On-line Temperature Monitoring Research Articles

A high‐precision voltage reference with a curvature‐compensated bandgap for fluorescence detection

SummaryFluorescent optical fiber temperature sensors require accurate online temperature monitoring in hazardous environments with strong electromagnetic fields, high voltages, flammability, or explosiveness. This imposes stringent requirements on the temperature coefficient stability of the bandgap reference (BGR) circuit. To address these challenges, this paper proposes a high‐order curvature compensation bandgap reference (HCC_BGR) circuit fabricated using a 0.18‐μm bipolar‐CMOS‐DMOS (BCD) process. A traditional first‐order bandgap reference (TRA_BGR) circuit is also fabricated for comparison. Experimental results demonstrate that the proposed HCC_BGR circuit generates a stable 1.22‐V reference voltage with a low‐temperature coefficient of 5.56 ppm/°C from −20°C to 85°C. Compared to the TRA_BGR circuit, the HCC_BGR reduces the temperature coefficient by 3.07 times. Furthermore, the low‐dropout regulator (LDO) using the proposed HCC_BGR exhibits excellent line sensitivity of 1.52%/V from 3.4 to 5 V.

Optimization and test of a ring-ring typed atmospheric pressure plasma jet for optical fabrication

In recent years, the atmospheric pressure plasma jet (APPJ) has gained considerable attention in the field of optical fabrication because the chemical etching approach offers the advantage of avoiding mechanical damage to workpieces. This paper presents the development of an atmospheric pressure plasma machining system with a ring-ring typed APPJ, which exhibits several favorable characteristics. It has a relatively low processing temperature, no electrode corrosion, no plasma contamination, and a long discharge plume, etc. Optimization of the dimensional parameters and analysis of reactive gas flow rate are conducted through experimental investigations. Comparative experiments are carried out with the commonly used needle-ring typed APPJ, revealing significant improvements of the ring-ring typed APPJ, i.e., a fourfold increase in machining distance, a tenfold increase in machining efficiency, and a 58% enhancement in the stability of the material volumetric removal rate. Furthermore, on-line temperature monitoring of the footprint has been achieved due to the specific traits of the extended discharge plume. Fabrication experiments are conducted to demonstrate the significant correlation between the temperature and material removal rate, which shows the possibility of improving the accuracy of optical fabrication based on the ring-ring typed APPJ.

Analysis of the Effect of Copper Doping on the Optoelectronic Properties of Indium Oxide Thin Films and the Thermoelectric Properties of an In2O3/Pt Thermocouple

The detection and real-time monitoring of temperature parameters are important, and indium oxide-based thin film thermocouples can be integrated on the surface of heaters because they operate normally under harsh conditions and provide accurate online temperature monitoring. The higher stability and appropriate optical and electrical properties of In2O3 make it very suitable as an electrode material for thermocouple sensors. This work demonstrates that copper doping can alter the optical and electrical properties of In2O3 films and regulate the output performance of thermocouples. Copper-doped In2O3 thin films were prepared using the magnetron co-sputtering method. The doping concentration of Cu was controlled using direct current (DC) power. An In2O3/Pt thermocouple sensor was prepared, and the optoelectronic and thermocouple properties were adjusted by changing the copper doping content. The thickness valve of the thin film sample was 300 nm. The results of the X-ray diffraction suggested that the structure of the doped In2O3 thin films was cubic. The results of the energy-dispersive X-ray analysis revealed that Cu was doped into the In2O3 thin films. All deposited films were n-type semiconductor materials according to Hall effect testing. The 4.09 at% Cu-doped thin films possessed the highest resistivity (30.2 × 10−3 Ω·cm), a larger carrier concentration (3.72 × 1020 cm−3), and the lowest carrier mobility (0.56 cm2V−1s−1). The optical band gap decreased from 3.76 to 2.71 eV with an increase in the doping concentration, and the transmittance of the film significantly reduced. When the DC power was increased, the variation range of Seebeck coefficient for the In2O3/Pt thermocouple was 152.1–170.5 μV/°C, and the range of thermal output value was 91.4–102.4 mV.

