A wiring inspection method for the primary circuit of a large motor started by a two-dragging-two frequency conversion

Abstract

The present invention relates to a method for checking the primary circuit wiring of a large motor starting with a two-dragging-two frequency conversion, including: construction preparation and preliminary line inspection; disconnecting the external cables at the input and output ends of the frequency converter; respectively using temporary wires to bridge the external cables at the input and output ends of the frequency converter to form the primary circuit wiring; completing the wiring treatment of the motor and selecting the measuring point at the machine terminal; connecting the test power supply; checking the starting wiring of the first motor driven by the first frequency converter; checking the starting wiring of the second motor driven by the first frequency converter; checking the starting wiring of the first motor driven by the second frequency converter; checking the starting wiring of the second motor driven by the second frequency converter; and restoring the line connection between the frequency converter and the motor. The present invention reasonably plans the detection content and operation steps, reducing the safety risks during the commissioning operation of the electrical system.

Description

Technical Field

[0001] The present invention relates to the field of installation and commissioning of electrical systems, and particularly to a method for checking the primary circuit wiring of a large motor started by two-to-two frequency conversion Background Art

[0002] The control mode of starting two motors with two frequency converters in a "two-to-two" manner makes the operation of the power grid and the motors safer and more reliable due to the redundant and backup design, and has been increasingly applied in industrial production. However, due to the large capacity of the motor during starting and the use of multi-parallel single-core cables in the primary system, there are many primary circuit cables and the connections are complex. If the line connections are incorrect, it may cause problems such as short circuit between cables, unexpected power supply, overload or overvoltage faults of the frequency converter, resulting in the inability of the motor to start normally, and instantaneous short circuit between phases when the motor completes starting and switches to bypass power frequency operation due to different phase sequences between the output of the frequency converter and the power supply bus. Whether the two-to-two system can be put into operation in time and operate normally is directly related to the construction safety, progress and final project quality. At present, the commonly used debugging methods do not have a unified operation sequence and are greatly affected by factors such as the arrival and installation of on-site equipment, the laying of cables, the production of cable heads and the wiring conditions, etc., and there are potential hazards in the normal operation of the motor and the power grid and personal safety. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for checking the primary circuit wiring of a large motor started by two-to-two frequency conversion, which reasonably plans the detection content and operation steps and reduces the safety risks during the commissioning operation of the electrical system.

[0004] The technical solution adopted by the present invention to solve its technical problems is: to provide a method for checking the primary circuit wiring of a large motor started by two-to-two frequency conversion, including the following steps:

[0005] S1. Construction preparation and preliminary line inspection;

[0006] S2. Disconnect the external cables at the input and output ends of the first frequency converter and the second frequency converter;

[0007] S3. Use temporary wires to respectively cross-connect the external cables at the input and output ends of the first frequency converter and the second frequency converter to form the primary circuit wiring;

[0008] S4. Complete the wiring treatment of the first motor and the second motor, and select the measurement points at the machine terminals;

[0009] S5. Connect the test power supply;

[0010] S6. Check the starting wiring of the first motor driven by the first frequency converter;

[0011] S7. Check the wiring for starting the second motor driven by the first frequency converter;

[0012] S8. Check the wiring for starting the first motor driven by the second frequency converter;

[0013] S9. Check the wiring for starting the second motor driven by the second frequency converter;

[0014] S10. Restore the line connections of the first frequency converter, the second frequency converter, the first motor, and the second motor.

[0015] The specific steps of step S1 include:

[0016] S1.1. Familiarize with the electrical system schematic diagram of the large motor started by two-in-two frequency conversion, and prepare the instruments, meters, and working tools for debugging;

[0017] S1.2. Check the section 1 busbar, section 2 busbar of the power supply system, and each switch connected to the busbar;

[0018] S1.3. Lay cables between each switch, the first frequency converter, the second frequency converter, the output reactor, the first motor, and the second motor, and complete the cable head production. After checking and testing the cable line according to the system single-line diagram and it is qualified, connect the cable line correctly in the order of phases A, B, and C, and confirm whether the wiring of the first motor and the second motor meets the requirements of the final rotation direction;

[0019] S1.4. Place each switch in the hot standby state.

