Automatic test method for multiple test items of three-phase asynchronous motor

Abstract

The invention relates to a multi-test-item automatic test method for a three-phase asynchronous motor. The method comprises the following steps: connecting a direct-current resistance test line, an insulation resistance test line and a motor power line with copper bars and test clamps of the three-phase asynchronous motor; based on the sequence of the direct current resistance test, the insulation resistance test, the starting current test and the no-load test, automatic test of the three-phase asynchronous motor is carried out, and a test result is obtained. Compared with the prior art, the method has the advantages of improving the accuracy and speed of testing each item of the motor and the like.

Description

Technical Field

[0001] The invention relates to the technical field of three-phase asynchronous motor testing, and in particular to an automated testing method for multiple test items of a three-phase asynchronous motor. Background Art

[0002] Three-phase asynchronous motors are widely used in many fields such as industry, agriculture, and transportation because of their simple structure, easy maintenance, and low cost. Therefore, it is very important to ensure the reliability and safety of their performance. With the development of industrial automation, the frequency of motor use has gradually increased, and the motors need to be frequently tested for functional performance and regularly maintained. The most commonly tested three-phase asynchronous motor tests are DC resistance, insulation resistance, and no-load performance. These three tests can intuitively show the current aging of the motor and facilitate subsequent accurate monitoring. For these tests, the traditional method requires multiple wiring according to the process, which is not only time-consuming, but also prone to test errors. The line control system of the automated test can use PLC, relays, host computer software, customized cables and other technologies to improve the convenience and reliability of the test.

[0003] There are many advantages to using a host computer and PLC to form a test line control system. The host computer supports multiple communication protocols. Through its own communication interface, it can monitor multiple instruments and PLCs, obtain real-time data and display them. Secondly, the host computer has powerful data processing capabilities and can integrate data into a friendly graphical user interface to improve the convenience and safety of operation. At the same time, the host computer can implement complex security strategies and visual alarm functions, which can effectively improve the efficiency and reliability of the system.

[0004] PLC is also programmable and easy to modify and expand control logic. Compared with traditional relay control systems, it can handle complex control tasks more easily. In addition, PLC expansion digital IO modules can monitor the status of the system while controlling the actuator, with higher integration, reducing the complexity of wiring, and improving the reliability and safety of the system. By controlling relays and contactors through PLC, the motor automation test system can not only achieve efficient and stable operation, but also reduce maintenance costs and improve the adaptability and flexibility of the system.

[0005] In the existing motor testing methods, the test order for various test items is unclear, which easily affects the accuracy of the test. In addition, the number of cables during wiring is large, and the test speed is slow. Summary of the invention

[0006] The purpose of the present invention is to provide an automated testing method for multiple test items of a three-phase asynchronous motor in order to improve the accuracy and speed of testing various items of the motor.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] An automated test method for multiple test items of a three-phase asynchronous motor, the method comprising the following steps:

[0009] Connect the DC resistance test wire, insulation resistance test wire and motor power wire to each copper busbar and test clip of the three-phase asynchronous motor;

[0010] The three-phase asynchronous motor is automatically tested based on the sequence of DC resistance test, insulation resistance test, starting current test and no-load test to obtain the test results.

[0011] Furthermore, the DC resistance test line, the insulation resistance test line and the power line are connected to each copper bus and the test clip of the three-phase asynchronous motor in detail:

[0012] The motor power line and the insulation resistance test line are combined into the same cable, wherein the first insulation resistance test line and the U-phase motor power line are combined into the first cable, the second insulation resistance test line and the V-phase motor power line are combined into the second cable, the third insulation resistance test line and the W-phase motor power line are combined into the second cable, the first cable is connected to the bus copper bar U, the second cable is connected to the bus copper bar V, and the third cable is connected to the bus copper bar W;

[0013] The DC resistance test line includes a DC resistance test line 1H, a DC resistance test line 3L, a DC resistance test line 1L, a DC resistance test line 2H, a DC resistance test line 2L and a DC resistance test line 3H, wherein the DC resistance test line 1H and the DC resistance test line 3L are combined into a same cable connected to a test clip U, the DC resistance test line 1L and the DC resistance test line 2H are combined into a same cable connected to a test clip V, and the DC resistance test line 2L and the DC resistance test line 3H are combined into a same cable connected to a test clip W.

[0014] Furthermore, the busbar U and the test clip U are connected together to the terminal U of the three-phase asynchronous motor, the busbar V and the test clip V are connected together to the terminal V of the three-phase asynchronous motor, and the busbar W and the test clip W are connected together to the terminal W of the three-phase asynchronous motor.

[0015] Furthermore, the insulation resistance test line also includes a fourth insulation resistance test line, and the fourth insulation resistance test line is connected to the motor housing.