Retracted: On-Line Temperature Monitoring System of Electrical Equipment Based on Passive Wireless Sensor

Retracted: On-Line Temperature Monitoring System of Electrical Equipment Based on Passive Wireless Sensor

A Junction Temperature Online Monitoring Method for IGBTs Based on Turn-off Delay Time

A Junction Temperature Online Monitoring Method for IGBTs Based on Turn-off Delay Time

Analysis of Electromagnetic Interference for Anti-Medal UHF RFID Temperature Tag in High Power Electronic Equipment

Being inches from the rapid development of new energy technology, the capacity of high-power power electronic equipment is increasing rapidly, and the requirements for its safe and reliable operation are also rising. As a result, the demand for online temperature monitoring of such equipment is becoming increasingly urgent. RFID temperature measurement technology can be used for real-time monitoring of the temperature of powered operation equipment. However, the operation of high-power electronic equipment generates strong electromagnetic interference, which can seriously affect the normal operation of RFID temperature measurement systems. For applications involving the internal temperature measurement of high-power power electronic equipment, this paper employs an RFID anti-metal temperature tag antenna with a short-circuit cutoff structure. This structure was tested in an excitation switchgear cabinet. During the low-power operation of the cabinet, the temperature tag functioned normally. By combining an RFID antenna model with an electromagnetic interference simulation model of the main circuit of the excitation switchgear cabinet, this paper establishes an electromagnetic interference simulation model for an RFID temperature tag. It analyzes how the tag’s antenna performance parameters change when subjected to interference. Through simulation, the failure mechanism of the RFID temperature tag during the high-power operation of the excitation switchgear cabinet is clarified. The analysis found that there are both conductive electromagnetic interference and radiated electromagnetic interference in the excitation switchgear cabinet, with the conductive electromagnetic interference having a more significant effect. Conductive electromagnetic interference can seriously impact the performance of RFID temperature tags in the excitation switchgear cabinet, significantly degrading their performance. In contrast, the effect of radiated electromagnetic interference on the tags is relatively small. Therefore, this paper employs anti-metal RFID temperature tags and simulates and analyzes their electromagnetic interference characteristics.

Numerical and experimental research on electromagnetic-thermal and leakage defects characteristics of the high voltage cable terminal

Thermal and insulation performance of the High Voltage Cable Terminal (HVCT) could effectively improve the reliability and economy of power energy transmission. In this paper, a numerical model of the electromagnetic heat flow field was proposed to analyze the heat transfer and temperature characteristics of HVCT under oil leakage defects. This model was the first validated using operation data from the actual equipment and the relative error was less than 1.51%. The effects of oil leakage fault on the global and local temperature distribution of the HVCT were then investigated under different load currents. In addition, the local temperature rise effect of different ambient temperatures on the HVCT oil leakage defect was also considered. Finally, combined with reference indicators such as oil level, temperature, and temperature gradient, a qualitative and quantitative evaluation of the oil leakage fault of HVCT was performed. The results showed that the temperature of the core, surface, and their maximum temperature gradient were linearly related to the ambient temperature. However, the temperature of the core at the oil leak exceeded the normal temperature by up to 7.2 °C with 1000A load current, and the temperature gradient change reaches 681.3 °C/m, which indicated that the convection heat dissipation effect of the oil-deficient part was poor, and the heat accumulates near the cable core. Therefore, the numerical model and analytical results presented in this paper provided an important method for online temperature monitoring and fault analysis of HVCTs.

Fluorescent sensing probe based on heterovalent doped Lu2W2.5Mo0.5O12:Er3+/Yb3+ phosphor for real-time chip temperature monitoring

The influence of Li+/Zn2+ heterovalent doping on the structural change and upconversion luminescence properties of Lu2W2.5Mo0.5O12:Er3+/Yb3+ phosphors was investigated in details. The gradual substitution of Li+/Zn2+ ions for Lu3+ ions result in the evolution from orthorhombic Lu2W2.5Mo0.5O12 to monoclinic (LiZn)2W2.5Mo0.5O12, which bring the structural distortion, the reduction of local symmetry and the crystallite growth. The green upconversion intensity of Er3+ ions at 536 nm and 550 nm were enhanced significantly by a factor of 8000 and 4000. The temperature sensing characteristics of a single (LiZn)2W2.5Mo0.5O12:Er3+/Yb3+ particle in all-fiber structure was explored and the unusual thermally-enhanced upconversion luminescence was observed, which is beneficial for achieving high-precision temperature measurement based on the fluorescence intensity ratio technology. The absolute temperature sensitivity reached a maximum of 0.0095 K−1 at 423 K and the temperature deviation was less than 0.6 K. The as-built all-fiber temperature sensor was successfully applied in the on-line monitoring of CPU temperature.

