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Shanghai Hongjing Automation Technology Co., Ltd
Internal components of control cabinet
NegotiableUpdate on 06/15
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Overview
Internal components of control cabinet
Product Details
Internal components of control cabinet
The motor (water pump) automatic control servo system is widely used in industrial production, water supply and drainage treatment systems, chemical storage, heating, cooling and other applications. It can adopt centralized or decentralized control according to process needs. In the application of water supply and heating systems, the process needs to be adjusted at any time due to changes in water supply pressure and flow rate, and the amount of cold water used is also constantly changing. We often install an electromagnetic flow meter at the main outlet of the water supply pipe (cold water) and hot water pipe (reuse), convert the flow difference value into a standard signal, and send it to the microprocessor (PLC). After the data is calculated by the processing system and compared with the set pressure value and flow difference, the PLC provides the output frequency after adjusting the ratio (PID adjustment) to change the speed of the water pump motor, thereby controlling the constant pressure difference between the water supply and return pipes, forming a complete closed-loop control system.
The following are application cases:
The control system is shown in the following figure:
Control principle of cold water (supply) and hot water (reuse) circulating water pump:
1) Cold water pump: When the flow rate of cold water increases, the speed of the variable frequency pump automatically increases; When the working frequency of the variable frequency pump rises to 50Hz but still cannot reach the set pressure, the PLC control system will automatically start a power frequency water pump to work. At this time, the variable frequency water pump and the power frequency water pump work in parallel, and the power frequency water pump provides a constant flow rate (flow rate under constant power frequency speed). The speed of the variable frequency water pump will change with the size of the water flow rate, thereby adjusting the water supply. When the flow rate of cold water decreases, the pressure in the pipeline increases, and the speed of the variable frequency speed control pump decreases. When the frequency drops to a certain value (such as 10Hz) and after a certain delay, the variable frequency water supply controller sends a command to automatically shut down a power frequency water pump for water supply. When the water flow rate approaches zero, the variable frequency water pump is in an automatic stop state, which can achieve no energy loss when not using water and has the best energy-saving effect. In order to reduce the impact (hydraulic or current impact) when the power frequency pump is automatically turned on or off, all pumps have a soft start function. The primary wiring of the cold water pump is shown in the following figure:
2) Hot water pump: The operating frequency is calculated based on the flow difference between the outlet flow rate of the cold water pump and the outlet flow rate of the hot water pump. When the difference between the total outlet flow rate of the cold water pump and the total outlet flow rate of the hot water pump is positive, the speed of the variable frequency pump automatically increases; When the working frequency of the variable frequency pump rises to 50Hz and the flow difference is still positive, the PLC control system will automatically start a power frequency water pump and put it into operation. At this time, the variable frequency water pump and the power frequency water pump work in parallel, and the power frequency water pump provides a constant flow rate (flow rate under constant power frequency speed). The speed of the variable frequency water pump will change with the difference in flow rate, thereby adjusting the water supply. When the flow rate of cold water decreases and the flow difference is negative, the speed of the variable frequency speed regulating pump decreases. When the frequency drops to a certain value (such as 10Hz) and after a certain delay, the PLC control system sends a command to automatically shut down a power frequency water pump for water supply. When the water flow rate approaches zero, the variable frequency water pump is in an automatic stop state, which can achieve no energy loss when not using water and has the best energy-saving effect. In order to reduce the impact (hydraulic or current impact) when the power frequency pump is automatically turned on or off, all pumps have a soft start function. The wiring of the hot water pump is shown in the following figure:
