Pub Date : 2024-06-01DOI: 10.23919/CJEE.2024.000059
Ali Zarghani;Mohammad Farahzadi;Aghil Ghaheri;Karim Abbaszadeh
Heat and thermal problems are major obstacles to achieving high power density in compact permanent magnet (PM) topologies. Consequently, a comprehensive, accurate, and rapid temperature rise estimation method is required for novel electric machines to ensure safe and reliable operations. A unique three-dimensional (3D) lumped parameter thermal network (LPTN) is presented for accurate thermal modeling of a newly developed outer-rotor hybrid-PM flux switching generator (OR-HPMFSG) for direct-drive applications. First, the losses of the OR-HPMFSG are calculated using 3D finite element analysis (FEA). Subsequently, all machine components considering the thermal contact resistance, anisotropic thermal conductivity of materials, and various heat flow paths are comprehensively modeled based on the thermal resistances. In the proposed 3-D LPTN, internal nodes are considered to predict the average temperature as well as the hot spots of all active and passive components. Experimental measurements are performed on a prototype OR-HPMFSG to validate the efficiency of the 3-D LPTN. A comparison of the results at various operating points between the developed 3-D LPTN, experimental test, and FEA indicates that the 3-D LPTN quickly approximates the hotspot and mean temperature of all components under both transient and steady states with high accuracy.
{"title":"Accurate 3D Thermal Network Development for Direct-Drive Outer-Rotor Hybrid-PM Flux-Switching Generator","authors":"Ali Zarghani;Mohammad Farahzadi;Aghil Ghaheri;Karim Abbaszadeh","doi":"10.23919/CJEE.2024.000059","DOIUrl":"https://doi.org/10.23919/CJEE.2024.000059","url":null,"abstract":"Heat and thermal problems are major obstacles to achieving high power density in compact permanent magnet (PM) topologies. Consequently, a comprehensive, accurate, and rapid temperature rise estimation method is required for novel electric machines to ensure safe and reliable operations. A unique three-dimensional (3D) lumped parameter thermal network (LPTN) is presented for accurate thermal modeling of a newly developed outer-rotor hybrid-PM flux switching generator (OR-HPMFSG) for direct-drive applications. First, the losses of the OR-HPMFSG are calculated using 3D finite element analysis (FEA). Subsequently, all machine components considering the thermal contact resistance, anisotropic thermal conductivity of materials, and various heat flow paths are comprehensively modeled based on the thermal resistances. In the proposed 3-D LPTN, internal nodes are considered to predict the average temperature as well as the hot spots of all active and passive components. Experimental measurements are performed on a prototype OR-HPMFSG to validate the efficiency of the 3-D LPTN. A comparison of the results at various operating points between the developed 3-D LPTN, experimental test, and FEA indicates that the 3-D LPTN quickly approximates the hotspot and mean temperature of all components under both transient and steady states with high accuracy.","PeriodicalId":36428,"journal":{"name":"Chinese Journal of Electrical Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10586892","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141543840","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Renewable energy has become important for electricity generation because of the high air pollution associated with conventional fossil-based energy systems. Conventional fossil-based power plants are gradually transitioning by incorporating renewable energy sources, such as photovoltaic (PV) cells. In a PV system, an inverter converts DC power from solar panels to AC power required to serve common electrical loads. A conventional H-bridge inverter topology has several disadvantages, such as the voltage being not sinusoidal, switching the DC voltage and high common-mode voltage. The common-mode voltage can cause a large leaked capacitive current, which can result in undesirable operation in solar power applications. A common solution to this problem is the addition of a large filter to the input or output of an inverter. An inherent sinusoidal voltage source inverter based on a modified Cuk converter as its basic cell, which simultaneously generates a sinusoidal output voltage and a lower common-mode voltage, is proposed. The proposed topology does not require additional input or output filters. Analytical expressions are derived to confirm the operation of the proposed topology. Simulation results confirm the mathematical analysis. A laboratory-scale experiment is performed to verify the proposed inverter.
