Main characteristic: 1) Smooth speed regulation performance, with hgih regulation precision 2)high regulation efficiency, power saving 3)super starting performance: Adopt liquid resistance to start, economical and reliable. The entire starting process switches automatically 4)Boost converter adopts new big power full-controlled IGBT. It no need assitant shut-off circuit, safe and reliable 5)Flexible and convenient control way: Free conversion of regulation ,full speed operation, open loop, close loop operation, in situ and distant control 6)complete protection way : Portection function as over voltage, three phase voltage unbalance, over current, short circuit, etc. 7)system automatically records malfunction information and put motor into full-speed operation or stop 8)independent DC power supply with several loops ,ensure the reliability of power supply operation 9) Quite strong ability of anti-interference Main technical parameters rated voltage AC380V+- 10% ( three phase and lines) speed regulation range (50-98) % ne + 100% ne average speed regulation efficiency >98.9% speed regulation precision: >99.8% current harmonic wave <4% over loading capacity 1.8 times > rated load working place indoor