In the past, the circulating cooling water system used two circulating water pumps (one for each prepared) to feed the water in the way of a constant speed pump. Under normal circumstances, the water pressure fluctuated greatly and the energy loss was large. When the workshop water consumption was large, the pipe network pressure Rapid decline, and the workshop to stop or reduce water consumption, pipe network pressure will rise rapidly, in fact, indirect flow changes lead to pipe network pressure changes caused by the circulating pump output power loss, the circulation pump outlet pressure instability caused Circulation pump operating point changes, so that the circulation pump group itself, the efficiency of the worse, virtually increase the consumption of electrical energy and equipment, mechanical wear and tear, likely to cause equipment failure rate increases, and in order to ensure normal production to the workshop expected Cooling effect, the pressure circulating pump usually remain too high, so the relative constant flow pump circulating water pump network water flow at the end of pipe network pressure at the end of the water flow hour pipe network pressure is high; the company circulating water There is no specific rules and restrictions on the use of the situation, sometimes there is no need to recycle the water in the workshop, but the circulating pump is on; sometimes But also because the circulating water level over the bottom of the pump group can not absorb the water do not know, circulating pump group was running at no load both waste of energy and accelerate the pump mechanical wear; the other hand, circulating pump drag motor Start-up mode using the star - delta buck instant start, start-up shock wave caused instability in the power grid and circulation pump group mechanical performance damage. In view of the above intention to use frequency conversion speed control closed-loop control. Since the advent of the universal frequency converter, frequency control technology has been widely used in all fields, the frequency converter with energy saving, safety, high quality and other advantages, in the practical application has been greatly developed, with the electronic With the rapid development of technology, the function of frequency converter is also getting stronger and stronger. In particular, it makes full use of the built-in PID regulation function of inverter, which is of great significance to the rational design of frequency control equipment and normal production. The company's circulating water pump water supply system through the frequency converter to change the pump out of the water capacity to meet the needs of the flow of the workshop, when the circulating pump speed changes, with the change of head characteristics, while the tube resistance characteristics are unchanged, the regulation Pipe network pressure flow. Because of the different time periods, the workshop water consumption is very large, in order to save energy, in order to use more and more to send more and less to use less open to send less principle, it usually requires "1 control X" switch. If the water supply is insufficient, the circulating pump speed is automatically increased to increase the pressure of the pump group outlet or to start the pump group 2 for frequency conversion control. On the contrary, when the workshop water consumption is reduced, the pump group No. 2 should be stopped to exit the work first, Pump frequency control system water supply. Inverter has a built-in PID adjustment operation function, so that the collected pressure signal (DC4-20mA) after the PID adjustment comparison and processing to get a new frequency of the given signal output (DC4-20mA), determine the inverter output frequency Of the size of the circulating pump to change the speed of the pump to achieve a constant pressure pipe network constitutes a closed loop set value control system can be automatically adjusted according to need to achieve real-time regulation of pipe network pressure steady, to avoid fluctuations in water pressure flow caused Of the impact of loss; a reasonable set of PID parameter values ​​can greatly reduce the system water pressure over the water supply pipe network caused by the power loss, saving energy and reduce mechanical wear and tear. In addition, the transitional setting of the circulating pump motor starting process by the frequency converter makes the starting current of the pump group gently increase and continuously start running, which avoids the impact of the high current on the power grid caused by the conventional rapid starting motor and the generated mechanical Impact; thus effectively reduce the wear of bearings and other wearing parts, generally reduce the mechanical stress, with energy-saving and extend the life of the motor, pump group effectiveness. In addition, the water level of the circulating water tank and the operation of the fan on the cooling pedal are interlocked with the closed-loop control system of the variable frequency speed regulation of the circulating pump set. According to the pool water level decided to boot, when the pool water level over the bottom can be automatically opened to supplement the inlet valve to the pool water, until it reaches the predetermined level. This ensures the normal operation of the entire system controllability.