由于传统的化石能源系统会造成严重的空气污染，因此可再生能源在发电方面变得非常重要。传统的化石能源发电厂正在逐步转型，采用可再生能源，如光伏（PV）电池。在光伏系统中，逆变器将太阳能电池板发出的直流电转换为普通电力负载所需的交流电。传统的 H 桥逆变器拓扑结构有几个缺点，如电压不是正弦波、直流电压开关和共模电压过高。共模电压会产生较大的泄漏电容电流，从而导致太阳能发电应用中的不良运行。解决这一问题的常见方法是在逆变器的输入或输出端增加一个大型滤波器。本文提出了一种以改进型 Cuk 转换器为基本单元的固有正弦电压源逆变器，它能同时产生正弦输出电压和较低的共模电压。所提出的拓扑结构不需要额外的输入或输出滤波器。分析表达式的推导证实了拟议拓扑结构的运行。仿真结果证实了数学分析。为验证所提出的逆变器，还进行了实验室规模的实验。
{"title":"Inherently Sinusoidal Single-Phase Voltage Source Inverter Based on Modified Cuk Cell","authors":"Misbahul Munir;Wisyahyadi;Arwindra Rizqiawan;Jihad Furqani","doi":"10.23919/CJEE.2024.000051","DOIUrl":"https://doi.org/10.23919/CJEE.2024.000051","url":null,"abstract":"Renewable energy has become important for electricity generation because of the high air pollution associated with conventional fossil-based energy systems. Conventional fossil-based power plants are gradually transitioning by incorporating renewable energy sources, such as photovoltaic (PV) cells. In a PV system, an inverter converts DC power from solar panels to AC power required to serve common electrical loads. A conventional H-bridge inverter topology has several disadvantages, such as the voltage being not sinusoidal, switching the DC voltage and high common-mode voltage. The common-mode voltage can cause a large leaked capacitive current, which can result in undesirable operation in solar power applications. A common solution to this problem is the addition of a large filter to the input or output of an inverter. An inherent sinusoidal voltage source inverter based on a modified Cuk converter as its basic cell, which simultaneously generates a sinusoidal output voltage and a lower common-mode voltage, is proposed. The proposed topology does not require additional input or output filters. Analytical expressions are derived to confirm the operation of the proposed topology. Simulation results confirm the mathematical analysis. A laboratory-scale experiment is performed to verify the proposed inverter.","PeriodicalId":36428,"journal":{"name":"Chinese Journal of Electrical Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10490168","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140345495","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-01DOI: 10.23919/CJEE.2023.000044
Zongying Li;Shuaibing Li;Yongqiang Kang;Zheng Li;Hongwei Li
With the growing demand for precise voltage adjustment and reactive regulation, the frequent operation of on-load tap changers (OLTCs) in oil-immersed systems has led to increased erosion of switch contacts by arcs during the switching process. This erosion causes significant wear on the contacts, thereby reducing their lifespan. Therefore, the present study aims to investigate the behavior and mechanism of arc erosion on contact surfaces in oil-immersed OLTCs. To achieve this, a self-designed friction and wear test device for OLTC contacts was utilized to conduct experiments at various sliding speeds and contact pressures. Additionally, finite element analysis was employed to validate the experimental results regarding the influence of sliding speed on arc energy. The surface morphology of the contacts was observed using an optical microscope. The findings revealed that as the sliding speed increased, the arc energy, arc initiation rate, and contact resistance initially exhibited an upward trend, then decreased, and eventually increased again. The minimum values were observed at a sliding speed of 90 mm/s. Moreover, the arc energy, arc initiation rate, and contact resistance decreased gradually as the contact pressure increased. After reaching a contact pressure of 1.5 N, the variation in the arc energy stabilized. At lower contact pressures, arc erosion dominated the wear on the contact surface. However, at higher contact pressures, the wear transitioned from predominantly arc erosion to a combination of mechanical wear and arc erosion. In summary, experimental and analytical investigations provided insights into the effects of sliding speed and contact pressure on the behavior of arc erosion, contact resistance, and surface damage of OLTC contacts in oil-immersed systems.
