Many "Mini Air Cooling Fan" business occurs in the production process equipment failure in one way or another, most of the reason may be due to the heat caused by, the following stall during rotation puts forward the possibility of judgment analysis. Rotor rotating stall frequency: When the normal operation of the cooling fan, "Mini Air Cooling Fan" with the direction of the impeller rotor is in the same direction, an exception occurs when the fluid direction, the rotor is abnormal vibration. So this is the reason causing the fan rotating stall. To prevent the "Mini Air Cooling Fan" unexpected failure resulting in unnecessary losses, we must make improvements from the design. Thus fundamental to dispel criticism, to change nature.