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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]

Cost-effective solutions for domestic induction heating appliances have become a priority in recent years. With this purpose, the implementation of Printed Circuit Board (PCB) inductors has entailed important research efforts. A proper litz structure is essential to achieve high-efficiency PCB inductors. This structure requires routing the traces by using vias in a double layer PCB to obtain the appropriate transposition pattern. In this paper, the optimal number of vias has been analyzed to minimize the power losses in the coil. This analysis has been carried out based on numerical calculations whose results have been experimentally verified. [ABSTRACT FROM AUTHOR]

We derive integral expressions of the equivalent impedance of ring-type coils for induction heating systems. These expressions are obtained by integrating the analytical solution of the field generated by a circular filamentary current placed between two linear and homogeneous semi-infinite media. Constant current density is assumed for the coils, since they are wound with an appropriate Litz wire. The model also gives the magnetic field in the cross section of the windings, which is necessary to calculate the proximity losses in the cables. The solution is given in terms of Bessel function integrals, showing an improvement of the convergence with respect to the filamentary model solution. We constructed several prototypes having different turns and layers and tested them with different substrates. Our measurements confirm the validity of the analytical models. [ABSTRACT FROM AUTHOR]

We present an analytical model of the equivalent impedance of an n-turn planar winding sandwiched between top and bottom multilayer media. Although the model's general and compact notation is valid for all systems involving magnetic dipoles and stratified media, perhaps its main application is domestic induction heating systems. The proposed model is based on the vector potential solution of a single-turn coil located between two multilayer media, and this result is extended to n-turn coils. We demonstrate the applicability of the model by a variety of examples. We present experimental results to justify the theoretical model. [ABSTRACT FROM AUTHOR]

Induction heating systems are evolving towards more flexible architectures, which imply highly variable induction loads. This becomes a challenge for the design of resonant converters with high efficiency in the whole range of output power and induction loads. To overcome this design problem, proposed is a variable snubber network which allows improving the efficiency for different operating conditions. The proposed network has been implemented and tested in a multiple-output induction heating system. [ABSTRACT FROM AUTHOR]

The use of resonant converters in high-frequency and high-efficiency power converters is widespread. Recent developments in wide bandgap materials, such as silicon carbide and gallium nitride, and their commercial availability, are boosting their use in power converters. Proposed is a reduced component-count gate drive circuit for the zero voltage switching operation of resonant converters featuring SiC JFETs and its design procedure is proposed. The trade-off between on-state losses and driver activation losses is detailed, reaching a point of maximum device efficiency. The proposal is experimentally verified using a resonant converter applied to domestic induction heating. [ABSTRACT FROM AUTHOR]

Nowadays users of domestic induction cookers demand heating areas larger than traditional ones because they are able to heat larger pan diameters. These heating areas consist of several concentric planar windings which have to be fed. A possible solution is to replace the traditional single-output inverter topologies by multiple-output inverter topologies. Proposed is a topology for three concentric planar windings based on an electronic board of a domestic cooker and an adaptation board. The different configurations according to the pan diameter are detailed and some experimental results are presented. The proposed topology minimises the semiconductor stress of the devices. [ABSTRACT FROM AUTHOR]

Results showing induction heating performance improvement when a planar winding is placed between two media are presented. One of the media is assumed to be the load and the other must be a non-conductive material with a high magnetic permeability. This improvement has been characterised by means of measuring the increase of the equivalent resistance, associated with the power dissipation in the load. The study has been applied to a domestic induction heating system. [ABSTRACT FROM AUTHOR]

Electroporation is a phenomenon produced in the cell membrane when it is exposed to high pulsed electric fields that increases its permeability. Among other application fields, this phenomenon can be exploited in a clinical environment for tumor ablation therapies. In this context to achieve optimum results, it is convenient to focus the treatment on the tumor tissue to minimize side effects. In this work, a pre-treatment tumor location method is developed, with the purpose of being able to precisely target the therapy. This is done by taking different impedance measurements with a multi-output electroporation generator in conjunction with a multi-electrode structure. Data are processed by means of a vector of independent artificial neural networks, trained and tested with simulation data, and validated with phantom gels. This algorithm proved to provide suitable accuracy in spite of the low electrode count compared to the number of electrodes of a standard electrical impedance tomography device., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Author(s). Published by Elsevier B.V. All rights reserved.)

