Electrothermal Research Articles

Identification Method of Transmission Line Parameters Considering Impact of Electro Thermal Coupling Effect

Abstract Studies for high voltage power networks generally ignore line resistance with the assumption of being far less than line reactance. However, this treatment could cause certain errors in analysing low-voltage distributed networks, causing the assumption to no longer be applicable. Such errors could be significant considering the impact of load carrying and ambient conditions, such as online resistance or temperature due to electro-thermal coupling (ETC). Then, it becomes an open question to accurately capture the system state of distribution networks due to changed line parameters. Integrating new style energy sources, such as renewable power generation, energy storage applications, and adjustable power load, will promote the deployment of measurement devices at distribution networks. With the assumption of sufficient accumulated data offered by online monitoring terminals, this study proposes a nonlinear regression method—Levenberg-Marquardt—to identify the parameters of the line. However, since it is difficult to access practical data, this study employs the electro-thermal coupling power flow (ETCPF) to simulate line operation and take the results as monitoring data for case studies. The identification results under various data volumes and error levels demonstrate the reliability and accuracy of the proposed approach.

Numerical Simulation and Modeling of Mechano–Electro–Thermal Behavior of Electrical Contact Using COMSOL Multiphysics

Electrical contacts are important circuit components with diverse industrial applications, and their failure can lead to multiple unwanted effects. Hence, the behavior of electrical contacts is a widely studied topic in the scientific literature based on various approaches, tools, and techniques. The present study proposes a new approach to numerical modeling and simulation based on the Holm contact theory, aiming to study the dependence between the electric potential and the temperature within an electrical contact. Structured in five sections, the research was conducted using COMSOL Multiphysics software and its solid-state mechanics, electric current, and heat transfer modules in order to highlight contact behavior from mechanical, electrical and thermal points of view: the von Mises stress, contact force, electric field amplitude, variation of the electrical potential along the current path, temperature gradient, and dependence of temperature along the contact elements edges were obtained by simulation, and are graphically represented. The results show that the temperature increase follows a parabolic curve, and that for values higher than 4 mV of voltage drop, the temperature of the contact increases to 79.25 degrees (and up to 123.81 degrees for 5 mV) over the ambient temperature, thus the integrity of insulation can be compromised. These values are close (10–12%) to the analytically calculated ones, and also in line with research assessed in the literature review.

Boosting the thermal stability of paralleled GaAs HBTs through temperature-dependent ballasting resistors: A proof-of-concept study

This paper explores the efficacy of base ballasting strategies in enhancing the electrothermal (ET) stability of paralleled InGaP/GaAs heterojunction bipolar transistors (HBTs) for radiofrequency (RF) applications. More specifically, technologically-feasible temperature-dependent base ballasting resistors are proposed as a solution to shift the collapse of current gain to higher power densities. A three-cell test device fabricated through a state-of-the-art process is considered as a simple case study. Extremely accurate DC and AC ET simulations are performed with SPICE to quantify the advantages of the proposed strategy with respect to traditional approaches.

Mixed-Transducer Micro-Origami for Efficient Motion and Decoupled Sensing.

This work introduces a mixed-transducer micro-origami to achieve efficient vibration, controllable motion, and decoupled sensing. Existing micro-origami systems tend to have only one type of transducer (actuator/sensor), which limits their versatility and functionality because any given transducer system has a narrow range of advantageous working conditions. However, it is possible to harness the benefit of different micro-transducer systems to enhance the performance of functional micro-origami. More specifically, this work introduces a micro-origami system that can integrate the advantages of three transducer systems: strained morph (SM) systems, polymer based electro-thermal (ET) systems, and thin-film lead zirconate titanate (PZT) systems. A versatile photolithography fabrication process is introduced to build this mixed-transducer micro-origami system, and their performance is investigated through experiments and simulation models. This work shows that mixed-transducer micro-origami can achieve power efficient vibration with high frequency, large vibration ranges, and little degradation; can produce decoupled folding motion with good controllability; and can accomplish simultaneous sensing and actuation to detect and interact with external environments and small-scale samples. The superior performance of mixed-transducer micro-origami systems makes them promising tools for micro-manipulation, micro-assembly, biomedical probes, self-sensing metamaterials, and more.

