If "AC Fan" centrifugal fan load is relatively large, it is necessary to duct inlet or outlet of the regulator valve to the next, so you can protect the fan motors, fan use to reduce the load, the fan tripped on the frequency of the phenomenon relatively low. Impeller rotating in the opposite direction, to promptly adjust the correct direction of rotation of the impeller; the line is bad or in phase caused by phase; poor performance accessory control box, or to fans of the line is bad cause phase; insufficient grid capacity, low voltage . Take line shell leakage; connection is not reliable, then after running for some time due to the heat at the break; motor wiring error; dual speed fan motor speed low wiring connection errors; two-speed fan control box is inconsistent with the actual high and low numbers; the fan speed does not match too. Trip of the circuit are several reasons for this result, and therefore in the process of detecting circuits must solve these problems one by one, so as to allow the fan to get a good solution.