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.

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.

Study of Frequency Effects on Hardness Profile of Spline Shaft Heat-Treated by Induction

This paper is devoted to the study of frequency effects on hardness profile of AISI 4340 spline shaft heat-treated by induction through an extensive 3D finite element method simulation and structured experimental investigation. Based on coupled electromagnetic and thermal fields analysis, the 3D model is used to estimate the temperature distribution and the hardness profile. The proposed study examines the hardening process parameters, such as frequency, induced current density and heating time, known to have an influence on hardened surface and builds the simulation model step by step. The established model can provide not only an accurate prediction of temperature distribution and hardness profile but also a comprehensive analysis of machine parameters effects, especially the frequency. The numerical results achieved by this model are good and present a great agreement to the experimental data.

Frequency dependence of plasma characteristics at different pressures in cylindrical inductively coupled plasma source

The effects of driving frequency on plasma parameters and electron heating efficiency are studied in cylindrical inductively coupled plasma(ICP) source. Measurements are made in an Ar discharge for driving frequency at 13.56/2 MHz, and pressures of 0.4-1.2 Pa. In 13.56 MHz discharge, higher electron density(n_e) and higher electron temperature(T_e) are observed in comparison with 2 MHz discharge at 0.6-1.2 Pa. However, slightly higher n_e and T_e are observed in 2 MHz discharge at 0.4 Pa. This observation is explained by enhanced electron heating efficiency due to the resonance between the oscillation of 2 MHz electromagnetic field and electron-neutral collision process at 0.4 Pa. It is also found that the variation of T_edistribution is different in 13.56 and 2 MHz discharge.For ICP at 13.56 MHz, T_eshows an edge-high profile at 0.4-1.2 Pa. For 2 MHz discharge, T_e remains an edge-high distribution at 0.4-0.8 Pa. However, the distribution pattern involves into a center-high profile at 0.9-1.2 Pa. The spatial profiles of n_e remain a center-high shape in both 13.56 and 2 MHz discharges, which indicates the nonlocal kinetics at low pressures. Better uniformity could be achieved by using 2 MHz discharge. The effects of gas pressure on plasma parameters are also examined. An increase in gas pressure necessitates the rise of n_e in both 13.56 and 2 MHz discharges. Meanwhile, T_e drops when gas pressure increases and shows a flatter distribution at higher pressure.

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.

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。

预应力钢绞线感应加热及其丝间接触模拟研究

预应力钢绞线感应加热是一复杂工艺过程,利用多物理场仿真软件对该过程进行模拟,可为工艺优化提供基础。对于几何方面,由于工艺的连续性,难以确定钢绞线丝间接触情况;对于物理场方面,感应加热是涉及多场的强耦合、强非线性过程。针对以上情况,根据两种丝间接触情况建立了三维钢绞线几何模型,描述了非线性材料参数,建立了相对磁导率关于温度和磁通密度的数值模型,测定了现场温度数据,判断了边丝间是否接触,分析了接触面宽度对加热效果的影响。结果表明:边丝之间是接触的,且现场温度数据与模拟结果较为吻合,验证了模拟的正确性。

Effect of Induction Heat on Initial Solidification During Electromagnetic Continuous Casting of Steel

A three-dimensional finite element model of electromagnetic field and temperature field was developed to investigate the effects of induction heat of high frequency electromagnetic field on the early solidification process of molten steel.The results show that the increases of exciting current frequency make the effects of induction heat on solidification increase remarkably.Contrarily,the effects of induction heat on solidification process are weakened sharply with the increase of casting speed.Especially,when the casting speed exceeds a certain value,the effects of induction heat on solidification process are nearly negligible.

中频加热电源模糊自适应PID控制系统的设计与实现

针对中频感应加热电源控制系统存在着严重的非线性、参数时变性以及滞后性和惯性缺陷,同时考虑采用常规PID控制很难取得较好的控制效果,设计了一种模糊自适应PID控制系统。该系统结合模糊控制和常规PID控制两种算法的优势,利用模糊控制在线性整定和修改PID的控制参数,较好地解决了系统的存在问题,获得了良好的动态性能和静态性能。在分析模糊自适应PID控制算法的基础上,详细介绍了模糊化处理、模糊控制规则建立表以及模糊判决和决策表等,分别给出了模糊自适应PID控制参数在线整定程序流程,上位机程序的设计方法,系统硬件组成和工作原理,以及主要部件特性等。通过对系统MATLAB仿真分析,其结果表明:该系统与常规PID控制相比较,具有控制精度高、响应速度快、稳定性好的特点,明显改善了中频感应加热电源的控制效果,具有一定的推广价值。

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。

接触轨融冰用电磁感应加热电源应用研究

开发了一种接触轨融冰用中频感应加热电源,输入为380 V/50 Hz的三相正弦交流电,输出为频率固定中频20 kHz,功率大小可调。首先分析了该中频感应加热电源系统的工作原理及产生的伴随效应,其次介绍了感应加热电源的结构,提出了一种基于移相PWM调功与频率跟踪相结合的复合控制方案,最后,建立了电源MATLAB/Simulink仿真模型和试验模型,通过仿真结果和试验结果证明了所开发的中频感应加热电源的可行性。