Circuit-Based Electrothermal Modeling of SiC Power Modules With Nonlinear Thermal Models

Silicon carbide (SiC) power devices have the potential to operate at high temperatures beyond the capabilities of silicon power devices. At increased temperatures, the temperature-dependent material properties of the SiC die and the package multilayer structure can influence the electrothermal (ET) device performance. In this article, a new step-back-correction technique implemented in a finite-difference-method-based thermal modeling tool is proposed to reduce the computational cost while maintaining a good accuracy of ET simulations for multichip power modules. The simulations take the temperature dependence of the thermal conductivity <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$k(T)$</tex-math></inline-formula> and both conduction and switching losses into account. The importance of considering <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$k(T)$</tex-math></inline-formula> for the accurate temperature prediction of SiC power devices is demonstrated for thermal impedance evaluations characterized by high-temperature swings, as well as for a 100-kHz boost converter with low device temperature amplitudes in the steady state. The proposed ET modeling is validated by COMSOL simulations and infrared camera measurements on an example of a custom-designed and custom-manufactured half-bridge SiC power module.

Analysis of Passive Intermodulation Distortion Caused by Asymmetric Electrical Contact

This article investigates the passive intermodulation (PIM) distortion induced by the asymmetric electrical contact. Based on the analytical model, it is found that the increased current path is the cause of the additional impedance, resulting in PIM distortion. To validate our theoretical analysis, different levels of asymmetric electrical contact are studied via simulation and experiments. The demonstrations not only confirm the validity of our theoretical findings, but also substantiate the simulations. To the best of our knowledge, this work is the first to identify the asymmetric electrical contact as a PIM source and discuss its underlying physical mechanisms of causing electro-thermal (ET) coupling PIM.

Investigating the Impact of Self-Heating Effects on some Thermal and Electrical Characteristics of Dielectric Pocket Gate-all-around (DPGAA) MOSFETs

The dielectric pocket gate-all-around (DPGAA) MOSFET is being considered the best suited candidate for ULSI electronic chips because of excellent electrostatic control over the channel. However, the phenomena of self-heating and hot carrier injection (HCI) severely affect the performance of the device, and make the behaviour of the DPGAA FET very unpredictable. In the present article, a comprehensive investigation under the influence of self-heating effects has been done for the variation in the lattice and carrier temperature against spacer length, ambient temperature, device length, and thermal contact resistance including ON and Off currents with gate bias voltage (VGS). In order to analyse the SHEs, the hydrodynamic (HD) and thermodynamic (TD) transport models have been used for three-dimensional (3D) electrothermal (ET) simulation. The Lucky (hot carrier injection) model has been used to study the HCI degradation in DPGAA MOSFET using Sentaurus 3D TCAD simulator.

Electro-Thermal Performance Boosting in Stacked Si Gate-all-Around Nanosheet FET With Engineered Source/Drain Contacts

In this article, we investigate the electro-thermal (ET) performance of stacked Si gate-all-around (GAA) nanosheet FET (NSHFET) by adopting the metal (M0) source/drain (S/D) engineered contacts such as M0-wrap around the Si S/D epitaxial regions and M0 filling through S/D trenched regions in addition to the conventional scheme where metal (M0) epi on the S/D. The device ET performance is enhanced by increasing the device on-state current (I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</sub> ) by more than 10% with better device lattice heat removal from the hot-spot location of the NSHFET. This results in decreased device self-heating by lowering lattice hot-spot temperature (T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L, max</sub> ) and device effective thermal resistance (R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th, eff</sub> ) by more than 11% compared to conventional M0-epi-based NSHFET design. The junction temperature difference between the nanosheet channels is also lowered, which decreases the inter-sheet threshold voltage (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> ) difference. The benchmarking study of the device designs reveals that M0-trench-based NSHFET gives the best performance from both electrical and thermal perspective for future sub-5-nm CMOS logic technologies.