[0016] Furthermore, the specific steps of the DC resistance test are:

[0017] Use a 4-phase contactor to obtain the test voltage and test current based on the DC resistance test line, and calculate the resistance imbalance based on the test voltage and test current. If the imbalance does not meet the requirements, check the motor status and perform the DC resistance test again after the inspection. Otherwise, continue to perform the insulation resistance test.

[0018] Furthermore, the specific steps of the insulation resistance test are:

[0019] Use a high-voltage relay to obtain the insulation voltage and insulation current based on the insulation resistance test line, and calculate the insulation resistance based on the insulation voltage and insulation current. If the insulation resistance is less than the limit value, it proves that there is an abnormality in the winding insulation layer of the current motor. It is necessary to check the motor status and perform the insulation resistance test again after the inspection. Otherwise, continue to perform the starting current test.

[0020] Furthermore, the specific steps of the starting current test are:

[0021] Power on the motor. For small power motors, direct start is used. During starting, the starting current of the motor is measured. If the starting current is too large, soft start is performed.

[0022] Furthermore, the no-load test is specifically as follows:

[0023] The voltage, current, power, vibration, speed and temperature parameters of the motor are detected by vibration sensors, current sensors and thermal imagers.

[0024] Furthermore, the switching of the DC resistance test, insulation resistance test, starting current test and no-load test is controlled based on PLC and host computer software.

[0025] Furthermore, the device communication of the host computer software includes three communication modes: TCP / IP, RS485, and USB HOST, and three communication protocols: SCPI, Modbus, and ADS.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The present invention combines the insulation resistance cable and the power cable into the same cable for the insulation resistance test of the winding; for the DC resistance test, by adjusting the line sequence of the unused cables, the four-wire DC resistance test cable is reduced from the previous 12 cables to 3 cables, and connected by a test clip, which is convenient for disassembly and assembly, and improves the test speed. The test will be tested according to the DC resistance test, insulation resistance test, starting current test, and no-load test. The test process starts with the DC resistance test to first determine whether the stator winding of the motor is intact and whether the imbalance meets the requirements. If it does not meet the requirements, it is necessary to check the motor state. The DC resistance of the winding reflects the internal fault degree of the stator. If the stator has failed, accidental power-on will cause irreversible damage to the motor. Placing the DC resistance test in the first place can prevent motor failure caused by the test. The second test is the insulation resistance test. If the insulation resistance is less than the limit value, it proves that the winding insulation layer of the current motor is abnormal, and a turn-to-turn short circuit fault may occur. At this time, the subsequent test is powered on, and the fault will worsen, resulting in motor damage. When the motor is normal after the DC resistance and insulation resistance tests, the subsequent power-on test can be entered. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is the overall block diagram of the system of the present invention;

[0029] Figure 2 It is a block diagram of the upper computer software composition of the present invention;

[0030] Figure 3 It is a block diagram of the PLC and the actuator of the present invention;

[0031] Figure 4 This is a connection diagram of the execution device of the present invention;

[0032] Figure 5 This is the test cable connection diagram. DETAILED DESCRIPTION

[0033] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0034] The present invention aims to enhance the convenience and safety of circuit switching in the automated test of multiple test items of a three-phase asynchronous motor by designing a host computer software, a PLC, a relay, a contactor and a variety of test instruments to achieve rapid circuit switching during the DC resistance test, the insulation resistance test and the no-load performance test of the three-phase asynchronous motor. The method comprises the following steps:

[0035] Connect the DC resistance test wire, insulation resistance test wire and motor power wire to each copper busbar and test clip of the three-phase asynchronous motor;

[0036] The three-phase asynchronous motor is automatically tested based on the sequence of DC resistance test, insulation resistance test, starting current test and no-load test to obtain the test results.

[0037] The present invention is mainly realized by a control system composed of host computer software, PLC, relays and contactors. The host computer software is the external interface of the line control system, and the operator can control the line through the software; the PLC is the main control mechanism, and the action of the relay and contactor is controlled through the digital input and output module; the relay and contactor are the actuators, which directly control the line switching.

[0038] The host computer software mainly consists of two parts, namely, equipment communication and operation interface. The DC resistance test, insulation resistance test and no-load performance test of the three-phase asynchronous motor all require different test instruments, including DC resistance tester, safety tester and power analyzer. In the process of automated testing, the host computer needs to connect the three instruments through different communication methods to achieve unified control of the three instruments. The device communication of the host computer software includes three communication methods: TCP / IP, RS485, and USB HOST, and three communication protocols: SCPI, Modbus, and ADS, to meet the communication between different test instruments and PLCs. The operation interface of the host computer software mainly realizes the issuance of instructions from instruments and PLCs, and realizes the automatic switching of the entire line control system. At the same time, as a human-machine interface, the operation interface needs to realize the system status display function, safety prompt function, line selection function and execution function. The system status display function needs to read the current status of various instruments through instrument communication, and display it to inform the operator; the safety prompt function is a pop-up window prompt of the system abnormal status, informing the operator of the current abnormal situation and handling the abnormal status immediately; the line selection function allows the operator to select any line of any test while ensuring safety; the execution function allows the operator to confirm the selected function and confirm the execution. The four operation interface functions are matched with each other to achieve fast and convenient automated testing.