随着对精确电压调节和无功调节的需求日益增长，油浸式系统中的有载分接开关（OLTC）频繁运行，导致开关触头在切换过程中受到电弧的侵蚀日益严重。这种侵蚀会导致触头严重磨损，从而缩短其使用寿命。因此，本研究旨在调查油浸式有载分接开关中电弧对触点表面侵蚀的行为和机理。为此，我们利用自行设计的有载分接开关触头摩擦和磨损测试装置，在各种滑动速度和接触压力下进行了实验。此外，还利用有限元分析验证了滑动速度对电弧能量影响的实验结果。使用光学显微镜观察了触头的表面形态。研究结果表明，随着滑动速度的增加，电弧能、起弧率和接触电阻最初呈上升趋势，然后下降，最后再次上升。在滑动速度为 90 mm/s 时观察到最小值。此外，电弧能、起弧率和接触电阻随着接触压力的增加而逐渐减小。接触压力达到 1.5 N 后，电弧能量的变化趋于稳定。在较低的接触压力下，电弧侵蚀主导着接触表面的磨损。然而，在较高的接触压力下，磨损从主要的电弧侵蚀过渡到机械磨损和电弧侵蚀的结合。总之，实验和分析研究深入揭示了滑动速度和接触压力对油浸系统中 OLTC 触头的电弧侵蚀、接触电阻和表面损坏行为的影响。
{"title":"Erosion Characteristics of Oil-Immersed On-Load Tap Changer Contacts Under Varying Contact Speeds and Pressures","authors":"Zongying Li;Shuaibing Li;Yongqiang Kang;Zheng Li;Hongwei Li","doi":"10.23919/CJEE.2023.000044","DOIUrl":"https://doi.org/10.23919/CJEE.2023.000044","url":null,"abstract":"With the growing demand for precise voltage adjustment and reactive regulation, the frequent operation of on-load tap changers (OLTCs) in oil-immersed systems has led to increased erosion of switch contacts by arcs during the switching process. This erosion causes significant wear on the contacts, thereby reducing their lifespan. Therefore, the present study aims to investigate the behavior and mechanism of arc erosion on contact surfaces in oil-immersed OLTCs. To achieve this, a self-designed friction and wear test device for OLTC contacts was utilized to conduct experiments at various sliding speeds and contact pressures. Additionally, finite element analysis was employed to validate the experimental results regarding the influence of sliding speed on arc energy. The surface morphology of the contacts was observed using an optical microscope. The findings revealed that as the sliding speed increased, the arc energy, arc initiation rate, and contact resistance initially exhibited an upward trend, then decreased, and eventually increased again. The minimum values were observed at a sliding speed of 90 mm/s. Moreover, the arc energy, arc initiation rate, and contact resistance decreased gradually as the contact pressure increased. After reaching a contact pressure of 1.5 N, the variation in the arc energy stabilized. At lower contact pressures, arc erosion dominated the wear on the contact surface. However, at higher contact pressures, the wear transitioned from predominantly arc erosion to a combination of mechanical wear and arc erosion. In summary, experimental and analytical investigations provided insights into the effects of sliding speed and contact pressure on the behavior of arc erosion, contact resistance, and surface damage of OLTC contacts in oil-immersed systems.","PeriodicalId":36428,"journal":{"name":"Chinese Journal of Electrical Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10490172","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140345460","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-01DOI: 10.23919/CJEE.2024.000055
The rapid development of clean and renewable energy technologies represented by wind and solar energy, as well as the continuous growth of load demand, have put forward higher requirements for the safe operation of the power equipment. The performance of power equipment based on traditional dielectric materials is often limited by various defects generated during molding, transportation, assembly, and operation, which cannot meet the reliability requirements of power systems in the new situation. Nondestructive detection is an essential technical method in industrial development, which can detect and evaluate the defect and damage status of in-service equipment, key components, and materials without damaging the object.
