Method and device for measuring resistance value of contact resistor of crimping tube and test loop for measuring resistance value of contact resistor of crimping tube

Abstract

The invention discloses a method and device for measuring the resistance value of a crimping tube contact resistor and a test loop for measuring the resistance value of the crimping tube contact resistor, and belongs to the field of cables. The method comprises the following steps: acquiring the total number of crimping pipes in a test loop, the first length of a reference cable, the reference temperature of a conductor in the reference cable and the total length of the cable except the length of the crimping pipes in the test loop; when the power frequency current enters the test loop and the real-time temperature of the reference cable reaches the reference temperature, acquiring the loop voltage and loop current of the test loop and the voltages at the two ends of the reference cable; according to the loop voltage, the loop current, the two-end voltage, the first length and the total length of the cable, the total contact resistance value of the test loop is calculated; and determining the contact resistance value of each crimping tube in the test loop according to the total number of the crimping tubes and the total contact resistance value. By implementing the application, the problem that the contact resistance cannot be effectively measured in the prior art can be solved.

Description

Technical Field

[0001] The present invention relates to the field of cables, and in particular to a method and device for measuring the contact resistance of a crimping tube, and a test circuit for measuring the contact resistance of a crimping tube. Background Art

[0002] Currently, crimp tubes, thanks to their efficient and convenient connection, have become a key component in the electrical connection of cable conductors. The contact resistance of a crimp tube is essentially the resistance generated when the inner wall of the crimp tube makes close contact with the cable core. This resistance directly affects the system's energy consumption, heat generation, and stability. Excessive contact resistance can not only cause severe heating at the connection and accelerate insulation aging, but can also potentially cause fires and other safety hazards.

[0003] Currently, for circuits containing multiple cable sections and multiple crimping tubes, existing technologies are unable to eliminate the interference of the cable's own resistance on the measurement results when the loop is energized, resulting in distorted contact resistance data. In addition, it is difficult to accurately distinguish the resistance of the contact interface between the inner wall of the crimping tube and the cable core, and cannot meet the needs of high-precision electrical performance quantitative evaluation. Summary of the Invention

[0004] The present invention provides a method and device for measuring the contact resistance of a crimping tube, and a test circuit for measuring the contact resistance of a crimping tube. The method can solve the problem that the prior art cannot effectively measure the contact resistance.

[0005] An embodiment of the present invention provides a method for measuring the contact resistance of a crimping tube, which is applicable to a test circuit, wherein the test circuit includes a reference cable, a plurality of measuring cables, a plurality of crimping tubes, and a current-boosting transformer;

[0006] The first end of the reference cable is connected to one end of the first measuring cable of the test loop in the current flow direction, and the second end of the reference cable is connected to one end of the current boosting transformer;

[0007] The measuring cables are crimped and connected via a crimping tube;

[0008] The other end of the current-boosting transformer is connected to one end of the last measuring cable in the current flow direction of the test loop;

[0009] The method for measuring the contact resistance of the crimping tube includes:

[0010] Obtaining the total number of crimping tubes in the test loop, a first length of a reference cable in the test loop, a reference temperature of a conductor in the reference cable, and a total length of the cables in the test loop excluding the length of the crimping tubes;

[0011] When a power frequency current is passed through the test circuit and the real-time temperature of the reference cable reaches the reference temperature, obtaining a loop voltage of the test circuit, a loop current of the test circuit, and a voltage across both ends of the reference cable in the test circuit;

[0012] Calculate the total contact resistance of the test loop according to the loop voltage, the loop current, the voltages at both ends, the first length, and the total length of the cable;

[0013] The contact resistance value of each crimping tube in the test loop is determined according to the total number of the crimping tubes and the total contact resistance value.

[0014] Furthermore, the reference temperature of the conductor in the reference cable is obtained by the following method, including:

[0015] When power frequency current is passed into the test loop, the conductor temperature of the reference cable and the temperature of the crimping tube of the crimping tube located in the middle of the test loop in the direction of current flow are obtained in real time;

[0016] When the conductor temperature reaches a preset first temperature threshold, determining whether the crimping tube temperature reaches a preset second temperature threshold; wherein the first temperature threshold is greater than the second temperature threshold;

[0017] If so, the conductor temperature is used as the reference temperature, and the flow of the power frequency current is stopped;

[0018] If not, maintain the flow of the industrial frequency current to continuously increase the conductor temperature, and when it is detected that the temperature of the crimping tube reaches the second temperature threshold, use the current conductor temperature as the reference temperature; when it is detected that the temperature of the crimping tube does not reach the second temperature threshold and the conductor temperature reaches a preset third temperature threshold, use the third temperature threshold as the reference temperature of the conductor in the reference cable; wherein, the third temperature threshold is greater than the first temperature threshold.

