Design of automatic detection system for the hotte

2022-08-22
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Design of automatic detection system for intelligent motor protector

SUN Lili

Abstract: in order to improve the accuracy and reliability of intelligent motor protector products, an automatic detection system is developed based on digital electronic technology, analog electronic circuits, single-chip microcomputer and host computer language. The software and hardware design of the system are introduced and tested for many times. The test results show that the system can automatically apply signals to the intelligent motor protector to test its accuracy, protection function and additional performance, automatically judge whether the test results meet the requirements of technical indicators, and automatically save and print the test data after the test. Compared with the conventional manual test system, it has the characteristics of high detection efficiency, standardized test process, high automation, high accuracy, strong versatility, convenient test data management and so on. The automatic detection system has been running normally on the company's assembly line and has been proved to be feasible

key words: intelligent motor protector; Automatic detection; singlechip; Upper computer software

0 introduction

intelligent motor protector has remote communication interface, analog input and output, switching input and output, and forms a control system with sensors, PLC, PC, etc., which can realize remote monitoring of motor operation [1], and is suitable for automatic control in coal mine, petrochemical, smelting, electric power, ship, sewage treatment and other fields, and intelligent management of civil buildings. Because users need various functions and complex protection functions, its reliability involves many indicators. In order to ensure the quality of products, all indicators of intelligent motor protector need to be strictly tested before leaving the factory. 28 (5) 033549016180 d=3a at present, its detection adopts manual mode, so there are problems such as cumbersome detection process, low efficiency, low reliability, non-standard detection process, troublesome storage of detection data and inability to print automatically, which increases the production cost of the product, restricts the improvement of production efficiency and benefit of the enterprise, and cannot meet the needs of modern large-scale efficient production and detection. In addition, customers' customization of product functions also has diversified characteristics, so it is of great significance to realize the automatic detection of intelligent motor protector

The development of high-precision electronic components, modern single-chip microcomputer technology and database technology makes it possible to automatically detect intelligent motor protectors. The whole detection process can be controlled by the upper computer, the signal generation and signal on-off can be controlled by the single-chip microcomputer technology, the serial port server technology can be used to control the multi epitope communication, and the remote server technology can be used to store the test data, so as to form an automatic detection system, so as to reduce the production cost, improve the detection efficiency, and eliminate the disadvantages of easy errors in manual recording [2,3,4]

1 basic requirements of the system

the system should be able to automatically complete the comprehensive detection of the set parameters, digital display accuracy, protection function, additional functions, etc. of the protector, and can automatically judge whether the detection results meet the requirements of product technical indicators. At the same time, it should also have the functions of storage, statistics, query and output of test results [5,6]. The main requirements and technical indicators of the system are as follows:

(1) scope of products used. It is suitable for intelligent motor protectors of various specifications

(2) working mode. Fully automatic and single detection items coexist automatically

(3) working environment. It has strong robustness and can deal with sudden power failure of the assembly line, personnel misoperation and other emergencies

(4) detection efficiency. Multiple motor protectors of the same specification can be tested at the same time, and the detection time is required to be short

(5) technical indicators of power source. Output voltage range: AC 3 30V ~ 3 450V; The range of current transmission is: AC 0.1a~800a; Phase shift range: 0~360; Voltage and current output frequency range: 45hz~65hz; When voltage and current sine wave are output, the waveform distortion is 0.5%; The voltage, current and power stability of the power source during sine wave output is 0.1%; It can drive resistive, inductive and capacitive (4uf) loads; It has built-in automatic detection and protection function of output voltage short circuit and output current open circuit

(6) extension control unit. It can communicate with the detected protector and the upper computer, collect the switch input and analog input of the protector, and has the function of switch output control and timing

2 system hardware structure principle

the basic principle block diagram of the system is shown in Figure 1. The main modules of the system include: PC, RS-485 extended communication module, waveform generation module, current and voltage power amplifier and switching device, extension control module, printer, etc

Figure 1 basic principle block diagram of the system

(1) PC. PC acts on the upper computer operation, mainly realizes the human-computer interaction function, and is responsible for the setting of detection parameters, the start and stop control of detection, the real-time monitoring of detection process, the storage and printing of detection results, etc. it is an indispensable equipment to complete the whole detection process

(2) RS-485 extended communication module. This module mainly completes the communication between PC, waveform generation module, extension control module and the detected protector

(3) waveform generation module. The waveform generation module (precision digital signal source) generates all kinds of signals required in the detection, controls the opening current and voltage output through the current and voltage switching device, and finally flows into the intelligent motor protector for the detection of precision, protection, switching value and other functions

(4) current and voltage power amplifier. The system power amplifier adopts PWM power amplification technology, and designs voltage short-circuit overload, current open circuit overload and fast current limiting protection measures to ensure the long-term stable and reliable operation of the power amplifier