[0020] The specific steps of step S2 include:

[0021] S2.1. Mark the external primary input cable and output cable connected to the first frequency converter in the phase sequence of A, B, and C, then disconnect them from the first frequency converter. Short-circuit each group of multi-parallel cables at the input and output ends of the first frequency converter with wires in the three phases of A, B, and C respectively, and make the distance between each phase more than the set distance to ensure reliable insulation against the ground and between phases;

[0022] S2.2. Mark the external primary input cable and output cable connected to the second frequency converter in the phase sequence of A, B, and C, then disconnect them from the second frequency converter. Short-circuit each group of multi-parallel cables at the input and output ends of the second frequency converter with wires in the three phases of A, B, and C respectively, and make the distance between each phase more than the set distance to ensure reliable insulation against the ground and between phases.

[0023] The specific steps of step S3 include:

[0024] S3.1. Make two groups of 3 temporary wires each, and mark the phase sequence at both ends of each temporary wire;

[0025] S3.2. Connect a set of three temporary wires to the external cables of the removed first frequency converter in corresponding phase-by-phase manner according to phases A, B, and C, so that the three-phase input cables and three-phase output cables of the first frequency converter are conductively connected in corresponding phases.

[0026] S3.3. Connect another set of three temporary wires to the external cables of the removed second frequency converter in corresponding phase-by-phase manner according to phases A, B, and C, so that the three-phase input cables and three-phase output cables of the second frequency converter are conductively connected in corresponding phases.

[0027] The specific steps of step S4 are as follows: Disconnect the short connection of the neutral points of the three-phase windings at the tails of the first motor and the second motor respectively, so that the three-phase windings of the first motor and the second motor are open at the tails, and maintain the insulation to the ground and between phases, and use the tails of each phase winding as the machine terminal voltage measurement points.

[0028] The specific steps of step S5 include:

[0029] S5.1. Change all switches in the system to the operating state.

[0030] S5.2. Measure the insulation at the machine terminal measurement point of the first motor.

[0031] S5.3. Change all switches to the hot standby state.

[0032] S5.4. Connect a temporary three-phase AC380V positive phase sequence test power supply to the first incoming line input terminal or the second incoming line input terminal, close the corresponding incoming line switch, and send the power to the corresponding section of the bus.

[0033] S5.5. Close the bus tie switch between the two sections of the bus to make the other section of the bus energized.

[0034] The processes of step S6 and step S8 are the same, including:

[0035] Close the power switch of the frequency converter.

[0036] Detect that the voltages of the leads A, B, and C of the output reactor of the frequency converter are positive sequence 380V. If the detection result does not meet the requirements, cut off the incoming line switch, check and adjust it, and re-detect after restoring power supply until the detection result meets the requirements.

[0037] Detect that there is no voltage at the machine terminal measurement point of the first motor, no voltage at the machine terminal measurement point of the second motor, no voltage at the output terminal of the power switch of the other frequency converter, no voltage in the leads A, B, and C of the output reactor of the other frequency converter, no voltage at the outgoing line terminal of the bypass switch cabinet of the first motor, and no voltage at the outgoing line terminal of the bypass switch cabinet of the second motor. If the detection result does not meet the requirements, cut off the incoming line switch, check and adjust it, and re-detect after restoring power supply until the detection result meets the requirements.

[0038] Close the output switch of the frequency converter driving the first motor;

[0039] Detect that the three-phase voltages at the measurement points A, B, and C at the terminal of the first motor are positive-sequence 380V, and the three-phase voltages at the outgoing line terminals A, B, and C of the bypass switch of the first motor are positive-sequence 380V. Perform a phase verification test between the upper and lower break contacts of the bypass switch of the first motor, and the voltage between the same phases is 0V. If the test results do not meet the requirements, cut off the incoming line switch and check and adjust it. After restoring power supply, re-detect until the test results meet the requirements;

[0040] Detect that there is no voltage in each phase at the measurement point at the terminal of the second motor, no voltage in each phase of the lead wire of the output reactor of the other frequency converter, and no voltage at the outgoing line terminals of the bypass switch of the second motor. If the test results do not meet the requirements, cut off the incoming line switch and check and adjust it. After restoring power supply, re-detect until the test results meet the requirements;

[0041] Open the output switch of the frequency converter driving the first motor;

[0042] Open the power switch of the frequency converter.

