Domestic Induction Heating Research Articles

Study of magnetic nonlinearities in materials with low Curie temperature applied to domestic induction heating

The analysis of the magnetic properties of alloys with low Curie temperature used in domestic induction heating is presented. These alloys allow the development of cookware with additional benefits with respect to regular cookware oriented to improve temperature control and the user’s safety. Firstly, an experimental method to characterize the magnetic permeability with respect to the magnetic field strength and temperature in the material is presented. Secondly, a finite element simulation method is proposed which, considering the previous characterization, allows the calculation of the electrical equivalent of an inductor-load system as a function of temperature and magnetic field. This method makes possible the application of finite element simulation in the frequency domain with nonlinear materials, which is of interest for the design of electronics associated with domestic applications of induction heating. Simulation results are experimentally verified with various ferromagnetic alloys with low Curie temperature at different power, temperature, and operating frequency ranges.

Homogeneous single-coil induction heating achieved by structure design

Domestic induction heating shows advantages over traditional open fire heating, but the uneven temperature distribution in the pan is still one of the problems to be solved. In this work, to improve the heating uniformity of the induction cooker, the finite element analysis (FEA) is employed to investigate the relationship between the structure of induction coil and the temperature distribution in the heating pan. The results indicate that the structure of single-coil can be optimized by varying the winding turns in different positions. More uniform temperature distribution in the pan has been obtained by increasing the number of turns at the center and edge of the coil. The advance of this design is to achieve uniform induction heating without redesigning the power source or adding an additional coil. Based on the simulation results, the refined induction coil has been fabricated and assembled into a commercial domestic induction cooker with little modification of the power supply system. A specific parameter named relative standard deviation (RSD) is proposed to define the temperature uniformity. By real-time temperature measurement, the improved heating uniformity has been demonstrated for the refined system. The present work provides a cost-effective and efficient solution to improve heating performance of domestic induction cooker.

GaN-Based Matrix Resonant Power Converter for Domestic Induction Heating

Flexible-surface induction cooktops must operate with a variety of induction heating loads with different behavior and power setpoints to be heated simultaneously. In this context, multi-output inverter topologies aim at achieving independent power management while featuring low power-device count and high power density. However, they suffer from limitations when applying classical modulation strategies to ensure soft switching, which is required to reduce transistor losses and achieve efficient operation. In this scenario, wide band-gap devices reduce switching losses, opening a new paradigm in power conversion where soft switching is not mandatory in order to achieve high efficiency. This paper proposes an implementation of a multi-output resonant inverter based on GaN HEMTs and evaluates various modulation strategies in terms of efficiency under different switching modes. The proposed approach is designed and experimentally validated by means of a 2-coil 2000 W prototype implementation.

A Comparative Evaluation of Wide-Bandgap Semiconductors for High-Performance Domestic Induction Heating

This paper presents a comparative evaluation of wide-bandgap power semiconductor devices for domestic induction heating application, which is currently a serious alternative to traditional heating techniques. In the induction heating system, the power transferred to the output depends on the equivalent resistance of the load, and the resistance depends on the operating frequency. Due to the switching characteristics of wide-bandgap power semiconductor devices, an induction heating system can be operated at higher operating frequencies. In this study, SiC and Si semiconductor devices are used in the comparison. These devices are compared according to different evaluation issues such as the turn-off energy losses, turn-off times, current fall time, the power losses of the internal diodes, and the conduction voltage drops issues. To perform the proposed evaluation, the series-resonant half-bridge inverter, which is frequently used in state-of-the-art induction heating systems, has been selected. The device suitability in an induction heating system is analyzed with the help of a test circuit. A comparison is made in terms of criteria determined by using the selected switches in the experimental circuit, which is operated in the 200 W to 1800 W power range and 45 kHz to 125 kHz switching frequency range. System efficiency is measured as 97.3% when Si IGBT is used. In the case of using SiC cascode JFET, the efficiency of the system is increased up to 99%.

Dual-Output Extended-Power-Range Quasi-Resonant Inverter for Induction Heating Appliances

Induction heating technology provides efficient and reliable heating processes that outperform other classical heating methods based on fossil fuels or resistive heating. Among its many industrial, domestic, and biomedical applications, domestic induction heating appliances are a popular choice due to these advantages. This technology requires high-performance and cost-effective inverters that take most of the power devices and the converter topology. Depending upon the desired performance and output-power range, different power converters are employed. However, currently, most platforms rely on the well-known series resonant half-bridge topology. Single-switch topologies offer a cost-effective implementation but are limited to the low-cost low-performance markets due to their limitations in terms of output power and power control. In this context, this paper proposes a high-performance dual-output quasi-resonant inverter for modern induction heating appliances. Unlike state-of-the-art proposals, this converter achieves a full-output-power operating range of up to 3.6 kW. Consequently, it provides a high-performance cost-effective alternative to current implementations. The proposed converter is analyzed in this paper and experimentally verified using a dual-output 3.6-kW induction heating appliance prototype.

