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The acquisition of information on heat inflow is essential to the control of thermal displays and the rendering of thermal sensations. This paper addresses a method of estimating the amount of heat inflow without using a heat flow sensor and demonstrates sensorless heat inflow control using a Peltier device, which is often employed as a thermal device in thermal displays. Moreover, this paper introduces a method of identifying the thermal contact resistance of the device needed for the proposed observer. The observer estimates heat inflow by using information on electrical currents and temperatures. By using the observer instead of a heat flow sensor, which generally has a larger thermal capacity than a temperature sensor, an improvement in the response of a thermal device is expected. The applicability of the proposal is tested by experiments. [ABSTRACT FROM PUBLISHER]

This paper addresses the problem of thermal energy control in shopping centers through the application of model predictive control (MPC) strategies. In particular, this paper uses an existing shopping center as pilot case, which is characterized by a large common multifloor space, which, in turn, gives rise to a significant vertical thermal stratification. This paper explores the importance of MPC parameters to energy efficiency and comfort levels. In addition, it addresses some notable extensions, from economic optimization, which paves the way to real-time pricing techniques, to integration with renewables, to robustness enforcement through Kalman filters, to hybrid control with switching signals mixed with continuous signals. [ABSTRACT FROM PUBLISHER]

Li-ion batteries have been widely used in electric vehicles, and battery internal state estimation plays an important role in the battery management system. However, it is technically challenging, in particular, for the estimation of the battery internal temperature and state-of-charge (SOC), which are two key state variables affecting the battery performance. In this paper, a novel method is proposed for realtime simultaneous estimation of these two internal states, thus leading to a significantly improved battery model for realtime SOC estimation. To achieve this, a simplified battery thermoelectric model is first built, which couples a thermal submodel and an electrical submodel. The interactions between the battery thermal and electrical behaviors are captured, thus offering a comprehensive description of the battery thermal and electrical behavior. To achieve more accurate internal state estimations, the model is trained by the simulation error minimization method, and model parameters are optimized by a hybrid optimization method combining a metaheuristic algorithm and the least-square approach. Further, time-varying model parameters under different heat dissipation conditions are considered, and a joint extended Kalman filter is used to simultaneously estimate both the battery internal states and time-varying model parameters in realtime. Experimental results based on the testing data of LiFePO$_4$ batteries confirm the efficacy of the proposed method. [ABSTRACT FROM PUBLISHER]

The aim of this paper is to demonstrate the impact of ambient air humidity on the efficiency of heat sink operation. It was observed that increased air humidity enabled higher power dissipation in a transistor used as a test device, without increasing its junction temperature. The presented simulation results are showing a correlation between air humidity and an estimated heat flux value. The paper also contains a mathematical analysis of humidity impact on the convective heat transfer coefficient. The natural convection phenomena are visualized in different infrared spectral ranges. A multispectral approach revealed that this convective air flow is best viewed in the MWIR spectral range. [ABSTRACT FROM AUTHOR]

Energy management of heating, ventilation, and cooling (HVAC) has become a primary concern for residential and commercial buildings. In order to save energy without compromising the comfort of occupants, various techniques have been explored to sense the real-time occupancy/vacancy of HVAC zones. Among all these approaches, wireless-camera-based sensing stands out for its potential application in surveillance and security in addition to energy management. However, limited lifetime and detection accuracy have prevented pervasiveness of wireless-camera-based occupancy detection. This paper presents a novel wireless device platform and prototype development that incorporates an infrared (IR) camera with an optical (OP) camera to provide collaborative intelligence at low power and enhanced accuracy. Compared to the single-sensor baseline design, the proposed fusion-based OP/IR design demonstrates $5\times$ miss rate improvement, $5\times$ reduction in false positive rate, and $3\times$ lifetime extension for battery usage with respect to a single-sensor-based design. Compared to a programmed thermostat and schedule-based HVAC control, the design saves a maximum of $26\%$ of HVAC energy. [ABSTRACT FROM AUTHOR]

Lithium (Li)-ion battery cells suffer from significant performance degradation at subzero temperatures. This paper presents a predictive control-based technique that exploits the increased internal resistance of Li-ion cells at subzero temperatures to increase the cell’s temperature until the desired power can be delivered. Specifically, the magnitude of a sequence of bidirectional currents is optimized such as to minimize total energy discharged. The magnitude of current is determined by solving an optimization problem that satisfies the battery manufacturer’s voltage and current constraints. Drawing bidirectional currents necessitates that a temporary energy reservoir for energy shuttling, such as an ultracapacitor or another battery, be available. When compared with the case when no penalty on energy withdrawn is imposed, simulations indicate that reductions of up to 20% in energy dispensed as heat in the battery as well as in the size of external storage elements can be achieved at the expense of longer warm-up operation time. [ABSTRACT FROM PUBLISHER]