[0043] The processes of step S7 and step S9 are the same and include:

[0044] Close the power switch of the frequency converter;

[0045] Close the output switch of the frequency converter driving the second motor;

[0046] Detect that the three-phase voltages at the measurement points A, B, and C at the terminal of the second motor are positive-sequence 380V, and the three-phase voltages at the outgoing line terminals A, B, and C of the bypass switch of the second motor are positive-sequence 380V. Perform a phase verification test between the upper and lower break contacts of the bypass switch of the second motor, and the voltage between the same phases is 0V. If the test results do not meet the requirements, cut off the incoming line switch and check and adjust it. After restoring power supply, re-detect until the test results meet the requirements;

[0047] Detect that there is no voltage in each phase at the measurement point at the terminal of the first motor, no voltage at the outgoing line terminals of the bypass switch of the first motor, and no voltage in each phase of the lead wire of the other frequency converter. If the test results do not meet the requirements, cut off the incoming line switch and check and adjust it. After restoring power supply, re-detect until the test results meet the requirements;

[0048] Open the output switch of the frequency converter driving the second motor;

[0049] Open the power switch of the frequency converter.

[0050] Beneficial effects

[0051] Due to the adoption of the above technical solution, compared with the prior art, the present invention has the following advantages and positive effects:

[0052] Based on the composition and characteristics of the primary circuit system for the "two-dragging-two" variable-frequency starting of large motors, the present invention reasonably plans the detection content and operation steps of the primary circuit of the two-dragging-two motor starting system, and scientifically and reasonably arranges the main content and testing methods. The present invention overcomes the problems in the conventional detection method that due to the multi-parallel and single-core cable connections in the primary system, there are many cables in the primary circuit and the connections are complex, and it is not easy to find some incorrect line connections. It avoids problems such as phase-to-phase short circuit of cables, unexpected power transmission, overload or overvoltage faults of the frequency converter resulting in abnormal starting of the motor, and instantaneous phase-to-phase short circuit caused by different phase sequences between the output of the frequency converter and the power supply bus when the motor starts and then switches to bypass power-frequency operation. While detecting the primary circuit, the present invention also facilitates the testing of some secondary interlock circuits of the motor. The detection content is systematic and complete, the method is scientific and reasonable, easy to operate, and avoids the inconvenience caused by repeated adjustments required after the formal power-on of the system due to some problems not being handled in time under conventional operations.

[0053] The present invention is convenient for organization and implementation. By reasonably planning the test steps and detection content, all electrical circuit inspections of the primary system are completed before the formal power-on of the system, reducing unnecessary rework caused by incorrect line connections. Thus, while ensuring the debugging quality and shortening the debugging period, the safety risks during the electrical system debugging operation are greatly reduced. Brief Description of the Drawings

[0054] Figure 1 is a schematic diagram of the primary circuit of the two-dragging-two variable-frequency starting motor;

[0055] Figure 2 is a flowchart of the implementation mode of the present invention;

[0056] Figure 3 is a schematic diagram of the measurement points at the motor terminal in the implementation mode of the present invention. Detailed Implementation Modes

[0057] The following further elaborates the present invention in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0058] Figure 1It is the primary circuit of a two - by - two frequency - conversion starting motor. Among them, IN1 is the incoming line of section 1, IN2 is the incoming line of section 2, ML is the bus tie switch between the bus of section 1 and the bus of section 2, M1 is the No. 1 motor, M2 is the No. 2 motor, BPQ1 is the No. 1 frequency converter, BPQ2 is the No. 2 frequency converter, QF1 is the power switch of the No. 1 frequency converter, QF2 is the power switch of the No. 2 frequency converter, PL1 is the bypass switch of the No. 1 motor, PL2 is the bypass switch of the No. 2 motor, L1 is the output reactor of the No. 1 frequency converter, L2 is the output reactor of the No. 2 frequency converter, K11 is the output switch of the No. 1 frequency converter driving the No. 1 motor, K21 is the output switch of the No. 2 frequency converter driving the No. 1 motor, K12 is the output switch of the No. 1 frequency converter driving the No. 2 motor, and K22 is the output switch of the No. 2 frequency converter driving the No. 2 motor.

