Search Results (68)

This paper presents a methodology for embedding coupled electromagnetic–thermal finite element (FE) models into a hardware-in-the-loop (HIL) platform to enable real-time prototyping of control strategies for advanced heating systems. The framework combines frequency-domain electromagnetic modeling and time-domain thermal simulation within a physics-based digital twin executed on real-time hardware. Electromagnetic simulations generate impedance maps as functions of coil–workpiece positions, which are parameterized into equivalent lumped circuit models for efficient converter-level simulation. In parallel, the thermal FE solver operates directly on the hardware simulator, accelerating the computation of the heated object’s energy transfer and thermal dynamics. The approach is validated through an induction-heating case study, demonstrating that integrating finite element modeling into a real-time simulator enables the realistic evaluation of energy conversion, control algorithms, and detection logic in complex electrothermal systems. Full article

This study employs 304 stainless steel perforated mesh (SS mesh) as the heating element for the resistance welding of continuous carbon fiber-reinforced polycarbonate (CCF/PC) sheets. An electro-thermal coupled finite element model is developed to investigate the effect of SS mesh structural parameters (aperture shape, aperture area, mesh thickness) and clamping distance on the welding temperature field. The model accurately predicts peak temperatures, with errors of 1–4% compared with experiments. Under identical aperture area, the SS mesh with longer effective current path length and smaller effective cross-sectional area has higher resistance. In addition, the resistance increases significantly with decreasing mesh thickness and increasing aperture size. Reducing the clamping distance effectively improves temperature uniformity across the weld zone and mitigates edge overheating. A novel mesh structure—featuring larger aperture in the welding region and smaller aperture in non-welding region, is designed to improve the temperature uniformity and joint quality. Under optimized welding parameters (14 A, 40 s welding/holding, 0.3 MPa), the joint achieves a maximum tensile shear force of 9.851 kN, a 13.1% improvement over conventional uniform-aperture mesh (8.713 kN). Full article

Closing resistors in ultra-high-voltage (UHV) gas-insulated circuit breakers (GCBs) are critical components designed to suppress inrush currents and transient overvoltages during switching operations. However, in practical service, these resistors are subjected to repeated mechanical impacts and transient electrical stresses, leading to degradation of their electrical contact interfaces, fluctuating resistance values, and potential failure of the entire breaker assembly. Existing studies mostly simplify the closing resistor as a constant resistance element, neglecting the coupled electro-thermal–mechanical effects that occur during transient events. In this work, a comprehensive modeling framework is developed to investigate the dynamic electrical contact characteristics of a 750 kV GCB closing resistor under transient closing impacts. First, an electromagnetic transient model is built to calculate the combined inrush and power-frequency currents flowing through the resistor during its pre-insertion period. A full-scale mechanical test platform is then used to capture acceleration signals representing the mechanical shock imparted to the resistor stack. These measured signals are fed into a finite element model incorporating the Cooper–Mikic–Yovanovich (CMY) electrical contact correlation to simulate stress evolution, current density distribution, and temperature rise at the resistor interface. The simulation reveals pronounced skin effect and current crowding at resistor edges, leading to localized heating, while transient mechanical impacts cause contact pressure to fluctuate dynamically—resulting in a temporary decrease and subsequent recovery of contact resistance. These findings provide insight into the real-time behavior of closing resistors under operational conditions and offer a theoretical basis for design optimization and lifetime assessment of UHV GCBs. Full article

Internal conductive defects in composite insulators severely degrade their insulation performance and are considered concealed defects, posing a significant threat to the safe and stable operation of the power grid. Focusing on this issue, this study develops an electro-thermal multi-physical field simulation model and uses finite element analysis to investigate the electric field distribution and temperature rise characteristics. Composite insulator specimens with varying defect lengths were fabricated using the electrical erosion test. Charged tests were then conducted on these defective specimens, as well as on field-decommissioned specimens. The impact of internal conductive defects on the infrared, ultraviolet, and electric field distribution characteristics of composite insulators during operation was analyzed. The results indicate that the surface electric field of composite insulators with internal conductive defects becomes highly concentrated along the defect path, with a significant increase in electric field strength at the defect’s end. The maximum field strength migrates toward the grounded end as the defect length increases. Conductive defects lead to partial discharge and abnormal temperature rise at the defect’s end and the bending points of the composite insulator. The temperature rise predominantly manifests as “bar-form temperature rise,” with temperature rise regions correlating well with discharge areas. Conductive defects accelerate the decay-like degradation process of composite insulators through a positive feedback loop formed by the coupling of electric field distortion, Joule heating, material degradation, and discharge activity. This study identifies the key characteristics of electrical and temperature rise changes in insulators with conductive defects, reveals the deterioration evolution process and degradation mechanisms of insulators, and provides effective criteria for on-site diagnosis of conductive defects. Full article

