The Application of PLC in the Automatic Control System of Diesel Generator Sets ZHANG Jinsong, CHEN Gang (Department of Mechanical Engineering, Hubei Institute of Technology, Wuhan 430068, Hubei Province, China) Introduces the main functions of stand-alone emergency diesel generator sets and the I/O settings in PLC control design The focus is on the design ideas and methods for unit operation, start-up, shutdown, regular self-lubrication and operation procedures.
Programmable controller; Diesel generator set; Automatic control; Program design Diesel generator set as a backup power supply, widely used in defense, industry, agriculture, commercial and other industries This article uses Huaguang Electronic Industry Co., Ltd. developed for small automatic The SH series PLC of the control system designs the automatic control system of the single emergency diesel generator set.
1 The diesel generator set automation function can set emergency power supply when the utility power fails.
2 PLC control design According to the automatic function of the diesel generator set configuration, the system uses SH-64R1-C type programmable logic controller, 17 points input, 24 points output, its configuration see.
Water temperature high report è±æ“‚é¼· Speeding alarm preparation Emergency stop oil pressure interlocking speed increase deceleration start stop magnetization electromechanical closing heater input pump input oil pump input power loss power supply under voltage machinery and equipment pressure water temperature high oil temperature high oil Depressing the generator switch Manually starting Manually opening the manual shutdown Self-checking running report Fighting test reset Since this unit is a stand-alone emergency automation unit, according to the requirements of GB/T4712 "Automation Diesel Generator Group Level Requirements", this unit is set up with the following automation functions.
Automatically start and load. When the utility power stops, the control unit starts automatically, raises the speed, and closes the power supply to the load. This process does not exceed 3 seconds. After the utility power returns to normal, the delay ls opens, the mains switch is closed, automatic switching is completed, and then the unit is automatically shut down after 5 minutes of cooling. If the utility power fails again during the cold process, the unit will be switched directly to provide automatic power protection to the load. During the operation of the unit, sound and light alarms should be performed if there is a fault in the water temperature or the oil temperature. If an overspeed or low oil pressure occurs, an audible and visual alarm is issued and an emergency shutdown occurs; if an overload, short circuit or voltage abnormality occurs , sound and light alarm signal and open.
Pre-feed function. When the unit is in the quasi-launch condition, the automatic pre-supply system is put into operation. Every 4 s, the unit is ready for emergency start at any time.
Test machine function. When the unit is continuously stopped for more than 15 days in the automatic state, the unit can start the test run by itself, check whether the automatic control function is normal, and fully lubricate the friction pairs of the unit to prepare the system I/O configuration according to the PLC external wiring diagram and Its control function, you can create a PLC control ladder diagram.
2.2 Program design 2.2.1 Preparatory operation The program is designed to ensure that the unit can smoothly start up and carry the power supply within 30 seconds after the mains power failure. The unit must be at all year long Zhang Jinyu (1971), female, Hubei Huanggang, lecturer at Hubei Institute of Technology, Master of Engineering, Research direction: mechanical design and theory - in preparation for operation. This state includes: 1) The temperature of diesel engine cooling water and lubricating oil must be kept within the temperature range of diesel engine load operation; 2) The diesel engine is pre-lubricated at regular intervals so that the oil film remains in each rotating part of the diesel engine to ensure that the unit is in emergency start-up. When it is quickly loaded, the diesel engine is not damaged.
Prepare to run the block diagram as shown.
Prepare the program run box. 2.2 Unit start-up procedure design Under the condition of maintaining the preparatory operation, the unit is interrupted from mains to the start of the unit, and the main switch is sent a closing signal to the load. The whole process must be completed within 30s. The working process is as follows: When the mains power is off or the external voltage is too low (20% voltage drop), after confirming that the start signal is sent to the diesel starter motor after 2s, when the unit start speed reaches 300r/min, a start signal is sent to exit the starter motor. , And speed up to the rated speed, at the same time, the unit magnetization build pressure. Under conditions of both voltage and speed, the unit automatically closes to supply power to the load (see ).
The start-up program running block diagram of the drying unit can be started 3 times in a row if the startup is unsuccessful during the start-up process. When the start-up is unsuccessful, the electromagnet is powered off for 6s and then the next startup is performed after the solenoid power-off delay is 4s. If all three start-ups are unsuccessful and the start-up delay time expires, a start-up failure sound and light alarm signal is issued and the standby machine is enabled. , 2.2.3 Unit shutdown program design When the utility power is restored, there are two automatic shutdown functions for selection. In the "auto-one" state, the unit will automatically switch the gate after confirming that the utility power is restored for 10 seconds, and complete the switchover. The power will be supplied from the utility power to the automatic two state. The operator should press the power generation when the switch is needed according to the usage of the load. The machine's opening button only changes the load to be powered by the mains.The above two working methods are the same except that the mains recovery switching mode is not the same, they are all reduced to 600r/min first. Stop after running 5min cold (see).
I Pump reset I block shutdown program operation block diagram If the utility power supply is interrupted during the shutdown process, it will directly return to the startup process.
2.2.4 Unit self-lubrication program design Self-test running time depends on the circumstances, generally set for 30min, the unit automatically starts, idle speed 5min, set idle speed 20min, and finally set idle speed 5min automatic shutdown. If the utility power failure occurs during the self-test operation, the unit automatically exits the self-lubrication state and enters normal emergency power supply status (see below).
I self-lubrication time to 1 I unit three times to start failed to report 1 I unit speed operation 20min | deceleration fw group again idle operation 5 ~ n I stop - machine I unit regular self-lubricating program running plant. 2.5 Unit Operation Program Design After the automatic unit has successfully loaded and operated normally, it begins to perform cyclic testing on the abnormality of the electromechanical system and the restoration of the utility power to maintain the normal operation of the unit. During the operation of the unit, if the oil temperature is high, an audible and visual alarm can be performed; if the oil pressure is low or overspeed, the emergency stop of the diesel engine can be controlled and an audible and visual alarm signal is issued; if the overcurrent occurs, the main switch is switched off to emit sound and light. Alarm signal opening, shutdown, sound and light reports, M opening, shutdown, sound and light alarm, M opening, sound and light sound and light alarm, electrical and electrical sub-gates, mains closing, power supply from the city power supply unit operation program BLOCK DIAGRAM Conclusion The working environment of the diesel generating set is often rather harsh. Therefore, using PLC can improve the anti-interference ability of its control system. In addition, the ladder diagram is simple, easy to understand, and easy to design. However, the automatic control of the diesel generator set is quite complex and involves various aspects. If the above-mentioned program design methods and ideas (which have been successfully applied in the simulation experiment) are used, the difficulty can be reduced.
Yang Yaochun. Practical electrical circuits and principles. Beijing: China Radio and TV Press, 1991. Huaguang Electronic Industry Co., Ltd. Programmable Controllers SH Series User's Manual (Version 1). 1997. Wan Taifu, Tang Xianyong. Programmable controller and its application. Chongqing: Chongqing University Press, 1994. (Continued from page 28) Zhou Shiyu. Dynamic Analysis of High-speed Seismic Roller Mechanisms. Bao Zhoushi, Ke Hui. Finite Element Method for Consolidation of Convexity Parameters of Idler Rolling Roller Mechanism . Journal of Hubei Institute of Technology, 1998 (4) Huang Xiaocheng. Research on Kinematics and Dynamics of High Speed ​​Corrugated Paperboard Forming Machines . Wuhan: School of Mechanical Engineering, Huazhong University of Science and Technology, 1997.
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