外文中英文翻译现代变频器技术分析.doc

Modern frequency changer technical analysis Cheng Xi (Heilongjiang longmay mining group co., ltd.) The general frequency changer by its merits and so on intellectualization, digitization, network receives peoples favor more and more, but along with the general frequency changer application scopes expansion, exposes some questions. In view of these questions, this article carried on has analyzed and proposed the countermeasure. First, overtone question and countermeasure. The general frequency changers main circuit form generally by the rectification part, the contra variant part and the filter part is composed. The rectification part for the three-phase bridge-type uncontrolled rectifier, the invertors part is the IGBT three-phase bridge-type invertors, and the output is the PWM profile. Because the general frequency changers rectification part uses the diode uncontrolled bridge-type leveling circuit, the middle filter part uses the big electric capacity to take the filter, therefore rectifiers input current in fact is capacitors charging current, assumes a higher more and precipitous pulse wave, its harmonic component is big. For the harmonic cancellation, may use: 1, Increases the frequency changer electric power supply internal resistance. Usually in the situation, power equipments internal resistance may play the cushion frequency changer concurrent filter electric capacitys reactive power role. This kind of internal resistance is transformers short-circuit impedance. When power source capacity relative frequency changer capacity hour, then the internal resistance value relatively is bigger, the harmonic content is smaller; When the power source capacity relative frequency changer capacity is bigger, then the internal resistance value relatively is bigger, the harmonic content is bigger. Therefore best choice short-circuit impedance big transformer. 2, Installs the reactor. Installs the reactor is actually increases the frequency changer electric power supplys