Coupled numerical modelling and experimental analysis of domestic induction heating systems

Continuous demands on resources of energy heighten the need for better and smarter use of available resources. Induction heating (IH) is a technology that is proved to be more efficient in many industrial applications compared to direct resistive heating. Also, IH can be used in domestic devices, as it provides clean and contactless regime of heating. In this paper, a fully coupled numerical approach of a domestic IH system for water boiling is presented. The approach couples the modelling of magnetic field generated in the system with both heat transfer and fluid flow phenomena. The nonlinear and temperature-dependent characteristics of materials are accounted for in the coupled numerical approach. The numerical approach is validated by experimental measurements that are implemented for four case studies. In addition, a detailed parametric study is presented to investigate the effects of different design parameters. The results provide a picture of the nonlinear, complex, transient buoyancy-driven fluid motion. It is found that the heating efficiency is highly affected by different design parameters such as susceptor material, thickness, and offset distance from the bowl base. These effects are highly nonlinear due to the inclusion of nonlinear magnetic and thermal characteristics. The results also highlight the importance of the investigation of IH systems as integrated systems, in contrast to most of existing similar studies. By this holistic approach, different thermal processes and effects of different design parameters are involved, and consequently the heating efficiency can be clearly assessed.

Small-Sized Immersible Water Heaters for Domestic Induction Heating Technology

Induction cooktops are a key element in home electrification. This paper presents a new use of induction cooktops, which allows the preparation of infusions directly in a ceramic mug. It is proposed the design of a water heater with an immersible metallic load. The dimensions of the load allow its embedding in small ceramic vessels. Despite being smaller than conventional inductors, the immersible load has a specific shape that allows it to efficiently receive the energy from the induction cooktops and quickly heat the liquid inside the mug. Its geometry consists of a flat disk with sidewalls on its edge, which provides low reluctance paths for the magnetic field, resulting in improved transmitted power and efficiency. The load is arranged in a multilayer structure consisting of a ferromagnetic alloy with low Curie temperature at the bottom and aluminum on the top, which confers self-detection capabilities against dangerous overheating. The study of the proposal has been carried out with a finite element analysis model, and the feasibility of this proposal has been demonstrated through experimental results of its performance. Finally, the immersible water heater, powered by an induction cooktop, has been compared to other liquid heating systems, such as the microwave and the kettle, with promising results.

Electromagnetic Modeling and Analysis of Multimaterial Cookware for Domestic Induction Heating

Electromagnetic Modeling and Analysis of Multimaterial Cookware for Domestic Induction Heating

Domestic Induction Heating System With Standard Primary Inductor for Reduced-Size and High Distance Cookware

In this article, a hybrid wireless power transfer system, which combines induction heating (IH) and inductive power transfer functionalities, is proposed to improve the performance of a domestic IH application with small loads weakly coupled to distant inductors. Considering the basic single-inductor domestic IH application, the proposed system adds a secondary inductor with a series compensation capacitor directly attached to the small ferromagnetic cookware. The extended distance can be used to implement the glassless induction concept, where the ceramic glass of typical cooktops is substituted by the kitchen surface itself. The design of the secondary coil is carried out by means of a combination of finite-element and electrical simulations. A design process, including the housing of the resonant capacitors and the selection of the secondary winding number of turns and cabling, is presented. As a result, a prototype is implemented and tested under working conditions up to 1500 W at several distances. Experimental results validate the electrical modeling and simulation. Moreover, thermal results confirm the feasibility of the proposal and validate the adopted strategies for the capacitor housing.