Electro–Thermal–Mechanical Coupled Analysis on Two High-Current Composite Umbilical Cable Cross Sections

Abstract A new type of umbilical cable named “high-current composite umbilical cable” is composed of electronic cables, optical cables, steel tubes, and structural strengthening components. It can be regarded as a key piece of industrial equipment in subsea production systems that provide control functions, high electric current, and hydraulic remote transmission. When it is oriented at a power supply with a relatively high rated current, power transmission will produce a lot of heat. Then, the cross-sectional temperature increases, which affects the performances of its material and mechanical responses. Therefore, electro–thermal–mechanical coupled analysis is critical for the cross-sectional design of the high-current composite umbilical cable. Accordingly, a multi-physics coupled analysis was performed based on two typical umbilical cable cross sections. Finite element models were established and subjected to electro–thermal analysis to obtain a temperature distribution of the two sections at different current capacities. Based on results of temperature field analysis, the section models were subjected to thermo–mechanical analysis. The results of the two types of analyses are compared and differences are discussed, which illustrate the multi-physics coupled effect cannot be neglected. The armored layers will relatively reduce the heat dissipation performance, but compared with the umbilical cable model without the armored layers, the model with double-armored layers is less affected by temperature, so its capacity of resistance external pressure is relatively better. The proposed coupled analysis methodology provides a new guidance for the design of the high-current composite umbilical cables.

Double-objective optimization of electro-thermal (E-T) micro-actuator for fiber switch

In this paper, a novel optimization method, in which composed of the genetic algorithm, particle swarm optimization (GA–PSO) and improved gradient descent algorithm, are used to conduct a double-objective optimization for the U-shaped actuator. In the procedure of optimization, two objectives, i.e. force and displacement, and four main sizes are utilized. Before, the deep reactive-ion etch (DRIE) technology is applied to the fabrication of the U-shaped actuator. When different voltages are applied on the actuator, the displacement obtained from numerical calculation always shows a good agreement with that from experiment by edge detection algorithm. Similar phenomenon can be also seen when an external force supplied by the nanoindentation system FemtoTools in the experiment is loaded on the actuator. Based on the validated simulation model of the U-shaped actuator, the improved gradient descent method ensures its displacement very close to 50 µm (target displacement) while the GA–PSO algorithm is used to maximize the output force. In this procedure, the hybrid optimization method implemented by Matlab is incorporated into ANSYS simulation. Preliminary analysis shows that the displacement and force of the particles in each iteration concentrate together with the iteration growing. Fine convergence, whose velocity only depends on the number of particle in the algorithm, is also found in each optimization. Furthermore, the optimized actuators have homologous value of the size variables. At 15 V voltage, the displacement and largest output force of the U-shaped actuator are 2 mN and 50.1 µm, respectively. Finally, an actuator with 30% improvement of the output force is obtained when the displacement condition is meet. According to the optimization result and further parametric scanning simulation analysis, the design range and fabrication error of the sizes of the U-shaped actuator are obtained.

A repetitive high current pulse generator for high flux electrothermal plasma jets.