This study aims to explore a new concept for a Power to Heat (P2H) device and demonstrate its effectiveness compared to a thermal heating method. The proposed concept is a medium-temperature system where electro-thermal conversion occurs via the Joule effect in a metallic tube (resistive element). This tube also serves as a heat exchange surface between the heat transfer fluid and the thermal storage medium. The heat storage material here proposed consists of base concrete formulated on purpose to ensure its operation at high temperatures, good performance and prolongated thermal stability. The addition of 10%_wt phase change material (i.e., solar salts) stabilized in shape through a diatomite porous matrix allows the energy density stored in the medium itself to increase (hybrid sensible/latent system). Testing of the heat storage module has been conducted within a temperature range of 220–280 °C. An experimental comparison of charging times has demonstrated that electric heating exhibits faster dynamics compared to thermal heating. In both electrical and thermal heating methods, the concrete module has achieved 86% of its theoretical storage capacity, limited by thermal losses. In conclusion, this study successfully demonstrates the viability and efficiency of the proposed hybrid sensible/latent P2H system, highlighting the faster charging dynamics of direct electrical heating compared to conventional thermal methods, while achieving a comparable storage capacity despite thermal losses. Full article

Electrothermal anti-/de-icing systems are widely used in aircraft, and the structures of these systems generally consist of multiple layers laminated together. In service, laminated structures are prone to structural deformation and delamination, which can significantly affect heat conduction. Therefore, it is essential to study the temperature field of these electrically heated anti-icing structures during operation and analyse the impact of delamination damage on the temperature distribution. In this thesis, a dynamic multiphysical field study of an electric heating anti-icing structure is conducted using a thermal expansion layer-by-layer/3D solid element method. By studying the electric heating process of composite plates experiencing pre-positioned delamination, the thermal expansion layer-by-layer/3D solid element method considers the thermal convection boundary conditions as well as a constant heat source. In addition, to considering the influences of the geometric shape and delamination damage, we apply the thermal expansion layer-by-layer/3D solid element method to the electric heating anti-icing process of aerofoil structures using a coordinate transformation matrix. The calculations show that when delamination damage is located above the heating layer, the maximum temperature of the structure reaches 450 °C at 50 s, which severely affects the normal functioning of the structure. Additionally, the surface temperature of the anti-icing system decreases to the ambient temperature at the delamination. In contrast, delamination damage located below the heating layer has a minimal effect on the surface temperature distribution. Moreover, the damage caused by multiple types of damage is greater than that caused by a single type of damage. Full article

Flexible actuators hold significant promise for applications in intelligent robotics, wearable devices, and biomimetic systems. However, conventional actuators face challenges such as high driving voltages, inadequate deformation control, and limited deformation modes, which hinder complex programmable dynamic deformations. This study presents an electrothermal actuator based on a conductive silver paste/Kapton/PDMS composite structure, enabling precise and adjustable deformation through programmable thermal control. Experimental results show that the actuator achieves a large-angle bending (∼203°) within 12 s under a low driving voltage of 2.0 V. Compared to the PTFE/MXene/PI structure, the proposed actuator achieves a 64% increase in bending angle, a 70% reduction in response time, and a 67% decrease in driving voltage. By independently controlling multiple heating elements, the actuator exhibits programmable deformation modes, including local, symmetric, and sinusoidal bending. The relationship between input voltage and deformation amplitude is described using a sinusoidal function model, experimentally validated for accuracy. Compared to traditional actuators, the proposed design offers significant improvements in bending angle, response speed, and voltage requirements. By optimizing the conductive silver paste pattern and voltage input strategy, this work develops a low-voltage, highly controllable, multi-mode programmable actuator with potential for applications in flexible robotics and space-deformable antennas. Full article