(5) current and voltage switching device. The schematic diagram of a single current switching device is shown in Figure 2. This device is mainly composed of short-circuit relay and output relay, which can effectively avoid current open circuit. By switching between the short-circuit relay and the output relay, the input current of the protector can be controlled; Single phase current or polyphase current can be obtained by selecting one or more circuits of short-circuit relay to close. Schematic diagram of single voltage switching device 4. Connect the power supply as shown in Figure 3, and decide whether to input the voltage signal by controlling the opening and closing of the relay

Figure 2 Schematic diagram of current switching device

Figure 3 Schematic diagram of voltage switching device

(6) extension control module. It has 9-channel switching value output and 5-channel switching value input, which can control and detect the switching value input and output status of the protector; With DC analog measurement signal, the range is Ma, which can detect the analog output of the protector; It adopts hardware clock timing, with accuracy of MS level, and can count the tripping time of faults; With RS485 communication interface, it can communicate with protector and PC

(7) printer. It is used to print the test results and form the product delivery inspection report

3 detection process and software

the software of intelligent motor protector automatic detection system mainly includes lower computer software and upper computer software. The lower computer mainly receives the instructions of the upper computer, completes the real-time control of the hardware of each part of the system, and collects the parameters and variables in the system in real time. The upper computer mainly realizes human-computer interaction, detection parameter setting, detection process control and other functions

3.1 lower computer software

the CPU of the system control module is STM32 single chip microcomputer with Cortex-M3 core, which is used for real-time control of each hardware module. The lower computer software is the MCU program, and its main program flow is shown in Figure 4. After the system is powered on, first initialize the system, including the configuration of MCU and the initialization of i/o port, and then input different control commands through the keyboard or upper computer to complete the control of various external modules

Figure 4 main flow chart of single chip microcomputer program

3.2 upper computer software

upper computer program flow chart is shown in Figure 5. After running the software, first input the serial number of the protector connected to the corresponding extension unit, and the system will automatically set the detection parameters; Then, start the detection process until the end of the detection

Figure 5 upper computer program flow chart

(1) detection of set parameters. Read and save the detected protector register value, and then compare it with the correct configuration parameters. Enter the next test after it is qualified, otherwise return it to the commissioning department, and conduct other tests after the commissioning is correct

(2) digital display accuracy detection. Raise the signal source to the signal required for the corresponding detection, wait for the signal source to work stably, read out the display value of the corresponding protector, calculate the error to judge, and end this accuracy detection. Among them, during the detection process, the researchers developed an injectable two-component pur (polynova reg;) Mechanism. The flow chart of accuracy detection is shown in Figure 6

Figure 6 accuracy detection flow chart

(3) protection function detection. Including overload, phase failure, grounding, residual current, locked rotor, blocking, imbalance and other function detection. The main detection process is shown in Figure 7. After the detection starts, in order to prevent the interference of the previous detection, first cut off the input signal of the current, then raise the corresponding fault signal according to the detection needs, open the tripping enabling bit of the corresponding detection item, and shield other tripping bits. Among them, in order to prevent the working state of the protector from tripping and affecting the detection results, it is necessary to conduct a remote reset operation on the protector, then operate the relay, input signals to the protector, and send a timing command to the extension unit (this command is a broadcast packet command), and then continuously read the running state of the protector. If it is read that the protector is in the tripping state, the extension sends the reading timing command to obtain the tripping time to judge whether it is qualified; Otherwise, if the protector still does not trip after exceeding the specified maximum set non trip threshold, it will be judged that the function of the protector is unqualified

Figure 7 flow chart of protection function detection

(4) additional function detection. According to the customer's order, carry out additional function detection, mainly including: under load, starting timeout, short circuit, under voltage, overvoltage, under power, over power, phase sequence and other protection, as well as fault records and switching values. The basic detection process is similar to the protection function detection, in which the detection of switching values requires a single switching value to be detected in turn to prevent short circuit between switching values

(5) restore factory settings. For the modification of the protector parameters during the detection process, the factory settings must be restored before the end of the detection to ensure that the protector meets the requirements of various technical indicators when leaving the factory

(6) save the results. The system stores the test data and results into the remote server database, and uses stored procedures to realize the operation of the database. After the data is saved, the inspector can use the report management module in the upper computer to output the factory inspection report. The report function of the system is realized through the enterprise report development tool

4 test results and analysis

the automatic detection system has been tested for many times by intelligent motor protectors of different specifications and models. The results show that the system can complete the detection process accurately, normatively and efficiently. Among them, the completion time of multiple full-function protectors is about 5min at a time, which greatly improves the production efficiency compared with the conventional manual detection. The primary accuracy test results and function test results of a full-function protector are shown in Table 1 and table 2 respectively

Table 1 accuracy test results

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