Zero-voltage switching converter absorbing parasitic parameters for super high frequency induction heating

This paper presents a novel mega-Hz-level super high frequency zero-voltage soft-switching converter for induction heating power supplies. The prominent advantage of this topology is that it can absorb both inductive and capacitive parasitic components in the converter. The switch devices operate in a zero-voltage soft-switching mode. Consequently, the high voltage and high current spikes caused by parasitic inductors or capacitors oscillation do not occur in this circuit, and the high power loss caused by high frequency switching can be greatly reduced. A large value inductor is adopted between the input capacitor and the switches, thus, this novel converter shares the benefits of both voltage-type and current-type circuits simultaneously, and there are no needs of dead time between two switches. The working principles in different modes are introduced. Results of simulation and experiments operated at around 1 MHz frequency verify the validity of parasitic components absorption and show that this convener is competent for super high frequency applications.

SIMULATION OF TEMPERATURE FIELD IN ULTRA-HIGH FREQUENCY INDUCTION HEATING AND VERIFICATION

An experimental and numerical study on the temperature field induced in the ultra-high frequency induction heating is carried out.With an aim of predicting the thermal history of the workpiece,the influence factors of temperature field,such as the induction frequency,the dimension of coil and the gap between coil and workpiece,are investigated considering temperature-dependent material properties by using FLUX 2Dsoftware.The temperature field characteristic in ultra-high induction heating is obtained and discussed.The numerical values are compared with the experimental results.A good agreement between them is observed with 7.9% errors.

Influence of heat treatment on high frequency soft magnetic properties of Finemet amorphous alloy

In order to study high-frequency soft magnetic properties of Finemet amorphous alloy,the microstructural change and nanocrystallization under different heat treatment conditions were investigated by XRD and TEM. The crystallite size of α-Fe was calculated from the XRD pattern using the Scherrer formula,while the high frequency magnetic properties were measured at room temperature by TPS-200SA exchange tester. The results of XRD and TEM indicate that the nanocrystallization occurs at 500 ℃. When the annealing temperature increases to 560 ℃,the amorphous alloy becomes totally nanocrystallized and the crystallites distribute homogeneously,thus an excellent combination of soft magnetic properties is obtained.

Study on high frequency brazing of brass-red copper

Two kinds of silver based medium temperature brazing filler metals(45AgCuZnSn and 60AgCuSn) were selected to braze and seal brass flange pipe and copper pipe by high frequency heating brazing. In this paper, the quality of the braze was evaluated by immersion ultrasound, and the microstructure of the brazed joint was observed by SEM and EDS. The experimental results show that the high frequency heating brazing can quickly achieve the device sealing;through the ultrasonic flaw detection image calculation, the brazed bonding rate obtained by 60AgCuSn brazing is 87%, and by 45AgCuZnSn brazing is 71%;the cross-sectional area of the brazed joint obtained by two kinds of silver based medium temperature brazing filler metals is observed, the brazed joint obtained by 45AgCuZnSn brazing has defects visual, and a large amount of Zn element gathered in the defects, there is no obvious porosity in the brazed joint by 60AgCuSn brazing,and the bonding layer is dense and coherent. Through the contrast test, the choice of 60AgCuSn alloy brazing can meet the needs of high frequency brazing of brass flange pipe and copper pipe.

High-Frequency Induction Heating of Needle-Shaped Mg-Ferrite for Ablation Therapy of Human Cancer

For application as a novel ablation therapy of human cancer,the heating property of a needle-shaped Mg-ferrite prepared by a sintering technique was studied in a high-frequency induction field at 370 kHz.When inserted into cylindrical clay,the increase in temperature(Δ7)was 31.2℃ for the specimen with a 1.5 mm diameter,while the 1.0mm diameter specimen exhibited a ΔT value of 15.7℃ after the induction time of 1200s.The ΔT exhibited a high value of 57.9℃ during the simultaneous insertion of 3 1.5mm diameter specimens.In the computer simulation images, the relatively lower magnetic flux density and concurrent neghgibly low current density were observed from the surface to the internal regions,being different from the behavior of a ferromagnetic Ni-rod with the same size.

S Zorb装置反应器接收器脱气线和再生器取热盘管改造

某公司对S Zorb装置首个运行周期内出现的反应器接收器脱气线泄漏、再生器取热盘管泄漏等运行问题开展了技术攻关,提出了工艺优化调整、工程技术改造建议。2019年大检修时对反应器脱气线进行扩径,由DN100扩径为DN150,控制气提量小于670 m^(3)/h,对再生系统取热蒸汽和再生风流控阀等进行了工程技术改造。第二运行周期未出现脱气线减薄泄漏和再生器取热盘管泄漏问题。2023年6月大检修时对上次大检修改造部位进行检查以验证工程改造的有效性,经全面检查,确认脱气线内部未发现冲刷痕迹,再生器取热盘管打压合格,外观正常,证明改造措施有效,可以满足“四年一修”目标要求。