[0039] The main function of PLC is to receive instructions from the host computer software and control the line switching actuator. PLC uses BeckhooF's CX9020 series embedded controller, with EL1809 digital input module and EL2809 digital output module. EL1809 has 16 digital input channels, which can monitor the working status of the system; EL2809 has 16 digital output channels, which can be used with 24V power supply to directly control the working status of relays or contactors.

[0040] For the selection of relay and contactor models, it is necessary to select them according to the voltage and current parameters during the test. The motor tested in this test is a three-phase asynchronous motor. According to the national standard for three-phase asynchronous motor testing, the insulation resistance applied voltage needs to reach 500V and the test time is 60s. Therefore, the insulation parameters of the shared cable part, relays, and contactors need to be greater than 500V, and the insulation resistance between the relays and contactors is greater than 50GΩ, which does not affect the measurement of the motor insulation resistance and DC resistance. For the motor power supply contactor, it is necessary to select it according to the power and current value of the motor. If you need to measure motors with different power ranges, you need to select multiple contactors with different parameters for segmented power supply. The DC resistance test of the three-phase asynchronous motor needs to measure the DC resistance of the three groups of coils of the motor, and the insulation resistance test needs to test the insulation resistance between the coils and the coil to the casing, so it is necessary to select a multi-channel test instrument for automated testing. The test instrument selected for DC resistance based on the test accuracy and number of channels is RK2518, which can perform 8-channel 4-wire DC resistance test. The test instrument selected for insulation resistance is AN96HC, which can perform 8-channel insulation resistance test. Therefore, the DC resistance test contactor needs to use a 4-phase contactor, and the insulation resistance test relay needs to use a 500V high-voltage relay.

[0041] The control system and actuator need to be used with special test cables. According to the function of the test cable, the external interfaces of the three test cables are divided into two categories. The first category is the high-voltage test line, which includes the motor power cable and the insulation resistance test cable; the second category is the high-precision test line, which includes the DC resistance test cable. The high-voltage test cables can be connected to the motor terminals through a common cable section after the copper busbar is merged; the high-precision test cables are redistributed through the line sequence, and 12 DC resistance test cables are integrated into 3 test clips and connected to the motor terminals. The line sequence distribution of the DC resistance test cable is as follows: Figure 5 shown.

[0042] The test of the present invention includes a DC resistance test, an insulation resistance test, a starting current test and a no-load test, and can test the static parameters and dynamic parameters of the motor. During the test, the tester needs to connect the power cable and the resistance test cable of the motor to the terminal respectively. Due to the optimization of the cable arrangement of this patent, the number of cables during wiring is reduced, and the test can be carried out conveniently and quickly. For the insulation resistance test of the winding, the insulation resistance cable and the power cable are combined into the same cable; for the DC resistance test, by adjusting the line sequence of the unused cables, the four-wire DC resistance test cable is reduced from the previous 12 cables to 3 cables, and connected by a test clip for easy disassembly and assembly. After the tester connects the power cable and the resistance test cable, the test will be carried out according to the DC resistance test, insulation resistance test, starting current test, and no-load test. The test process starts with the DC resistance test, first judging whether the stator winding of the motor is intact and whether the imbalance meets the requirements. If it does not meet the requirements, the motor status needs to be checked. The DC resistance of the winding reflects the degree of internal fault of the stator. If the stator has failed, accidental power-on will cause irreversible damage to the motor. Therefore, this test puts the DC resistance test first.

[0043] The second test is the insulation resistance test, which mainly targets the phase-to-phase insulation of the stator winding and the insulation of the winding to the casing. The insulation resistance of the winding can reflect the state of the insulation layer in its coil. If the insulation resistance is less than the limit value, it proves that there is an abnormality in the insulation layer of the winding of the current motor, and a turn-to-turn short circuit fault may occur. At this time, the subsequent test is powered on, and the fault will worsen, causing damage to the motor. When the motor is normal after the DC resistance and insulation resistance tests, the subsequent power-on test can be entered. When the motor is powered on, different power-on methods are used according to the power size. For low-power motors (15KW, up to 30KW), direct start can be used. When starting, the starting current of the motor is measured. If the starting current is too large, it is necessary to consider whether to use a soft start method during subsequent start-up. After the motor is started, the voltage, current, power, vibration, speed, and temperature parameters of the motor will be monitored through vibration sensors, current sensors, thermal imagers and other equipment. After analyzing the signals during the operation of the motor, it can be known whether the current state of the motor is normal. The overall block diagram of the system of the present invention is as follows Figure 1 As shown; the upper computer software composition block diagram of the present invention is as shown Figure 2 As shown; the block diagram of the PLC and the actuator of the present invention is as shown Figure 3 As shown; the connection diagram of the execution device of the present invention is as shown Figure 4 shown.