[0059] The embodiment of the present invention relates to a method for checking the wiring of the primary circuit of a two - by - two frequency - conversion starting large - scale motor, as Figure 2 shown, which includes the following steps:

[0060] S1. Construction preparation and preliminary line inspection;

[0061] S1.1. Familiarize with the schematic diagram of the two - by - two electrical system, and prepare the instruments and tools for debugging;

[0062] S1.2. Check the bus of section 1, the bus of section 2, and each switch connected to the bus of the power supply system. The connection is correct, the installation and test are completed, and it meets the power - receiving conditions;

[0063] S1.3. After the cable laying and cable - head production between each switch, frequency converter, output reactor, and motor are completed, check and test the cable line according to the single - line diagram of the system. Then, correctly connect the cable line in the order of phases A, B, and C, and confirm that the motor wiring meets the requirements of the final rotation direction;

[0064] S1.4. Place each switch in the hot standby state.

[0065] S2. Disconnect the external cables at the input and output ends of the frequency converter;

[0066] S2.1. Mark the external primary input and output cables connected to the No. 1 frequency converter BPQ1 in the phase sequence of A, B, and C, and then disconnect them from the No. 1 frequency converter BPQ1. The multi - parallel cables at the input and output ends are short - circuited separately with wires in the three phases of A, B, and C, and the distance between each phase is kept more than 10 cm to ensure reliable insulation between the ground and the phases;

[0067] S2.2. Mark the external primary input and output cables connected to the No. 2 frequency converter BPQ2 in the phase sequence of A, B, C, and then disconnect them from the No. 2 frequency converter BPQ2. The multi-parallel cables of each group at the input and output ends are short-circuited separately with wires in the three phases of A, B, C, and the distance between each phase is kept more than 10 cm to ensure reliable insulation against the ground and between phases.

[0068] S3. Connect the external primary circuit wiring at the input and output ends of the frequency converter with temporary wires;

[0069] S3.1. Make two groups of 3 temporary wires each with appropriate lengths, and mark the phase sequence at both ends of each wire;

[0070] S3.2. Connect one group of 3 temporary wires in step S3.1 to the external cables of the removed No. 1 frequency converter BPQ1 in step S2.1 in corresponding phases of A, B, C, so that the three-phase input cables and three-phase output cables of the No. 1 frequency converter BPQ1 are conductively connected in corresponding phases;

[0071] S3.3. Connect the other group of 3 temporary wires in step S3.1 to the external cables of the removed No. 2 frequency converter BPQ2 in step S2.2 in corresponding phases of A, B, C, so that the three-phase input cables and three-phase output cables of the No. 2 frequency converter BPQ2 are conductively connected in corresponding phases.

[0072] S4. Motor wiring treatment and selection of measurement points at the machine end

[0073] Disconnect the neutral points at the tails of the No. 1 motor M1 and the No. 2 motor M2. The treatment method is as follows:

[0074] As Figure 3 shown, disconnect the short connection of the neutral points of the three-phase windings at the tail of the motor, open the three-phase windings at the tail of the motor, and maintain insulation against the ground and between phases. The tails of each phase winding are used as the measurement points for the voltage at the machine end.

[0075] S5. Connect the test power supply

[0076] S5.1. Change all switches in the system to the operating state;

[0077] S5.2. Measure the insulation at the measurement points at the machine end of the No. 1 motor M1. The insulation resistance between phases and against the ground is not less than 1 MΩ;

[0078] S5.3. Change all switches to the hot standby state;

[0079] S5.4. Connect a temporary three-phase AC380V positive phase sequence test power supply to the input end of the No. 1 incoming line IN1 or the input end of the No. 2 incoming line IN2, close the corresponding incoming line switch, and send the power to the corresponding section of the bus;

[0080] S5.5. Close the bus tie switch ML between the two sections of busbars to energize the other section of busbar.