{"title":"Editorial for the Special Issue on Emerging Technology and Advanced Application of Nondestructive Detection for Power Equipment","authors":"","doi":"10.23919/CJEE.2024.000055","DOIUrl":"https://doi.org/10.23919/CJEE.2024.000055","url":null,"abstract":"The rapid development of clean and renewable energy technologies represented by wind and solar energy, as well as the continuous growth of load demand, have put forward higher requirements for the safe operation of the power equipment. The performance of power equipment based on traditional dielectric materials is often limited by various defects generated during molding, transportation, assembly, and operation, which cannot meet the reliability requirements of power systems in the new situation. Nondestructive detection is an essential technical method in industrial development, which can detect and evaluate the defect and damage status of in-service equipment, key components, and materials without damaging the object.","PeriodicalId":36428,"journal":{"name":"Chinese Journal of Electrical Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10490187","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140345497","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-01DOI: 10.23919/CJEE.2024.000049
Rani S;Jayapragash R
Switched reluctance motors (SRMs) are becoming increasingly popular in the automotive sector owing to their robust design. Moreover, SRMs are preferred particularly for EV applications owing to their fault tolerance, magnet-free structure, and high power/torque density. The main concerns of SRM compared to other machines include torque ripple and vibration. The primary cause of vibration is the radial force created by the SRM. A geometry-based modification of the SRM to reduce the radial force without significantly changing the average torque produced is proposed. The primary goal is to design a 4-phase, 8/6 SRM with a lower radial force. Two possible geometrical alterations are proposed: one with square windows and the other with circular holes on the rotor core. The windows are sized and positioned to avoid flux saturation. General criteria are developed for the optimal window size and placement. Finite element analysis (FEA) modelling of the SRM is used to validate its performance. The FEA results are compared with the performance parameters obtained using the analytical method. Utilizes the multiphysics design tool ANSYS to obtain the natural frequencies and associated deformations through modal analysis. Compared to the conventional geometry, the radial force is significantly reduced by providing windows.
{"title":"FEA-based Geometrical Modification of Switched Reluctance Motor for Radial Force Reduction","authors":"Rani S;Jayapragash R","doi":"10.23919/CJEE.2024.000049","DOIUrl":"https://doi.org/10.23919/CJEE.2024.000049","url":null,"abstract":"Switched reluctance motors (SRMs) are becoming increasingly popular in the automotive sector owing to their robust design. Moreover, SRMs are preferred particularly for EV applications owing to their fault tolerance, magnet-free structure, and high power/torque density. The main concerns of SRM compared to other machines include torque ripple and vibration. The primary cause of vibration is the radial force created by the SRM. A geometry-based modification of the SRM to reduce the radial force without significantly changing the average torque produced is proposed. The primary goal is to design a 4-phase, 8/6 SRM with a lower radial force. Two possible geometrical alterations are proposed: one with square windows and the other with circular holes on the rotor core. The windows are sized and positioned to avoid flux saturation. General criteria are developed for the optimal window size and placement. Finite element analysis (FEA) modelling of the SRM is used to validate its performance. The FEA results are compared with the performance parameters obtained using the analytical method. Utilizes the multiphysics design tool ANSYS to obtain the natural frequencies and associated deformations through modal analysis. Compared to the conventional geometry, the radial force is significantly reduced by providing windows.","PeriodicalId":36428,"journal":{"name":"Chinese Journal of Electrical Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10490166","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140345480","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Hot-spot temperature of transformer windings is a crucial indicator of internal defects. However, current methods for measuring the hot-spot temperature of transformers do not apply to those already in operation and suffer from data lag. This study introduces a novel inversion method that combines ultrasonic sensing technology, multiphysics simulation, and the K-nearest neighbors algorithm. Leveraging the penetrative ability and temperature sensitivity of ultrasonic sensing, a detailed physical field simulation model was established. This study extensively investigates the characteristics of ultrasonic wave signals inside transformers. The investigation includes different temperature fields, ranging from 40 °C to 110 °C at 10 °C intervals, and various ultrasonic wave emitter conditions. By extracting the key features of the acoustic signals, such as the peak time, propagation time, and peak amplitude, an accurate inversion of the winding hot-spot temperature is successfully achieved. The results demonstrate that this method achieves a high accuracy rate (98.57%) in inverting the internal winding hot-spot temperatures of transformers, offering an efficient and reliable new approach for measuring winding hot-spot temperatures.
