In the load of water pump and fan, the power output of the motor can be controlled by adjusting the frequency, so as to realize the energy saving of the system.
The working point of the pump is the intersection of the lift curve of the pump and the resistance characteristic curve of the pipeline. P=QH (P power, Q flow, H head), power is the area enclosed by the curve under the operating point.
Traditionally, water flow is regulated by valves. This method works by increasing the resistance characteristics of the pipeline. When adjusting the valve, although Q decreases, H increases and the efficiency decreases. Therefore, its energy saving effect is quite limited.
Changing the speed changes the operating characteristic curve of the pump without changing the resistance characteristics of the pipeline. According to the similarity principle, the head H decreases with a square relationship, while the power P decreases with a cubic relationship, and the original high efficiency is maintained. So this method is an effective energy-saving method. When the traffic is reduced to 80% of the original, the power consumption is only 51% of the original, saving 49%. When using the regulating valve, only about 5% of the energy is saved.
Using the frequency converter can effectively improve the power factor. From the data in the above table, the reactive power is reduced by 21.3% after the frequency conversion is used. At the same time, the frequency converter has dual filter devices for inlet and outlet, which eliminates the impact of motor starting and electromagnetic interference on the power grid. The use of the inverter is to adjust the motor speed according to the load: when the load is low, the motor speed regulation decreases; when the load increases, the motor speed increases accordingly. It is guaranteed that the pump motor will not have low-speed and high-load working conditions, and will not have over-speed operation that is higher than the rated current frequency. When the motor is running at low speed, due to the low current frequency, the coil enameled wire generates less heat and less temperature rise, which is beneficial to prolong the service life of the motor coil. Other mechanical components are also beneficial for extended service life due to their low operating speed.
The frequency conversion system has the function of soft start, which provides a flexible, gentle, non-jump start-stop process for the mechanical connection between the pump and the motor, avoids mechanical impact, and can prolong the service life of the mechanical connection parts between the motor and the pump.
To sum up, under the load conditions of fans and pumps, the use of variable frequency motors will produce better economic benefits, and at the same time, due to the smoothness of variable frequency starting, it has a good inhibitory effect on the vibration and noise of the entire fan and pump system.
Post time: 2022-02-22