[0081] S6. Check the starting wiring of the No. 1 motor M1 driven by the No. 1 frequency converter BPQ1;

[0082] S6.1. Close the power switch QF1 of the No. 1 frequency converter;

[0083] S6.2. Detect that the three-phase voltages of the leads A, B, and C of the output reactor of the No. 1 frequency converter are positive sequence 380V. If the detection result does not meet the requirements, cut off the power supply of the incoming line switch in S5.4 and then check and adjust it. After restoring the power supply, re-detect until the detection result meets the requirements;

[0084] S6.3. Detect that there is no voltage at the measuring point at the motor terminal of the No. 1 motor M1, no voltage at the measuring point at the motor terminal of the No. 2 motor M2, no voltage at the output terminal of the power switch QF2 of the No. 2 frequency converter, no voltage in the three phases of the leads A, B, and C of the output reactor L2 of the No. 2 frequency converter, no voltage at the outgoing line end of the bypass switch PL1 of the No. 1 motor, and no voltage at the outgoing line end of the bypass switch PL2 of the No. 2 motor. If the detection result does not meet the requirements, cut off the power supply of the incoming line switch in S5.4 and then check and adjust it. After restoring the power supply, re-detect until the detection result meets the requirements;

[0085] S6.4. Close the output switch K11 of the No. 1 frequency converter driving the No. 1 motor;

[0086] S6.5. Detect that the three-phase voltages of the measuring points A, B, and C at the motor terminal of the No. 1 motor M1 are positive sequence 380V, and the three-phase voltages of the outgoing line ends A, B, and C of the bypass switch PL1 of the No. 1 motor are positive sequence 380V. Perform a phase verification test between the upper and lower break points of the bypass switch PL1 of the No. 1 motor, and the voltage between the same phases is 0V. If the detection result does not meet the requirements, cut off the power supply of the incoming line switch in S5.4 and then check and adjust it. After restoring the power supply, re-detect until the detection result meets the requirements;

[0087] S6.7. Detect that there is no voltage in each phase at the measuring point at the motor terminal of the No. 2 motor M2, no voltage in each phase of the leads of the output reactor L2 of the No. 2 frequency converter, and no voltage at the outgoing line end of the bypass switch PL2 of the No. 2 motor. If the detection result does not meet the requirements, cut off the power supply of the incoming line switch in S5.4 and then check and adjust it. After restoring the power supply, re-detect until the detection result meets the requirements;

[0088] S6.8. Open the output switch K11 of the No. 1 frequency converter driving the No. 1 motor.

[0089] S7. Check the starting wiring of the No. 2 motor M2 driven by the No. 1 frequency converter BPQ1;

[0090] S7.1. Close the output switch K12 of the No. 1 frequency converter driving the No. 2 motor;

[0091] S7.2. Measure the three-phase voltages at the terminals of the No. 2 motor M2 at measurement points A, B, and C, which are 380V in positive sequence. The three-phase voltages at the outgoing terminals A, B, and C of the bypass switch PL2 of the No. 2 motor are also 380V in positive sequence. Conduct a phase verification test on the upper and lower breakpoints of the bypass switch PL2 of the No. 2 motor. The voltage between the same phases is 0V. If the test results do not meet the requirements, cut off the incoming line switch in S5.4, then check and adjust it. After restoring power supply, conduct the test again until the test results meet the requirements;

[0092] S7.3. Measure that there is no voltage at the terminals of the No. 1 motor M1, no voltage at the outgoing terminals of the bypass switch PL1 of the No. 1 motor, and no voltage on each phase of the lead wire of the output reactor L2 of the No. 2 frequency converter. If the test results do not meet the requirements, cut off the incoming line switch in S5.4, then check and adjust it. After restoring power supply, conduct the test again until the test results meet the requirements;

[0093] S7.4. Disconnect the output switch K12 of the No. 1 frequency converter for driving the No. 2 motor;

[0094] S7.5. Disconnect the power switch QF1 of the No. 1 frequency converter.