热处理对薄壁TA1焊管高频感应焊接接头显微组织和力学性能的影响

首先对壁厚0.4 mm的薄壁TA1焊管进行高频感应焊接,随后,在不同温度下对焊接接头进行5 min的热处理。利用光学显微镜和扫描电镜分析了热处理前后焊接接头的显微组织,并对焊接接头的力学性能进行了测试。结果表明:热处理使TA1焊管焊接接头的显微组织和力学性能发生显著变化,当热处理温度为600℃时,焊接接头发生了完全再结晶,晶粒细小,抗拉强度略有下降,塑性增强,拉伸断口呈典型的韧性断裂特征,这主要是针状马氏体消失和细晶强化所致。

大功率高频变压器关键技术与发展趋势

大功率高频变压器是固态变压器的核心部件,在未来新能源并网、海上风电、中压配网、轨道交通和数据中心供电中需求广泛。该文综述了大功率高频变压器研究的关键问题与发展趋势,论述了大功率高频铁芯的材料、损耗、结构设计与制造现状,分析了绕组材料与结构设计,指出了大功率高频铁芯与绕组的关键问题。同时讨论了高频高压绝缘与散热问题,分析了绝缘失效、可靠性与散热设计中的矛盾问题。最后阐述了大功率高频变压器在设计、测试与应用等方面研究现状,讨论了其高效高功率密度设计方法,深入分析了大功率高频变压器在效率、绝缘以及温升等性能测试方面存在的关键问题。

基于高频变极性电流源的交叉耦合电弧焊摆动行为抑制

交叉耦合电弧焊工艺理论上可以实现焊接过程中传热、传质解耦和独立控制,具有很大的发展潜力,然而,传统的交叉耦合电弧工艺中旁路电弧电流一般由低频交流焊接热源提供,工作过程中会出现主电弧随着旁路电弧的极性改变而发生电弧摆动现象,使各个电弧之间的热力分配不平衡,传热、传质解耦不彻底.在增材制造应用中,会面临熔滴落点位置不可控、成型精度低等问题,为了解决主电弧的摆动问题,设计开发了旁路电弧为高频变极性电弧的交叉耦合电弧焊接热源.试验结果表明,这种焊接热源可以通过提高旁路电弧的变极性频率,有效地抑制主电弧的摆动行为,进一步实现交叉电弧中填充焊丝熔化速率与工件热输入之间的传热解耦,同时,抑制主电弧摆动后的现象表现为主电弧高频小幅度振动,理论上可以实现对熔池的搅拌作用,利于枝晶破碎、促进焊缝晶粒细化.

六维压电风洞盒式天平研究

风洞试验是气动力载荷的精确测量手段。针对风洞试验中高频多维气动力的测量特点,采用压电测量元件,开发了一种适用于风洞试验中高频六维气动力测量的盒式天平。根据力与力矩平衡关系建立了输入与输出之间的理论输出模型,通过力传递关系及有限元仿真对气动热作用下天平被动输出进行了分析,并通过标定试验获得了天平性能指标。结果表明,该盒式天平在结构和材料上可抵抗测试过程中的温变干扰,温变影响系数小于0.5%,线性度和重复性误差分别低于0.4%和0.5%,最大相间干扰解耦后低于1.5%,三向一阶固有频率皆高于3000Hz,具有高固有频率、高精度的优良性能。

高功率密度中高频变压器绝缘与散热研究进展与展望

围绕大容量电力电子变压器的发展需求,针对其中关键部件“高功率密度中高频变压器”的绝缘与散热研究进行综述分析。高功率密度对固体绝缘与散热性能提出新的挑战。首先,论述了高功率密度中高频变压器设计与应用时绝缘和散热的矛盾。其次,主要论述了高频绝缘失效的研究进展,包括绝缘击穿、局部放电、沿面放电、电树枝劣化等特性。然后,分析了目前高频绝缘的失效机理研究,包括热击穿、空间电荷效应、高频电导与自由体积效应。最后,论述了高频绝缘寿命的研究,分析了频率、温度、电压变化率du/dt等对绝缘耐电晕寿命的影响以及寿命模型。基于研究进展,提出了高频绝缘与散热的研究展望。该文综述研究对大容量电力电子变压器的设计与应用具有重要意义。

氮化镓功率器件在宇航电源中的发展与应用

随着航天器功率需求不断增大,对宇航电源的效率提出了更高的要求。第三代宽禁带半导体—氮化镓(GaN)功率器件具有更低的导通损耗、纳秒量级的开关速度等优点,能够使宇航电源的效率得到进一步提高。该文分析了GaN功率器件的结构特性与电气性能优势,针对GaN功率器件在国内外宇航电源中的应用情况进行总结;并提出GaN功率器件以及高频电源在宇航环境中广泛使用面临的关键问题。分析认为GaN功率器件应侧重于单粒子辐照加固以及耐辐照稳定性驱动方案研究,而宇航电源的整体研究则应该关注高频电源集成技术以及散热问题。