Synchronous reluctance motors (SynRMs) are gaining in popularity in industrial drives due to their permanent magnet-free, competitive performance, and robust features. This paper studies the power losses in a 90-kW converter-fed SynRM drive by a calorimetric method in comparison of the traditional input–output method. After the converter and the motor were measured simultaneously in separate chambers, the converter was installed inside the large-size chamber next to the motor and the total drive system losses were obtained using one chamber. The uncertainty of both measurement methods is analyzed and discussed. [ABSTRACT FROM AUTHOR]

This paper presents a computationally efficient thermo-fluid model to predict the temperature and flow distribution in an oil-cooled electrical machine with a segmented stator. The Yokeless and Segmented Armature axial flux machine was used as a case study in which a numerical model was set up and validated to within 6% of experimental results. The model was adapted to predict the temperature distribution of the segmented stator of a machine, identifying the hotspot temperatures and their location. Changes to the flow geometry on the stator temperature distribution were investigated. It was shown how by carefully controlling the flow distribution in the stator, the temperature distribution is improved and the hot spot temperature is reduced by 13 K. This benefits the machine by doubling the insulation lifetime or by increasing the current density by approximately 7%. [ABSTRACT FROM AUTHOR]

Thermal properties are a key issue in many applications associated with electrical machines. Because of its special configuration, an axial-flux electrical machine usually uses self-ventilation. However, this cooling method has a significant impact degrading the machine operating characteristics, and thus, an independent cooling system is desirable. The focus of this paper is on the steady-state thermal modeling and laboratory testing of an axial-flux permanent-magnet (AFPM) electrical machine intended for a traction application. The proposed hybrid cooling arrangement consists of a frame cooling circuit with a water flow inside, a set of copper bars inserted in the teeth, and a segment of potting material around the end windings. Computational fluid dynamics and finite-element analysis are applied for the preliminary design. This paper provides experimental verification of the simulation results on a 100-kW AFPM electrical machine. [ABSTRACT FROM PUBLISHER]

Permanent-magnet synchronous machines (PMSMs) are well suited for high-speed (HS) applications due to their high efficiency, power density, and dynamic response capability. The heat extraction area decreases as the speed increases, making thermal effects more dominant at high speed. The temperature-dependent properties of permanent magnets necessitate high-detail thermal models. This paper presents a 2-D analytical model for a HS PMSM magnet. The diffusion equation is solved where three of the PM boundaries experience convection heat flow; as the case is in radial flux machines. The heat generated on the rotor surface due to eddy currents is also taken into account. The model is verified using numerical techniques and shows good correlation (within 1.5%). The model is also validated through experiments performed on a 4 kW, 30 000 r/min PMSM. [ABSTRACT FROM PUBLISHER]

The objective of this paper is to analyze the dynamics of heat flow in thermal structures working under constant temperature operation. This analysis is made using the tools of sliding mode controllers. The theory is developed considering that the thermal system can be described using diffusive representation. The experimental corroboration has been made with a prototype of a wind sensor for Mars atmosphere being controlled by a thermal sigma–delta modulator. This sensor structure allows to analyze the time-varying case experimentally since changes in wind conditions imply changes in the corresponding thermal models. The diffusive symbols of the experimental structures have been obtained from open-loop measurements in which pseudorandom binary sequences of heat are injected in the sensor. With the proposed approach, it is possible to predict heat flux transient waveforms in systems described by any arbitrary number of poles. This allows for the first time the analysis of lumped and distributed systems without any limitation on the number of poles describing it. [ABSTRACT FROM PUBLISHER]

Condition monitoring (CM), fault diagnosis (FD), and nondestructive testing (NDT) are currently considered crucial means to increase the reliability and availability of wind turbines. Many research works have focused on CM and FD for different components of wind turbine. Gear is typically used in a wind turbine. There is insufficient space to locate the sensors for long-term monitoring of fatigue state of gear, thus, offline inspection using NDT in both manufacturing and maintenance processes are critically important. This paper proposes an inductive thermography method for gear inspection. The ability to track the properties variation in gear such as electrical conductivity, magnetic permeability, and thermal conductivity has promising potential for the evaluation of material state undertaken by contact fatigue. Conventional thermography characterization methods are built based on single physical field analysis such as heat conduction or in-plane eddy current field. This study develops a physics-based multidimensional spatial-transient-stage tensor model to describe the thermo optical flow pattern for evaluating the contact fatigue damage. A helical gear with different cycles of contact fatigue tests was investigated and the proposed method was verified. It indicates that the proposed methods are effective tool for gear inspection and fatigue evaluation, which is important for early warning and condition-based maintenance. [ABSTRACT FROM PUBLISHER]

Many types of steel are treated with heat to increase toughness and resistance to wear. Induction heating seems to be appropriate and provides several advantages in comparison with conventional techniques. In this paper, control techniques for full-bridge resonant inverter aimed to induction heating are evaluated comprehensively, through simulation and experiment, and compared to each other in terms of heating rate, efficiency and input power factor, using one metal sample hardened to 1 mm in depth up to 600 °C, with a 400 W power supply. These techniques are implemented digitally in way to allow a high-resolution power control. The simulation results obtained are satisfactory, and agree with those of the experiments. Furthermore, the study shows the control strategy based on frequency may not be sufficient, but should be associated with other control techniques in order to address appropriately the hardening process, bearing in mind processing time, efficiency and input power factor. The strategy with the input dc voltage and the pulse density modulation controls appear to suit the surface metal treating for large temperature variation, and enable the heating process to perform well when compared to the other techniques based on phase-shift and pulse width modulation duty cycle control. [ABSTRACT FROM PUBLISHER]