变压器绕组的热点温度是内部缺陷的一个重要指标。然而，目前测量变压器热点温度的方法不适用于已在运行的变压器，而且存在数据滞后的问题。本研究介绍了一种结合超声波传感技术、多物理场仿真和 K 近邻算法的新型反演方法。利用超声波传感的穿透能力和温度敏感性，建立了详细的物理现场模拟模型。本研究广泛研究了变压器内部超声波信号的特性。调查包括不同的温度场（从 40 °C 到 110 °C，间隔 10 °C）和各种超声波发射器条件。通过提取声波信号的峰值时间、传播时间和峰值振幅等关键特征，成功实现了绕组热点温度的精确反演。结果表明，该方法在反演变压器内部绕组热点温度方面实现了较高的准确率（98.57%），为测量绕组热点温度提供了一种高效可靠的新方法。
{"title":"Simulation of Ultrasonic Propagation in Transformers within Thermal Fields and Intelligent Methodology for Hot-Spot Temperature Recognition","authors":"Dongxin He;Dechao Yang;Xinhua Guo;Jiefeng Liu;Haoxin Guo;Qingquan Li;Gilbert Teyssedre","doi":"10.23919/CJEE.2024.000052","DOIUrl":"https://doi.org/10.23919/CJEE.2024.000052","url":null,"abstract":"Hot-spot temperature of transformer windings is a crucial indicator of internal defects. However, current methods for measuring the hot-spot temperature of transformers do not apply to those already in operation and suffer from data lag. This study introduces a novel inversion method that combines ultrasonic sensing technology, multiphysics simulation, and the K-nearest neighbors algorithm. Leveraging the penetrative ability and temperature sensitivity of ultrasonic sensing, a detailed physical field simulation model was established. This study extensively investigates the characteristics of ultrasonic wave signals inside transformers. The investigation includes different temperature fields, ranging from 40 °C to 110 °C at 10 °C intervals, and various ultrasonic wave emitter conditions. By extracting the key features of the acoustic signals, such as the peak time, propagation time, and peak amplitude, an accurate inversion of the winding hot-spot temperature is successfully achieved. The results demonstrate that this method achieves a high accuracy rate (98.57%) in inverting the internal winding hot-spot temperatures of transformers, offering an efficient and reliable new approach for measuring winding hot-spot temperatures.","PeriodicalId":36428,"journal":{"name":"Chinese Journal of Electrical Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10490167","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140345522","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-01DOI: 10.23919/CJEE.2023.000048
Ming Cheng;Jiawei Zhou;Wei Qian;Bo Wang;Chenchen Zhao;Peng Han
Recent technological advancements have propelled remarkable progress in servo systems, resulting in their extensive utilization across various high-end applications. A comprehensive review of high-quality servo system technologies, focusing specifically on electrical motor topologies and control strategies is presented. In terms of motor topology, this study outlines the mainstream servo motors used across different periods, as well as the latest theories and technologies surrounding contemporary servo motors. In terms of control strategies, two well-established approaches are presented: field-oriented control and direct torque control. Additionally, it discusses advanced control strategies employed in servo systems, such as model predictive control (MPC) and fault tolerance control, among others.