Parallel Contactless Transmission of Power and Rotor Temperature of Electrical Machines via Magnetically-Coupled Resonance and Capacitive Radio Frequency

Over-temperature of the rotor may cause a series of insulation deterioration of electrical machines. In severe cases, it can lead to insulation failure and even faults, such as broken rotor bars and end ring fracture. The temperature online monitoring can effectively avoid the aforementioned insulation failure; however, the conventional temperature measurement by embedded sensors is difficult to utilize due to the power and data transmission of sensors at the rotor side. This paper proposes a contactless strategy to supply power and send rotor temperature data between the stator and rotor sides of electrical machines. With the proposed method, contactless power transfer is realized by means of magnetically-coupled resonance, while the data signal is transferred by capacitive radio frequency (RF) technology. An experimental prototype was developed and installed on a 22-kW induction motor. The results show that the embedded sensors are contactless powered effectively. At the same time clear temperature data signal can be received on the stator side without filtering, and rotor temperature can be monitored in real-time accurately.

Prediction model of transformer top oil temperature based on data quality enhancement.

Top oil temperature (TOT) is an important parameter to evaluate the running state of a transformer. According to the variation trend of TOT, the internal thermal state of transformers can be predicted so as to arrange operation and maintenance reasonably and prevent the occurrence of accidents. However, due to the complex working environment in the field, there are often a large number of missing values in online monitoring data, which seriously affects the prediction of TOT. At the same time, it is affected by various factors such as load, ambient temperature, wind speed, and solar radiation, which cause the information of different time scales to be mixed in its monitoring data. Therefore, it is difficult to achieve the desired accuracy with a single model. In this article, a model for predicting TOT based on data quality enhancement is proposed. First, the Markov model is used to complete the online monitoring data containing missing values to obtain a complete and continuous time series. Then, using the ensemble empirical modal decomposition method, the time series of TOT is decomposed into multiple time series components to eliminate the interaction between different time scales of information, thus reducing the prediction difficulty. Finally, the sub-prediction model of the extreme learning machine is constructed, and the prediction results of all the sub-models are reconstructed to obtain the final prediction results of TOT. In order to verify the effectiveness of the model, the TOT of an operating transformer for the next two days is predicted in the article, and its mean absolute percentage error (MAPE) is 5.27% and its root mean square error (RMSE) is 2.46. Compared with the BP neural network model and the support vector machines (SVM) model, the MAPE is reduced by 69.56% and 61.92%, respectively, and the RMSE is reduced by 67.02% and 59.87%. The results of this study will provide important support for the fault diagnosis of the top oil temperature online monitoring system.

Online Monitoring Method of P-I-N Diode Temperature Based on Maximum Recovery Current

The P-i-N diode is as important as insulated gate bipolar translators (IGBTs) in power electronic devices, and its junction temperature is a significant indicator when evaluating the reliability of power electronics. Thus, an online junction temperature monitoring method with the maximum recovery current for P-i-N diodes is proposed in this paper. Firstly, the relationship among maximum recovery current, on-state current and junction temperature of diode has been deduced in theory. The linear correlation among the maximum recovery current, temperature, and on-state current have been illustrated. Secondly, a sampling circuit based on a current transformer has been designed. And then, the mathematical model of junction temperature online monitoring based on the maximum recovery current and sampling circuit has been obtained. Finally, the experimental platform based on the DSP TMS320F28335 has been developed. The experimental results verify the correctness of the relationship among maximum recovery current, on-state current and junction temperature of the diode, and high accuracy of the proposed online monitoring method in practice application, where the maximum temperature error and error percentage are 4.7℃ and 4.49%, respectively. In addition, the proposed method has advantages of simplicity, small size, low cost, convenient installation, and high linearity.

Evolution of thermal cracking, temperature distribution and deformation at mineral scale of Beishan granite during heating and cooling

Thermo-mechanical property of rock is of great importance for the long-term safety of the high-level radioactive waste (HLW) geological disposal engineering. Thermal cracking, temperature and meso-deformation on the mineral grain size scale of Beishan granite were investigated during heating (160 °C ∼ 200 °C) and cooling process using online temperature, deformation and acoustic emission monitoring system. During the heating process, the temperature difference in different mineral grain was evident that the highest temperature was observed in feldspar while lower temperature in quartz and mica, and the temperature difference reached 20%. Meanwhile the feldspar expanded as the quartz and mica being compressed during heating. During the temperature holding and cooling process, the temperature difference between different mineral grain reduced and stabilized around 5%. The thermal induced expansion was recovered gradually but irreversible deformation was left, which also demonstrated by the nuclear magnetic resonance measurement that size and volume of large pore in granite both decreased after heated. The thermal cracking emerged from 25 °C ∼ 35 °C, and the thermal cracking activity was active once temperature changed during heating and cooling stage, which was calm during temperature holding stage. In addition, the cracking process was investigated by numerical modelling. The ‘confining pressure effect’ was observed during heating process, and the mechanism of thermal strengthening effect was discussed. Overall, the mild high temperature caused by decay heat of HLW could play positive role for the long-term safety of the repository, since the tightness and strength could be both enhanced by mild high temperature.

