A flexible cooking zone composed of partially overlapped inductors

Domestic induction cookers are evolving from fixed cooking areas to flexible surfaces in such a way that the pot can be placed at any position. This implies the use of a larger number of reduced-sized inductors, which present a lower efficiency. As a solution to increase the efficiency while maintaining the flexibility, we propose the use of partially overlapped inductors of a larger size. This concept is currently in use in wireless power transfer systems, where the transmitter arrangement consists of several overlapped coils. The aim of this paper is to evaluate this concept applied to domestic induction heating appliances, with special emphasis in analyzing the effects of introducing the multicoil system with dissipative media. Moreover, the losses in the winding will be studied in detail. The system will be prototyped and tested, delivering up to 3.7 kW

Induction Heating of Two Magnetically Independent Loads With a Single Transmitter

This article introduces the design of a system capable of heating two magnetically independent ferromagnetic loads placed on different horizontal planes, which uses a combination of induction heating and inductive coupling, called inductively coupled heating. The system uses a single primary inductor acting as a transmitter to transfer power to a secondary inductor attached to the bottom load, which is connected electrically with a third inductor that heats the top load. Since power of the whole system is supplied by a simple half-bridge inverter, the ratio of the delivered power to each of the loads, which is critical for cooking results, is entirely dependent on the system's geometry, coil's number of turns, and compensation capacitors. A finite-element model is used to simulate the magnetic fields generated by inductor currents and calculate the impedance matrix. With the impedance, capacitor values and inductors’ number of turns are selected with the objective of achieving a high power ratio between the top and bottom zones, as well as minimizing stress in the electronics. First, a prototype was built to validate the impedance results in the small-signal regime, and then, the full power regime was used to verify power and current simulation

Modeling and design of cookware for induction heating technology with balanced electromagnetic and thermal characteristics

Improving the cooking experience of induction-heating users involves, among other factors, an optimized power distribution at the bottom of the cooking vessel. Conventional ferromagnetic cookware presents high efficiency but unequal temperature distribution with flat inductors, which subsequently leads to uneven cooking results. In this work, we propose an alternative to the traditional cookware arrangement by inserting some aluminum pieces in the ferromagnetic bottom of cookware. This arrangement combines the optimal inductive performance of the ferromagnetic iron an the high thermal conductivity of aluminum. The performance of the proposed arrangement is analyzed by means of a multiphysics tool including electromagnetic and heat transfer sub-models which is applied to predict both the equivalent electrical circuit and the temperature distribution in cookware. As a result, a balanced trade-off between efficiency and temperature distribution is evidenced with the proposed solution. Experimental results also corroborates the predictions of the proposed solution. Autho

Adapting of Non-Metallic Cookware for Induction Heating Technology via Thin-Layer Non-Magnetic Conductive Coatings

We analyze the feasibility of heating non-metallic cookware, unappropriate for heating by means of induced currents, with the purpose of extending the applicability range of the current induction heating cooktops. In order to turn materials as glass, ceramic, wood or plastic into suitable for the induction heating technology, we propose the use of thin layers of a metal (not necessarily a ferromagnetic material) which can be deposited on a surface by means of a thin or thick layer technology. For this purpose, the inductive performance of these layers is investigated by means of an analytical electromagnetic model, finite element simulations and experimental measurements. Calculations point out that for a specific induction arrangement working at a fixed frequency, it exists a thickness which maximizes the induction efficiency for each layer material. The suitability of this result is tested by means of a set of samples with copper thin layers whose thicknesses range from one hundred of nanometers to tens of micrometers, which are implemented using a phase vapor deposition (PVD) technology. The obtained induction efficiency and equivalent resistance are compared with those obtained with conventional ferromagnetic materials. As a proof of concept, the inner and outer bottoms of two glass pots are covered with a copper layer of 2µm, and 1.5µm , respectively, and 1 kW is inductively supplied by means of a series resonant inverter, reaching the boiling water conditions

Investigation of Auxiliary winding harmonic resonance phenomena in single phase induction motors

In recent years, the proliferation of single phase power electronics based loads has given rise to a number of power quality issues in the power grid. Harmonics in voltage and current waveforms are one of the biggest problems in this family of power quality issues. Until some years back, power system utilities did not consider harmonics due to small single phase loads to be a big problem. In fact, only large loads were considered as potential hotspots for power quality problems. However, the advent of compact fluorescent lamps (CFLs), personal computers and consumer electronic devices, which utilize rectifier front ends, have changed the scenario drastically. All these devices are rich sources of harmonics and their sheer volume makes them a serious power quality hazard. Recent work done by the Clemson University Power Quality and Industrial Applications (PQIA) lab has shown that capacitor run single phase induction motors also exacerbate the problem because of their behavior in the presence of harmonic infested voltage. This thesis attempts to study the behavior of capacitor run single phase induction motors in the presence of voltage harmonics. It incorporates laboratory results which show that the capacitor start capacitor run single phase motor actually `amplifies\u27 the amount of harmonic distortion present in the source because of harmonic resonance in its auxiliary winding. This resonance behavior implies that machine impedance is a function of supply frequency and that the impedance hits a low value at the resonant frequency of the auxiliary winding circuit. This resonance leads to extra heating losses in the auxiliary winding circuit. However, during the course of investigation, an interesting phenomenon was observed. In the presence of single phase full wave rectifiers, this resonance phenomenon causes the single phase motor to behave as a harmonic filter. This harmonic filter helps `clean up\u27 the voltage source by reducing the amount of harmonic current drawn by the motor-rectifier combination. Thus, resonance in the auxiliary winding of the single phase induction motor is not necessarily an unwanted phenomenon. This thesis presents experimental proof for all the phenomena outlined and makes an attempt to explain them. Arguments have then been presented for and against this peculiar behavior of the motor. Finally, the thesis concludes by outlining the scope for future work and the particular direction in which the power industry is headed with regards to single phase induction motors