[0019] Furthermore, when the power frequency current is passed into the test circuit and the real-time temperature of the reference cable reaches the reference temperature, obtaining the loop voltage of the test circuit, the loop current of the test circuit, and the voltage across both ends of the reference cable in the test circuit includes:

[0020] Determining the power frequency current step levels according to the reference temperature;

[0021] When power frequency current is passed through the test circuit, the original circuit voltage of the test circuit, the original circuit current of the test circuit, and the original voltage across the reference cable in the test circuit are obtained at each power frequency current step.

[0022] averaging all the acquired original loop voltages to obtain the loop voltage of the test loop;

[0023] averaging all the original loop currents obtained to obtain the loop current of the test loop;

[0024] The voltages at both ends of the reference cable in the test loop are obtained by averaging all the original voltages at both ends obtained.

[0025] Furthermore, the total contact resistance of the test loop is calculated based on the loop voltage, the loop current, the voltages at both ends, the first length, and the total length of the cable, including:

[0026] Calculating the total resistance of the test loop based on the loop voltage and the loop current;

[0027] Calculating a reference resistance of the reference cable according to the voltages at both ends and the loop current;

[0028] Dividing the total length of the cable by the first length to obtain a first ratio;

[0029] multiplying the reference resistance by the first ratio to obtain a total cable resistance;

[0030] The total contact resistance is obtained by subtracting the total cable resistance from the total resistance.

[0031] Furthermore, determining the contact resistance value of each crimping tube in the test circuit according to the total number of the crimping tubes and the total contact resistance value includes:

[0032] The total contact resistance value is divided by the total number of the crimping tubes to obtain the contact resistance value of each crimping tube in the test loop.

[0033] Furthermore, the real-time acquisition of the temperature of the crimping tube of the crimping tube located in the middle of the test loop in the direction of current flow and the conductor temperature of the reference cable includes:

[0034] Obtaining a temperature of the crimping tube at a middle position of the test loop in the direction of current flow, as collected by a first thermocouple; wherein the first thermocouple is disposed at the center of a cross section of a crimping mark formed after the crimping tube at the middle position in the test loop is crimped;

[0035] The conductor temperature of the reference cable collected by a second thermocouple is obtained; wherein the second thermocouple is arranged inside the reference cable.

[0036] An embodiment of the present invention further provides a device for measuring the contact resistance of a crimped tube, comprising: a first data acquisition module, a second data acquisition module, a first contact resistance calculation module, and a second contact resistance calculation module;

[0037] The first data acquisition module is configured to acquire the total number of crimping tubes in the test loop, a first length of a reference cable in the test loop, a reference temperature of a conductor in the reference cable, and a total length of the cables in the test loop excluding the length of the crimping tubes;

[0038] The second data acquisition module is configured to acquire the loop voltage of the test loop, the loop current of the test loop, and the voltage across both ends of the reference cable in the test loop when the power frequency current is passed into the test loop and the real-time temperature of the reference cable reaches the reference temperature;

[0039] The first contact resistance calculation module is used to calculate the total contact resistance of the test loop according to the loop voltage, the loop current, the voltages at both ends, the first length, and the total length of the cable;

[0040] The second contact resistance calculation module is used to determine the contact resistance of each crimping tube in the test loop according to the total number of the crimping tubes and the total contact resistance.

[0041] An embodiment of the present invention further provides a test circuit for measuring the contact resistance of a crimping tube, comprising: a reference cable, a plurality of measuring cables, a plurality of crimping tubes, and a current-boosting transformer;

[0042] The first end of the reference cable is connected to one end of the first measuring cable of the test loop in the current flow direction, and the second end of the reference cable is connected to one end of the current boosting transformer;

[0043] The measuring cables are crimped and connected via a crimping tube;

[0044] The other end of the current-boosting transformer is connected to one end of the last measuring cable in the test loop in the current flow direction.

