The frequency changer is (50Hz or 60Hz) transforms the power frequency power source Cheng Ge to plant the frequency the alternating current supply, realizes electrical machinery's speed change movement equipment, the control circuit completes to the main circuit the control, the leveling circuit transforms the alternating current the direct current, the direct-current intermediate circuit carries on to leveling circuit's output the smooth filter, inverted the electric circuit the direct current again counter deal discharge. The frequency conversion velocity modulation is achieves the velocity modulation through the change electrical machinery stator winding power supply frequency the goal.
The frequency conversion technology is should the alternating current machine stepless speed regulation need to be born. After the 1960s, the electric power electronic device experienced SCR (thyristor), GTO (gate to be possible to shut off thyristor, BJT (double pole power transistor), MOSFET (metal oxide compound field effect tube), SIT (electrostatic induction transistor), SITH (electrostatic induction thyristor), MGT (MOS control transistor), MCT (MOS control thyristor), IGBT (insulation grid double pole transistor), HVIGBT (bore high-pressured insulation grid double pole thyristor) the developing process extremely), component's renewal promoted the electric power electron converter technique unceasing development. In the 1970s started, the pulse-duration modulation live pressure frequency conversion (PWM-VVVF) velocity modulation research caused the people to take seriously. In the 1980s, was attracting people's strong interest as the frequency conversion technology core's PWM pattern optimization question, and obtained many optimized patterns, was best by the saddle shape wave PWM pattern effect. 20 shiji 80 niandai houbanqi the start, US and Japan, Germany, UK and so on developed country's VVVF frequency changer put into the market and has obtained the widespread application.
Key word: Frequency changer; Velocity modulation transmission; Invertor; Electric motor principle