Multi-output AC–AC converter for domestic induction heating

Multi-output AC–AC converter for domestic induction heating

A Dual-Resonant Topology-Reconfigurable Inverter for All-Metal Induction Heating

Traditionally, domestic induction heating (IH) is designed to heat the ferromagnetic (FM) pan. However, it is incompetent to heat the non-FM (NFM) pan since the small equivalent resistance of the pan will easily result in overcurrent on the inverter. Inspired by the compensation network in the wireless power transfer (WPT), the series–parallel resonance (SPR) network with a relay switch is newly integrated into the IH technology to develop a dual-resonant topology-reconfigurable inverter for all-metal IH. The proposed system can be purposely configured to a half-bridge series resonant inverter with the pulse width modulation (PWM) to heat the FM pan, or a full-bridge SPR-based inverter with the phase shift control (PSC) to heat the NFM pan, respectively. Moreover, the output–input current gain of the SPR network equals the heating-coil quality factor, thereby readily eliminating the overcurrent issue of the inverter. For exemplification, a 1-kW prototype has been built with system efficiencies of 94.32% and 91.05% for heating FM and NFM pans, respectively. Finally, the proposed system can be evolved to achieve automatic load detection and impedance matching to ensure uninterrupted resonance. Both the calculated and measured results are given to validate the flexibility and feasibility of the proposed system.

Power factor correction stage and matrix zero voltage switching resonant inverter for domestic induction heating appliances

Power factor correction stage and matrix zero voltage switching resonant inverter for domestic induction heating appliances

Load Estimation for Induction Heating Cookers Based on Series RLC Natural Resonant Current

In domestic induction heating applications, cookware can be considered an equivalent load in a series resistor–inductor–capacitor resonant converter. Therefore, the electrical parameters of an equivalent circuit change according to the cookware material, size and the cookware position on the heating coil. This study proposes an online estimation method for detecting the cookware status, determining the material and estimating the equivalent heating resistance of cookware on an induction heating cooker (IHC) for power control. The proposed method could turn off the circuit in abnormal situations such as low equivalent heating coverage rate or non-ferromagnetic cookware and adjust the power in normal situations. In the method, a half-bridge series resonant converter (HBSRC) generates two test patterns with three resonant voltage pulses to detect cookware every 10 ms, only the current feedback information is needed to avoid the calculation loads and times necessary for complex signal operations in software. To verify the proposed method, a digital signal processor based HBSRC with 1000 W was constructed. The maximum errors between the estimated and measured resistance and inductance were 7.14% and 2.91%, respectively. Moreover, power control in emulated user operation reveal that the proposed method and control system can effectively estimate load online to detect cookware status and determine whether to turn off or vary the heating power for an IHC.

Deep Learning Implementation of Model Predictive Control for Multioutput Resonant Converters

Flexible-surface induction cooktops rely on multi-coil structures which are powered by means of advanced resonant power converters that achieve high versatility while maintaining high efficiency and power density. The study of multi-output converters has led to cost-effective and reliable implementations even if they present complex control challenges to provide high performance. For this scenario, model predictive control arises as a modern control technique that is capable of handling multivariable problems while dealing with nonlinearities and constraints. However, these controllers are based on the computationally-demanding solution of an optimization problem, which is a challenge for high-frequency real-time implementations. In this context, deep learning presents a potent solution to approximate the optimal control policy while achieving a time-efficient evaluation, which permits an online implementation. This paper proposes and evaluates a multi-output-resonant-inverter model predictive controller and its implementation on an embedded system by means of a deep neural network. The proposal is experimentally validated by a resonant converter applied to domestic induction heating featuring a two-coil 3.6 kW architecture controlled by means of a FPGA.

A Simple Two-Stage AC-AC Circuit Topology Employed as High-Frequency Controller for Domestic Induction Heating System

The induction heating process at a domestic level is getting attention nowadays as this power converting topology ensures clean, reliable, flexible, and fast operation. The low input frequency is converted to required regulated high output frequency with indirect and direct power converting approaches. The circuit and control complexity and high conversion losses associated with indirect power converting approaches lower their uses for domestic induction systems. The direct ac-ac power conversion approach is one of the viable solutions for low and medium power level loads, especially for domestic induction heating loads. The circuit complexity, cost, and conversion losses of the direct power converting systems depend on the number of the controlled switching devices as each controlled switch requires one gate driving circuit and one isolated dc supply. Simplified pulse width modulation (PWM) switching control also lower their control effort. Therefore, in this article, a simplified direct ac-ac power converting approach is introduced for a high-frequency domestic induction heating system. Here, the regulation of the high output frequency is achieved by simply cascading the single-phase full-bridge rectifier with a full-bridge inverter with a simple control strategy. The characteristics of the developed topology are validated through simulation results of the Simulink-based platform and practical results of the developed practical setup.