In a photovoltaic power enhancer system, when it is operated in current-control mode, significant nonuniform temperature distribution occurs in the converter due to thermal coupling effects, dissipative boundary conditions, and differences in device losses within the in-phase bridge. Accurate on-site estimation of the power device’s junction temperature is critical in the system design. To address this problem, a novel thermal behavior estimation model based on electro-thermal analysis is proposed in this paper, which can be used for asymmetric power MOSFETs in a photovoltaic power enhancer system. Thermal coupling effects and dissipative boundary conditions are, firstly, analyzed in a three-dimensional finite element model. A coupling impedance matrix is constructed through step power response extraction to describe the significant thermal coupling effects among devices. The complete heat sink is decoupled into several sub-parts representing different dissipative boundary conditions. A compact RC network model for estimating junction temperature is established based on the combination of the coupling impedance and the sub-heat-sink impedance. The proposed model is verified by finite element simulation and experimental measurement. Full article

The reliability of GaN-based devices operating under high temperatures is crucial for their application in extreme environments. To identify the fundamental mechanisms behind high-temperature degradation, we investigated GaN-on-sapphire Schottky barrier diodes (SBDs) under simultaneous heating and electrical biasing. We observed the degradation mechanisms in situ inside a transmission electron microscope (TEM) using a custom-fabricated chip for simultaneous thermal and electrical control. The pristine device exhibited a high density of extended defects, primarily due to lattice mismatch and thermal expansion differences between the GaN and sapphire. TEM and STEM imaging, coupled with energy-dispersive X-ray spectroscopy (EDS), revealed the progressive degradation of the diode with increasing bias and temperature. At higher bias levels (4–5 V) and elevated temperatures (300–455 °C), the interdiffusion and alloying of the Au/Pd Schottky metal stack with GaN, along with defect generation near the interface, resulted in Schottky contact failure and catastrophic device degradation. A geometric phase analysis further identified strain localization and lattice distortions induced by thermal and electrical stresses, which facilitated diffusion pathways for rapid metal atom migration. These findings highlight that defect-mediated electrothermal degradation and interfacial chemical reactions are critical elements in the high-temperature failure physics of GaN Schottky diodes. Full article

A method of electro-thermal co-optimization design for the Gallium nitride (GaN) monolithic microwave integrated circuit (MMIC) power amplifier (PA) is introduced in this paper. Due to the self-heating effect of the GaN high electron mobility transistor (HEMT), it is necessary to pay attention to the influence of thermal resistance change on circuit performance when designing a high-power RF PA. For this purpose, a three-dimensional finite element analysis model of GaN multi-gate HEMT is developed. The thermal resistance and junction temperature of the device under a RF dynamic current are extracted by heat transfer simulation and can be substituted into the temperature node of the transistor model for PA circuit simulation design. To verify the proposed method, a Class AB MMIC PA was designed and tested using a 0.15-μm GaN-on-SiC process. Through the application of the above methods, the designed PA performance is optimized and achieves the performance of over 60% power-added efficiency (PAE) and 38 dBm saturation power (Psat) within a compact area of 1.6 mm × 2.2 mm. It is demonstrated that the proposed method can effectively improve the consistency of simulation results and measurement results, which can be a valuable reference for high-power MMIC PA design. Full article