Experimental research on online monitoring of high temperature and high speed airflow ablation of quartz ceramic thermal protection structure using guided wave

Thermal protection structure (TPS) plays a key role in protecting hypersonic flight vehicles from harsh service environment and has been widely used. As a common ablative thermal protection material, quartz ceramic TPS realizes thermal insulation by generating ablation during the reentry phases. The structural state of quartz ceramic TPS therefore is of great importance to the service performance and safety of hypersonic flight vehicles, and shows an urgent need for structural health monitoring (SHM). However, the monitoring of real ablation of quartz ceramic structure is barely considered in the current study, let alone online monitoring under harsh service environment, which brings a great challenge to the implementation of reliable ablation monitoring. Aiming at online ablation monitoring of quartz ceramic structure, this paper performs experimental research by taking advantage of guided wave (GW)-based monitoring method. An ablation experiment and monitoring system is built to generate real ablation under high temperature and high speed airflow and perform GW monitoring. The maximal temperature of the system can reach about 2100 °C. The feasibility of ablation monitoring is verified by analyzing ablation-induced influence on GW signals. Gaussian mixture model (GMM) is adopted to combine with GW method to suppress the high temperature variation caused by uncertainty influence on GW signals during the ablation process, so that reliable monitoring of ablation can be realized. Experimental results show that online monitoring of ablation propagation of quartz ceramic structure under high temperature variation is achieved, which can be further used for ablation quantification evaluation.

Investigation of the Influence of Temperature on Stress Waves at the Turn-Off Moment in IGBT

Condition monitoring (CM) technology plays an important role in ensuring the reliable operation of power semiconductor devices. Power semiconductor devices can generate stress waves when turned on and off, and the stress waves released by the device can be detected by the acoustic emission (AE) sensor. AE detection technology has the characteristics of both nondestructive and real-time, and is expected to be applied to the CM of power semiconductor devices in the future. However, temperature and electromagnetic fields can both affect the output characteristics of the AE sensor, which is not conducive to the application of AE detection technology. In addition, it is not clear how temperature affects the stress waves generated by power semiconductor devices. In this article, a novel stress wave extraction method for power semiconductor devices is proposed, and the influence of temperature on the stress wave generated by insulated gate bipolar transistor (IGBT) at the turn-off moment is explored. Besides, a signal characteristic of the stress waves associated with the junction temperature of the device is extracted as the temperature-sensitive acoustic parameter, which will lay the foundation for the future research of new methods for online monitoring of junction temperature.

Application of Passive Wireless Temperature Online Monitoring System Based on Internet of Things Technology in Substation

With the improvement of the automation level of the power system, the number of operation and maintenance personnel continues to decrease, but the use of switchgear is quite large. Since the switchgear is a metal armoured device with a closed shell, the hot spots inside the switchgear cannot be detected in time during operation. Effective temperature measurement and the safety of equipment cannot be effectively guaranteed. In order to avoid the aging caused by the excessive current load of the switch cabinet, poor contact of cable joints and contacts, or long-term operation, which will cause heat in the place, forming a vicious circle and eventually leading to insulation breakdown or fire accidents, Establish a wireless temperature measurement system for switch cabinets to monitor the temperature of the parts where the equipment is prone to overheat, and issue an alarm message when the temperature rises abnormally. At present, the manual inspection of switch cabinets in the power supply system cannot effectively and timely detect fire hazards, so the problem of online monitoring of switch cabinet temperature is particularly prominent. Using the Internet of Things sensing technology and communication technology, build an Internet of Things-based electrical connection point temperature online monitoring system, the all-weather real-time monitoring of the connection parts of high-voltage electrical equipment can effectively reduce the equipment failure rate, promote the condition maintenance of power equipment, and ensure the safe and economical operation of the power system.

