Keywords: intelligent motor protector; automatic detection; single chip microcomputer; host computer software;

0 Preface
The intelligent motor protector has a remote communication interface, analog input and output, switch input and output, and a control system composed of sensors, PLC, PC, etc., which can realize remote monitoring of motor operation [1], suitable for coal mine, petrochemical, smelting, power , Ship, sewage treatment and other fields of automatic management and control, intelligent management of civil buildings. Because the user needs diverse functions and complex protection functions, its reliability involves many indicators. In order to ensure the quality of the product, all indicators of the intelligent motor protector need to undergo strict testing before leaving the factory. At present, the manual method is adopted for its detection, so there are problems such as cumbersome detection process, low work efficiency, low reliability, non-standard detection process, troublesome storage of detection data and automatic printing, which increases the production cost of the product and restricts The increase in production efficiency and efficiency of enterprises cannot meet the needs of modern large-scale efficient production and testing. In addition, there are diversified characteristics in the customization of product functions by customers, so it is of great significance to realize the automatic detection of intelligent motor protectors.
The development of high-precision electronic components, modern single-chip technology and database technology makes it possible to automatically detect intelligent motor protectors. You can control the entire detection process through the host computer, use single-chip technology to achieve signal generation and control the signal on and off, apply serial server technology to control multi-epitope communication, and use remote server technology to store test data to form an automatic detection system to Reduce the production cost, improve the detection efficiency, and eliminate the shortcomings of manual recording, which are prone to errors [2,3,4].

1 Basic system requirements
The system needs to be able to automatically complete the comprehensive detection of the set parameters, digital display accuracy, protection functions, additional functions, etc. of the protector, and to automatically determine whether the detection results meet the requirements of product technical indicators, and should also have the storage of test results , Statistics, query and test report output [5,6]. The main requirements and technical indicators of the system are as follows:
(1) Use product range. Suitable for intelligent motor protectors of various specifications.
(2) Working mode. Fully automatic and single detection items coexist automatically.
(3) Working environment. It is robust and can deal with unexpected situations such as sudden power failure of the pipeline and personnel misoperation.
(4) Detection efficiency. It can detect multiple motor protectors of the same specification at the same time, and requires a short detection time.
(5) Technical specifications of power source. Output voltage range: AC 3 × 30V ~ 3 × 450V; output current range: AC 0.1A ~ 800A; phase shift range: 0 ~ 360 °; voltage and current output frequency range: 45Hz ~ 65Hz; voltage and current sine Waveform distortion <0.5% at wave output; power source voltage, current, power stability <0.1% at sine wave output; can drive resistive, inductive, capacitive (<4uF) loads; with built-in output voltage short And output current open circuit automatic detection protection function.
(6) Extension control unit. It can communicate with the detected protector and the host computer, can collect the switch input and analog input of the protector, and has switch output control and timing functions.

2 System hardware structure principle
The basic 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, printer, etc.

Figure 1 Basic block diagram of the system

(1) PC. The PC is used for the operation of the host computer and mainly realizes the human-computer interaction function. It is responsible for completing the setting of the detection parameters, the start and stop control of the detection, the real-time monitoring of the detection process, the saving and printing of the detection results, etc. Or missing equipment.
(2) RS-485 expansion 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. The waveform generation module (precision digital signal source) generates all kinds of signals required for detection, controls the current and voltage output through the current and voltage switching devices, and finally flows into the intelligent motor protector for precision, protection, switching and other functions Of detection.
(4) Current and voltage power amplifiers. 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. The device is mainly composed of a short-circuit relay and an output relay, which can effectively avoid current open circuit. Through the 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 a certain circuit or circuits of the short-circuit relay to be closed, single-phase current or multi-phase current can be obtained. A schematic diagram of a single voltage switching device is shown in FIG. 3, by controlling the opening and closing of the relay, it is determined whether to input a voltage signal.

Figure 2 Schematic diagram of current switching device

Figure 3 Schematic diagram of voltage switching device

(6) Extension control module. With 9-channel switch output and 5-channel switch input, it can control and detect the switch input and output status of the protector; with DC analog measurement signal, the range is 4-20mA, and can detect the analog output of the protector; Adopt hardware clock to time, the precision is ms level, can count the trip time of the fault; It has RS485 communication interface, and can communicate with the protector and PC.
(7) Printer. It is used to print the test results and form a product factory inspection report.