基于电驱系统高频注入的电动汽车电池包快速加热控制算法

对锂离子电池进行低温加热是缓解其低温环境性能衰减的有效措施。该文从电动汽车整体架构出发,提出一种多周期偏置方波注入法,向电机d轴混叠注入直流电流与高频电压,使得电池母线端激励正负交变电流,该电流流过电池内阻产生焦耳热,实现电池自发热。所提控制方法,仅采用原有电驱系统硬件结构,在矢量控制基础上增加注入信号,实现方式简单,适配所有包含电驱系统的电动汽车。该文详细分析注入高频可在母线产生交变激励电流的原理,针对电池自发热目标,通过调节注入信号的频率与幅值,实现激励电流灵活可调。实验结果表明,所提控制策略能在电池侧有效激励交变电流,且幅值、频率可调。与理论分析一致。最后,搭建整车环境仓电池自发热平台,进一步验证所提方法在实际场景应用中的可行性。

高频感应热辊在转移印花工艺中的应用分析

文章介绍了自制高频感应电磁加热辊与传统导热油热辊在升温、保温、降温阶段能耗对比实验,结果表明:在相同测试条件下,高频感应电磁加热辊表面温度均匀性好,热效率高,节能降耗明显,为高频感应热辊在印染行业中的产业化应用提供参考。

高频加热-红外光谱法测定氯化熔盐中碳含量

碳是熔盐氯化的重要反应物之一,其含量影响氯化反应的进度。因此,准确测定熔盐中碳含量,对指导生产有重要意义。氯化熔盐属高氯样品,目前用管式炉或高频炉燃烧,红外吸收法测定熔盐中碳含量时,存在无相应标准样品建立仪器标准工本曲线和燃烧产生的氯气易腐蚀仪器的问题。实验提出用氯化钠稀释石油焦标准样品,配制不同浓度的碳校准样品,同时对仪器试剂管改装,以石英砂-氢氧化钙(3∶1)吸收氯气,可以有效解决上述问题。此外,实验还研究了高频功率、助熔剂对碳测定的影响,以高频加热-红外吸收法测定氯化熔盐中碳含量。实验结果表明:加入0.5 g纯铁、1.0 g钨锡混合助熔剂,高频功率为70%时,碳完全氧化成二氧化碳;采用人工合成校准样品建立标准曲线,碳的质量分数在0.86%~6.46%范围内,线性良好,满足生产控制要求。

铁芯叠装强度与护套过盈量分析

该文采用有限元法对电机铁芯加工中典型的叠铆工艺进行仿真分析,分别计算量中过盈量状态下的叠铆强度,随着过盈量的增加,冲片之间的叠铆强度越高。采用高频加热护套后当过盈量为0.03 mm时,护套上的应力约为75 MPa;当过盈量为0.04 mm时,护套内的应力大于300 MPa达到了330 MPa。为避免护套在装配和翻遍过程中破损,应选择转子护套的过盈量为0.03 mm。

低功耗新型均匀加热的高频电磁加热装置

针对高频加热装置目前存在加热效率低下、耗电量大、加热温度不均匀等缺点,基于电磁场基本理论与平行磁场同向矢量叠加磁场增强原理,研究发明了一种新型温度场均匀分布、低功耗的高频电磁加热装置。通过仿真实验对电磁线圈的排列方式、线圈匝数、线圈之间的间隔以及线圈与加热板距离等结构及参数进行优化研究,获得平行线圈之间的最佳优化间隙为15 mm,导磁加热板和加热线圈的最佳距离为5 mm,实现了低功耗、中心和边缘加热温差小的性能。

宝钢烧结余热回收利用实践

烧结作为铁前最主要的工序之一,余热资源丰富,能耗水平提升空间大。在总结了超高料层烧结技术、热风烧结技术、烟气循环技术等烧结主要节能技术的基础上,针对烧结机运行现状和存在问题,实施超高料层改造,增设热风烧结,将液密封环冷机改造为转臂式环冷机,将落地式余热锅炉改造为直联炉罩式余热锅炉,对主排风机进行变频改造。改造后大幅提升了能源利用效率,使工序能耗达到国内先进水平。

基于电磁感应的道岔融雪设备

针对现有电阻式道岔融雪设备需要多层热传导、预热时间长、钢轨温升慢、电转热效率低等缺点,开展了电磁感应式道岔融雪设备的研究。电磁感应式道岔融雪设备是通过高频逆变源在电磁感应线圈上加载高频交变电流从而产生交变磁场,利用交变磁场在钢轨上产生的涡流而使钢轨自发热,减少了热传导过程,提高了钢轨的温升速率,且电磁感应式道岔融雪设备本身没有高温热源,从而降低了空气中的热损耗,能量利用率高,最终实现低碳减排和节能降本效果。详细介绍了电磁感应式道岔融雪设备的工作原理、系统组成及各个功能模块设计与实现,并对两种加热方式的融冰效果进行对比测试,相同条件下,电磁感应式道岔融雪设备融冰效果要明显优于电阻式道岔融雪设备。