Power sources play an important role in the characteristics and the applications of the electrothermal (ET) plasma as an edge localized mode (ELM) heat flux simulator. A repetitive high current ET plasma source with the capability of working at a 10 Hz repetition rate and peak current 7.5 kA is presented in this paper. By controlling the sequence of discharge of ten pulse power modules, a repetitive high heat flux plasma jet can be generated. A two-stage capillary structure is presented, and its repetitive trigger driving circuit based on surface flashover ignition is designed to achieve reliable and repetitive discharge. The topology of the inductive and capacitive (LC) series resonant circuit is applied to the charging system of the pulsed power source. The charging current is limited to 500 A with a charging time of 3.5 ms, and the ratio of the charging voltage to the operating voltage is 1.85. A diode and a power resistor in series are used to suppress the negative overvoltage, which is helpful to increase the thyristors' operating reliability. Using the designed repetitive ET plasma source, the characteristics of the ET plasma jet are investigated by measuring the voltages and currents and by obtaining images of the discharges. Experimental results show that the repetitive ET plasma generator can be used as an appropriate way to simulate the ELM-like heat flux plasma.

Electro–Thermal 1D model of the SIS100 superconducting dipole magnet

The FAIR Project – a new international Facility for Antiproton and Ion Research is under construction in Darmstadt, Germany. The core machine at FAIR is the SIS100 synchrotron which utilises superconducting magnets in order to guide the heavy ion beam. The bending component of the magnetic field is generated by super-ferric window-frame dipole magnets symmetrically distributed over the six arc sections of the accelerator ring. The dipole coils are wound with a LTS low AC loss Nuclotron-type cable. Due to the very thick inter-turn insulation, the coil is characterized by a strong anisotropy of thermal conductivity which enables application of a 1D electro-thermal model. This work presents the latest version of the magnet model used for the simulation of magnet’s operating modes at the test facility (including quench). Since currently the series dipole magnets undergo acceptance tests at cryogenic conditions, the simulation results are compared to the available measurements.

Simulation study on MEMS based Electro Thermal Actuator for Robotic Application

Simulation study on MEMS based Electro Thermal Actuator for Robotic Application

A low voltage, flexible, graphene-based electrothermal heater for wearable electronics and localized heating applications

Recent years have seen a rapid increase in the level of sophistication in modern day devices which has given rise to the demand for better performance in all of their components, one of which is the heating element. Two excellent approaches to this need would be to improve the materials from which these Joule’s heating elements are made and the other to design improved heater geometries for best temperature distribution. In this paper, we discuss a high performance electrothermal heater prepared from laser reduced graphene oxide (LrGO) deposited on Polyethylene Terephthalate (PET) flexible Substrate. The surface morphology and structural properties of the prepared LrGO films were investigated by means of Scanning Electron Microcopy (SEM), X-Ray Diffraction (XRD) and Raman Spectroscopy (RS). Electrothermal (ET) responses of the fabricated electrothermal heaters to different driving DC voltages were studied by Infrared thermal Imagery. An electrothermal heater with a low Sheet resistance of ∼52 O/square was fabricated and it can attained a steady state temperature of up to 135 °C in only 10 s when a low voltage of 9 V was applied. A finite Element model (FEM) was prepared for this heater which agreed well with the experimental results. Power consumption for this heater is as low as 0.389 W/cm2, making it a suitable candidate for energy-saving applications such as wearable electronic.

TDR Prediction Method for PIM Distortion in Loose Contact Coaxial Connectors

This paper proposes a new method to comprehensively predict the passive intermodulation (PIM) distortion in loose contact coaxial connectors by the time-domain reflectometry (TDR) test. The proposed approach treats the insulating film current and the electrothermal (ET) coupling as PIM sources. An ET coupling model is introduced to analyze the generating process of the PIM caused by the ET coupling in the loose contact coaxial connectors. The simulation and measurement results show good agreement. The proposed method is a cost-effective approach for the evaluation of the PIM distortion, because it uses a common TDR method to replace professional PIM test instruments. The proposed method can also be extended to all the loose metallic contact cases.

