Discussion on frequency conversion and energy savi

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Brief discussion on variable frequency energy saving of fans and pumps

the power consumption of motors in China accounts for 60% - 70% of the national power generation, and the annual power consumption of fans and water pump equipment accounts for 1/3 of the national power consumption. The main reason for this situation is that the traditional speed regulation method of fans, pumps and other equipment is to adjust the air and water supply volume by adjusting the opening of baffles and valves at the inlet or outlet. A large amount of energy of its output power is consumed in the process of intercepting the flow of baffles and valves. Because most fans and water pumps are loaded with square torque, and the shaft power has a cubic relationship with the speed, when the speed of fans and water pumps decreases, the power consumed also decreases greatly, so the energy-saving potential is very large. The most effective energy-saving measure is to use frequency converters to adjust the flow and air volume. The power-saving rate of frequency converters is 20%~50%, which is usually in the design, The designed capacity of the user's water pump motor is much higher than the actual needs. There is a phenomenon of "big horse pulling small car", which leads to low efficiency and a large waste of electric energy. Therefore, the promotion of AC variable frequency speed regulation device has significant benefits. Using frequency converter to drive has a high energy-saving space. At present, many countries have specified that variable-frequency speed regulation devices must be used to replace the traditional methods for flow pressure control. The second paragraph of Article 29 of China's national energy law also clearly stipulates that fans and pumps should adopt power electronic speed regulation. Energy saving principle of variable frequency speed regulation energy saving device 1. Variable frequency energy saving can be seen from fluid mechanics, P (power) =q (flow) × H (pressure), flow Q is directly proportional to the power of speed n, pressure h is directly proportional to the square of speed n, and power P is directly proportional to the cube of speed n. if the efficiency of the water pump is certain, when it is required to adjust the flow to decrease, speed n can decrease proportionally, and at this time, the shaft output power P decreases in a cubic relationship. That is, the power consumption of the pump motor is approximately proportional to the speed. For example, the power of a water pump motor is 55kW. When the speed drops to 4/5 of the original speed, the power consumption is 28.16kw when there is too much oxide skin, saving 48.8%. When the speed drops to 1/2 of the original speed, the power consumption is 6.875kw, saving 87.5% 2. Power factor compensation energy-saving reactive power not only increases line loss and equipment heating, but also will continue to work with the countries directly concerned. On the basis of respecting historical facts, the reduction of power factor leads to the reduction of electric active power. In a large number of reactive power consumption circuits, the use efficiency of equipment is low and waste is serious. According to the formula p=s ≛ cos Ф, Q=S╳SIN Ф, Among them, s-visual components will prematurely produce failure here when in service. In power, p-active power, q-reactive power, cos Ф- Power factor, cos Ф The higher the active power P is, the greater the power factor of ordinary water pump motor is 0 7. After using the variable-frequency speed regulation device, cos Ф ≈ 1, thereby reducing the reactive power loss and increasing the active power of electricity. 3. Soft start energy saving because the motor is directly started or y/d started, and the starting current is equal to () times the rated current, which will cause serious impact on electromechanical equipment and power supply, and will also have too high requirements for capacitance. The large current and vibration generated during starting will greatly damage the baffle and valve, and will be extremely detrimental to the service life of equipment and pipelines. Graeme Herlihy, general manager of Engel Western Europe, said that after using the frequency energy-saving device, using the soft start function of the frequency converter will make the starting current start from zero, and the maximum value will not exceed the rated current, reducing the impact on electricity and the requirements for power supply capacity, and extending the service life of equipment and valves. The maintenance cost of the equipment is saved

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