On-Line Temperature Monitoring System of Electrical Equipment Based on Passive Wireless Sensor

In order to solve the temperature measurement problem of fully enclosed equipment for power equipment operation inspection, the authors propose an online temperature monitoring system for electrical equipment based on passive wireless sensors. Aiming at the disadvantages of traditional temperature monitoring methods, the system adopts radio frequency technology. The scheme mainly expounds the key technologies and switchgear implementation in the monitoring system research and discusses the feasibility of the system scheme through experiments. Monitor all important components at different times, and establish a temperature monitoring network to complete monitoring and management. According to the test results, in the case of overheating, the temperature can rise to more than 75°C, and the temperature difference measured wirelessly is 0.5°C, which is sufficient to indicate the health of the change. Electrical equipment, the accuracy, and real-time performance of temperature monitoring are guaranteed.

Morphological and heat transfer characteristics of biomass briquette during steam gasification process

The morphological evolution and heat transfer characteristics of biomass briquette greatly affect the directional regulation of target products during steam gasification process. In this work, a visual gasifier with an on-line temperature monitoring system was developed to investigate the coupling relationship between the morphological change and temperature distribution of biomass briquette. The gasification behaviors of biomass briquette at different temperatures and steam concentrations were comprehensively examined and compared. The shrinkage rate and heating rate of biomass briquette both reached the maximum at 1–2 min. The morphological evolution of biomass briquette in the heating process was shrinking particle mode, then changed to the shrinking core mode when the biomass temperature kept relatively stable. The high-quality syngas with a high H2/CO ratio of 3.07 at 50 vol% steam concentration and 700 °C was obtained, which were idealized to synthesize other fuels/chemicals.

Research on Operation Management Technology of Cable Joints of Ring Network Cabinet Based on Temperature Sensors

In this paper, aiming at the operation and maintenance of the internal cable joints of the ring main unit, the research on the operation and management technology of the ring main unit cable joints based on temperature sensors is carried out. Starting from the principle of temperature sensing technology for cable joints, an online temperature monitoring system for the cable joints of the ring network cabinet is developed during the operating cycle. Comprehensive consideration of factors such as seasons, ambient temperature and humidity, line load current, etc., to evaluate the operating status of the cable joint temperature data as the main basis. A simple and adjustable bracket suitable for the fixed installation of the non-contact temperature sensor of the ring main unit has been developed. A method of managing the cable joints of the ring main unit during the operating cycle is proposed to realize the effective evaluation of the cable joint status. It can greatly improve the accuracy of condition monitoring, and improve the efficiency and level of operation and maintenance.

Assessment of Graphical Methods for Determination of the Limiting Current Density in Complex Electrodialysis-Feed Solutions.

Electrodialysis (ED) is a promising technology suitable for nutrient recovery from a wide variety of liquid waste streams. For optimal operating conditions, the limiting current density (LCD) has to be determined separately for each treated feed and ED equipment. LCD is most frequently assessed in the NaCl solutions. In this paper, five graphical methods available in literature were reviewed for LCD determination in a series of five feed solutions with different levels of complexity in ion and matrix composition. Wastewater from microbial fermentation was included among the feed solutions, containing charged and uncharged particles. The experiments, running in the batch ED with an online conductivity, temperature, and pH monitoring, were conducted to obtain data for the comparison of various LCD determination methods. The results revealed complements and divergences between the applied LCD methods with increasing feed concentrations and composition complexity. The Cowan and Brown method had the most consistent results for all of the feed solutions. Online conductivity monitoring was linearly correlated with the decreasing ion concentration in the feed solution and corresponding LCD. Therefore, the results obtained in this study can be applied as a base for the automatized dynamic control of the operating current density–voltage in the batch ED. Conductivity alone should not be used for the ED control since LCD depends on the ion exchange membranes, feed flow, temperature and concentration, ionic species, their concentration ratios, and uncharged particles of the feed solution.

Gear life and failure mode versus meshing stress in polyacetal/carbon black nanocomposite gears

The life and failure mode of polyoxymethylene (POM) and POM/carbon black (CB) spur gears were assessed under different torque levels. A new experimental approach was performed to obtain the transition torque of polymer based gears by employing the online temperature monitoring and step-loading. The gear life versus contact stress was experimentally investigated and a life prediction model was proposed. Dynamic mechanical thermal analysis (DMTA) assessment was employed to determine the viscoelastic behavior of gear materials. The POM/CB gears exhibited improved load capacity, heat performance and service life. The POM/CB gear material demonstrated higher storage modulus and lower hysteresis heating as compared to pure POM gear material. The addition of CB nanoparticles switched the failure mode from fracture to tooth thinning and tooth tip plastic deformation at lower levels of torque (6, 8 and 10 Nm). At higher torque levels (12 and 14 Nm), the POM/CB gears showed 52% and 65.2% increases in the service life, compared to the pure POM gears, and finally failed under thermal material flowing.