Motor is the heart of "24V DC Cooling Fan" in general by the stator and rotor of two parts. Motor running when stationary part called the stator. Runtime rotating part called the rotor. DC motor speed control mode has two voltage control and frequency modulation speed. The latter is the mainstream applications. Can achieve good demand for fan speed control. The thermostat "24V DC Cooling Fan" on the PCB can be installed by a thermistor. Sensing temperature changes speed, the higher the temperature, the faster the fan speed. However, the cooling fan blades are singular Why? It is because you want to keep the fan running balance and reduce the impact as much as possible to bring the resonance. Singular "24V DC Cooling Fan" fan is the best choice in the mold is difficult to do double the number of blades symmetrical balance point so for fans, the double is not a good thing;. "Not all good pairs"