外文翻译 外文文献 英文文献 现代变频器技术分析道.doc

Modern frequency changer technical analysis Cheng Xi Heilongjiang longmay mining group co. ltd. The general frequency changer by its merits and so on intellectualizationdigitization network receives peoples favor more and more but along with thegeneral frequency changer application scopes expansion exposes some questions. Inview of these questions this article carried on has analyzed and proposed thecountermeasure. First overtone question and countermeasure. The general frequency changers main circuit form generally by the rectificationpart the contra variant part and the filter part is composed. The rectification part forthe three-phase bridge-type uncontrolled rectifier the invertors part is the IGBTthree-phase bridge-type invertors and the output is the PWM profile. Because thegeneral frequency changers rectification part uses the diode uncontrolled bridge-typeleveling circuit the middle filter part uses the big electric capacity to take the filtertherefore rectifiers input current in fact is capacitors charging current assumes ahigher more and precipitous pulse wave its harmonic component is big. For theharmonic cancellation may use: 1 Increases the frequency changer electric power supply internal resistance.Usually in the situation power equipments internal resistance may play the cushionfrequency changer concurrent filter electric capacitys reactive power role. This kindof internal resistance is transformers short-circuit impedance. When power sourcecapacity relative frequency changer capacity hour then the internal resistance valuerelatively is bigger the harmonic content is smaller When the power source capacityrelative frequency changer capacity is bigger then the internal resistance valuerelatively is bigger the harmonic content is bigger. Therefore best choice short-circuitimpedance big transformer. 2 Installs the reactor. Installs the reactor is actually increases the frequencychanger electric power supplys internal resistance from exterior. Installs the