Saving energy using dimmable electronic ballasts for fluorescent lamps is becoming a popular solution. Under dimming operation, lamp lifetime can be drastically reduced, if electrode auxiliary heating is not correctly set. In this paper, electrode degradation of a dimmed fluorescent lamp is investigated. Electrode degradation is evaluated by a simple electrical measurement, giving indirectly a measure of barium losses from the electrode surface. This paper shows how the experimental setup has been implemented. Then it shows experimental results obtained on a test run, and finally discusses setup limits. It is shown that strong electrode degradation caused by excessive heating conditions is identifiable within 500 h of operation using this technique. [ABSTRACT FROM AUTHOR]

This paper introduces a novel single-phase buck–boost noninverting variable-frequency ac–ac converter that offers higher efficiency compared to the competitors. This converter utilizes a lower number of semiconductors. A simple and flexible switching strategy is also proposed, which generates the desired output waveform avoiding unnecessary high-frequency switching operation of semiconductor devices. A high reliable operation due to the elimination of the input source shoot-through risk, an inherent commutation capability that mitigates the voltage spikes across the semiconductors, a lower semiconductors rating requirement, an improved input current waveform quality, and a smaller required input filter inductor are the main advantages of the proposed converter. Thus, the proposed converter can be successfully applied to many industrial applications such as medium-frequency transformer isolation for traction and wind turbine converters, ac–dc high-voltage conversion based on Cockcroft–Walton circuit and induction heating systems. The theoretical achievements and claims are all confirmed through extensive experimental tests on a 200-W laboratory setup. [ABSTRACT FROM AUTHOR]

In this paper, a GaN light-emitting diode (LED) with sapphire structure and a thin-film LED without sapphire structure are characterized in the photoelectrothermal modeling framework for comparison. Starting from the analysis and modeling of internal quantum efficiency as a function of current and temperature of blue LED, this work develops the thin-film LED device model and derives its optical power and the heat dissipation coefficient. The device parameters of the two LED devices with different structural designs are then compared. Practical optical power measurements are compared with theoretical predictions based on the two types of fabricated devices. It is shown that the thin-film LED device has much lower thermal resistance and optical power loss. [ABSTRACT FROM PUBLISHER]

In this paper, the different aging mechanisms taking place in photovoltaic modules are discussed, and the cause–effect links, which exist among such mechanisms, are evidenced. It is also shown that a closed-loop link exists between aging and mismatching since aging (which is nonuniform by its nature) causes mismatching among cells, whereas mismatching, in turn, mainly due to its thermal effects, leads to nonuniform aging. [ABSTRACT FROM PUBLISHER]

Integrated power electronics modules (IPEMs) represent an innovative typology of power electronics assemblies able to guarantee several advantages such as increasing of power density, better management of the thermal flows, and a significant reduction of the package sizes. Their characteristics make them suitable for applications like motor drives or power conditioning. IPEM usage in emerging fields like hybrid automotive traction and electric generation from renewable energy sources is continuously increasing. In this paper, we describe the implementation of a devised flow to generate the layer-based electrothermal PSpice model of an IPEM and the simulation flow of the model. The proposed modeling methodology allows reducing an electrothermal multidomain problem to an electrical single one. The general PSpice-like nature of the proposed model makes it suitable for a wide range of simulation frameworks where the integration of heterogeneous multiphysics models could be a difficult task. The outlining of both electrical and thermal PSpice layers is discussed, and the implementation into the final model, by the assistance of custom electronic-design-automation flow, is presented. Moreover, we describe the validation procedure of the proposed approach, and the results are compared with the ones obtained by a commercial finite-element-based package used as a benchmark. Two simulation approaches related to specific conversion systems, and related issues, are presented and discussed. [ABSTRACT FROM PUBLISHER]

This paper presents a new estimation method for the equivalent thermal conductivities of the compact slot windings formed from round conductors. The estimation accuracy of thermal conductivities is essential for peak temperature prediction to avoid overheating failures in the high power density electromagnetic devices. The compact windings with orderly wound conductors perform better on heat dissipation and take smaller slot space than the random wound types. In recent years, the winding technology has made great improvement, and the compactness of conductors is significantly elevated. After observing the cross section of the windings, the randomness of the wire's layout is greatly reduced and a certain regularity is shown. The proposed estimation method takes the geometric characteristics of the internal structure into account to improve the estimation accuracy of the traditional methods, which use the proportion of each material only. Considering the layout of conductors is not completely regular, the impact of the dislocation between conductors is explored. Then, the conclusion is used to modify the analytical result. The experimental test result shows that the proposed theoretical method is easy to apply and meanwhile performs satisfactory in terms of high accuracy and low computation. [ABSTRACT FROM AUTHOR]