变频感应加热炉电网频率波动下低压智能断路器过流保护控制

电网频率波动会导致电流波形在短时间内发生变化,从而影响过流保护控制的响应速度。为了保障电网频率波动下低压智能断路器过流保护控制的稳定可靠性,提高变频感应加热炉电力系统的保护性能,提出变频感应加热炉电网频率波动下低压智能断路器过流保护控制方法。利用PCL-818L数据采集卡,采集变频感应加热炉供电系统中的电压电流信号;通过强化学习Q-Learning算法,消除信号中的电网频率波动,提高断路器的稳定性;采用引入滑动时间窗口的三段电流保护方法,实现低压智能断路器的过流保护控制。实验结果表明,所提方法能够在有效消除电网频率波动干扰的情况下,提高断路器过流保护控制精度、效率以及稳定性。

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。

基于压缩感知的中频感应加热设备边缘用电数据缺失重构方法

为解决因用电数据缺失造成的电量失衡问题,确保重构后的中频感应加热设备能够保持相对稳定的运行状态,设计基于压缩感知的中频感应加热设备边缘用电数据缺失重构方法。对用电数据样本进行两次转化处理,得到电信号稀疏变换结果,通过构建压缩矩阵的方式,描述中频感应加热设备边缘用电数据的失稳现象,求解基于压缩感知的中频感应加热设备边缘用电数据脆弱性函数。设置电网网格结构,按照缺失数据的自编码形式,计算连续重构阈值指标的取值范围,完成压缩感知下中频感应加热设备边缘用电数据缺失重构方法的设计。实验结果表明,数据缺失区域内的最大电压数值只能达到30.0 V,电网主机可以根据实时电压的不同,确定缺失数据所处区间,对于解决电量失衡问题、增强重构后电网的运行稳定性可以起到促进性影响作用。

30CrMnSiNi2A钢螺栓螺纹感应回火工艺研究

通过对30Cr Mn Si Ni2A钢螺栓的感应回火处理要求进行分析,提出螺栓螺纹感应回火方案,对比分析不同感应加热方式对螺栓回火区、热影响区硬度的分布,确定最佳的30Cr Mn Si Ni2A钢螺栓螺纹感应回火工艺,使螺栓的感应回火技术指标满足要求,最终通过重复性试验验证,进行硬度、金相检测,完成对30CrMnSiNi2A钢螺栓螺纹感应回火工艺的研究。

串联谐振式高频感应焊接逆变电源

传统的高频感应加热电源通过改变逆变器的工作频率来调节输出功率,逆变器的输出功率因数很低,而且逆变器开关管工作在硬开关状态,开关损耗大,效率低。按照大功率发电机。变压器铜排绕组焊接工艺和不同规格铜排的焊接要求,这种设备不适合这类应用。作者研究了新型频率跟踪电路,控制逆变器工作在谐振状态,负载等效阻抗呈电阻性,逆变器的输出功率因数接近1,大大减小了开关器件的功率损耗,提高了整机的效率。功率调节采用直流斩波调压实现。设计并制作了20kHz/30kw串联谐振式高频感应焊接逆变电源,改变了传统的焊接工艺,具有体积小、效率高、加热速度快等优点。

PI调节逆变式IGBT感应加热电源频率自动跟踪技术

针对感应加热过程中谐振频率不断变化的问题 ,采用以SG35 2 5A为核心的感应加热电源 ,检测电源输出电压与输出电流之间的相位差大小 ,并以此信号作为PI调节的输入 ,通过该调节器控制感应加热电源的工作频率 ,实现了系统谐振频率的自动跟踪。该方法具有跟随速度快、频率跟踪准确、电路设计简单、工作可靠等优点。对上述方法的原理、电路设计以及实验结果等做了详细的分析和介绍。

倍频式IGBT高频感应加热电源的研究

倍频式感应加热电源负载输出频率为功率开关管工作频率的二倍,且功率开关器件工作时具有软开关特性,在需要高频应用的场合很有意义。文中以IGBT来实现倍频式高频感应加热电源,比较了不同频率比下的电路工作状态,得出电路工作在断态下更适合电路功率调节的结论。详细分析了断态下电路工作状况,得出直流等效电阻与交流负载等效电阻的关系,并给出了选取电路参数的经典方法。根据该方法设计了一台样机,通过实验验证了理论分析及参数选取方法的正确性。

20kW／300kHz高频感应加热电源

以功率ＭＯＳＦＥＴ为开关元件，采用多管并联方式研制出２０ｋＷ／３００ｋＨｚ高频感应加热电源。本文对该电源的逆变电路、控制电路、多管并联驱动等问题做了研究和试验。

基于新型移相控制的感应加热电源的研究

针对电压型感应加热电源频率跟踪的要求 ,提出了一种新型的移相控制策略。这种策略逻辑明确 ,控制性能优越 ,实现简单、可靠。针对在实现过程中的关键问题 ,提出新的解决方法。所有的分析都得到实验验证。