Performance of Capillary Plasma Source With Combustible Materials

Application of an energetic material (EM) in a liquid or gaseous form to electrothermal (ET) plasma discharge systems can provide an energetic plasma jet that has desirable parameters for launching applications. In this energetic ET concept, the EM is basically injected into the plasma source that is operated in an ablation-free regime. The discharge and EM combustion processes have been simulated using the ETFlowCom code, which is an in-house developed energetic ET plasma model. In this article, the ETFlowCom code is used to predict the energetic plasma jet parameters such as temperature, pressure, heat flux, and exit velocity. Different computational case studies have been conducted using a variety of EM mixtures. The simulation results show that the generated energetic plasma jet has the density on the order of 10271/m3, kinetic pressure on the order of hundreds of MPa, and an exit velocity that can reach up to 6 km/s. These parameters are found to be functions of the EM type and the mixing ratio as well. The jet parameters show strong potential for launching applicability.

Recent Developments in Dual-Laser Digital Holography for Plasma-Facing Surface Characterization

A digital holography device is currently undergoing development at the Oak Ridge National Laboratory for the purpose of measuring surface topography, with the goal of deployment as a real-time plasma-facing component diagnostic for the study of materials that could be utilized in a nuclear fusion device. The holography system utilizes one or two lasers depending on the scale of surface features under measurement. Measurements of surface roughness were performed in a single-laser mode and compared with the data from profilometry, with a linear correlation of increased holographic measurement fidelity as surfaces became smoother. Characterization of the dual-laser operating mode has been performed via surface measurement of stainless steel targets with “stair-step” features in various sizes. Results demonstrated that surface features with known sizes as small as 25.4 μm could be resolved. Measurements were within ~55 μm or less deviation from the actual sizes, and measurement accuracy was improved as feature size was increased, corresponding to the effect of noise becoming less pronounced. A target exposed to plasma generated by an electrothermal (ET) arc source was analyzed with flatfield correction and averaging of sequential image frames to demonstrate the improved measurement quality in preparation for future use of holography on ET arc-exposed targets.

Electro Thermal Modelling of Electrical Discharge Machining of Be-Cu Alloy by Varying Fraction of Energy

Electro Thermal Modelling of Electrical Discharge Machining of Be-Cu Alloy by Varying Fraction of Energy

Electro Thermal Effects of Geometrically Modified MEMS-Based Micro Heater for Gas Sensing Applications

Micro heaters play a major role in gas sensing applications owing to their accuracy, selectivity and low power consumption. The proposed micro heater employs a window type polysilicon micro-hotplate structure, which is a square cell of side 500 μm, designed using COMSOL Multiphysics. It is highly imperative that an evenly distributed temperature is necessary over the broad area of the heater in order to improve its gas sensitivity and selectivity. In this paper, we have explained the design and analysis of a novel window-type micro heater made of polysilicon. The main aim of the work is to achieve temperature uniformity and low power consumption. By optimizing the geometry of the micro heater, we can obtain both temperature uniformity and low power consumption. This geometrical optimization also improves the sensitivity and response time of the sensor. To support them, we have carried out simulations using COMSOL Multiphysics. The proposed structure has obtained a uniform temperature of 1134.1 K and an average temperature of 1130.39 K. Such high and uniform temperatures finds applications in gas sensors. This work also analyzes the proper choice and placement of electrodes across the geometry of the heater.

Ultralow-voltage electrothermal MEMS based fiber-optic scanning probe for forward-viewing endoscopic OCT.

We report an ultralow-voltage, electrothermal (ET) micro-electro-mechanical system (MEMS) based probe for forward-viewing endoscopic optical coherence tomography (OCT) imaging. The fully assembled probe has a diameter of 5.5mm and a length of 55mm, including the imaging optics and a 40mm long fiber-optic cantilever attached on a micro-platform of the bimorph ET MEMS actuator. The ET MEMS actuator provides a sufficient mechanical actuation force as well as a large vertical displacement, achieving up to a 3mm optical scanning range with only a 3 VACp-p drive voltage with a 1.5 VDC offset. The imaging probe was integrated with a swept-source OCT system of a 100kHz A-scan rate, and its performance was successfully demonstrated with cross-sectional imaging of biological tissues ex vivo and in vivo at a speed up to 200 frames per second.