{"title":"Advanced Electrical Motors and Control Strategies for High-quality Servo Systems - A Comprehensive Review","authors":"Ming Cheng;Jiawei Zhou;Wei Qian;Bo Wang;Chenchen Zhao;Peng Han","doi":"10.23919/CJEE.2023.000048","DOIUrl":"https://doi.org/10.23919/CJEE.2023.000048","url":null,"abstract":"Recent technological advancements have propelled remarkable progress in servo systems, resulting in their extensive utilization across various high-end applications. A comprehensive review of high-quality servo system technologies, focusing specifically on electrical motor topologies and control strategies is presented. In terms of motor topology, this study outlines the mainstream servo motors used across different periods, as well as the latest theories and technologies surrounding contemporary servo motors. In terms of control strategies, two well-established approaches are presented: field-oriented control and direct torque control. Additionally, it discusses advanced control strategies employed in servo systems, such as model predictive control (MPC) and fault tolerance control, among others.","PeriodicalId":36428,"journal":{"name":"Chinese Journal of Electrical Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10490170","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140345482","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Epoxy resin is widely used in the support, insulation, and packaging components of electrical equipment owing to their excellent insulation, thermal, and mechanical properties. However, epoxy-resin insulation often suffers from thermal and mechanical stresses under extreme environmental conditions and a compact design, which can induce electrical tree degradation and insulation failure in electrical equipment. In this study, the photoelastic method is employed to investigate the thermal-mechanical coupling stress dependence of the electrical treeing behavior of epoxy resin. Typical electrical tree growth morphology and stress distribution were observed using the photoelastic method. The correlation between the tree length and overall accumulated damage with an increase in mechanical stress is determined. The results show that compressive stress retards the growth of electrical trees along the electric field, while tensile stress has accelerating effects. This proves that the presence of thermal stress can induce more severe accumulated damage.
{"title":"Characterization of Electrical Tree Degradation of Epoxy Resin under Thermal and Temperature Stresses by Photoelastic Effect","authors":"Hein Htet Aung;Yuhuai Wang;Jin Li;Ying Zhang;Tatsuo Takada","doi":"10.23919/CJEE.2023.000047","DOIUrl":"https://doi.org/10.23919/CJEE.2023.000047","url":null,"abstract":"Epoxy resin is widely used in the support, insulation, and packaging components of electrical equipment owing to their excellent insulation, thermal, and mechanical properties. However, epoxy-resin insulation often suffers from thermal and mechanical stresses under extreme environmental conditions and a compact design, which can induce electrical tree degradation and insulation failure in electrical equipment. In this study, the photoelastic method is employed to investigate the thermal-mechanical coupling stress dependence of the electrical treeing behavior of epoxy resin. Typical electrical tree growth morphology and stress distribution were observed using the photoelastic method. The correlation between the tree length and overall accumulated damage with an increase in mechanical stress is determined. The results show that compressive stress retards the growth of electrical trees along the electric field, while tensile stress has accelerating effects. This proves that the presence of thermal stress can induce more severe accumulated damage.","PeriodicalId":36428,"journal":{"name":"Chinese Journal of Electrical Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10490171","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140345498","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
DC-link capacitors play a vital role in managing ripple voltage and current in converters and various devices. This study focuses on exploring the aging characteristics of DC-link capacitors in alternating humid and thermal environments aligned with the operational conditions in photovoltaic and wind power applications. Adhering to relevant power equipment standards, we designed a 24-h alternating humid and thermal aging environment tailored to the requirements of DC-link capacitors. An aging test platform is established, and 20 widely used metallized polypropylene film capacitors are selected for evaluation. Parameters such as the capacitance, equivalent series resistance (ESR), and phase angle are assessed during aging, as well as the onset time and extent of aging at various intervals. This study focuses on the aging mechanisms, analyzing electrode corrosion, the self-healing process, and dielectric aging. Fitting the aging characteristics enabled us to calculate the lifespan of the capacitor and predict it under different degrees of capacitance decay. The results show that under alternating humid and thermal conditions, capacitance attenuation and ESR increase exhibit exponential nonlinearity, influenced by factors such as the oxidation and self-healing of capacitive metal electrodes, dielectric main-chain fracture, and crystal transformation. This study underscores the pivotal role of encapsulation in determining the aging decay time.