[0045] Furthermore, a difference between an inner diameter of the crimping tube and an outer diameter of the measuring cable is in a range of 1 mm to 2 mm.

[0046] Furthermore, a difference between an inner diameter of the crimping tube and an outer diameter of the reference cable is in a range of 1 mm to 2 mm.

[0047] The following beneficial effects are achieved by implementing the present invention:

[0048] The present invention provides a method and device for measuring the contact resistance of a crimping tube, and a test circuit for measuring the contact resistance of a crimping tube. The method obtains the loop voltage of the test circuit, the loop current of the test circuit, and the voltage at both ends of the reference cable in the test circuit when an industrial frequency current is passed through the test circuit and the real-time temperature of the reference cable reaches the reference temperature; the total contact resistance of the test circuit is calculated based on the loop voltage, the loop current, the voltage at both ends, the first length, and the total length of the cable; thereby, by accurately controlling the real-time temperature of the reference cable to the reference temperature, the interference of temperature on the resistance measurement is eliminated, ensuring that the measurement results under different conditions are comparable; then, based on the total number of the crimping tubes and the total contact resistance, the contact resistance of each crimping tube in the test circuit is determined, and data such as the loop voltage, current, and the voltage at both ends of the reference cable are used to separate the cable body resistance and the crimping tube contact resistance, thereby solving the problem of aliasing between the two, and being unaffected by the cable length, thereby effectively measuring the contact resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings required for use in the implementation. Obviously, the drawings described below are only some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0050] Figure 1 This is a flow chart of a method for measuring the contact resistance of a crimped tube provided in one embodiment of the present application;

[0051] Figure 2 This is a schematic diagram of the structure of a test circuit provided in one embodiment of the present application;

[0052] Figure 3 is a schematic diagram of a cross section of a crimped tube after crimping provided by an embodiment of the present application;

[0053] Figure 4 is a structural diagram of a test circuit provided by another embodiment of the present application;

[0054] Figure 5 It is a structural schematic diagram of a device for measuring the contact resistance of a crimped tube provided in one embodiment of the present application. DETAILED DESCRIPTION

[0055] To make the objectives, technical solutions, and advantages of this application more clear, the technical solutions in this application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of this application.

[0056] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0057] In the description of the embodiments of this application, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly specify the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0058] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0059] In the description of the embodiments of this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the following three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0060] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0061] In the description of the embodiments of the present application, unless otherwise expressly specified or limited, technical terms such as "installed," "connected," "connected," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; internal connections between two components or interactions between two components. Those skilled in the art can understand the specific meanings of the above terms in the embodiments of the present application based on specific circumstances.

[0062] See also Figure 1 To solve the problem that the existing technology cannot effectively measure contact resistance, an embodiment of the present invention provides a method for measuring the contact resistance of a crimping tube, which is applicable to a test circuit. The test circuit includes a reference cable, a plurality of measuring cables, a plurality of crimping tubes, and a current-boosting transformer.

[0063] The first end of the reference cable is connected to one end of the first measuring cable of the test loop in the current flow direction, and the second end of the reference cable is connected to one end of the current boosting transformer;

[0064] The measuring cables are crimped and connected via a crimping tube;

[0065] The other end of the current-boosting transformer is connected to one end of the last measuring cable in the current flow direction of the test loop;

[0066] The method for measuring the contact resistance of the crimping tube includes:

[0067] S1. Obtaining the total number of crimping tubes in the test loop, a first length of a reference cable in the test loop, a reference temperature of a conductor in the reference cable, and a total length of the cables in the test loop excluding the length of the crimping tubes;

[0068] S2. When a power frequency current is passed through the test circuit and the real-time temperature of the reference cable reaches the reference temperature, obtaining a loop voltage of the test circuit, a loop current of the test circuit, and a voltage across both ends of the reference cable in the test circuit;

[0069] S3. Calculate the total contact resistance of the test loop according to the loop voltage, the loop current, the voltages at both ends, the first length, and the total length of the cable;

[0070] S4. Determine the contact resistance value of each crimping tube in the test circuit according to the total number of the crimping tubes and the total contact resistance value;

