Intelligent explosion-proof combination switch solution based on Delta electromechanical products

1 Introduction

The six-circuit electromagnetic starter for explosion-proof and intrinsically safe mine is referred to as the mine combination switch. The mine combination switch is used for starting and stopping of single or multiple (no more than six) three-phase squirrel cage asynchronous motors with a rated voltage of 1140V or 660V power supply line in a mine environment containing explosive gas (methane) and coal dust for control and protection. The mine combination switch is an intelligent mine motor dedicated monitoring system with reliable performance, strong anti-interference ability, convenient operation and good human-machine interface. The mine combination switch has at least one main isolating switch group and one auxiliary isolating switch group between the power supply and the load. Each main isolating switch group includes a main isolating switch, a vacuum contactor, a leakage lockout detection, a voltage transformer and a current transformer. The auxiliary isolating switch group includes an auxiliary isolating switch, a power transformer, a filter, an isolation transformer and a power module. It also has a data processing module, a display module, a control module and a pilot module. The intelligent mine combination switch product is shown in Figure 1.

Figure 1 Intelligent mining combination switch

2 System Solution

2.1 Hardware Configuration

The hardware composition of the mine combination switch control system based on the PLC system is shown in Table 1.

Table 1 Hardware components

2.2 System Principle

(1) System architecture. The system consists of two sets of PLCs and a Delta touch screen to form a human-machine interface. The three serial communication ports of Delta's 10.4' high-brightness TFT LCD touch screen DOPA10THTD1 have the ability to simultaneously connect to controllers with different communication formats. In this case, two PLCs of different brands are connected at the same time to form a heterogeneous integrated automation system, as shown in Figure 2.

Figure 2 System architecture

(2) Main controller. The combined switch protection and main control system adopts the German Siemens S7-200 series PLC to realize system monitoring and control, and complete the protection functions such as leakage lockout, overload, short circuit, phase failure, undervoltage and overvoltage. It has the advantages of high intelligence, stable performance and reliable operation.

(3) Auxiliary controller. The explosion-proof field data input of the combination switch is the reason why the dual PLC architecture is adopted in this case. Since non-explosion-proof electrical appliances are not allowed to be installed at the explosion-proof site, an explosion-proof human-machine unit must be designed. Considering the data input requirements of the intelligent combination switch, a 4*4 explosion-proof matrix keyboard is selected, as shown in Figure 3.

Figure 3 4*4 matrix explosion-proof keyboard

The keyboard data is read using Delta DVP12SA11T small PLC, and the PLC keyboard data reading circuit principle using the matrix drive principle is shown in Figure 4.

Figure 4 PLC keyboard data input principle

An example of a data display screen is shown in Figure 5.

Figure 5 Data display screen

2.3 Monitoring function design

(1) Delta's all-Chinese LCD display screen is used in conjunction with Delta's small PLC to display and memorize the working status, parameters and fault types of the combination switch, and to modify and adjust specific parameters. The user-friendly interface and good human-computer dialogue function can greatly improve the efficiency of fault diagnosis and troubleshooting.

(2) All analog signals are processed into digital signals, which have the characteristics of strong anti-interference ability, simple wiring, large amount of information, reliable and accurate control, etc.

(3) It has complete self-checking, self-diagnosis and fault simulation test functions, which can easily check whether the protection and control system is normal.

2.4 Technical indicator design

This combination switch fully considers the working environment of coal mines, and integrates mechanical manufacturing, automation, measurement and control technology, instrumentation, computer application science and technology and other disciplines. Its main technical indicators are as follows:

(1) Voltage level: 1140/660V; Frequency: 50Hz

(2) Total rated current: 800A, 1200A, single unit working current can reach 400A

(3) Current setting range: 30-399A

(4) Leakage lockout protection: Additional DC detection, 1140V-40kΩ, 660V-22kΩ.

(5) Pilot control (intrinsically safe control): Igmax<10mA, Idmax<15mA.

(6) Overload protection: inverse time.

(7) Short circuit protection: amplitude detection (7-10 times), sensitive (3-5 times).

(8) Phase failure protection: negative sequence detection, time limit;

(9) Control mode: single machine single speed, single machine double speed, double machine double speed, program control and other control modes.

3 Conclusion

This combination switch application case demonstrates the powerful communication and human-computer interaction functions of Delta touch screens, as well as the unique keyboard input application characteristics of PLCs. It greatly improves the application of touch screens in underground explosion protection, replacing the shortcomings of conventional touch screens that can only display memory. While improving labor productivity and ensuring underground safety production, it also demonstrates the characteristics of Delta products.