Metal–oxide–semiconductor field-effect transistors (MOSFETs) are critical in power electronic modules due to their high-power density and rapid switching capabilities. Therefore, effective thermal management is crucial for ensuring reliability and superior performance. This study used finite element analysis (FEA) to evaluate the electro-thermal behavior of MOSFETs with copper clip bonding, showing a significant improvement over aluminum wire bonding. The aluminum wire model reached a maximum temperature of 102.8 °C, while the copper clip reduced this to 74.6 °C. To further optimize the thermal performance, Latin Hypercube Sampling (LHS) generated diverse design points. The FEA results were used to select the Kriging regression model, chosen for its superior accuracy (MSE = 0.036, R² = 0.997, adjusted R² = 0.997). The Kriging model was integrated with a Genetic Algorithm (GA), further reducing the maximum temperature to 71.5 °C, a 4.20% improvement over the original copper clip design and a 43.8% reduction compared to aluminum wire bonding. This integration of Kriging and the GA to the MOSFET copper clip package led to a significant improvement in the heat dissipation and overall thermal performance of the MOSFET package, while also reducing the computational power requirements, providing a reliable and efficient solution for the optimization of MOSFET copper clip packages. Full article

The self-sensing technology of microactuators utilizes a smart material to concurrently actuate and sense in a closed-loop control system. This work aimed to develop a position feedback-control system of nickel electrothermal microactuators using a resistivity self-sensing technique. The system utilizes the change in heating/sensing elements’ resistance, due to the Joule heat, as the control parameter. Using this technique, the heating/sensing elements would concurrently sense and actuate in a closed loop control making the structures of microactuators simple. From a series of experiments, the proposed self-sensing feedback control system was successfully demonstrated. The tip’s displacement error was smaller than 3 µm out of the displacement span of 60 µm. In addition, the system was less sensitive to the abrupt temperature change in surroundings as it was able to displace the microactuator’s tip back to the desired position within 5 s, which was much faster than a feed-forward control system. Full article

Electrothermal piezoresistive resonant cantilever sensors have been fabricated with embedded actuating (heating resistor) and sensing (piezo resistors) parts, with the latter configured in a Wheatstone bridge circuit. Due to the close spacing between these two elements, a direct thermal parasitic effect on the resonant sensor during the actuating-sensing process leads to asymmetric amplitude and reversing phase spectral responses. Such a condition affects the precise determination of the cantilever’s resonant frequency, f₀. Moreover, in the context of phase-locked loop-based (PLL) resonance tracking, a reversing phase spectral response hinders the resonance locking due to its ambiguity. In this work, a replica of the baseline spectral was applied to remove the thermal parasitic effect on the resonance spectra of the cantilever sensor, and its capability was simulated through mathematical analysis. This replica spectral was subtracted from the parasitized spectral using a particular calculation, resulting in optimized spectral responses. An assessment using cigarette smoke particles performed a desired spectral shifting into symmetrical amplitude shapes and monotonic phase transitions, subsequently allowing for real-time PLL-based frequency tracking. Full article

In this paper, a new defective phononic crystal (PC) microbeam model in a thermal environment is developed with the application of modified couple stress theory (MCST). By using Hamilton’s principle, the wave equation and complete boundary conditions of a heated Bernoulli–Euler microbeam are obtained. The band structures of the perfect and defective heated PC microbeams are solved by employing the transfer matrix method and supercell technology. The accuracy of the new model is validated using the finite element model, and the parametric analysis is conducted to examine the influences of size and temperature effects, as well as defect segment length, on the band structures of current microbeams. The results indicate that the size effect induces microstructure hardening, while the increase in temperature has a softening impact, decreasing the band gap frequencies. The inclusion of defect cells leads to the localization of elastic waves. These findings have significant implications for the design of microdevices, including applications in micro-energy harvesters, energy absorbers, and micro-electro-mechanical systems (MEMS). Full article

In this study, we have fabricated a 368 nm LED with an epitaxial Indium Tin Oxide (ITO) contact layer. We analyze the thermal performance of the flip-chip LED with a symmetric electrode and metal reflective layer, applying ANSYS to build a coupled electro-thermal finite element model (FEM) of the temperature distribution in the multiple quantum wells (MQWs). We compare our system with the traditional Au-bump flip-chip LED and a flip-chip LED with a Distributed Bragg Reflector (DBR) layer. The simulation results have shown that the flip-chip LED with a metal reflective layer and symmetric electrode exhibits better heat dissipation performance, particularly at high input power. The influence of the insulating layer on the LED chip junction temperature is also examined. The simulation data establish an effect due to the thermal conductivity of the insulating layer in terms of heat dissipation, but this effect is negligible at an insulation layer thickness ≤1 µm. Full article