Zheng Yuejie 1 Chen Jiang 2 Li Haiquan 1 Cai Lei 1
Abstract: In order to improve the precision and reliability of smart motor protector products, an automatic detection system was developed based on digital electronics, analog electronic circuits, single-chip microcomputers and host computer language. Introduced the system's hardware and software design, and conducted multiple tests. Test results show that the system can automatically apply signals to the smart motor protector to verify its accuracy, protection function and additional performance, automatically determine whether the test results meet the technical requirements, and after the end of the test can automatically save the test data and print . Compared with the conventional manual test system, it has the characteristics of high detection efficiency, standardized test procedure, high degree of automation, high accuracy, versatility, and convenient test data management. The automatic detection system has been operating normally on the company's assembly line and has proven to be practical.
Keywords :smart motor protector;automatic detection;single chip microcomputer;upper computer software;
0 PrefaceIntelligent motor protector has long-distance communication interface, analog input and output, digital input and output, and sensor, PLC, PC and other control systems, can realize remote monitoring of motor operation [1], suitable for coal mine, petrochemical, smelting, electricity , ship, sewage treatment and other areas of automated control, intelligent management of civil construction. Because the user needs various functions and the protection function is complex, the reliability thereof involves various indicators. In order to ensure the quality of the products, various indicators of the smart motor protector need to undergo rigorous testing before leaving the factory. At present, the detection method is manual, so there are problems such as cumbersome detection procedures, low work efficiency, low reliability, non-standard test flow, troublesome test data storage, and inability to print automatically, which increases the production cost of the product and restricts it. The improvement of production efficiency and efficiency of enterprises cannot meet the needs of modern large-scale efficient production and testing. In addition, customer customization of product features still has a variety of features, so it is of great significance to implement automatic detection of intelligent motor protectors.
The development of high-precision electronic components, modern microcontroller technology, and database technology make it possible to automatically detect smart motor protectors. The entire detection process can be controlled by the upper computer, the signal generation and control signal switching can be realized by the single-chip microcomputer technology, the serial port server technology can be used to control the multi-table communication, and the remote server technology can be used to store the test data to form an automatic detection system. Reduce the production costs, improve the detection efficiency, and eliminate errors that are easy to generate when manually recording [2, 3, 4].
1 system basic requirementsThe system needs to be able to automatically perform comprehensive testing on the set-up parameters, digital display accuracy, protection functions, and additional functions of the protector, and it can automatically determine whether the test result conforms to the requirements of the product's technical specifications. It should also have the storage of test results. , statistics, query, and test report output functions [5,6]. The main requirements and technical specifications of the system are as follows:
(1) Use product range. Suitable for a variety of different specifications of smart motor protectors.
(2) Work mode. Fully automatic and single detection items co-exist.
(3) Work environment. Robust, able to deal with sudden power outages in the assembly line, accidental operation of personnel, etc.
(4) Testing efficiency. Multiple motor protectors of the same specification can be tested at the same time and require a short detection time.
(5) Technical specifications of the power source. Output voltage range: AC 3 × 30V ~ 3 × 450V; current range: AC 0.1A ~ 800A; phase shift range: 0 ~ 360 °; voltage and current output frequency range: 45Hz ~ 65Hz; voltage, current sine Waveform output waveform distortion <0.5%; sine wave output power source voltage, current, power stability <0.1%; can drive resistive, inductive, capacitive (<4uF) load; with built-in output voltage short circuit And output current open circuit automatic detection protection function.
(6) Extension control unit. It can communicate with the detected protector and the host computer, and can collect the protector's switch input and analog input, and has the switch output control and timing function.
2 system hardware structure principleThe basic system block diagram of the system is shown in Figure 1. The main modules of the system include: PC, RS-485 expansion communication module, waveform generation module, current and voltage power amplifier and switching device, extension control module, and printer.
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Figure 1 basic system block diagram
(1) PC. The PC acts on the host computer to realize the human-computer interaction function, and is responsible for completing the setting of detection parameters, the start/stop control of the detection, the real-time monitoring of the detection process, the saving and printing of the detection results, etc. It is not possible to complete the entire detection process. Or missing equipment.
(2) RS-485 extended communication module. This module mainly completes the communication between the PC, the waveform generation module, the extension control module, and the detected protector.
(3) Waveform generation module. Waveform generation module (precise digital signal source) generates various types of signals required for detection, and controls current and voltage output through current and voltage switching devices, and finally flows into smart motor protectors for accuracy, protection, and switching functions. Detection.
(4) current, voltage power amplifier. The system power amplifier adopts PWM power amplification technology and designs voltage short circuit overload, open current overload and fast current limiting protection measures to ensure stable and reliable power amplifier operation for a long time.