In this paper, an automotive onboard heater equalizer is proposed to heat low-temperature batteries and balance cell voltages without the requirement of external power supplies. The proposed integrated topology only needs one MOSFET for one cell, resulting in a compact size and low cost, which can be easily applied to electric vehicles. In particular, all MOSFETs are driven by one high-frequency pulsewidth modulation signal and the batteries can be heated internally by the ohmic and electrochemical losses and warmed externally by the switching and conduction losses of MOSFETs, leading to a high heating speed and efficiency. Further, a thermoelectric model for the internal and external combined heating is developed to provide guidance for the optimized design of the proposed heater. In addition, the proposed topology can realize passive balancing of series-connected battery strings at a higher switching frequency and a smaller duty cycle. Experimental results show that the proposed heater, by generating a periodic ramped discharge current with an rms value of 1.8 C at a switching frequency of 150 kHz, can heat the lithium-ion batteries from −20 to 0 °C within 1.9 min, consuming about 5% of the cell energy. [ABSTRACT FROM AUTHOR]

In this paper, a novel direct load control (DLC) planning based on providing free energy credits to residential end-users for their heating, ventilation, and air conditioning load during demand response (DR) events is proposed. The obtained credit can then be used by the end-users during relatively higher price periods free-of-cost to enable them lowering their energy procurement costs. Furthermore, the resulting reduction in the total household energy consumption considerably decreases the critical load demands in power systems, which is of vital importance for load-serving entities in maintaining the balance between supply and demand during peak load periods. In this regard, the aforementioned energy credits-based incentive mechanism is proposed for end-users enrolled in the DLC-based DR program, as a new contribution to the existing literature, testing it in a stochastic day-ahead planning context. [ABSTRACT FROM AUTHOR]

The control design for many practical applications involves a need to specifically treat parameter uncertainty and disturbances. As shown in previous work of the authors, techniques from interval analysis can be used for this purpose in an efficient way. The two options that have been considered so far are the use of interval analysis in either a framework for model predictive control or in a framework for variable-structure sliding mode design. In the latter case, interval techniques can be used efficiently for a robust stabilization of continuous-time dynamic systems despite bounded uncertainty. To avoid unnecessarily conservative control strategies, it has to be shown in real time that the closed-loop control system is guaranteed to remain asymptotically stable despite bounded error variables. This online stability proof is performed on the basis of suitable candidates for Lyapunov functions, whereas functionalities for interval analysis are provided by C++ software libraries. Required partial derivatives, for transformations of state equations into suitable canonical forms and for the estimation of a finite number of time derivatives of the controlled variables, are efficiently computed by algorithmic differentiation. This paper presents an overview of interval-based variable-structure control approaches for the thermal behavior of solid oxide fuel cells. These approaches consist of trajectory tracking during nonstationary heating phases and disturbance compensation at high-temperature operating points. Finally, they rigorously account for state and actuator constraints. [ABSTRACT FROM PUBLISHER]

Continuous monitoring of temperature distribution in lithium-ion (Li-ion) batteries is critical in preventing rapid degradation, mismatch in cell capacity, and potentially thermal runaway. A model based on virtual thermal sensor (VTS) for automotive grade Li-ion batteries is presented in this paper. This model, using a small number of physical sensors, is able to estimate temperature distribution throughout the battery in real time. First, the thermal model of the battery is developed and the characteristic parameters of the battery are tuned using the prediction error minimization method. Then, the tuned model is combined with a Kalman filter to estimate the temperature distribution of the battery under unknown initial values and model uncertainty. The proposed model-based VTS has been experimentally validated on an automotive grade 70-Ah lithium iron phosphate (\LiFePO4) battery. [ABSTRACT FROM PUBLISHER]

In the smelting process of fused magnesium furnaces (FMFs), frequent changes in the raw material granule size and impurity constituent will cause the arc resistance between the lower end of the electrode and the surface of the molten pool to vary, and thus, the smelting currents fluctuate. Consequently, abnormal conditions, which can arise if the setpoints of electrode currents are not properly adjusted on time, will causethe performance to deteriorate or even the overall operation to stall. Through analysis of the characteristics of different operating conditions, this paper presents a data-driven abnormal condition identification and self-healing control system. The proposed system extracts the identification rules according to the current tracking error, as well as the rate and duration of the current fluctuations, and identifies the abnormal conditions based on rule-based reasoning. The self-healing control is developed using case-based reasoning to correct the current setpoints based on the identification results. The outputs of the control loop track the corrected setpoints, thereby forcing the process to recover from the abnormal conditions. The proposed method and the developed control system have been applied to a real FMF, and substantial improvement is achieved with many benefits provided to the factory. The implementation results show that occurrence of abnormal conditions has been reduced by more than 50%, and the product quality has been increased by more than 2%. [ABSTRACT FROM PUBLISHER]

