变频调速传动系统的电磁兼容分析

在变频调速传动系统中,变频器会产生和受到各种电磁干扰。本文分析了变频调速传动系统的主要电磁干扰源和耦合途径,并阐述了抑制其电磁干扰的措施。     

THEORETICAL INVESTIGATION ON BY-ONLY-CURRENT ELECTROMAGNETIC SEPARATION OF INCLUSION FROM MOLTEN METALS

The electromagnetic field under applied AC and DC current in round and rectangular pipe was systematically investigated, then a concept of "equivalent current density" was proposed for evaluating the inhomogeneous electromagnetic pinch force, and the mono-component removal efficiency and the overall removal efficiency of inclusion were formulated. It is founded that flat pipe is superior to round pipe for the electromagnetic removal of inclusion, and DC current can get a higher removal efficiency than A C current due to absence of skin phenomenon. Under usual condition, a removal efficiency of 52% for 10μm inclusion or more than 92% for 20μm inclusion can be achieved by imposing a current density of 3×106A/m2 in a flat pipe.     

磁性纤维随机混合媒质等效电磁参数的计算

为计及强散射偶极子间的相互作用,引入参量εh和μh,利用广义多重散射理论及MATLAB计算机软件对在2 GHz～18 GHz频率下的体积占空比为8%的铁纤维随机混合媒质等效磁导率的实验值进行曲线的拟合,导出了耦合系数εh和μh,并在此基础上,对体积占空比分别为30%和20%的铁纤维随机混合媒质等效磁导率进行了计算,计算结果与实验吻合良好.     

水平电磁连铸空心铜管坯组织和性能研究

提出在中试水平的空心铜管坯水平连铸过程中施加工频电磁场,分析其对铜管坯组织和性能的影响.结果表明：与未施加电磁场时相比,施加电流强度为140A的工频电磁场后,水平连铸空心铜管坯的组织显著细化,平均晶粒度由未施加磁场时的3.1提高到8.3,周向组织均匀性也得到明显改善;抗拉强度提高40%左右,延伸率提高50%左右.     

国内弧焊设备电磁兼容性研究进展

焊弧设备的电磁兼容性问题日益突出，受到越来越多的关注。针对我国的实际情况，对国内弧焊设备的研究现状进行了综合分析，同时指出了今后的研究方向。     

A NEW ELECTROMAGNETIC IMAGING SCHEME

ＡＮＥＷＥＬＥＣＴＲＯＭＡＧＮＥＴＩＣＩＭＡＧＩＮＧＳＣＨＥＭＥ①ＺｈａｎｇＲｏｎｇｆｅｎｇ，ＨｅＪｉｓｈａｎＣｏｌｅｇｅｏｆＲｅｓｏｕｒｃｅ，ＥｎｖｉｒｏｎｍｅｎｔａｎｄＣｉｖｉｌＥｎｇｉｎｅｒｉｎｇ，ＣｅｎｔｒａｌＳｏｕｔｈＵｎｉｖｅｒｓｉｔｙｏ...     

工艺参数对电磁铸造铝板坯温度场的影响

采用数值方法模拟电磁铸造过程的温度场，详细讨论了各种工艺参数，如宽厚比，浇注温度，铸造速度，冷却水量，喷水位置，喷水孔分布，感应热等对铝板坯凝固过程和温度场分布的影响规律，为电磁铸造工艺参数设计提供可靠依据。     

NUMERICAL SIMULATION OF ALTERNATIVE HORIZONTAL LEVITATION ELECTROMAGNETIC CONTINUOUS CASTING（Ⅱ）

ＮＵＭＥＲＩＣＡＬＳＩＭＵＬＡＴＩＯＮＯＦＡＬＴＥＲＮＡＴＩＶＥＨＯＲＩＺＯＮＴＡＬＬＥＶＩＴＡＴＩＯＮＥＬＥＣＴＲＯＭＡＧＮＥＴＩＣＣＯＮＴＩＮＵＯＵＳＣＡＳＴＩＮＧ（Ⅱ）￥ＺｈｕＳｈｏｕｊｕｎ；ＲｅｎＺｈｏｎｇｍｉｎｇ；ＤｅｎｇＫａｎｇ；Ｊｉａｎ...     

Continuous cleaning of A356 alloy melt using high frequency electromagnetic field

A set of device for electromagnetic separation (EMS) was designed and applied to process the continuous flowing melt. Tensile test was employed to compare effect of electromagnetic separation with that of the traditional processes. Compared with filtration by ceramic foam filter and process without filtration, multiple process combined with filtration and electromagnetic separation can effectively remove most of inclusions with diameter finer than 10μm in A356 alloy casting, hence improve its tensile properties. After being processed by electromagnetic filtration,the tensile strength of A356 scrap is enhanced by 8.27%, approaching the level of fresh A356 alloy.     

电磁成形中的测量

本文简要介绍了电磁成形中放电电流、管坯与线圈间隙中的磁场测量 ,以及管坯动态变形过程测量的各种方法。通过各种方法的比较分析 ,得出分流器法测放电电流、探测线圈法测感生磁场是切实可行的方法。金属坯料在电磁力作用下的变形过程可用撞针法和高速摄影的办法进行测量 ,每种方法各有其优势和适用范围 ,测量时 ,根据实际情况进行选用。