Converter cost more and more high, more and more small size, face the market competition, we continue to frequency converter for more perfect improvement.
Inverter power semiconductor devices is the use of role will be off-frequency power conversion to another frequency electric energy control device, can achieve the AC asynchronous motor soft start, inverter, improve the operation accuracy, change the power factor, current / voltage / overload protection function. Motor frequency converter ’s role is to control, and reduce the starting current. In order to produce a variable voltage and frequency, the device first to supply alternating current is converted into DC electric ( DC ), this process is called rectification. The direct current ( DC ) transform into alternating current ( AC ) device, the scientific term for " inverter " ( inverter ). General inverter is the DC power supply inverter for a certain fixed frequency and voltage of the inverter power supply. The inverter for adjustable frequency, adjustable voltage inverter we called inverter. The inverter output waveform is analog sine wave, is mainly used in three-phase asynchronous motor speed control by frequency conversion governor, also called. For use mainly in instruments testing equipment in the high requirement of waveform variable frequency inverter, to the waveform finishing, can output the standard sine wave, called variable frequency power supply. General variable frequency power inverter price is 15--20 times. Inverter system as the important power conversion unit, to provide controllable high performance variable voltage variable frequency AC power and get swift and violent development.
Converter performance advantages and disadvantages, a look at the output AC voltage harmonic effect on motor, two depends on harmonic pollution and input power factor, three depends on their energy loss ( i.e. efficiency )? Here only with the large volume of AC-DC-AC frequency converter as the example, elaborated it development trend: the main circuit switch off, modular, integrated, intelligent, switching frequency and constantly improve, to further reduce the switching loss. Converter grid side converter device for low pressure and small capacity often uses the 6 pulse converter, and for medium voltage large capacity device using multiple 12 pulse above the converter. The load side converter with low pressure and small capacity device used for two level inverter for medium voltage large capacity, and the device adopts multilevel inverter. For the four quadrant operation transmission, in order to realize the regeneration energy to the grid inverter feedback and save energy, the grid-side converter should be reversible converter, and the emergence of power can flow in both directions of the double PWM frequency converter grid side converter, to properly control can make the input current to a sine wave, to reduce the pollution of power grid. At present, low, medium voltage frequency converter has this kind of product.