Permanent-magnet synchronous linear motors (PMSLMs) are more and more frequently used as all-electric direct-drive actuators in those applications where a force needs to be developed along a fixed direction. In this paper, an accurate 3-D thermal model of a PMSLM is derived through a lumped-parameter network approach which exploits all the symmetries in the actuator structure to maximize the spatial density of nodes. Numerically efficient techniques are then proposed to solve the thermal network analytically. Some experimental validations are finally presented based on the thermal testing of a laboratory prototype. [ABSTRACT FROM PUBLISHER]

The output power of thermoelectric generation systems (TEGSs) is significantly susceptible to the dynamically varying temperature profile of the heat sources, owing to the electrical mismatch of the interconnected thermoelectric modules (TEMs) constituting a TEGS. This paper proposes a new control concept to tackle such mismatch power losses by adaptively removing the severely underheated TEMs from the TEGS, as well as reviving them if their thermal condition becomes suitable for generating operation again. The proposed control method is realized by LabVIEW; particularly, the cosimulation between the LabVIEW program and a TEGS model based on MultiSim SPICE is used to interact with the real-time sensor feedback and the performance predictions of various TEGS configurations in an online manner and a hierarchical structure. Output characteristics validate the effectiveness of the proposed control method, where significant improvement on the power track is successfully demonstrated by comparisons with the conventional maximum-power point tracking. [ABSTRACT FROM PUBLISHER]

In this paper, we present an electrothermal actuator with two degrees of freedom that can achieve independent in-plane and out-of-plane motions. The device is fabricated with the MetalMUMPs, which offers silicon nitride, polysilicon, and nickel as the major structural materials. The electrothermal actuator achieves large movement. The in-plane tip displacement is 82 \mu\m at 0.039 W. The out-of-plane swing of the tip is 18 \mu\m as the applied voltage varies from 0 to 90 V (0 to 0.36 W) and vice versa. A versatile microelectromechanical systems gripper that is capable of 2-D manipulation can be constructed with two such actuators, each of which serves as the gripper arm. [ABSTRACT FROM PUBLISHER]

The air gap of tubular linear motors moves linearly, causing heat transfer states of the motor to alternate repeatedly. Thus, the heat transfer coefficients of the mover inner surface and the stator outer surface vary constantly. In this paper, the combination model of the thermal circuit and temperature field is established to calculate the transient temperature rise of a tubular linear motor with short and movable primary. The equivalent thermal circuit model of the moving air gap and the temperature field models of the primary (also named as mover) and secondary (also named as stator) are established. The thermal boundary conditions and the correlations among them are analyzed. By this method, the complicated variation and distribution of the heat transfer coefficients are gained. Moreover, the transient temperature rise of the motor is calculated. This method takes advantage of the flexibility of the thermal circuit method and the accuracy of the temperature field method. The calculated and tested results of the prototype are compared and analyzed. [ABSTRACT FROM PUBLISHER]

An accurate measurement of power or heat losses of high-efficiency electrical devices is difficult with input and output powers. In the calorimetric method, these losses are measured directly. In this paper, a functional heat loss measurement concept with adequate data processing methods is suggested for heat losses up to 2 kW. Such a heat loss range can be applied to present-day power electronic converters with the rated power of up to 110 kW and motors up to 37 kW. The measurement system does not require a complex mechanical structure or a large footprint area on the measurement site. The concept is scalable to different sizes. New features to the balance type calorimeter data processing are introduced. These include a mass flow correction, a technique to detect the thermal equilibrium, and a method to correct measured heat losses to improve the measurement repeatability and reduce the measurement uncertainty. The measurement uncertainty of the proposed calorimetric concept is 0.4%. Laboratory measurements are carried out both for a commercial frequency converter and an electric motor. These are measured at the same time with two calorimeters. The losses of these devices are measured both by the input-output and calorimetric methods. [ABSTRACT FROM PUBLISHER]

In this paper, a control strategy for reduced acoustic noise and sensorless operation of a switched reluctance (SR) motor is proposed for heating, ventilation, and air conditioning (HVAC) application, where the magnitude of the dc-bus voltage is controlled as a function of speed and the motor is operated in a single-pulse mode for all speed range. The dc-bus voltage is controlled by incorporating a dc chopper between the three-phase line rectifier and a split dc-link capacitor-type four-switch power converter. Such controller reduces the acoustic noise, provides more accurate position estimation for sensorless operation, and improves the life expectancy of the motor. The algorithm is first simulated through MATLAB/SIMULINK and then tested on a four-phase 8/6-pole 4-kW SR motor. The test results of achieved acoustic noise and improved sensorless operation are presented. Through the proposed method, the acoustic noise is reduced by almost 15 dB compared to the conventional scheme at low-speed regime. The proposed method is intended to drive a fan type of load in HVAC applications, where the dynamic performance requirement is not a stringent criterion. [ABSTRACT FROM AUTHOR]

