Skin effect is the tendency for alternating current to flow near the sruface of the conductor in lieu of flowing in a manner as to utilize the entire cross - sectional area of the conductor . this phenomenon causes the resistance of the conductor to increase . the magnetic field associated with the current in the conductor causes eddy currents near the center of the conductor which opposes the flow of the main current near the center of the conductor . the main current flow is forced further to the surface as the frequency of the alternating current increase 表面疚是指交流电流较倾向于导体的表面传导而非流经整个导体截面的趋势，这些现象会造成导体的电阻提高，与导体中的电流有关的磁场在导体中心部位产生过电流而阻碍了中心部位的主要电流，当交流电的频率增加时，主要电流的流向会进一步被推挤到导体表面。
This product , adopted pwm integrated circuit and mosfet , igbt that were imported from the overseas , has the following merits : quick - response , strong interfere - proof , stable frequency and voltage , low consumption when light loading , high efficiency and reliable performance , it can be applicable to the family use , pasture region , work with the wind generator and some other places where the power failure often occurs 本品采用pwm （脉宽调制）集成电路和进口大功率mosfet 、 igbt等器件，具有应变快、抗干扰、自动稳定频率和电压、空载损耗低、效率高、性能可靠，是家庭，牧区，风力发电机配套以及其它野外经常停电地区提供交流电的必备的电器。
（ 2 ） the major circuit has been established , composed of rectifier 、 buck - chopper 、 push - pull inverter and matching network , which realizes high - power supersonic ac output . to achieve maximal output power , the pulse frequency modulation ( pfm ) has been applied to auto - adjustment of output frequency , which corresponds to the load ' s resonant frequency （ 2 ）建立了超声电源主电路，其中包括：整流、直流斩波、推挽逆变器和匹配网络等部分，实现了大功率超声频交流电的输出，输出频率的脉频调制（ pfm ）和输出功率的脉宽调制（ pwm ） 。
This article makes a numerical simulation and analysis of the skin effect of the downhole heating cable conductor by using the finite element method , thereby finds out the distribution characteristics of the current density of the cable , and indicates the effect of the frequency of alternating current on the skin depth 摘要运用有限元法，对交频井下伴热电缆导体内部的集肤效应现象进行了数值模拟和分析，比较直观地得出交频电缆中电流密度的分布特性，以及交流电的不同频率对导体集肤深度的影响。