{"title":"Aging Mechanism and Life Estimation of Photovoltaic Inverter DC-link Capacitors in Alternating Humid and Thermal Environment","authors":"Quanyi Gao;Shuaibing Li;Yi Cui;Yongqiang Kang;Haiying Dong","doi":"10.23919/CJEE.2024.000054","DOIUrl":"https://doi.org/10.23919/CJEE.2024.000054","url":null,"abstract":"DC-link capacitors play a vital role in managing ripple voltage and current in converters and various devices. This study focuses on exploring the aging characteristics of DC-link capacitors in alternating humid and thermal environments aligned with the operational conditions in photovoltaic and wind power applications. Adhering to relevant power equipment standards, we designed a 24-h alternating humid and thermal aging environment tailored to the requirements of DC-link capacitors. An aging test platform is established, and 20 widely used metallized polypropylene film capacitors are selected for evaluation. Parameters such as the capacitance, equivalent series resistance (ESR), and phase angle are assessed during aging, as well as the onset time and extent of aging at various intervals. This study focuses on the aging mechanisms, analyzing electrode corrosion, the self-healing process, and dielectric aging. Fitting the aging characteristics enabled us to calculate the lifespan of the capacitor and predict it under different degrees of capacitance decay. The results show that under alternating humid and thermal conditions, capacitance attenuation and ESR increase exhibit exponential nonlinearity, influenced by factors such as the oxidation and self-healing of capacitive metal electrodes, dielectric main-chain fracture, and crystal transformation. This study underscores the pivotal role of encapsulation in determining the aging decay time.","PeriodicalId":36428,"journal":{"name":"Chinese Journal of Electrical Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10490169","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140345502","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-06DOI: 10.23919/CJEE.2023.000034
Shuohang Chen;Guidong Zhang;Samson S. Yu;Yi Mei;Yun Zhang
In today's fast-paced, information-driven world, data centers can offer high-speed, intricate capabilities on a larger scale owing to the ever-growing demand for networks and information systems. Because data centers process and transmit information, stability and reliability are important. Data center power supply architectures rely heavily on isolated bidirectional DC-DC converters to ensure safety and stability. For the smooth operation of a data center, the power supply must be reliable and uninterrupted. In this study, we summarize the basic principle, topology, switch conversion strategy, and control technology of the existing isolated bidirectional DC-DC converters. Subsequently, existing research results and problems with isolated bidirectional DC-DC converters are reviewed. Finally, future trends in the development of isolated bidirectional DC-DC converters for data centers are presented, which offer valuable insights for solving engineering obstacles and future research directions in the field.
{"title":"A Review of Isolated Bidirectional DC-DC Converters for Data Centers","authors":"Shuohang Chen;Guidong Zhang;Samson S. Yu;Yi Mei;Yun Zhang","doi":"10.23919/CJEE.2023.000034","DOIUrl":"https://doi.org/10.23919/CJEE.2023.000034","url":null,"abstract":"In today's fast-paced, information-driven world, data centers can offer high-speed, intricate capabilities on a larger scale owing to the ever-growing demand for networks and information systems. Because data centers process and transmit information, stability and reliability are important. Data center power supply architectures rely heavily on isolated bidirectional DC-DC converters to ensure safety and stability. For the smooth operation of a data center, the power supply must be reliable and uninterrupted. In this study, we summarize the basic principle, topology, switch conversion strategy, and control technology of the existing isolated bidirectional DC-DC converters. Subsequently, existing research results and problems with isolated bidirectional DC-DC converters are reviewed. Finally, future trends in the development of isolated bidirectional DC-DC converters for data centers are presented, which offer valuable insights for solving engineering obstacles and future research directions in the field.","PeriodicalId":36428,"journal":{"name":"Chinese Journal of Electrical Engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10345659","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139090544","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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