This paper presents a real-time estimation method for the temperature distribution of cylindrical batteries under boundary air cooling. A space-/time-separation-based analytical model is developed using Karhunen–Loève decomposition and Galerkin's method. The model parameters can be identified and optimized using data-based approaches. The developed analytical model demonstrates the robustness to variation of thermal parameters. However, the change of boundary cooling will significantly degrade the performance of the developed analytical model. For the known boundary cooling, the compensation model for cooling effects can be derived to improve the modeling performance. For the unknown boundary cooling in real practice, a dual-extended Kalman filter can be used to simultaneously estimate coupled parameters and convection coefficient in the compensation model. The proposed method can achieve satisfactory performance in the battery duty-cycle experiments. [ABSTRACT FROM PUBLISHER]

This paper presents a new single-stage utility frequency ac–high-frequency ac resonant power converter for high-frequency induction heating applications. The newly proposed ac–ac converter features a boost converter and a full-bridge resonant inverter integrated circuit with a source voltage sensorless control system. The experimental results of a 3.0 kW–40 kHz prototype are demonstrated on zero-voltage soft switching and steady-state characteristics, then, the validity of the proposed ac–ac converter is revealed from a practical viewpoint. [ABSTRACT FROM PUBLISHER]

This paper presents a wearable thermoelectric power generator using body heat to supply power to low-power human diagnosis devices (especially sensor nodes), thus a new type of thermoelectric generator (TEG) integrated into clothes that combines the TEG technology with fashion sports equipment: wrist guards, leg guards, headbands, and sports tights is also proposed. As a result of this integration, any difference in the appearance of a wearable thermoelectric power generator is not significant when compared with the original clothing. Through the design and experiment of wearable TEG, here several key factors that affect the human body heat energy: ambient temperatures, skin temperatures, wind, human activity, and the connection mode of the TEG module are analyzed. The experimental results show that the power of a single TEG module can reach about 250 μW at 5 °C, while the power of the multiple TEG modules including only four TEG can be close to 1 mW after the integration of sports tight. Finally, the flexible supercapacitor is utilized as the energy storage element, which shows excellent storage character and good effect of conjunction with clothing. [ABSTRACT FROM AUTHOR]

This paper presents a new driving method for a sulfur plasma lamp in low-power applications. The newly developed magnetron power supply (MPS) is a series-resonance type with a full-bridge topology controlled by the phase shift to track the beam current of the magnetron. To drive the sulfur plasma lamp optimally, the MPS should: 1) provide peak power above a discharge condition to excite the sulfur plasma lamp, and 2) allow average power control of the light dimmer while satisfying condition 1. The newly developed driving method uses the burst mode, which enables both peak and average power controls to satisfy these conditions. Furthermore, a magnetizing current offset balancer is developed; it guarantees zero-voltage switching of all field-effect transistors, although the MPS operates in the burst mode. Thus, the proposed method provides easy lighting and relighting under optimized conditions with high efficiency. The power of the MPS delivered by the proposed method reached 1.6 kW with variable average power of 200 ∼ 400 W by adjusting burst-on time proportionally. Experimental results proved the feasibility of the proposed driving method. [ABSTRACT FROM PUBLISHER]

The ac-side terminal voltages of parallel-connected converters are different if the line reactive drops of the individual converters are different. This could result either from differences in per-phase inductances or from differences in the line currents of the converters. In such cases, the modulating signals are different for the converters. Hence, the common-mode (CM) voltages for the converters, injected by conventional space vector pulsewidth modulation (CSVPWM) to increase dc-bus utilization, are different. Consequently, significant low-frequency zero-sequence circulating currents result. This paper proposes a new modulation method for parallel-connected converters with unequal terminal voltages. This method does not cause low-frequency zero-sequence circulating currents and is comparable with CSVPWM in terms of dc-bus utilization and device power loss. Experimental results are presented at a power level of 150 kVA from a circulating-power test setup, where the differences in converter terminal voltages are quite significant. [ABSTRACT FROM PUBLISHER]

In large power transformers, the presence of stray currents in the structural elements near the high current bushings can be considerable, and this leads to hot spots. This work presents a practical analysis of overheating in the bolts that join the tank and the cover, which are near the high current bushings of the transformer. Overheating results are analyzed and discussed for the case of a 420-MVA transformer. The hot spots in the flange–bolt regions are discovered by thermal maps that are obtained during power transformer operation as a part of a preventive maintenance program. In this paper, we use copper links to ensure the connection of both the cover and tank body, significantly reducing the overheating of the flange–bolt region. The copper link solution has been validated by measurements. We have used calibrated measurement instruments in all the experiments. Moreover, a 3-D finite-element analysis of the geometry of interest has been used to verify the copper link solution. [ABSTRACT FROM PUBLISHER]

The prediction of the thermal behavior of an electrical machine in the design process basically depends on the used boundary conditions such as the convective heat transfer coefficient. Due to the complicated shape of the end windings, the heat transfer coefficient has to be identified empirically by using thermopiles as heat flux sensors placed at certain positions on the end windings, because an analytical derivation is not feasible. This paper presents the results of the measured values of the heat transfer on the end windings of an electrical machine. The gained coefficients are compared to the results obtained by numerical simulations using commercial software for computational fluid dynamics. The simulation results are discussed according to the validity of the gained heat transfer coefficient. The configuration of the simulation has been tested on a cylindrical shape in a cross-flow. [ABSTRACT FROM PUBLISHER]

