the roll-to-roll hot embossing system a more even temperature distribution on the surface of the heating roll compared to that of previous systems, which used an electric wire for heating. This internal induction heating roll can keep the working environment much cleaner because there is no oil leakage compared to the oiled heating roll. This paper describes the principles and provides an analysis of this proposed system; some evaluation has also been performed for the system. A real R2R hot embossing heating roll system was fabricated and some experiments on micro-pattering have been performed. After that, evaluation has been performed on the results. [ABSTRACT FROM AUTHOR]

LQR and H2 controllers require access to the states of the controlled system. The method based on description function with Fourier series results in a model with immeasurable states. For this reason, we proposed a Kalman filter based state estimator, which not only filters the input signals, but also computes the unobservable states of the system. The algorithm of the filter was implemented in LabVIEW v8.6 and tested on recorded data obtained from a 10-40 kHz series load frequency controlled induction heating inverter. [ABSTRACT FROM AUTHOR]

An ultrasonic induction heating (UIH) deposited monetite coating on (NH)SO treated (NT) C/C composites was subjected to a hydrothermal treatment to form a hydroxyapatite (HA) coating. This HA coating was then placed in a NaF solution and hydrothermally treated a second time to produce a fluorinated hydroxyapatite (FHA) coating. The structure, morphology and chemical composition of the HA and FHA coatings were characterized by XRD, FTIR, XPS SEM and EDS, and the adhesiveness of the two coatings to the NT-C/C substrates was evaluated by a scratch test. The results showed that after the NaF treatment, the FHA coating was a mixture of FHA and HA with some calcium oxides, and the FHA showed a higher degree of crystallization than the HA coating though the morphologies were similar. In addition, the EDS-determined Ca/P atomic ratio for the FHA coating was about 1.78 which was larger than 1.69 ratio of the HA coating. The bonding strength of the HA coating on C/C could reach a critical load of 60.3 N, while that of the as-prepared F-containing HA coating only had a critical load of 42.4 N. The reason of the lower adhesion for the FHA coating than that for the HA coating is suggested to be correlated with the constituent and structure of the two coatings. [ABSTRACT FROM AUTHOR]