"220V AC Cooling Fan is the need to use direct current, which is simple and easy to understand the problem. Even without explanation, we should be able to guess about it! Although aware of these basic questions, but we know how DC works it? this question, everyone can not answer it! very simple, brush less "220V AC Cooling Fan needs a rectangular wave current, the current rating of the invert continuous run time refers to the peak of the rectangular wave. Induction motor requires sine wave current, the current rating of the invert generally refers to continuous operation is the effective value of a sine wave. In order to maintain "220V AC Cooling Fan invert to control the motor current, DC voltage between the invert and the motor EMF should be sufficient difference.