Application of Phosphate Fertilizer and Fertilizer Schneider Soft Starter on Screw Air Compressor Fang Xiaoping (Electrical Workshop of Yanan Lunan Chemical Co., Ltd., Tengzhou 277527, Shandong Province) introduces the working principle, main function and screw function of Schneider soft starter Application on the press. Schneider soft starter is a soft start-soft stop control unit composed of 6 thyristors. Compared with the traditional step-down start, the Schneider soft starter has simple control mode, stable current change and perfect protection function, which is beneficial to the safe operation of the equipment.
Schneider soft starter; function; screw air compressor; application traditionally, for large chestnut and fan load, use Y/A step-down start, and some use reactor or autotransformer and other starting methods, but these methods There is a waste of resources and manpower, and unreliable factors increase. In recent years, with the development of power electronics technology, inverters and soft starters have been widely used. For constant torque load, if the cost of the inverter is higher, the soft starter can realize the smooth start of the motor, and it can play the same function as the motor protector, and the maintenance is convenient and the parameter setting is fast, so in the chemical industry And other industries have been widely used.
1 Schneider soft starter working principle Schneider soft starter (hereinafter referred to as soft starter) has overcurrent, short circuit, overvoltage, undervoltage and other functions, and can achieve motor step-down start and soft stop, is a suitable New equipment selected by chemical companies. It is mainly realized by the conduction of the thyristor, which is mainly composed of 6 thyristors, wherein each phase is connected in parallel, then connected in series in the main loop, and the acquired signal is judged by the single-chip microcomputer fuzzy control system to control the thyristor. The firing angle causes the output voltage to change. Moreover, according to the needs of the user, the bypass contactor can be set to control the operation of the bypass contactor after the step-down start by the output of the single-chip microcomputer. The soft starter works as shown. In the figure, R, S, T are the soft starter input power, U, V, W are the output power, SCR is the thyristor, JC is the bypass contactor normally open contact, when used for bypass operation, this The node is turned on and the motor is running normally.
The working principle of the soft starter 2 The function of the soft starter and its application on the screw air compressor 2.1 Main functions of the soft starter 1) Main protection function: 1 Starter thermal protection. The PTC sensor mounted on the radiator and the temperature rise of the thyristor are used to raise the phosphate fertilizer and the compound fertilizer for heat protection. 2 motor thermal protection. The temperature rise of the motor is continuously calculated based on the controlled rated current and the actual absorbed current. If the motor exceeds the critical temperature rise value, the thermal fault will stop the motor. 3 long boot time protection. If the motor start-up time exceeds the long start-time protection setpoint, the starter will trip protectively. 4 starter over current protection. During operation of the soft starter, the module or thyristor heat is severely tripped due to the heavy load. 5 input, output phase loss protection. Poor contact, out-of-phase or motor damage of all power supplies, starters, motors and their electrical isolation devices (contactors, circuit breakers, etc.) can cause input and output phase loss protection.
2) Display, alarm, parameter setting function: The operation status, running current and voltage of the motor can be viewed through the liquid crystal display of the soft starter. If the device fails, the soft starter will display the fault code and also enable online adjustment of the parameters.
3) Start and stop control mode: The soft starter startup mode is relatively reliable. When the control loop starts and the stop button changes accordingly, the soft starter sends a corresponding start/stop signal according to the CPU acquisition. The control modes are mainly as follows: 12-line control mode; 23-line control mode; 3 forced free-stop (LIA) mode; 4 forced to local control mode (LIL).
2.2 Application of soft starter on screw air compressor 2.2.1 Structure of screw air compressor application soft starter control system The structure of control system of our company in screw air compressor application is as shown. The main loop system includes a soft starter, a bypass contactor and a power cable. The control system is mainly composed of a secondary circuit, a programmable controller (PLC) and a pressure sensor.
Screw air compressor application soft starter control system Note: Ll, L2, L3 in the figure is 380V AC power supply.
2.2.2 Screw air compressor application Soft starter control working principle Firstly set the starting pressure value of the air compressor to the programmable controller, the pressure signal is collected by the pressure sensor, when the pressure in the gas tank drops to the set value The programmable controller sends a start signal, and the soft starter sends a pulse after receiving the start signal, triggering the thyristor to conduct, so that the air compressor motor starts slowly under no-load condition. When the motor runs at full speed, the soft starter controls the bypass contactor coil to be energized, the bypass contactor pulls in, the system switches to bypass operation, and the programmable controller controls the intake solenoid valve through a preset delay time. Open, the air compressor starts to run with load. When the pressure in the gas tank reaches the set value, the programmable controller controls the solenoid valve to close, the air compressor enters the no-load state again, and the programmable controller sends a parking command to the soft starter after a set delay time. The soft starter is free to stop after receiving the command. The air compressor can be started or stopped in an automatic/manual mode, which can be solved by the transfer switch.
When the transfer switch is cut to the automatic working mode, the soft starter collects the tank pressure control through the programmable controller; when the transfer switch is switched to the manual mode, the programmable controller loses its function, and the operator needs to be in the soft starter control panel. The air compressor can be started and stopped manually. The start and stop terminals can also be led to the control room through the control line, and the air compressor can be started and stopped by buttons or meter configuration. 2.2.3 Effect of soft starter applied to screw air compressor In 201 years, our company's 100,000 t/a acetic anhydride project screw air compressor motor adopts ATS48C25Q soft starter. After nearly 2 years of operation, its starting mode and tradition Compared with the voltage drop start, the reliability is stronger, mainly reflected in the following points: 1) The soft starter is directly connected in series to the main circuit, and the control mode is output by the internal program. After the motor is fully started and restored to full voltage operation, the internal The program is controlled by the node output control bypass contactor, which avoids the heating of the soft starter main circuit due to long-term charging.
2) The soft starter has a stable current change during the start-up process, and the harmonics are small, which improves the impact of the grid or harmonic pollution due to the large starting current.
3) The starting device mainly consists of two-way thyristor, which avoids the adhesion caused by long-term contact with the contactor and the burning of the contact.
4) The start and stop processes are smooth, the power system is stable, and the service life of the equipment is extended.
5) It has superior protection function than motor protector, collecting signal and response is sensitive and reliable, various bad operating conditions appearing in air compressor operation, soft starter will alarm or issue trip command, basically realize free maintenance. Greatly reduced maintenance costs.
6) User-friendly LCD screen, g real-time display of various signals in operation, easy for operators to fully understand the operation of the equipment.
7) The parameter setting is convenient and concise, and there is no occurrence of failure to start or false trip due to a certain redundant parameter not being set.
3 Conclusion At present, our company is more than 110kW motor, all of which are selected to use this series of soft starters, mainly used in air compressors, circulating water pumps, boiler fans and other equipment. Due to its well-controlled functions and sensitive and reliable protection, it will still be used in subsequent projects.
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