The speed of the fan is an important factor that affects the performance of the fan. When the speed changes, the airflow, pressure, and power of the fan will change. For fans of the same airflow and pressure, the speed of the speed will affect the size of the impeller, that is, the diameter and the width of the outlet.

The relationship between the speed of the fan and the main characteristic parameters is: the airflow is proportional to the speed; the pressure is proportional to the square of the speed; the power is proportional to the cube of the speed.

The above relationship is called the proportional law of the fan.