[0071] Specifically, the reference cable serves as a standard reference component in the test loop. It is not directly connected to the crimping tube to ensure the accuracy and stability of the measurement results. Instead, each measuring cable is crimped together via a crimping tube. The test loop does not limit the specific number of crimping tubes and measuring cables. However, it should be noted that when the number of measuring cables is N (N is a positive integer), the number of crimping tubes should be N-1. The lengths of the reference cable and the measuring cable should be the same and should not be too long. In this embodiment, the lengths of the reference cable and the measuring cable are both 3 meters, so that each cable in the test loop can simulate the transmission characteristics of an actual cable within a certain distance, reducing measurement errors caused by cables that are too long or too short.

[0072] Specifically, see Figure 2 , is a schematic diagram of the structure of the test circuit described in this embodiment, taking 4 measuring cables and 3 crimping tubes as an example, Figure 2 The system includes a current-boosting transformer MC1 (including a primary winding L1 and a secondary winding L2), a reference cable R1, measuring cables R2-R5 and crimping tubes G1-G3; a current transformer CT is inserted into the measuring loop;

[0073] In addition, the edge of the insulation layer of the tested cable conductor and the edge of the crimping tube should retain at least 10 cm of the core conductor length;

[0074] Specifically, the insulation layer of each measuring cable is processed to ensure that the conductor surface is clean; then, a crimping tube is installed at a position more than 10 cm away from the incision of the insulation layer. This reserved length can not only prevent the insulation layer from breaking or shifting due to force during the crimping process, but also provide sufficient operating space for the crimping operation, thereby ensuring the stability of the connection structure.

[0075] In a preferred embodiment, the reference temperature of the conductor in the reference cable is obtained by the following method, including:

[0076] When power frequency current is passed into the test loop, the conductor temperature of the reference cable and the temperature of the crimping tube of the crimping tube located in the middle of the test loop in the direction of current flow are obtained in real time;

[0077] When the conductor temperature reaches a preset first temperature threshold, determining whether the crimping tube temperature reaches a preset second temperature threshold; wherein the first temperature threshold is greater than the second temperature threshold;

[0078] If so, the conductor temperature is used as the reference temperature, and the flow of the power frequency current is stopped;

[0079] If not, then maintaining the flow of the power frequency current to continuously increase the conductor temperature, and when detecting that the temperature of the crimping tube reaches the second temperature threshold, using the current conductor temperature as the reference temperature, and when detecting that the temperature of the crimping tube does not reach the second temperature threshold and the conductor temperature reaches a preset third temperature threshold, using the third temperature threshold as the reference temperature of the conductor in the reference cable; wherein the third temperature threshold is greater than the first temperature threshold;

[0080] Specifically, the power frequency current is fed into the test circuit via the current boosting transformer in the test circuit, and a current equalizer is used in this process to ensure uniform current distribution; see Figure 2 , the crimping tube in the middle position of the test circuit in the direction of current flow is G2;

[0081] Schematically, when power frequency current is passed through the test circuit, the temperature of the crimping tube and the reference cable will increase with the duration of power-on and the current load. In order to ensure that the temperature difference between the conductor in the reference cable and the middle conductor of the crimping circuit is small, thereby eliminating the interference of temperature differences on the measurement results, it is necessary to determine the reference temperature of the conductor in the reference cable.

[0082] Specifically, the first temperature threshold is 90 degrees Celsius, the second temperature threshold is 80 degrees Celsius, and the third temperature threshold is 100 degrees Celsius;

[0083] First, the conductor temperature of the reference cable needs to be raised to 90 degrees Celsius and in a stable state; wherein, when the conductor temperature of the reference cable reaches 90 degrees Celsius and the fluctuation is not greater than a preset fluctuation range, it is determined that the reference cable is currently in a stable state;

[0084] Then, it is determined whether the temperature of the crimping tube reaches a preset second temperature threshold, that is, whether the temperature of the crimping tube in the middle position of the test loop in the direction of current flow reaches 80 degrees Celsius. If it reaches 80 degrees Celsius, the first temperature threshold is used as the reference temperature of the conductor in the reference cable.