Heating Effects Through Harmonic Distortion on Electric Cables in the Built Environment

Under ideal circumstances, electric power supply voltage and current waveforms should be sinusoidal. However, this is very seldom the case in the built environment, due to the proliferation of non-linear loads. Examples of non-linear loads are those containing switched mode power supplies, reactors and electronic rectifiers/inverters. Common devices such as personal computers, fluorescent lighting, electric motors, variable speed drives, transformers and reactors and virtually all other electronic equipment are examples of non-linear loads. Non-linear loads are the norm in the built environment rather than the exception. Such loads produce complex current and voltage waves and simple spectral analysis of these complex waves shows that they can be represented by a wave at the fundamental power frequency plus other wave forms at integer and non-integer multiples of this frequency. These harmonics produce an overall effect called \u27Harmonic Distortion\u27 which can give rise to overheating in plant, equipment and the power cables supplying them, leading to reduced efficiency, operational life and sometimes failure. Over the last few decades, harmonic distortion in power supplies has increased significantly due to the increasing use of electronic components in industry and elsewhere. Buildings such as modern office blocks, commercial premises, factories, hospitals, etc.,contain equipment that generates harmonic loads as described above. Each item of equipment produces a unique harmonic signature and therefore a harmonic distortion which can be predicted if the equipment in use can be determined in advance. This thesis seeks to identify the harmonic signatures of different types of equipment commonly used and to predict the thermal loading effects on distribution cables caused by the skin and proximity effects of harmonic currents

Parameter Identification Method for a 3-phase Induction Heating System

This paper describes a new method for the on-line 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 off-line 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 “pseudo-energy” 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 3-phase coupled resonant system supplied with voltage inverters with satisfying results

Теоретичні основи електротехніки[

The Theory of Electrical Engineering is presented in three parts: the Basic Theories of Steady-State and Transients in Electrical Circuits and the Basic Theory of Electromagnetic Field. For students of electrotechnical specialties of higher educational establishments, as well as for scientific and technical specialists dealing with modern problems in the theory and practice of electric power engineering and electromechanics.Викладено теоретичні основи електротехніки в трьох частинах: теорія стаціонарних процесів в електричних колах, теорія перехідних процесів в електричних колах і теорія електромагнітного поля. Для студентів електротехнічних спеціальностей вищих навчальних закладів, а також для науково-технічних фахівців, що займаються сучасними проблемами в теорії і практиці електроенергетики та електромеханіки

Induction heating converter's design, control and modeling applied to continuous wire heating

Induction heating is a heating method for electrically conductive materials that takes advantage of the heat generated by the Eddy currents originated by means of a varying magnetic field. Since Michael Faraday discovered electromagnetic induction in 1831, this phenomena has been widely studied in many applications like transformers, motors or generators' design. At the turn of the 20th century, induction started to be studied as a heating method, leading to the construction of the first industrial induction melting equipment by the Electric Furnace Company in 1927. At first, the varying magnetic fields were obtained with spark-gap generators, vacuum-tube generators and low frequency motor-generator sets. With the emergence of reliable semiconductors in the late 1960's, motor-generators were replaced by solid-state converters for low frequency applications. With regard to the characterization of the inductor-workpiece system, the first models used to understand the load's behavior were based on analytical methods. These methods were useful to analyze the overall behavior of the load, but they were not accurate enough for a precise analysis and were limited to simple geometries. With the emergence of computers, numerical methods experienced a tremendous growth in the 1990's and started to be applied in the induction heating field. Nowadays, the development of commercial softwares that allow this type of analysis have started to make the use of numerical methods popular among research centers and enterprises. This type of softwares allow a great variety of complex analysis with high precision, consequently diminishing the trial and error process. The research realized in last decades, the increase in the utilization of numerical modeling and the appearance and improvement of semiconductor devices, with their corresponding cost reduction, have caused the spread of induction heating in many fields. Induction heating equipments can be found in many applications, since domestic cookers to high-power aluminum melting furnaces or automotive sealing equipments, and are becoming more and more popular thanks to their easy control, quick heating and the energy savings obtained. The present thesis focuses on the application of induction heating to wire heating. The wire heating is a continuous heating method in which the wire is continuously feeding the heating inductor. This heating method allows high production rates with reduced space requirements and is usually found in medium to high power industrial processes working 24 hours per day. The first chapters of this study introduce the induction heating phenomena, its modeling and the converters and tanks used. Afterwards, a multichannel converter for high-power and high-frequency applications is designed and implemented with the aim of providing modularity to the converter and reduce the designing time, the production cost and its maintenance. Moreover, this type of structure provides reliability to the system and enables low repairing times, which is an extremely interesting feature for 24 hours processes. Additionally, a software phase-locked loop for induction heating applications is designed and implemented to prove its flexibility and reliability. This type of control allows the use of the same hardware for different applications, which is attractive for the case of industrial applications. This phase-locked loop is afterwards used to design and implement a load-adaptative control that varies the references to have soft-switching according to load's variation, improving converter's performance. Finally, the modeling of a continuous induction wire hardening system is realized, solving the difficulty of considering the mutual influence between the thermal, electromagnetic and electric parameters. In this thesis, a continuous process is modeled and tested using numerical methods and considering converter's operation and influence in the process.Postprint (published version