(5) Current and voltage switching devices. A single current switching device schematic diagram shown in Figure 2, the device is mainly composed of short-circuit relays and output relays, which can effectively avoid open current. By switching between the short-circuit relay and the output relay, the presence or absence of the input current of the protector can be controlled. By selecting one or more of the short-circuit relays to be closed, single-phase current or multi-phase current can be obtained. A single voltage switching device schematic diagram shown in Figure 3, through the control relay open and close, to determine whether the input voltage signal.
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Figure 2 Current Switching Device Schematic
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Figure 3 Voltage Switching Device Schematic
(6) Extension Control Module. With 9 channels of digital output and 5 channels of digital inputs, it can control and detect the digital input and output status of the protector. It has a DC analog measurement signal with a range of 4-20mA and can detect the analog output of the protector. Using hardware clock timing, the accuracy is ms level, and the fault trip time can be counted. With RS485 communication interface, it can communicate with protector and PC.
(7) The printer. Used to print test results to form a product inspection report.
3 detection process and softwareThe intelligent motor protector automatic detection system software mainly includes two parts: 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 the functions of human-computer interaction, setting of detection parameters, and detection flow control.
3.1 lower computer softwareThe CPU of the system control module is a Cortex-M3 core STM32 microcontroller and is used for real-time control of various hardware modules. The lower machine software is the one-chip computer program, its main program flow is shown as in Fig. 4. After the system is powered on, the system is initialized first, including the configuration of the SCM, the initialization of the I/O port, etc. Then, different control commands are input through the keyboard or the host computer to complete the control of various external modules.
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Figure 4 main flowchart of the microcontroller program
3.2 PC softwareThe upper computer program flow chart shown in Figure 5. After running the software, first input the serial number of the protector that the corresponding extension unit accesses, the system will automatically set the detection parameters; then, start the detection process until the end of the detection.
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Figure 5 upper computer program flow chart
(1) Detection of parameters has been set. The protected register value to be detected is read and saved, and then it is compared with the correct configuration parameters. After passing the test, the system enters the next test. Otherwise, it will be returned to the debugging department, and other items can be tested after the adjustment is correct.
(2) Digital display accuracy detection. Raise the signal source to the signal required for the corresponding detection. After waiting for the signal source to work stably, read out the corresponding display value of the protector, calculate the error to judge, and end the accuracy test. Among them, the message confirmation mechanism is started during the detection process. The flow chart of precision detection is shown in Figure 6.
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Figure 6 Accuracy detection flow chart
(3) Protection function detection. Including overload, phase failure, grounding, residual current, stalling, blocking, unbalance and other functional testing, the main detection process shown in Figure 7. After the start of the test, in order to prevent the interference of the previous item, the input signal of the current is cut off first, and then according to the detection requirement, the corresponding fault signal is raised, the trip enable bit of the corresponding detection item is turned on, and other trip positions are shielded. Among them, in order to prevent the protector working state from tripping and affecting the detection result, it is necessary to perform a remote reset operation on the protector, then operate the relay, input a signal to the protector, and send a timing command to the extension unit (this command is a broadcast packet. Command), and then continuously read the protector operating status. If the protector is read as a tripping state, the extension sends a read timing command and obtains the trip time to judge whether it is qualified; otherwise, it judges the protection if it does not trip after exceeding the specified maximum set non-trip threshold. This function is not qualified.
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Figure 7 protection function detection flow chart
(4) Additional function detection. According to the customer's order form, additional function tests include: underload, start overtime, short circuit, undervoltage, overvoltage, underpower, overpower, phase sequence protection, and fault recording and switching. The basic detection process is similar to the protection function detection, in which the detection of the switch quantity requires a single switch quantity to be detected in order to prevent a short circuit between the switch quantity.
(5) Restore factory settings. For the modification of the protector parameters in the detection process, the factory settings must be restored before the end of the test, so as to ensure that the protector meets the requirements of various technical indicators when it leaves the factory.
(6) Save the result. The system stores the test data and results in a remote server database and uses stored procedures to implement the database operations. 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 enterprise-level report development tools.
4 test results and analysisThe automated detection system has been tested several times by smart motor protectors of different specifications and models. The results show that the system can complete the detection process accurately, standardly, and efficiently. The complete detection time of multiple full-function protectors is about 5 minutes, which is more convenient than conventional manual detection, which greatly improves the production efficiency. The accuracy test result and function test result of a full-function protector are shown in Table 1 and Table 2, respectively.
Table 1 Accuracy test results
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Table 2 Functional Test Results
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The intelligent motor protector automatic detection system has the advantages of friendly human-machine interface, simple operation and high automation. The test results show that the system has reached the expected technical indicators. Throughout the testing process, there is basically no need for human intervention. The degree of automation of the test is high, and the standardization of the test process and the objectivity of the test results are guaranteed to the maximum. After testing, in the automatic detection mode, the time required for multiple full-function protectors to complete the entire inspection process has been greatly shortened. In addition, the system can be used for automatic detection of other instruments with slight modifications, and has a wide range of applications.
Article from: "Low-voltage electrical appliances" 2013 the 22nd period.
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