Aims: Radiofrequency ablation (RFA) of tumors by means of internally cooled (ICE) or multitined expandable electrodes combined with infusion of saline into the tissue may improve results. Our aim was to determine the efficacy of a previously optimized hybrid ICE system (ICE combined with infusion of saline into the tissue at a distance of 2mm) in comparison with a conventional ICE cluster electrode in porcine liver in vivo., Methods: A total of 32 RFA were performed on a total of 10 farm pigs using two RFA systems: Group A (n=16): Cluster electrode. Group B (n=16): Hybrid system (with continuous infusion of 100ml/h of 20% NaCl at 2mm distance from the electrode shaft by an independent isolated needle). Livers were removed for macroscopic and histological assessment after the procedure. Coagulation volume, coagulation diameters, coefficient of variability (CV) of coagulation volume, sphericity ratio (SR), deposited power (DP), deposited energy (DE), deposited energy per coagulation volume (DEV) and rise of animal temperature during the procedure were compared and correlated among groups. Additionally, linear regression analysis was modeled to study the relationship between deposited energy and either coagulation volume and rise of animal temperature during the procedure in both groups., Results: Both coagulation volume and short diameter of coagulation were significantly greater (p<0.05) in group B compared to group A (22.7+/-11.0 cm(3) and 3.1+/-0.7 cm vs. 13.5+/-7.7 cm(3) and 2.5+/-0.5 cm, respectively). A similar CV and SR was observed among groups (57.1% and 1.4+/-0.3 vs. 48.6% and 1.3+/-0.2 for groups B and A, respectively). In group B, DE and DP were more than double group A, but DEV was nearly twice as high (9782 J/cm(3) vs. 5342 J/cm(3), for groups B and A, respectively). No significant relationship between DE and coagulation volume was encountered., Conclusion: Efficacy of a single ICE may be improved with continuous infusion of saline at around 2 mm from the electrode shaft. Coagulation volume obtained with this improved system may be even greater than that obtained with a cluster electrode.

Background: Efficient and safe liver parenchymal transection is dependent on the ability to address both parenchymal division and hemostasis simultaneously. In this article we describe and compare with a saline-linked instrument a new radiofrequency (RF)-assisted device specifically designed for tissue thermocoagulation and division of the liver used on an in vivo pig liver model., Methods: In total, 20 partial hepatectomies were performed on pigs through laparotomy. Two groups were studied: group A (n=8) with hepatectomy performed using only the proposed RF-assisted device and group B (n=8) with hepatectomy performed using only a saline-linked device. Main outcome measures were: transection time, blood loss during transection, transection area, transection speed and blood loss per transection area. Secondary measures were: risk of biliary leakage, tissue coagulation depth and the need for hemostatic stitches. Tissue viability was evaluated in selected samples by staining of tissue NADH., Results: In group A both blood loss and blood loss per transection area were lower (p=0.001) than in group B (70+/-74 ml and 2+/-2 ml/cm(2) vs. 527+/-273 ml and 13+/-6 ml/cm(2), for groups A and B, respectively). An increase in mean transection speed when using the proposed device over the saline-linked device group was also demonstrated (3+/-0 and 2+/-1cm(2)/min for group A and B, respectively) (p=0.002). Tissue coagulation depth was greater (p=0.005) in group A than in group B (6+/-2 mm and 3+/-1 mm, for groups A and B, respectively). Neither macroscopic nor microscopic differences were encountered in transection surfaces between both groups., Conclusions: The proposed RF-assisted device was shown to address parenchymal division and hemostasis simultaneously, with less blood loss and faster transection time than saline-linked technology in this experimental model.

Rationale and Objectives: The authors' purpose was to create larger and more regular liver lesions in vitro by testing a new hyperthermia approach that uses a bipolar saline-enhanced electrode for radiofrequency (RF) in the audible spectrum and a greater power supply., Materials and Methods: The authors' hyperthermia approach (group A, n = 23) was used in excised porcine livers, and the results were compared with those of a previously described monopolar saline-enhanced electrode procedure (group B, n = 23). In each set of experiments, RF in the audible spectrum current (50 Hz) was provided for 15 minutes with a similar ablation protocol. Electrical variables (impedance, current, voltage, power, and energy), temperatures in the lesions, volume size, regularity ratio of the lesion, and microscopic findings were measured., Results: In group A, the mean volume size and the mean regularity ratio values were 144.8 cm3 +/- 59.8 and 0.78 +/- 0.1, respectively. In group B, the mean volume size and regularity ratio values were 62.1 cm3 +/- 36.4 and 0.62 +/- 0.1, respectively. The values in group B were thus significantly lower than those in group A (P < .01). The lesions in group A were also more homogeneous. No significant differences were found in electrical variables., Conclusion: The new bipolar saline-enhanced electrode produced larger, more regular, and more homogeneous lesions ex vivo than the previously used monopolar saline-enhanced electrode method. Using a greater power supply increased the amount of coagulative necrosis.