[0095] S8. Check the starting wiring of the No. 1 motor M1 driven by the No. 2 frequency converter BPQ2;

[0096] S8.1. Close the power switch QF2 of the No. 2 frequency converter;

[0097] S8.2. Measure that the three-phase voltages of the lead wires A, B, and C of the output reactor L2 of the No. 2 frequency converter are 380V in positive sequence. If the test results do not meet the requirements, cut off the incoming line switch in S5.4, then check and adjust it. After restoring power supply, conduct the test again until the test results meet the requirements;

[0098] S8.3. Measure that there is no voltage at the terminals of the No. 1 motor M1, no voltage at the terminals of the No. 2 motor M2, no voltage detected at the output terminal of the power switch QF1 of the No. 1 frequency converter, no voltage on each phase of the lead wires A, B, and C of the output reactor L1 of the No. 1 frequency converter, no voltage at the outgoing terminals of the bypass switch PL1 of the No. 1 motor, and no voltage at the outgoing terminals of the bypass switch PL2 of the No. 2 motor. If the test results do not meet the requirements, cut off the incoming line switch in S5.4, then check and adjust it. After restoring power supply, conduct the test again until the test results meet the requirements;

[0099] S8.4. Close the output switch K21 of the No. 2 frequency converter for driving the No. 1 motor;

[0100] S8.5. Measure the three-phase voltages at the terminal measurement points A, B, and C of Motor M1, and the three-phase voltages at the outgoing line terminals A, B, and C of the bypass switch PL1 of Motor M1 are all positive-sequence 380V. Conduct a phase verification test at the upper and lower break points of the bypass switch PL1 of Motor M1, and the voltage between the same phases is 0V. If the test results do not meet the requirements, cut off the incoming line switch in S5.4, check and adjust it, and then re-test after restoring power supply until the test results meet the requirements;

[0101] S8.6. Measure that there is no voltage at the terminal measurement points of Motor M2, no voltage at the outgoing line terminals of the bypass switch PL2 of Motor M2, and no voltage at each phase of the lead wire of the output reactor L1 of Inverter 1. If the test results do not meet the requirements, cut off the incoming line switch in S5.4, check and adjust it, and then re-test after restoring power supply until the test results meet the requirements;

[0102] S8.7. Disconnect the output switch K21 of Inverter 2 driving Motor M1.

[0103] S9. Check the starting wiring of Inverter 2 (BPQ2) driving Motor M2;

[0104] S9.1. Close the output switch K22 of Inverter 2 driving Motor M2;

[0105] S9.2. Measure the three-phase voltages at the terminal measurement points A, B, and C of Motor M2, and the three-phase voltages at the outgoing line terminals A, B, and C of the bypass switch PL2 of Motor M2 are all positive-sequence 380V. Conduct a phase verification test at the upper and lower break points of the bypass switch PL1 of Motor M2, and the voltage between the same phases is 0V. If the test results do not meet the requirements, cut off the incoming line switch in S5.4, check and adjust it, and then re-test after restoring power supply until the test results meet the requirements;

[0106] S9.3. Measure that there is no voltage at each phase of the terminal measurement points of Motor M1, no voltage at the outgoing line of the bypass switch PL1 of Motor M1, and no voltage at each phase of the lead wire of the output reactor L1 of Inverter 1. If the test results do not meet the requirements, cut off the incoming line switch in S5.4, check and adjust it, and then re-test after restoring power supply until the test results meet the requirements;

[0107] S9.4. Disconnect the output switch K22 of Inverter 2 driving Motor M2;

[0108] S9.5. Disconnect the power switch QF2 of Inverter 2;

[0109] S9.6. Disconnect the incoming line switch IN1 and the bus tie switch ML in S5.4, cut off the temporary test power supply, and then remove the temporary power supply;

[0110] S9.7. Change each circuit breaker to the cold standby state.

[0111] S10. Line restoration

[0112] S10.1. Remove the temporary test lines, jumper wires, and short - circuit wires during the test process

[0113] S10.2. Restore the line connections of the No. 1 frequency converter and the No. 2 frequency converter;

[0114] S10.3. Restore the line connections of the No. 1 motor and the No. 2 motor.

