Strand wire winding method in a solenoidal coil with limited geometry for good impedance matching

This paper reports a new strand wire winding method in a solenoidal coil with limited geometry that enables good impedance matching. In the proposed method strand wires are wound layer-by-layer on top of each other allowing one to set equivalent inductance and resistance of the coil to desired values while obtaining dense magnetic flux and high current carrying capacity. As a proof-of-concept demonstration, simple model setups were constructed with solenoidal coils composed of copper wire strands wound according to the proposed method, and a plastic pipe. The measurements were repeated with a metal shell placed inside the coil to model a complete heating system. System inductance and resistance were measured at two different frequencies. The results show that with the new winding method it is possible to increase a coil’s turn number and the number of strand layers composed by the coil. Also, adding and removing strand layers in the proposed coil architectures enable inductance and resistance values to decrease and increase, respectively, in a controlled way. To understand changes of system parameters, simulations were also performed. The calculated inductance and resistance values in the simulations agree well with the measurement results and magnetic flux distribution created in the system demonstrates the changes

Multiple-Output ZVS Resonant Inverter Architecture for Flexible Induction Heating Appliances

Flexible cooking surfaces have changed the domestic induction heating product paradigm enabling the use of a wider range of cookware materials, shapes, and positions. In order to implement such systems, multiple-output resonant inverters featuring high-performance and high-efficiency operation while achieving a cost-effective implementation are required. This paper proposes a multiple-output zero-voltage-switching resonant inverter for flexible induction heating appliances. The proposed converter features a matrix structure, enabling a cost-effective implementation with a reduced number of power devices while achieving high performance and low switching losses. It has been tested by means of an experimental prototype featuring 48 induction heating coils, proving the feasibility of the proposed approach

Asymmetrical Noncomplementary Modulation Strategies for Independent Power Control in Multioutput Resonant Inverters

Domestic induction heating (IH) design trends aim at improving user experience by increasing the cooking surface flexibility while maintaining a cost-effective implementation. The design of multioutput topologies is a key development for this purpose. However, due to their complexity, output power control usually relies on low-frequency pulse density modulations that, in addition to the slow response due to significant power averaging times, present severe restrictions as a consequence of power pulsation regulations. This article proposes two different noncomplementary asymmetrical modulation strategies that allow continuous operation avoiding both flicker and heating performance issues and obtaining a fast-response load power control. In order to prove the feasibility of the proposed modulations, a prototype featuring 12 IH loads of 2000-W maximum rated power has been built, and both strategies have been tested

Analysis and Modeling of the Forces Exerted on the Cookware in Induction Heating Applications

We present a semianalytical model for calculating the forces exerted on cookware in domestic induction heating applications. The developed model is based on the Maxwell''s stress tensor and is also based on the existing semianalytic expressions of the electromagnetic fields in planar induction heating systems, which are expressed in terms of Fourier-Bessel series. Taking advantage of the axial symmetry of usual domestic induction heating systems, the flux of the vertical component of the Maxwell''s stress tensor is analytically integrated and the vertical force is obtained. The proposed model captures both eddy currents and magnetization that occurs in typical ferromagnetic cookware. The model is verified by means of two-dimensional Finite Element simulations and also is tested by means of measurements of the change of the weight experimented by cookware due to the forces during the heating process

Vessel Recognition in Induction Heating Appliances - A Deep-Learning Approach

The selection of a vessel by an induction-hob user has a significant impact on the performance of the appliance. Due to the induction heating physical phenomena, there exist many factors that modify the equivalent impedance of induction hobs and, consequently, the operational conditions of the inverter. In particular, the type of vessel, which is a sole decision of the user, strongly affects these parameters. Besides, the ferromagnetic properties of the different materials the vessels are made with, vary differently with the excitation level, and given that most of the domestic induction hobs are based on an ac-bus voltage arrangement, the excitation level continuously varies. The algorithm proposed in this work takes advantage of this fact to identify the equivalent impedance of the load and recognize the pot. This is accomplished through a phase-sensitive detector that was already proposed in the literature and the application of deep learning. Different convolutional neural networks are tested on an augmented experimental-based dataset and the proposed algorithm is implemented in an experimental prototype with a system-on-chip. The proposed implementation is presented as an effective and accurate method to characterize and discriminate between different pots that could enable further functionalities in new generations of induction hobs

All-surface induction heating with high efficiency and space invariance enabled by arraying squircle coils in square lattice

This paper reports an all-surface induction heating system that enables efficient heating at a constant speed all over the surface independent of the specific location on the surface. In the proposed induction system, squircle coils are placed tangentially in a two-dimensional square lattice as opposed to commonly used hexagonal packing. As a proof-of-concept demonstration, a simple model setup was constructed using a 3 × 3 coil array along with a steel plate to be inductively heated. To model surface heating, a set of six locations for the plate was designated considering symmetry points. For all of these cases, power dissipated by the system and the plate's transient heating were recorded. Independent from the specific plate position, almost equal heating speeds were measured for the similar levels of dissipated energies in the system. Using full three-dimensional electromagnetic solutions, the experimental results were also verified. The findings indicate that the proposed system is proved to enable energy efficient space-invariant heating in all-surface induction hobs.Accepted versio