In the field of urban transport, supercapacitors are submitted to relative high charge and discharge currents and therefore significant heat generation occurs. It has been shown that the temperature has a great influence on the aging mechanism of supercapacitors and, by consequence, on the lifetime of the system. That is why the thermal management becomes a key issue in the study of the performance of a supercapacitors stack. In this paper, thermal modeling of a supercapacitors stack is presented and a matrix representation of the model is deduced. Validation of the model has been carried out using measurement on a developed test bench. Sensitivity of the model according to input uncertainties is finally discussed. [ABSTRACT FROM PUBLISHER]

This paper analyzes the impact of a nonuniform temperature distribution inside insulated-gate bipolar transistor (IGBT) power modules on the reliability of railway power inverters. The interaction between the chosen cooling system (a heat-pipe-based one) and the power module is considered in detail. After showing the experimental setup and thermal conditions, thermal mapping inside the power module is carried out. Then, the effects of the thermal cycles on the constitutive elements of the IGBT module are pointed out when considering a real mission profile. Finally, the experimental results from the thermal cycles are linked to problems on the power-inverter reliability. Concretely, the thermal-grease distribution is analyzed on failed IGBT modules coming from the field, and the solder-delamination pattern observed in IGBT modules after endurance cycling tests is also reported. [ABSTRACT FROM AUTHOR]

A novel advanced cooling technique for electric machines, which is termed the direct winding heat exchanger (DWHX), is presented. This technique uses a microfeature enhanced heat exchanger that is inserted between the stator winding bundles. The DWHX is innovative, with the capability of generating large heat transfer coefficients, i.e., \sim\!\! 30\,000 \ \W/m^2\cdot \K, due to the small channel size and microfeatures. This cooling technique significantly reduces the thermal resistance from the stator windings to the ambient. The cooling technique is explained in detail, and an initial DWHX technology demonstrator electric machine is presented. The technology demonstrator is shown to be capable of steady current densities in excess of 24.7 \A/mm^2 and transient current densities in excess of 40 \A/mm^2 for class F insulation. [ABSTRACT FROM PUBLISHER]

With increased turbogenerator capacity and electromagnetic load, overheating of the complex end parts has become one of the main problems affecting safe and stable turbogenerator operation. In this research, a flow network was built representing the structural and ventilation characteristics of a 330-MW turbogenerator. The fan inlet velocity and pressures (boundary conditions) of each end-region outlet were obtained by the flow network method. The 3-D transient electromagnetic field in the turbogenerator end was calculated, and the eddy current losses (heat sources) of the end parts were obtained by the finite-element method. To study the surface heat-transfer coefficient distribution on the stator-end winding surface, fluid and thermal mathematical and geometric models of the whole turbogenerator end region were given. Using the finite-volume method, the surface heat-transfer coefficient distribution on the complex 3-D stator-end winding surface, fluid-flow distribution, and temperature distribution of the end parts were investigated under rated-load conditions. The calculated temperature results match well with measured data. This research can provide a theoretical basis for calculating the heat-transfer coefficients of the outer surfaces of large turbogenerators. [ABSTRACT FROM PUBLISHER]

Electro-hydrostatic actuator (EHA) is a type of actuator in more electric aircraft, which is a highly integrated local volume control hydraulic actuator, and can improve the reliability and efficiency. However, the motor heating can hardly be taken out due to the feature of the local closed hydrostatic system, especially under heavy load. In order to solve the problem, direct load sensitive EHA is an effective way to reduce heat, but the dynamic performance is inevitably sacrificed. To achieve the targets of both low heat generation and high dynamic response, a novel active load sensitive EHA (ALS) is proposed in this article. The key characteristic of ALS is that a special pressure following valve (PFV) is added between the load sensitive pressure point and the actuator of the swash plate in the pump. Furthermore, the PFV is actively controlled to adjust the load sensitive pressure. Based on this concept, detailed analysis and design of the system are presented. Following, the load sensitivity is controlled based on the fuzzy algorithm and the main loop is controlled by traditional proportional−integral differential. Finally, compared with the results of simulation and experiments, ALS can effectively reduce motor heating and maintain high dynamic performance, simultaneously. [ABSTRACT FROM AUTHOR]

An alternative way of induction heating of nonmagnetic cylindrical billets is modeled. The billet rotates in static magnetic field generated by permanent magnets. The mathematical model of the process consisting of two second-order partial differential equations describing the distributions of magnetic and temperature fields is solved numerically in the quasi-coupled formulation. The computations are carried out by a fully adaptive higher order finite-element method that is implemented in own codes Agros2D and library Hermes. The most important results are verified experimentally on a prototype device built in our laboratory. [ABSTRACT FROM PUBLISHER]