[0085] If the temperature does not reach 80 degrees Celsius, the power frequency current is maintained to continuously increase the conductor temperature, and the temperature of the crimping tube is detected in real time to determine whether it has reached the second temperature threshold. If the temperature of the crimping tube has not yet reached the second temperature threshold and the conductor temperature has reached 100 degrees Celsius, the third temperature threshold is used as the reference temperature. If the temperature of the crimping tube reaches the second temperature threshold before the conductor temperature reaches the third temperature threshold, the current conductor temperature is used as the reference temperature.

[0086] In a preferred embodiment, the real-time acquisition of the temperature of the crimping tube of the crimping tube in the middle position of the test loop in the current flow direction and the conductor temperature of the reference cable includes:

[0087] Obtaining a temperature of the crimping tube at a middle position of the test loop in the direction of current flow, as collected by a first thermocouple; wherein the first thermocouple is disposed at the center of a cross section of a crimping mark formed after the crimping tube at the middle position in the test loop is crimped;

[0088] Acquiring the conductor temperature of the reference cable collected by a second thermocouple; wherein the second thermocouple is disposed inside the reference cable;

[0089] Schematically, in order to accurately determine the reference temperature, thermocouples are installed in the crimping tube located in the middle of the test loop in the direction of current flow and in the reference cable;

[0090] Specifically, a thermocouple is placed at the center of the cross section of a crimping mark formed after crimping of the crimping tube located in the middle of the test loop in the direction of current flow, and the thermocouple is used as the first thermocouple;

[0091] See also Figure 3 , is the cross section of the crimped tube after crimping; where, Figure 3 The edge of the regular hexagon in the figure is the pressure channel, which refers to the part where the crimping tool (such as hydraulic pliers, crimping pliers) directly squeezes the crimped tube during the crimping process, usually forming an obvious concave mark on the surface of the crimped tube; Figure 3 The circle surrounding the regular hexagon is the non-pressing area, which refers to the area on the crimping tube that is not directly squeezed by the crimping tool, usually located at both ends or around the crimping area;

[0092] In this embodiment, the first thermocouple is arranged at Figure 3 The specific setting position can be adjusted according to actual conditions within the circle surrounded by the regular hexagon (i.e., in the grid shadow);

[0093] Specifically, a thermocouple is provided inside the reference cable, and the thermocouple serves as the second thermocouple.

[0094] In a preferred embodiment, when the power frequency current is passed into the test circuit and the real-time temperature of the reference cable reaches the reference temperature, obtaining the loop voltage of the test circuit, the loop current of the test circuit, and the voltage across both ends of the reference cable in the test circuit includes:

[0095] Determining the power frequency current step levels according to the reference temperature;

[0096] When power frequency current is passed through the test circuit, the original circuit voltage of the test circuit, the original circuit current of the test circuit, and the original voltage across the reference cable in the test circuit are obtained at each power frequency current step.

[0097] averaging all the acquired original loop voltages to obtain the loop voltage of the test loop;

[0098] averaging all the original loop currents obtained to obtain the loop current of the test loop;

[0099] averaging all the original voltages across the two terminals to obtain the voltage across the two terminals of the reference cable in the test loop;

[0100] Indicatively, after determining the reference temperature, it is necessary to determine the power frequency current step levels according to the reference temperature;

[0101] Specifically, taking the reference temperature as 90 degrees Celsius as an example, the interval between each gear is set to 10 degrees Celsius. Then, after the power frequency current is passed into the test circuit again, assuming that the current room temperature is 25 degrees Celsius, it is necessary to collect operating data (including the original loop voltages of several test circuits, the original loop currents of several test circuits, and the original voltages at both ends of the reference cables in several test circuits) every 10 degrees Celsius from 25 degrees Celsius to 90 degrees Celsius, and then average the operating data obtained at each level of the power frequency current ladder gear;

[0102] Specifically, averaging all the original loop voltages obtained to obtain the loop voltage of the test loop, averaging all the original loop currents obtained to obtain the loop current of the test loop, and averaging all the original two-end voltages obtained to obtain the two-end voltage of the reference cable in the test loop;

[0103] It should be noted that, see Figure 4 , collecting the original loop voltage by inserting the voltage sampling terminal into the test loop; collecting the original two-end voltage by setting the voltage sampling terminals at both ends of the reference cable in the test loop, and measuring the induced current on the secondary side of the current transformer CT coil by inserting the current transformer CT into the measurement loop to read the original loop current.

