Frequency converter is a power control device that converts the power frequency power supply to another frequency by using the on-off action of power semiconductor devices. With the rapid development of modern power electronic technology and microelectronics technology, high voltage and high power frequency conversion speed regulation devices continue to mature, the original has been difficult to solve the high voltage problem, in recent years through the device series or unit series has been a good solution.
High voltage and high power variable frequency speed regulating device is widely used in large mining production plant, petrochemical, municipal water supply, metallurgical steel, power energy and other industries of all kinds of fans, pumps, compressors, rolling machines and so on.
Pump loads, which are widely used in industries such as metallurgy, chemical industry, electric power, municipal water supply and mining, account for about 40% of the energy consumption of the entire electrical equipment, and the electricity bill even accounts for 50% of the cost of water production in waterworks. This is because: on the one hand, the equipment is usually designed with a certain margin; On the other hand, due to the change of working conditions, the pump needs to output different flow rates. With the development of market economy and automation, the improvement of the degree of intelligence, the use of high voltage frequency converter for speed control of pump load, not only to improve the process, improve product quality is good, but also the requirements of energy saving and equipment economic operation, is an inevitable trend of sustainable development. There are many advantages to speed control of pump loads. From the application examples, most of them have achieved good results (some energy saving up to 30%-40%), greatly reducing the cost of water production in the waterworks, improving the degree of automation, and conducive to the step-down operation of the pump and pipe network, reducing leakage and pipe explosion, and extending the service life of the equipment.
Method and principle of flow regulation of pump type load, The pump load is usually controlled by the liquid flow rate delivered, so two methods of valve control and speed control are often used.
1.Valve control
This method adjusts the flow rate by changing the size of the outlet valve opening. It is a mechanical method that has been around for a long time. The essence of valve control is to change the size of the fluid resistance in the pipeline to change the flow rate. Because the speed of the pump is unchanged, its head characteristic curve H-Q remains unchanged.
When the valve is fully open, the pipe resistance characteristic curve R1-Q and the head characteristic curve H-Q intersect at point A, the flow rate is Qa, and the pump outlet pressure head is Ha. If the valve is turned down, the pipe resistance characteristic curve becomes R2-Q, the intersection point between it and the head characteristic curve H-Q moves to point B, the flow rate is Qb, and the pump outlet pressure head rises to Hb. Then the increase of pressure head is ΔHb=Hb-Ha. This results in the energy loss shown in the negative line: ΔPb=ΔHb×Qb.
2.Speed control
By changing the speed of the pump to adjust the flow, this is an advanced electronic control method. The essence of speed control is to change the flow rate by changing the energy of the liquid delivered. Because only the speed changes, the opening of the valve does not change, and the pipe resistance characteristic curve R1-Q remains unchanged. The head characteristic curve HA-Q at rated speed intersects the pipe resistance characteristic curve at point A, the flow rate is Qa, and the outlet head is Ha. When the speed decreases, the head characteristic curve becomes Hc-Q, and the intersection point between it and the pipe resistance characteristic curve R1-Q will move down to C, and the flow becomes Qc. At this time, it is assumed that the flow Qc is controlled as the flow Qb under the valve control mode, then the outlet head of the pump will be reduced to Hc. Thus, the pressure head is reduced compared to the valve control mode: ΔHc=Ha-Hc. According to this, the energy can be saved as: ΔPc=ΔHc×Qb. Compared with the valve control mode, the energy saved is: P=ΔPb+ΔPc=(ΔHb-ΔHc)×Qb.
Comparing the two methods, it can be seen that in the case of the same flow rate, the speed control avoids the energy loss caused by the increase of the pressure head and the increase of the pipe resistance under the valve control. When the flow rate is reduced, the speed control causes the indenter to be greatly reduced, so it only requires a much smaller power loss than the valve control to be fully utilized.
The high voltage inverter produced by Noker Electric is widely used in fans, pumps, belts and other occasions, and the energy saving effect is obvious, which has been recognized by customers.
Post time: Jun-15-2023