3 Testing process and software
The software of the automatic detection system of the intelligent motor protector mainly includes the software of the lower computer and the software of the upper computer. 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 host computer mainly realizes the functions of human-computer interaction, detection parameter setting, and detection process control.
3.1 Lower computer software The CPU of the system control module is the STM32 microcontroller of Cortex-M3 core, which is used for real-time control of each hardware module. The lower computer software is the single-chip computer program, and its main program flow is shown in Figure 4. After the system is powered on, the system is initialized first, including the configuration of the single-chip microcomputer and the I / O port initialization. Then, different control commands are input through the keyboard or the host computer to complete the control of various external modules.

Figure 4 The main flow chart of the single-chip microcomputer program

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

Figure 5 Program flow chart of the host computer

(1) Detection of set parameters. Read and save the value of the detected protector register, and then compare it with the correct configuration parameters. After passing the test, enter the next test, otherwise return to the debugging department, and wait for the correct debugging before proceeding to other tests.
(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, the message confirmation mechanism is started during the detection process. The flow chart of accuracy detection is shown in Figure 6.

Figure 6 Flow chart of accuracy detection

(3) Protection function detection. Including overload, phase failure, grounding, residual current, stalled, blocked, unbalanced and other functional tests, the main test process is shown in Figure 7. After the detection starts, in order to prevent the interference of the previous detection, first cut off the current input signal, then raise the corresponding fault signal according to the detection needs, turn on the trip enable bit of the corresponding detection item, and shield other trip positions. Among them, in order to prevent the working state of the protector 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 read the running status of the protector continuously. If it is read that the protector is in the trip state, the extension sends a read timing command to obtain the trip time to judge whether it is qualified; otherwise, if it does not trip after exceeding the specified maximum set no trip threshold, the protection is judged The function of the device is not qualified.

Figure 7 Protection function detection flowchart

(4) Additional function detection. According to the customer's purchase order, additional function testing is carried out, mainly including: underload, start overtime, short circuit, undervoltage, overvoltage, underpower, overpower, phase sequence and other protections as well as fault records and switching values. The basic detection process is similar to the protection function detection, in which the detection of the switching value requires a single switching value to be detected in sequence to prevent short-circuiting between the switching values.
(5) Restore factory settings. For the modification of the parameters of the protector during the detection process, the factory settings must be restored before the end of the test to ensure that the protector meets the requirements of various technical indicators when it leaves the factory.
(6) Save the results. The system stores the test data and results in the remote server database, and uses stored procedures to implement database operations. After the data is saved, the inspector can use the report management module in the host 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 by intelligent motor protectors of different specifications and models for many times. The results show that the system can complete the detection process accurately, standardly and efficiently. Among them, the complete detection time of multiple full-function protectors at one time is about 5min. Compared with the conventional manual detection, the production efficiency is greatly improved. The accuracy test results and function test results of a certain full-function protector are shown in Table 1 and Table 2, respectively.

Table 1 Accuracy test results

Table 2 Function test results

5 Conclusion
The intelligent motor protector automatic detection system has the advantages of friendly man-machine interface, simple operation and high degree of automation. The test results show that the system has reached the expected technical indicators. In the entire testing process, there is basically no need for human intervention, and the degree of testing automation is high, which ensures the standardization of the testing process and the objectivity of the test results. After testing, in the automatic detection mode, the time required for multiple full-function protectors to complete the entire detection process has been greatly shortened. In addition, the system can be used for automatic detection of other instruments with slight modification, and has the characteristics of wide application range.

The article comes from: "Low Voltage Electrical Appliances" No. 22, 2013.

references
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[4] Zhao Bo, Zhou Zhong, Huang Shaojie. On the design principle of ARD3 motor protector [J]. Relay, 2008, 36 (9): 80-83.
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About the Author:

Yu Jing, female, undergraduate, engineer of Wuhan Ankerui Electric Co., Ltd., the main research direction is intelligent power monitoring and power management system

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