[0104] In a preferred embodiment, the total contact resistance of the test loop is calculated based on the loop voltage, the loop current, the voltages at both ends, the first length, and the total length of the cable, including:

[0105] Calculating the total resistance of the test loop based on the loop voltage and the loop current;

[0106] Calculating a reference resistance of the reference cable according to the voltages at both ends and the loop current;

[0107] Dividing the total length of the cable by the first length to obtain a first ratio;

[0108] multiplying the reference resistance by the first ratio to obtain a total cable resistance;

[0109] Subtracting the total cable resistance from the total resistance to obtain the total contact resistance;

[0110] Specifically, the total resistance of the test loop is calculated based on the loop voltage and the loop current. The specific expression is as follows:

[0111]

[0112] Where R total is the total resistance, U1 is the loop voltage, I is the loop current, and φ1 is the phase difference angle between the loop voltage and the loop current;

[0113] Specifically, the reference resistance of the reference cable is calculated based on the voltages at both ends and the loop current. The specific expression is as follows:

[0114]

[0115] Where R1 is the reference resistor, U c is the voltage at both ends, I is the loop current, and φ1 is the phase difference angle between the voltage at both ends and the loop current;

[0116] Specifically, the total cable length is divided by the first length to obtain a first ratio, and the reference resistance is multiplied by the first ratio to obtain a total cable resistance. The specific expression is as follows:

[0117]

[0118] Where R ac is the total cable resistance, L c is the total length of the cable, L1 is the first length;

[0119] Specifically, the total contact resistance is obtained by subtracting the total cable resistance from the total resistance. The specific expression is as follows:

[0120] R g =R total -R ac ;

[0121] Where R g is the total contact resistance.

[0122] In a preferred embodiment, determining the contact resistance value of each crimping tube in the test circuit according to the total number of the crimping tubes and the total contact resistance value includes:

[0123] Dividing the total contact resistance by the total number of the crimping tubes to obtain the contact resistance of each crimping tube in the test loop;

[0124] Specifically, the total contact resistance is divided by the total number of the crimping tubes to obtain the contact resistance of each crimping tube in the test circuit. The specific expression is as follows:

[0125] R g' =R g / n g ;

[0126] Where R g' is the contact resistance, n g is the total number of compression tubes.

[0127] Specifically, the power frequency current can be passed into the test circuit multiple times, and after each time the test circuit is passed and the reference cable reaches the reference temperature, the passing of the power frequency current is stopped, and the contact resistance value of each crimping tube is calculated after the temperature drops to room temperature, thereby determining the aging degree of each crimping tube in the test circuit based on the contact resistance value of each crimping tube calculated each time.

[0128] See Figure 5 , is a contact resistance measurement device for a crimped tube provided by an embodiment of the present invention, comprising: a first data acquisition module, a second data acquisition module, a first contact resistance calculation module, and a second contact resistance calculation module;

[0129] The first data acquisition module is configured to acquire the total number of crimping tubes in the test loop, a first length of a reference cable in the test loop, a reference temperature of a conductor in the reference cable, and a total length of the cables in the test loop excluding the length of the crimping tubes;

[0130] The second data acquisition module is configured to acquire the loop voltage of the test loop, the loop current of the test loop, and the voltage across both ends of the reference cable in the test loop when the power frequency current is passed into the test loop and the real-time temperature of the reference cable reaches the reference temperature;

[0131] The first contact resistance calculation module is used to calculate the total contact resistance of the test loop according to the loop voltage, the loop current, the voltages at both ends, the first length, and the total length of the cable;

[0132] The second contact resistance calculation module is used to determine the contact resistance of each crimping tube in the test loop according to the total number of the crimping tubes and the total contact resistance.

[0133] See Figure 2 , is a test circuit for measuring the contact resistance of a crimping tube provided by one embodiment of the present invention, comprising: a reference cable, a plurality of measuring cables, a plurality of crimping tubes and a current-boosting transformer;

[0134] The first end of the reference cable is connected to one end of the first measuring cable of the test loop in the current flow direction, and the second end of the reference cable is connected to one end of the current boosting transformer;

[0135] The measuring cables are crimped and connected via a crimping tube;

[0136] The other end of the current-boosting transformer is connected to one end of the last measuring cable in the test loop in the current flow direction.