In this article, we present a new microwave system with the tunable ability of the heating region and heating effect. The heating region is changed by choosing different antennas above different heating region, which leads to larger heating range. And this system can be utilized in precise temperature control in ammonia synthesis phase. The frequency-space domain modulation technology is ingeniously suggested in our heating system. The different antennas above different heating region is then selected by changing the input working frequency. Based on the frequency-space domain modulation, we further add time domain modulation to increase the tunability of heating effect at different heating regions. By adjusting the frequency distribution of the input microwave source in time domain, where we named as time-frequency-space domain synthesis modulation method, the tunable heating region and effect is finally achieved. A simple microwave system is fabricated, and different heating effects are measured. The proposed heating method and system has benefits as following, simple structure, low cost, uniform heating, and controllable heating effect, which results in great improvement in microwave heating. [ABSTRACT FROM AUTHOR]

A soft robot with locomotive abilities controlled by body deformations is modeled, analyzed, and then constructed in this study. The robot is composed of a thin steel shell, four sensors, and four shape memory alloy (SMA) springs. Due to the force exerted by the SMAs, the thin steel shell deforms and causes the robot to roll and move forward continuously. The study is conducted in four tiers. Initially, after producing a model of the soft robot, the constraint conditions of rolling actions from deformations are analyzed. Then, the relationship between the deformation and the heating time of SMAs is studied. A dynamic analysis on the rolling motion is presented based on the deformation of SMAs and the change in the robot's center of gravity. A dynamic simulation is also conducted to test the feasibility of the theory. The third tier consists of designing a closed-loop controller based on feedback data from the four deformable sensors, a feature that has never been applied to soft robots in previous studies. Finally, a prototype of the soft robot is built, and an experiment is conducted and compared to prove the validity of the theory. [ABSTRACT FROM AUTHOR]

The technique to consider the anisotropic thermal conductivity and thermal contact resistances, as well as convection heat transfer in the air gap in the 3-D thermal modeling of electrical machines, is elaborated in detail and incorporated in the finite-element (FE) package developed with the FE program generator (FEPG) for thermal modeling of the flux-switching permanent-magnet (FSPM) machine. A dissymmetric model to simulate the convection heat transfer in the air gap with different stator and rotor poles is proposed. Moreover, a lumped parameter (LP) thermal model of this machine is also established to calculate the temperatures of the main machine components for comparative study purpose. The calculation results with different methods are verified with experiments. The conclusion highlights the importance of considering thermal contact resistance between windings and the stator core. The proposed model can reduce the total number of mesh comparing with traditional FE thermal model and eliminate complicated establishment of the thermal network and calculation of thermal resistances comparing with LP method. [ABSTRACT FROM PUBLISHER]

The functionality and consumption of a Radio Frequency IDentification Integrated Circuit (RFID IC) supplied by inductive power transfer has been noninvasively analyzed. This has been done by means of an InfraRed Lock-In Thermography (IR-LIT) system and frequency modulating the RFID IC powering scheme by biasing the external powering coil considering several amplitude modulation waveforms. This generates thermal harmonics at the beating frequency in all IC blocks, enabling their detection as heat sources by IR-LIT. The main aspects addressed in this investigation have been the following: the suitability study of the proposed modulation strategies, the characterization of the coupling between coils and its effects on the RFID blocks, the RFID IC functional analysis, and the dependence of the local energy consumption on the total power delivered to the die. In addition, it has been determined that the RFID IC presents a dysfunction due to the deactivation of some blocks during operation. Results suggest that this unexpected behavior is due to a desynchronization between some of the RFID blocks. Consequently, this stops the internal control signal, deactivates some specific RFID blocks, and ceases the back-telemetry block operation. [ABSTRACT FROM PUBLISHER]

An adaptive reconfiguration controller is proposed to improve the power performance of thermoelectric module (TEM) arrays when the heat source temperature profile is not uniform and/or a portion of the TEMs in the system is degraded. Distributed control algorithms are also implemented by using wireless sensor networks (WSNs), where remotely deployed temperature and voltage sensors as well as latching relays can be organized as a whole to intelligently identify and execute the optimal interconnection of TEM strings. A reconfigurable TEM array with a WSN controller and a maximum power point tracking load is presented, and experimental results demonstrate that a significant amount of power can be recovered through the proposed reconfiguration. [ABSTRACT FROM AUTHOR]

An optimization of the thermal behavior of a high-power salient-pole electrical machine is presented. Temperatures are calculated with the lumped method, which provides the thermal trends with relatively low computational cost. This model is used to define an aggregated objective function of our nonlinear thermal optimization problem by combining the mean solid temperature with the maximum temperature criteria. The 13 design variables correspond to the main volumetric flow rates in the electrical machine, which are bounded and subjected to a nonlinear constraint, assuming a fixed geometry. Two MATLAB optimization algorithms were tested: the Active-set (FMINCON solver) and the genetic algorithm (GA). Due to the strong nonlinearities of the model and the resulting nonconvex optimization problem, the GA is likely to give better results. Minimizing the mean solid temperature was demonstrated to be more important than the maximum temperature criterion. A strategic flow configuration is found to send fresh air to the second half of the cooling circuit, where air usually arrives heated. This optimal configuration provides better cooling than its current modeled configuration. This methodology should be of interest during the development phase. [ABSTRACT FROM PUBLISHER]