[0115] During the implementation process of the present invention, if there is a disconnector in the circuit, just close the disconnector. Since the connection between the disconnector and other devices is intuitive and it is not easy to have connection errors, it only needs to be confirmed that its connection is correct before detection. The switch for the frequency converter to drive the motor output in the present invention can also be a contactor. The frequency converter described in the present invention can be a frequency converter placed within a switch cabinet, or a group of frequency converter switch cabinets composed of voltage transformation, rectification, and inverter output, etc. When the frequency converter is composed of a switch cabinet group, only consider its input and output as a whole. The present invention is also applicable to the primary circuit inspection of the motor for "one - drive - two" starting (i.e., one frequency converter drives two motors), and only several steps need to be omitted. The present invention can also be used as a reference for the primary circuit inspection of systems such as "two - drive - three" (i.e., two frequency converters drive three motors) and "two - drive - four" (i.e., two frequency converters drive four motors).

Claims

1. A wiring inspection method for the primary circuit of a large motor with a two-drive-two variable-frequency starting, characterized in that, It includes the following steps: S1. Construction preparation and preliminary line inspection; S2. Disconnect the external cables at the input and output ends of the first frequency converter and the second frequency converter; S3. Use temporary wires to respectively cross-connect the external cables at the input and output ends of the first frequency converter and the second frequency converter to form a primary circuit wiring; S4. Complete the wiring treatment of the first motor and the second motor, and select the machine terminal measurement points; S5. Connect the test power supply; S6. Check the starting wiring of the first motor driven by the first frequency converter; S7. Check the starting wiring of the second motor driven by the first frequency converter; S8. Check the starting wiring of the first motor driven by the second frequency converter; S9. Check the starting wiring of the second motor driven by the second frequency converter; S10. Restore the line connections of the first frequency converter, the second frequency converter, the first motor and the second motor.

2. The method for checking the primary circuit wiring of a large motor with a two-drag-two frequency conversion starting as claimed in claim 1, wherein The specific steps of S1 include: S1.

1. Familiarize with the electrical system schematic diagram of the large motor with two-in-two frequency conversion starting, and prepare the instruments, meters and working tools for debugging; S1.

2. Check the section 1 busbar, section 2 busbar of the power supply system, and each switch connected to the busbar; S1.

3. Lay cables between each switch, the first frequency converter, the second frequency converter, the output reactor, the first motor and the second motor, and complete the cable head production. After checking and testing the cable line according to the system single-line diagram and passing the test, connect the cable line correctly in the order of phases A, B, and C, and confirm whether the wiring of the first motor and the second motor meets the requirements of the final rotation direction; S1.

4. Place each switch in the hot standby state.

3. The wiring inspection method for the primary circuit of a large motor with a two-drive-two frequency conversion starting as claimed in claim 1, wherein The specific steps of S2 include: S2.

1. Mark the external primary input cable and output cable connected to the first frequency converter in the phase sequence of A, B, and C, then disconnect them from the first frequency converter. Short-circuit each group of multi-parallel cables at the input and output ends of the first frequency converter with wires in the three phases of A, B, and C respectively, so that the distance between each phase is above the set distance to ensure reliable insulation against the ground and between phases; S2.

2. Mark the external primary input cable and output cable connected to the second frequency converter in the phase sequence of A, B, and C, then disconnect them from the second frequency converter. Short-circuit each group of multi-parallel cables at the input and output ends of the second frequency converter with wires in the three phases of A, B, and C respectively, so that the distance between each phase is above the set distance to ensure reliable insulation against the ground and between phases.

4. The wiring inspection method for the primary circuit of a large motor with a two-drive-two frequency conversion starting as claimed in claim 1, characterized in that, The specific steps of S3 include: S3.

1. Make two groups of 3 temporary wires each, and mark the phase sequence at both ends of each temporary wire; S3.

2. Cross-connect a group of 3 temporary wires with the removed external cable of the first frequency converter in the corresponding three phases of A, B, and C to make the three-phase input cable and three-phase output cable of the first frequency converter conduct correspondingly; S3.

3. Cross-connect the other group of 3 temporary wires with the removed external cable of the second frequency converter in the corresponding three phases of A, B, and C to make the three-phase input cable and three-phase output cable of the second frequency converter conduct correspondingly.