Design and Simulation of Solar-based Induction Heating System

Solar energy is abundantly available energy for the generation of heat, and one the best appliances used for this purpose is Induction heaters. For the heat generation application, the combination of solar energy with the induction heat generation technique is the productive solution. Due to high efficiency and high-power density, resonant converters with soft switching are commonly utilized in domestic induction heating applications. For induction heating applications, a low profile and an improved efficiency resonant inverter design and implementation procedure are presented. Reducing conduction losses by using automotive-grade MOSFET devices against the classical IGBT-based converter. Conversion efficiency can be increased by decreasing switching losses which can be done by reducing switching times of MOSFET devices. Heating the metallic pan with circulating eddy currents induced by a high-frequency AC magnetic field is the principle of the induction cooker. If the load has an electrically conducting base, then the coil within the induction cooker and the load (pan/pot) acts as a transformer. The power will be transferred with high efficiency if the conducting base is ferromagnetic. An efficient control scheme incorporated in class E resonance heating by using solar power is presented. The simulation analysis is done in MATLAB-SIMULINK. Index Terms: induction heating, solar energy, class E resonant converter, MOSFET, MATLAB-SIMULINK

Constant-Current Gate Driver for GaN HEMTs Applied to Resonant Power Conversion

New semiconductor technology is enabling the design of more reliable and high-performance power converters. In particular, wide bandgap (WBG) silicon carbide (SiC) and gallium nitride (GaN) technologies provide faster switching times, higher operating temperature, and higher blocking voltage. Recently, high-voltage GaN devices have opened the design window to new applications with high performance and cost-effective implementation. However, one of the main drawbacks is that these devices require accurate base current control to ensure safe and efficient operation. As a consequence, the base drive circuit becomes more complex and the final efficiency is decreased. This paper presents an improved gate driver circuit for GaN devices based on the use of a constant current regulator (CCR). The proposed circuit achieves constant current regardless of the operating conditions, solving variations with temperature, aging and operating conditions that may degrade the converter performance. Besides, the proposed circuit is reliable and cost-effective, being applicable to a wide range of commercial, industrial and automotive applications. In this paper, its application to a zero-voltage switching resonant inverter for domestic induction heating was performed to prove the feasibility of this concept.

Mains-Synchronized Pulse Density Modulation Strategy Applied to a ZVS Resonant Matrix Inverter

Multi-output inverters have become a key enabling technology to increase surface flexibility in domestic induction heating appliances. The most commonly used power converter topologies are based on electromechanical relays in order to multiplex the connected loads and obtain a proper heat distribution. This solution, which is used in combination with other modulations such as square waveform, relies on the thermal inertia of the pot as it needs long power-averaging periods to reduce the reiteration of the switching noise. However, it presents a significant limitation in terms of acoustic noise, reliability, and thermal performance. To overcome these limitations, complete solid-state inverters that can be operated at higher frequencies are proposed. This change in the design paradigm of the pulse density modulation strategies leads to improved thermal control in the pot and better user experience, but at the same time increases challenges due to design constraints imposed by electromagnetic compatibility regulations. This article analyzes the possibilities of a new mains-synchronized pulse density modulation applied to a flexible induction cooktop that uses a multiple-output ZVS resonant inverter topology. The feasibility of the control strategies has been tested by means of a prototype featuring 12 2-kW induction heating loads.

Practical Design Methodology of IH and IPT Dual-Functional Apparatus

A domestic induction heating (IH) apparatus uses series resonance to transfer the electric energy to the IH vessel. Similarly, an inductive power transfer (IPT) utilizes the resonance to transfer power to the secondary side. Therefore, the IPT function can be integrated into the IH apparatus by sharing the IH power stage as the primary side of the IPT. In this article, a practical design methodology of the IH and IPT (IH-IPT) dual-functional apparatus is proposed. The design considerations of the IPT mode are discussed, such as the power stage design limitation and practical implementation to increase the compatibility to the IH apparatus. Moreover, the design methodology of the IPT mode is provided based on the design considerations. The validity of the proposed design methodology is evaluated through experimental results with an IH-IPT prototype.

RETRACTED ARTICLE: Performance evaluation of half bridge AC–AC resonant converter by using various load in domestic purpose of induction heating application

A new 28 kHz is proposed for the generation of output power of 775 watts with a high frequency to drive a domestic induction heating application using AC convertor. The proposed system deals with the output parameters of THD, PF, and output power in the simulation. The simulation carried out for the various loaded conditions and selected with respect to various parameters like power factor, THD, temperature, time, higher power, uniform distribution of heat through the IH system. The requirement of the proposed system is to have a highly reliable and adaptable to different loaded condition. A prototype of the proposed system was implemented and verified with the system developed. Experiment was carried out with different medium (liquid) and results are measured and graphically represented. The validations of the electrical and thermal parameters are focused in the proposed and implemented system.