The most popular one is about the system transform

2022-08-01
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About the system transformation of 55kW circulating cooling water pump

Abstract: since the advent of the general variable frequency governor, the variable frequency governor technology has been widely used in various fields. The variable frequency governor has been greatly developed in practical application with the advantages of energy saving, safety and high quality. With the rapid development of electronic technology, the function of the variable frequency governor is becoming stronger and stronger, In particular, making full use of the built-in PID regulation function of the frequency converter is of great significance to the rational design of the frequency converter speed regulation equipment and to ensure the strength inspection results of the embedded T-joint in the normal production

key words: Transformation of 55kW circulating cooling water pump system frequency converter

in the past, our company's circulating cooling water system used two circulating water pumps (one for use and one for standby) to supply water in the form of constant speed pumps. Generally, the water pressure fluctuates greatly and the energy loss is large. Once the water consumption in the workshop is large, the pipe pressure will drop rapidly, and when the water consumption in the workshop is stopped or reduced, the pipe pressure will rise rapidly, In fact, the indirect change of flow leads to the change of pipe pressure, resulting in the loss of output power of the circulating pump. The unstable outlet pressure of the circulating pump causes the change of the working point of the circulating pump, which makes the efficiency of the circulating pump set worse, virtually increases the consumption of electric energy and mechanical wear of equipment, and is easy to cause the increase of equipment failure rate. In order to ensure normal production and achieve the expected cooling effect of the workshop, At ordinary times, the pressure behind the circulating pump is kept too high, so the pipe pressure is low when the water flow in the water supply pipe of the constant speed circulating pump is large, and the pipe pressure is high when the water flow is small; The company has no specific regulations and constraints on the use of circulating water in the workshop. Sometimes, the workshop has no circulating water and the circulating pump is turned on; Sometimes, because the water level of the circulating pool is too low, the pump unit can not absorb water, but the circulating pump unit is running without load, which not only wastes electric energy, but also accelerates the mechanical wear of the pump unit; On the other hand, the driving motor of the circulating water pump is started by star delta step-down instantaneous starting, and the shock wave during starting causes electrical instability and damage to the mechanical performance of the circulating pump unit. In view of the above points, it is intended to use the closed-loop control mode of variable frequency speed regulation to control

since the advent of the general variable frequency governor, the variable frequency governor technology has been widely used in various fields. The variable frequency governor has made great progress in practical application with its advantages of energy saving, safety and high quality. With the rapid development of electronic technology, the function of the variable frequency governor is becoming stronger and stronger. In particular, the built-in PID regulation function of the variable frequency governor is fully used to reasonably design the variable frequency governor equipment, It is of great significance to ensure normal production. The company's circulating water pump water supply system adapts to the flow demand of each workshop by changing the water output capacity of the pump unit through the frequency converter. When the speed of the circulating water pump changes, the head characteristics change with the change, while the pipe resistance characteristics remain unchanged, so the pipe pressure flow is adjusted. Since the water consumption of the workshop varies greatly in different time periods, in order to save energy, the principle of "1 control X" switching is usually required based on the principle of "more use, more open and more send, less use, less open and less send". If the water supply is insufficient, automatically increase the speed of the circulating pump to increase the outlet flow pressure of the pump set or start the No. 2 pump set for frequency conversion control; On the contrary, when the water consumption in the workshop decreases, the No. 2 pump unit will be stopped and the water will only be supplied by the frequency conversion control system of No. 1 pump unit. The variable frequency governor has built-in PID adjustment and calculation function, so that the collected pressure signal (dc4-20ma) can obtain a new frequency given signal output (dc4-20ma) after PID adjustment and comparison processing, which determines the output frequency of the variable frequency governor, thus changing the speed of the circulating pump to achieve constant pipe pressure, forming a closed-loop constant value control system, which can automatically adjust the speed on demand, and achieve stable and constant real-time regulation of pipe water pressure, Avoid impact loss caused by water pressure flow fluctuation; Reasonable setting of PID parameters can greatly reduce the power loss caused by excessive water pressure in the water supply pipe of the system, save energy and reduce mechanical wear. In addition, the effective setting of the service life of the machine can be guaranteed through the over-regulation of the starting process of the circulating pump motor by the frequency converter, so that the starting current of the pump unit can be increased smoothly, and the continuous starting operation can avoid the impact of the large current generated by the conventional fast starting motor on the electricity and the mechanical impact; So as to effectively reduce the wear of bearings and other vulnerable parts, generally reduce mechanical stress, and have the effect of saving electricity and prolonging the service life of motors and pumps

in addition, the water level of the circulating water tank and the fan operation of the cooling pedal shall be interlocked with the closed-loop control system of variable frequency speed regulation of the circulating pump unit. It is decided to start the machine according to the water level of the pool. Once the water level of the pool is too low, it can automatically open the make-up water inlet valve to add water to the pool until the predetermined water level is reached. This ensures the controllability of the normal operation of the whole system

attached drawings of specific scheme drawings:

main electrical wiring schematic diagram of control system

internal wiring schematic diagram of variable frequency governor (general fan and water pump type)

unit: Zhejiang Puluo Chemical Co., Ltd.

No.: dykr

prepared by: Ren Xuefeng date:

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