[0137] In a preferred embodiment, the difference between the inner diameter of the crimping tube and the outer diameter of the measuring cable is in the range of 1 mm to 2 mm;

[0138] Specifically, if the inner diameter of the crimping tube is too small, not only will excessive external force be applied during installation, causing damage to the cable core or deformation of the crimping tube, but it may also cause increased local resistance due to uneven contact stress. On the other hand, if the inner diameter is too large, the connection will become loose, the contact resistance will increase significantly, and the power transmission loss will be aggravated.

[0139] Therefore, in order to take into account both tight connection and convenient installation, this embodiment has been verified through a large number of experiments, and the inner diameter of the crimping tube is set to be 1 mm to 2 mm larger than the outer diameter of the measuring cable. This size difference can not only ensure that the cable is in full contact with the inner wall of the crimping tube during the crimping process, effectively reducing the contact resistance, but also avoid the installation difficulties and cable damage risks caused by interference fit, providing reliable protection for improving the stability and energy efficiency of the electrical connection.

[0140] In a preferred embodiment, the difference between the inner diameter of the crimping tube and the outer diameter of the reference cable is in the range of 1 mm to 2 mm;

[0141] Specifically, if the inner diameter of the crimping tube is too small, not only will excessive external force be applied during installation, causing damage to the cable core or deformation of the crimping tube, but it may also cause increased local resistance due to uneven contact stress. On the other hand, if the inner diameter is too large, the connection will become loose, the contact resistance will increase significantly, and the power transmission loss will be aggravated.

[0142] Therefore, in order to take into account both tight connection and convenient installation, this embodiment has been verified through a large number of experiments, and the inner diameter of the crimping tube is set to be 1 mm to 2 mm larger than the outer diameter of the reference cable. This size difference can not only ensure that the cable is in full contact with the inner wall of the crimping tube during the crimping process, effectively reducing the contact resistance, but also avoid the installation difficulties and cable damage risks caused by interference fit, providing reliable protection for improving the stability and energy efficiency of the electrical connection.

[0143] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for measuring the contact resistance of a crimped tube, characterized in that: Suitable for a test circuit comprising a reference cable, a plurality of measuring cables, a plurality of crimping tubes and a current step-up transformer; The first end of the reference cable is connected to one end of the first measuring cable of the test loop in the current flow direction, and the second end of the reference cable is connected to one end of the current boosting transformer; The measuring cables are crimped and connected via a crimping tube; The other end of the current-boosting transformer is connected to one end of the last measuring cable in the current flow direction of the test loop; The method for measuring the contact resistance of the crimping tube includes: Obtaining the total number of crimping tubes in the test loop, a first length of a reference cable in the test loop, a reference temperature of a conductor in the reference cable, and a total length of the cables in the test loop excluding the length of the crimping tubes; When a power frequency current is passed through the test circuit and the real-time temperature of the reference cable reaches the reference temperature, obtaining a loop voltage of the test circuit, a loop current of the test circuit, and a voltage across both ends of the reference cable in the test circuit; Calculate the total contact resistance of the test loop according to the loop voltage, the loop current, the voltages at both ends, the first length, and the total length of the cable; The contact resistance value of each crimping tube in the test loop is determined according to the total number of the crimping tubes and the total contact resistance value.

2. The method for measuring the contact resistance of a crimped tube according to claim 1, wherein: The reference temperature of the conductor in the reference cable is obtained by the following method, including: When power frequency current is passed into the test loop, the conductor temperature of the reference cable and the temperature of the crimping tube of the crimping tube located in the middle of the test loop in the direction of current flow are obtained in real time; When the conductor temperature reaches a preset first temperature threshold, determining whether the crimping tube temperature reaches a preset second temperature threshold; wherein the first temperature threshold is greater than the second temperature threshold; If so, the conductor temperature is used as the reference temperature, and the flow of the power frequency current is stopped; If not, maintain the flow of the industrial frequency current to continuously increase the conductor temperature, and when it is detected that the temperature of the crimping tube reaches the second temperature threshold, use the current conductor temperature as the reference temperature; when it is detected that the temperature of the crimping tube does not reach the second temperature threshold and the conductor temperature reaches a preset third temperature threshold, use the third temperature threshold as the reference temperature of the conductor in the reference cable; wherein, the third temperature threshold is greater than the first temperature threshold.

