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(1) Start a single air compressor in the control room and stop the operation.
(2) After the operation of a single air compressor, the corresponding air compressor butterfly valve is linked.
(3) The three instruments are started separately by the air compressor, and the starting level is #1, #2, #3. The specific requirements are as follows: When the #1 air compressor is running and the compressed air main pipe pressure is low, start #2 Air compressor, if the startup fails, start the #3 air compressor.
When the #2 air compressor is running and the compressed air main pipe pressure is low, the #1 air compressor is started, and if the startup fails, the #3 air compressor is started. ! When the #3 air compressor is running and the compressed air main pipe pressure is low, the #1 air compressor is started, and if the startup fails, the #2 air compressor is started.
(4) When one air compressor is in operation, the other two air compressors are unconditionally started at the same time.
(5) In the control room to achieve the operation of stopping the air compressor, the following conditions must be met: the pressure of the compressed air main pipe is not low. The other two air compressors must have one operation.
2PLC selection and hardware configuration
2.1 Determination of input/output points
The number of input points depends on the following aspects: (1) operation room and machine side operation, (2) operation status feedback, (3) mother tube pressure detection, and (4) fault reset operation.
The number of output points depends on the following aspects: (1) air compressor start stop control and signal display, (2) butterfly valve control and signal display, (3) air compressor accident trip alarm, (4) air compressor start Failure alarm.
2.2PC selection and configuration
The SIMATICS7300 is low-cost, its CPU has a higher intelligent PLC; its I/O arrangement density is high, the speed is fast, the expansion is flexible, it is a modular structure without slot limitation; it has user-friendly WindowsSTEP7 programming software. For the reliability of the system operation, the 220VAC operating voltage is selected for the input/output signals. The input module selects 3 6ES7321-1FF01-OAAO (8 points 230VAC), and the output module selects 3 6ES7 322-1FF01-OAAO (8 points 230VAC 1A). ), the output uses an intermediate relay isolation method. The speed of CPU313.CPU313 is 1000 instructions/0.7ms. The system using CPU313 has a maximum I/O capacity of 128 points and 32 channels of analog. The power module adopts PS307-1E, 5 A, and can withstand surge current 45A. 2.3 System software design
The STEP7 programming software used in S7 series PLC is structured programming, that is, the system only scans the management program OB1, and other programs are called by OB1.
In order to facilitate debugging and fault diagnosis, the control programs of the #1, #2, #3 air compressors are programmed in the program blocks FC1, FC2, and FC3, and are executed by OB1.
For the reliability of the mother tube pressure detection, take 3 detection points. Only two or more detection signals must be the same to be considered valid. The mother pipe pressure is judged as the common condition of the three air compressors, so it is placed in OB1.
Each air compressor has three starting modes: (1) operation start; (2) self-starting of low pressure of the main pipe and failure of the previous start; and (3) self-starting after any other trip.
There are two kinds of stop modes for each air compressor: (1) the console stops (one of the other two is under normal pressure); (2) the machine stops (unconditional).
After the air compressor is started for 30 seconds, the corresponding butterfly valve is opened. If there is no running signal return after the start command is issued for 1 min, it is regarded as the startup failure, the #start failure flag is set, and the #start failure alarm signal is set at the machine side and the operation room. After the air compressor is started, the #running flag is set. If the #running flag exists and there is an air compressor #stop running signal return, it is regarded as a fault trip, and a #fault trip alarm signal is set in the machine and in the operating room. After troubleshooting, the #Fault Reset button can be used to clear the # Fault Trip and #Start Failure Flags.
The #2, #3 air compressor control program is the same as #1.
In the control program of #2 air compressor, the contents of the dotted line box should be: (1) the pressure of the mother pipe is low; (2) the air compressor of #1 is running. Or (1) the pressure of the mother pipe is low; (2) the #3 air compressor is running; (3) the #1 air compressor fails to start.
In the control program of the #3 air compressor, the contents of the dotted line frame should be: (1) the mother pipe pressure is low; (2) the #1 air compressor is running; the #2 air compressor starts failing. Or (1) the mother pipe pressure is low; (2) #2 air compressor is running; #1 air compressor starts failing.
3CPU313 mode selection switch use
(1) RUN-P mode RUN-P is the program operation mode. When the selector switch is placed at this position, the CPU scans the user program. The key cannot be pulled out at this position. The programmer and the CPU can transfer programs to each other. The program is modified.
(2) RUN mode RUN is the operation mode. When this position is selected, the CPU scans the user program and the key can be pulled out to prevent anyone from changing the operation mode. The program in the CPU can be read by the programmer, but it cannot be modified.
(3) STOP mode STOP is the stop mode. When this mode is selected, the CPU does not scan the user program and the key can be pulled out to prevent the operation mode from being changed. Programs can be transferred between the programmer and the CPU.
(4) MRES mode MRES is a memory mode for clearing the CPU. The switch instantly turns on this position to clear the memory of the CPU. The specific operations are: 1) turn the key to the ATOP position; 2) turn the key to the MRES position (about 3s) until the STOP LED lights up again; 3) immediately turn the key back to STOP after the STOPLED lights up again Position and then pull back to the MRES position. If the STOPLED flashes for about 3 seconds and then lights up, the CPU memory has been reset.
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