This paper presents a comparison of various numerical algorithms based on Kalman filters (KF) for identifying the equivalent electrical impedance of a domestic induction heating system (DIH). The objective is to determine which KF variant yields the best identification results. The identification process utilises current and voltage waveforms obtained through time-domain simulations, assuming a time-dependent variation in the magnetic permeability of the material that constitutes the induction load. To assess the performance of the algorithms the results from the algorithms are compared with those obtained from frequency-domain simulations using a finite element simulation tool, which serve as the reference. The KF variants particularised to the identification problem of the DIH system are described, along with the electromagnetic simulation model used. Additionally, an analysis of the simulation results is provided, focusing on changes in the switching frequency and the introduction of noise into the input waveforms.

Due to the growing use of the popular wireless power transmission (WPT) technology, an innovative method of coil design and optimization is presented in this paper. This method has been applied to develop spiral printed circuit board (PCB) coils with litz-wire structure. From the geometry definition, the design process is carried out by means of finite element analysis (FEA). In addition, as a complement to the design process, some prototypes of spiral PCB coils were built to contrast the simulation results and experimental measurements by means of the small-signal characterization, which reflects the success of the applied method.

One of the most important factors in the development of a home appliance is the safety of the users. For this reason, the temperature control and the protection against human errors, such as the abandonment of the cookware while cooking, are always of interest in induction heating applications. This paper presents a solution for self-limiting the temperature in cooking vessels that prevents its overheating, protecting the system and preventing food from burning. It is proposed the manufacture of cookware with materials whose electromagnetic properties change at a preset temperature within the range of interest in cooking, these changes cause the power transmitted to the load to drop considerably providing self-protection capabilities against overheating. This solution does not require additional sensors or communication with the induction cooktop, making it a simple and economical option. The performance of the proposed solution has been analyzed using a multiphysics tool, which includes electromagnetic and thermal submodels, and allows to obtain the temperature distribution and the changes in the system as the vessel heats up. Finally, an experimental verification of the model and the solution has also been presented.

The use of materials with controlled electromagnetic properties, such as Curie temperature, for the development of different domestic induction heating applications can improve their safety, energy efficiency and performance.In this article, a measurement system for the magnetic characterization of ferromagnetic materials is presented. The study focuses on materials with low Curie temperature, since typically the information provided by the manufacturers of this type of alloys is limited, giving only the Curie point. It has been obtained the value of its magnetic permeability for different conditions of temperature, excitation current and frequency. These data are useful to carry out simulations of different induction heating applications and design power converters for these systems.The results obtained confirm the manufacturer’s Curie point and also provide the magnetic permeability values and their dependencies for use in simulations or system design.

LED lighting technology provides new functionalities to the systems in which it is incorporated. In the particular case of induction cooktops, the light elements have been used to transmit information to the user and have generally been placed outside the area occupied by the inductor. Several interference and temperature issues have arisen when electronic components have been placed on areas nearby the inductor. In this paper, the design of a panel of configurable LEDs that is capable of representing information in a domestic induction cooker placed in the cooking surface is presented. The presence of electronics devices in this part of the inductor cooker can present two main problems, thermal stress as well as electromagnetic interference. Minimization of electromagnetic interference was addressed by describing this effect from the simulation point of view in order to propose solutions based on the optimized routing of the printed circuit board of the electronics. Finally, a fully functional prototype has been built.

Litz wires with large number of strands are usually manufactured by twisting several bundles of a moderate number of strands. Apart from manufacturing advantages, this technique also provides extra characteristics as current balancing between strands and, consequently, power loss balancing and optimal use of cross sectional copper area. However, complex twisting configurations carry analysis, modeling and design problems which make choosing the parameters of a particular arrangement difficult. A complete 3D finite element model that explicitly includes the effect of twisting at several bundle levels is introduced. This model captures the twisting details and allows observing the actual current density in the strands at the different positions in the wire for both net driven current and induced current by an external field. The model is implemented by using the rigourous mathematical description of trajectories of strands and it is used to analyze the effect of several parameters as bundle levels, pitch and isolation between strands.

PCB technology provides an alternative to conventional Wireless Power Transfer (WPT) coils made of wound copper wire. The most common wires for conventional coils are either a single wire or a multistranded cable conforming a litz wire structure. On the other hand, the implementation on printed board is suitable for medium-low power applications, presenting advantages as low cost, high repetibility and compact design. Moreover, for reduced losses, the litz wire structure can be adapted to a PCB implementation. In this paper, a mathematical description of the PCB litz structure is presented together with a method to automatically generate PCB layouts of custom coils. Following this method, several prototypes were built and tested. The experimental characterization of the samples shows that coils with PCB litz structure present reduced losses.

Sources of the power losses in inductor systems for induction heating home appliances are described in this paper. Energy efficiency is one of the main concerns in the design of this kind of components, thus, the power losses estimation based on computational methods constitutes a powerful tool to achieve optimal results. However, classical model neglects the contribution of the power losses in the flux concentrator usually made of ferrite. This work is focused on the assessment of the importance of this contribution with the support of numerical simulations performed in COMSOL®. Finally, the power losses in the ferrites carried out from the simulation are compared to the total power consumption of the induction heating system in order to determine the importance of the power losses in the flux concentrators.

In this paper, the efficiency of the induction system composed of 4 small coils with a given connection among them for cooking applications is analyzed. The 4-coil configuration has several advantages with respect to the single-coil induction system, for instance, higher flexibility and better heat distribution in the pan. Different configurations can be arranged according to series or parallel connections of the coils and the polarity of the currents. However, the selected configuration connection has a direct impact on the efficiency of the power transference into the pot. Therefore, in this work the efficiency of the different 4-coil configurations is analyzed. The analysis is carried out in terms of equivalent impedances. The experimental test based on impedance measurements is performed to verify the preceding analysis.

Domestic induction heating system employ the output power as control variable. The users select the desired power level among a set of possible values. The advantage of this strategy is related to the control of the associated power electronics. However, temperature control is preferred for cooking applications but it increases the complexity of the system due to the difficulties associated with the temperature estimation of the cookware. Temperature can be measured by means of contact or non-contact technique. This application demands non-contact temperature measurement due to the cooking surface, generally made of glass-ceramic, separates the cookware to the induction heating system placed bellow. Among others, temperature estimation based on radiation detectors, for instance, thermopiles, constitutes one of the most promising methods due to the immediate determination of the measure, but, the optimization of this method required a complex procedure. The aim of this paper is to provide the numerical model of this kind of the system suitable to be used for design purposes. The simulation results have been compared with analytical and experimental measurements in order to verify the correctness of the numerical model.

Switched-mode power supplies applied to induction heating provide conditioned power to a wide range of loads. One of the main issues in the design of these systems is the identification of the main characteristics of the load, i.e. electrical equivalent, as it to be modeled by means of a reduced set of variables. This paper proposes the procedure to extract the electrical equivalent model of the inductor system composed of a coupled double concentric coil for induction heating purposes. The parameters have been obtained by means of a method based on the Fourier analysis of experimental measurement under adequate operation conditions. The equivalent model has been validated for different working conditions in order to prove the feasibility of the proposed procedure.

In this paper, an analysis of the resistance of multi-track coils in printed circuit board (PCB) implementations, where the conductors have rectangular cross-section, for spiral planar coils is carried out. For this purpose, different analytical losses models for the mentioned conductors have been reviewed. From this review, we conclude that for the range of frequencies, the coil dimensions and the planar configuration typically used in domestic induction heating, the application in which we focus, these analysis are unsatisfactory. Therefore, in this work the resistance of multi-track winding has been calculated by means of finite element analysis (FEA) tool. These simulations provide us some design guidelines that allow us to optimize the design of multi-track coils for domestic induction heating. Furthermore, several prototypes are used to verify the simulated results, both single-turn coils and multi-turn coils.