[0044] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A method for automated testing of multiple test items for a three-phase asynchronous motor, characterized in that: The method comprises the following steps: Connect the DC resistance test wire, insulation resistance test wire and motor power line to each copper busbar and test clip of the three-phase asynchronous motor; The three-phase asynchronous motor is automatically tested based on the sequence of DC resistance test, insulation resistance test, starting current test and no-load test to obtain the test results.

2. The method for automated testing of multiple test items for a three-phase asynchronous motor according to claim 1, characterized in that: The method of connecting the DC resistance test line, the insulation resistance test line and the power line to each copper bus and the test clip of the three-phase asynchronous motor is specifically as follows: The motor power line and the insulation resistance test line are combined into the same cable, wherein the first insulation resistance test line and the U-phase motor power line are combined into the first cable, the second insulation resistance test line and the V-phase motor power line are combined into the second cable, the third insulation resistance test line and the W-phase motor power line are combined into the second cable, the first cable is connected to the bus copper bar U, the second cable is connected to the bus copper bar V, and the third cable is connected to the bus copper bar W; The DC resistance test line includes a DC resistance test line 1H, a DC resistance test line 3L, a DC resistance test line 1L, a DC resistance test line 2H, a DC resistance test line 2L and a DC resistance test line 3H, wherein the DC resistance test line 1H and the DC resistance test line 3L are combined into a same cable connected to a test clip U, the DC resistance test line 1L and the DC resistance test line 2H are combined into a same cable connected to a test clip V, and the DC resistance test line 2L and the DC resistance test line 3H are combined into a same cable connected to a test clip W.

3. The method for automated testing of multiple test items for a three-phase asynchronous motor according to claim 2, characterized in that: The busbar U and the test clip U are connected together to the terminal U of the three-phase asynchronous motor, the busbar V and the test clip V are connected together to the terminal V of the three-phase asynchronous motor, and the busbar W and the test clip W are connected together to the terminal W of the three-phase asynchronous motor.

4. The method for automated testing of multiple test items for a three-phase asynchronous motor according to claim 3, characterized in that: The insulation resistance test line also includes a fourth insulation resistance test line, and the fourth insulation resistance test line is connected to the motor housing.

5. The method for automated testing of multiple test items for a three-phase asynchronous motor according to claim 1, characterized in that: The specific steps of DC resistance test are: Use a 4-phase contactor to obtain the test voltage and test current based on the DC resistance test line, and calculate the resistance imbalance based on the test voltage and test current. If the imbalance does not meet the requirements, check the motor status and perform the DC resistance test again after the inspection. Otherwise, continue to perform the insulation resistance test.

6. The method for automated testing of multiple test items for a three-phase asynchronous motor according to claim 5, characterized in that: The specific steps of insulation resistance test are: Use a high-voltage relay to obtain the insulation voltage and insulation current based on the insulation resistance test line, and calculate the insulation resistance based on the insulation voltage and insulation current. If the insulation resistance is less than the limit value, it proves that there is an abnormality in the winding insulation layer of the current motor. It is necessary to check the motor status and perform the insulation resistance test again after the inspection. Otherwise, continue to perform the starting current test.

7. The method for automated testing of multiple test items for a three-phase asynchronous motor according to claim 1, characterized in that: The specific steps of the starting current test are: Power on the motor. For small power motors, direct start is used. During starting, the starting current of the motor is measured. If the starting current is too large, soft start is performed.

8. The method for automated testing of multiple test items for a three-phase asynchronous motor according to claim 7, characterized in that: The no-load test is as follows: The voltage, current, power, vibration, speed and temperature parameters of the motor are detected by vibration sensors, current sensors and thermal imagers.

9. The method for automated testing of multiple test items for a three-phase asynchronous motor according to claim 1, characterized in that: The switching of the DC resistance test, insulation resistance test, starting current test and no-load test is controlled based on PLC and host computer software.

10. The method for automated testing of multiple test items for a three-phase asynchronous motor according to claim 9, characterized in that: The device communication of the host computer software includes three communication modes: TCP / IP, RS485, and USB HOST, and three communication protocols: SCPI, Modbus, and ADS.

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