Application of the hottest micro programmable cont

Application of micro programmable controller in pump starting control

Abstract: soft starting control mode is often used in drainage pumps. The soft start control system based on micro programmable controller realizes the start and stop control, operation monitoring and protection functions of the water pump

key words: micro programmable controller pump starting control

1. Preface

the pump power used in the drainage pump station is generally relatively large. In order to avoid the impact of impulse current generated when the pump motor is directly started on electricity, the indirect method is generally used to start the pump. The commonly used indirect starting methods include Y-D starting method, auto coupling step-down starting method and soft starting method. For these starting modes, the traditional secondary control circuit usually uses multiple intermediate relays and time relays. With the development of technology, many equipment need to be transformed, such as the upgrading of starting mode and components; Many devices need to be adjusted in remote operation and use methods, such as changing local control to remote control or computer control. For the renewal of these technologies, the shortcomings of the traditional control loop design method, such as the large number of components, complex wiring, poor versatility and so on, have brought more difficulties to the transformation and maintenance of the equipment

therefore, it is necessary to improve the control circuit of the indirect starting water pump, so that the control circuit is simple, reliable, adaptable and functional. A new micro programmable controller with its own programmer can achieve this purpose

2. Comparison between micro programmable controller and traditional control mode

2.1 introduction of micro programmable controller

logo of general logic control module produced by Siemens! For example, it integrates the control function, the interface of operation and display unit, power supply, program module, adjustable basic functions (such as on and off time delay relay and pulse relay, etc.), time switch, binary indicator, text display, replace the broken indicator with the spare reed relay Li Liangbin, chairman of Jiangxi Ganfeng Lithium Industry Co., Ltd., a micro programmable controller with input/output functions of various equipment types. A standard controller has 8 switching inputs and 4 carefully nested relay outputs, and its size is 72x90x55mm. It is produced to save the space occupied by the system, simplify the installation complexity, and facilitate the manufacturing and standardization of the system. The user's control program can not only be input, compiled and displayed by using the six operation buttons and LCD panel integrated in the controller itself, but also be compiled, tested, simulated and printed by using software on the PC

2.2 comparison with traditional control mode

comparison with traditional relay control mode LOGO! There are many advantages:

(1) it can greatly reduce the number of relays and the complexity of circuits, so as to simplify the installation and maintenance of equipment and improve the reliability of the system

(2) with logo! The hardware connection of the pump starting control circuit as the core has strong compatibility. There is only a small difference in the hardware of Y-D starting mode, auto coupling step-down starting mode and soft starting mode, which can be used for each other with a little change, which is conducive to the realization of standardized design and the transformation of old equipment

(3) the control logic of the starting control system is almost completely controlled by the logo! The internal program is completed. During the manufacturing and operation, the program can be modified as needed at any time, making the use and maintenance of the system very convenient

(4) it has the function of communicating with the upper computer, which lays a foundation for the pump control system to further improve the degree of automation and realize remote monitoring

although the controller has many advantages, it also has some disadvantages

(1) compared with traditional relay control, logo! The investment of control mode components is slightly larger

(2) except for hardware connection, logo! The controller needs programming to realize control, which increases the workload of programming and debugging. Now it has been replaced by numerical control equipment and PC software

(3) the input and output points of control are controlled by LOGO! The limited number of input and output ports of the controller itself is limited, and there is nothing to do with the system with more control points

in short, although the logo! The controller has some disadvantages, but its advantages are very suitable for the control of water pump starting

3. Take the soft start mode as an example to introduce the composition of the system

3.1 system overview

a pump station uses three soft starters to realize one-to-one soft start control of three rainwater pumps respectively. Every LOGO! The controller and a soft starter are installed in the water pump control cabinet in the control room of the pump station. The operator can control the start and stop of the water pump according to the liquid level value displayed by the ultrasonic liquid level meter transmitter installed in the control room. Each control cabinet is mainly divided into two parts: primary system and secondary system

3.2 primary system

refer to the primary system schematic diagram. The main electrical equipment of the primary system in the cabinet includes: a Siemens 3rw34 soft starter, a set of 3np4070 load switch with protective semiconductor element fuse, a group of bypass AC contactors and three current transformers. After the control side sends the command, the soft starter starts to start the water pump. After the start is completed, the contactor automatically bypasses the soft starter to realize the protection of the soft starter

3.3 functions of each loop of the secondary system

refer to the schematic diagram of the secondary system. The control core of the water pump soft start system is the logo produced by Siemens! 230rc# microcontroller. It has 8 switching input points and 4 relay output points. These input and output points can be used to control the soft start system. Details are as follows:

* the "L" and "n" ends of the controller are the working power input ends, and the input working power supply is 220VAC. In order to eliminate the damage of the peak voltage of the line to the internal electronic components of the controller, a metal oxide varistor RV must be connected in parallel at the "L" and "n" ends, and the working voltage of the RV should be at least 20% greater than the rated working voltage

* "I1" end is the starting end, press the SA1 button to start the water pump

* "I2" end is the stop end, press the SA2 button to stop the water pump

* "I3" end introduces the working signal of contactor km to reflect that the water pump enters the working state

* "I4" introduces the integrated protector signal of thermal relay and water pump. Thermal relay fr indicates overload, locked rotor and phase failure of water pump motor; Relay KA1 indicates the fault condition in the underwater seal chamber of the submersible pump

* "i5" introduces the low liquid level protection switch of ultrasonic liquid level gauge