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Fan capacity is selected according to the maximum amount of air required for the process equipment, but the actual amount of air required for the operation of the equipment is small. Therefore, according to the operation required to adjust the fan air flow is to achieve the fan energy-saving operation of the common methods, usually in the following two ways: 1. Control input or output of the air valve; 2. Control the motor rotation speed.

The use of regulating the opening of the air valve to control the amount of air: in industrial production often use the motor constant speed operation, with a closed air valve to reduce the fan load start and adjust the opening of the damper control air volume. In this adjustment of the air flow process, the motor shaft power and air volume is proportional to.

The advantage of using the regulating air valve to control the air volume method is that the initial investment is small and the control is simple, which is the method that has been used in industrial production. But its drawback is in the regulation of the air valve to control the air volume, the fan equipment operating efficiency is significantly reduced, power loss, energy saving effect is not obvious.

The use of speed control air volume: the use of control fan drag motor speed to adjust the air flow is based on the principle of energy, pressure, speed, torque, air flow and speed is proportional to the motor shaft power and speed is proportional to the cube. When the ventilation system only needs half the air volume, the motor speed can be reduced by 50%, then the motor output power is only 12.5%. Control the speed control air volume, so that the lowest power loss, energy saving effect is considerable.

The use of speed control air flow energy saving method is ideal. There are many kinds of motor speed control, such as variable pole speed, stator voltage control, frequency control and so on. With the development and popularization of frequency conversion technology, the inverter products have high performance, and the energy saving of the fan is realized by the frequency converter to gradually replace the fan control scheme.