5. The wiring inspection method for the primary circuit of a large motor with two-drive-two variable-frequency starting according to claim 1, characterized in that, The specific steps of step S4 are as follows: Disconnect the neutral point short - circuit of the three - phase windings at the tails of the first motor and the second motor respectively, open - circuit the 3 - phase windings of the first motor and the second motor at the tails, and maintain the insulation between the windings and the ground and between phases. Take the tails of each phase winding as the measuring points for the terminal voltage.

6. The method for checking the primary circuit wiring of a large motor with two-drive-two-frequency conversion starting according to claim 1, characterized in that, The specific steps of step S5 include: S5.

1. Change all switches in the system to the operating state; S5.

2. Measure the insulation at the measuring point of the terminal of the first motor; S5.

3. Change all switches to the hot standby state; S5.

4. Connect a temporary three - phase AC380V positive - phase - sequence test power supply to either the first incoming line input terminal or the second incoming line input terminal, close the corresponding incoming line switch, and send the power to the corresponding section of the bus; S5.

5. Close the bus tie switch between the two sections of the bus to energize the other section of the bus.

7. The method for checking the primary circuit wiring of a large motor with a two-drive-two variable-frequency starting as claimed in claim 1, wherein The processes of step S6 and step S8 are the same and include: Close the power switch of the frequency converter; Detect that the voltages of the three - phase leads A, B, and C of the output reactor of the frequency converter are positive - sequence 380V. If the detection result does not meet the requirements, cut off the incoming line switch, check and adjust it, and then re - detect after restoring the power supply until the detection result meets the requirements; Detect that there is no voltage at the measuring point of the terminal of the first motor, no voltage at the measuring point of the terminal of the second motor, no voltage at the output terminal of the power switch of the other frequency converter, no voltage in the three - phase leads A, B, and C of the output reactor of the other frequency converter, no voltage at the outgoing line terminal of the bypass switch cabinet of the first motor, and no voltage at the outgoing line terminal of the bypass switch cabinet of the second motor. If the detection result does not meet the requirements, cut off the incoming line switch, check and adjust it, and then re - detect after restoring the power supply until the detection result meets the requirements; Close the output switch of the frequency converter driving the first motor; Detect that the voltages of the three - phase leads A, B, and C at the measuring point of the terminal of the first motor are positive - sequence 380V, and the voltages of the three - phase leads A, B, and C at the outgoing line terminal of the bypass switch of the first motor are positive - sequence 380V. Conduct a phase - checking test between the upper and lower break - points of the bypass switch of the first motor, and the voltage between the same phases is 0V. If the detection result does not meet the requirements, cut off the incoming line switch, check and adjust it, and then re - detect after restoring the power supply until the detection result meets the requirements; Detect that there is no voltage in each phase at the measuring point of the terminal of the second motor, no voltage in each phase of the output reactor lead of the other frequency converter, and no voltage at the outgoing line terminal of the bypass switch of the second motor. If the detection result does not meet the requirements, cut off the incoming line switch, check and adjust it, and then re - detect after restoring the power supply until the detection result meets the requirements; Open the output switch of the frequency converter driving the first motor; Open the power switch of the frequency converter.

8. The method for checking the primary circuit wiring of a large motor with a two-dragging-two frequency conversion starting according to claim 1, characterized in that, The processes of step S7 and step S9 are the same and include: Close the power switch of the frequency converter; Close the output switch of the frequency converter driving the second motor; The phase voltages of the machine terminal measurement points A, B, and C of the second motor are positive-sequence 380V, and the phase voltages of the outgoing line terminals A, B, and C of the bypass switch of the second motor are positive-sequence 380V. The voltage between the same phases during the phase verification test at the upper and lower breakpoints of the bypass switch of the second motor is 0V. If the test results do not meet the requirements, the incoming line switch shall be de-energized for inspection and adjustment, and after power supply is restored, the test shall be repeated until the test results meet the requirements; There is no voltage on each phase of the machine terminal measurement point of the first motor, there is no voltage on the outgoing line terminal of the bypass switch of the first motor, and there is no voltage on each phase of the lead wire of the output reactor of another frequency converter. If the test results do not meet the requirements, the incoming line switch shall be de-energized for inspection and adjustment, and after power supply is restored, the test shall be repeated until the test results meet the requirements; Disconnect the output switch of the frequency converter driving the second motor; Disconnect the power switch of the frequency converter.

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