3. The method for measuring the contact resistance of a crimped tube according to claim 1, wherein: When the power frequency current is passed into the test circuit and the real-time temperature of the reference cable reaches the reference temperature, obtaining the loop voltage of the test circuit, the loop current of the test circuit, and the voltages at both ends of the reference cable in the test circuit, includes: Determining the power frequency current step levels according to the reference temperature; When power frequency current is passed through the test circuit, the original circuit voltage of the test circuit, the original circuit current of the test circuit, and the original voltage across the reference cable in the test circuit are obtained at each power frequency current step. averaging all the acquired original loop voltages to obtain the loop voltage of the test loop; averaging all the original loop currents obtained to obtain the loop current of the test loop; The voltages at both ends of the reference cable in the test loop are obtained by averaging all the original voltages at both ends obtained.

4. The method for measuring the contact resistance of a crimped tube according to claim 1, wherein: The calculating of the total contact resistance of the test loop according to the loop voltage, the loop current, the voltages at both ends, the first length, and the total length of the cable comprises: Calculating the total resistance of the test loop based on the loop voltage and the loop current; Calculating a reference resistance of the reference cable according to the voltages at both ends and the loop current; Dividing the total length of the cable by the first length to obtain a first ratio; multiplying the reference resistance by the first ratio to obtain a total cable resistance; The total contact resistance is obtained by subtracting the total cable resistance from the total resistance.

5. The method for measuring the contact resistance of a crimped tube according to claim 1, wherein: Determining the contact resistance value of each crimping tube in the test circuit according to the total number of the crimping tubes and the total contact resistance value includes: The total contact resistance value is divided by the total number of the crimping tubes to obtain the contact resistance value of each crimping tube in the test loop.

6. The method for measuring the contact resistance of a crimped tube according to claim 2, wherein: The real-time acquisition of the temperature of the crimping tube of the crimping tube located in the middle of the test loop in the current flow direction and the conductor temperature of the reference cable includes: Obtaining a temperature of the crimping tube at a middle position of the test loop in the direction of current flow, as collected by a first thermocouple; wherein the first thermocouple is disposed at the center of a cross section of a crimping mark formed after the crimping tube at the middle position in the test loop is crimped; The conductor temperature of the reference cable collected by a second thermocouple is obtained; wherein the second thermocouple is arranged inside the reference cable.

7. A device for measuring the contact resistance of a crimped tube, characterized in that: include: A first data acquisition module, a second data acquisition module, a first contact resistance value calculation module, and a second contact resistance value calculation module; The first data acquisition module is configured to acquire the total number of crimping tubes in the test loop, a first length of a reference cable in the test loop, a reference temperature of a conductor in the reference cable, and a total length of the cables in the test loop excluding the length of the crimping tubes; The second data acquisition module is configured to acquire the loop voltage of the test loop, the loop current of the test loop, and the voltage across both ends of the reference cable in the test loop when the power frequency current is passed into the test loop and the real-time temperature of the reference cable reaches the reference temperature; The first contact resistance calculation module is used to calculate the total contact resistance of the test loop according to the loop voltage, the loop current, the voltages at both ends, the first length, and the total length of the cable; The second contact resistance calculation module is used to determine the contact resistance of each crimping tube in the test loop according to the total number of the crimping tubes and the total contact resistance.

8. A test circuit for measuring the contact resistance of a crimped tube, characterized in that: include: Reference cable, several measuring cables, several crimping tubes and current step-up transformer; The first end of the reference cable is connected to one end of the first measuring cable of the test loop in the current flow direction, and the second end of the reference cable is connected to one end of the current boosting transformer; The measuring cables are crimped and connected via a crimping tube; The other end of the current-boosting transformer is connected to one end of the last measuring cable in the test loop in the current flow direction.

9. The test circuit for measuring the contact resistance of a crimped tube according to claim 8, characterized in that: The difference between the inner diameter of the crimping tube and the outer diameter of the measuring cable is in the range of 1 mm to 2 mm.

10. The test circuit for measuring the contact resistance of a crimped tube according to claim 9, characterized in that: The difference between the inner diameter of the crimping tube and the outer diameter of the reference cable is in the range of 1 mm to 2 mm.

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