A device for automatically measuring the DC resistance of an instrument transformer

Abstract

The present invention discloses a DC resistance automatic measurement device for mutual inductors, comprising: a conveying device, a primary terminal crimping device, a secondary terminal crimping device, and a DC resistance measurement unit. The upper part of the primary terminal crimping device is connected to a bracket and is driven by a crimping cylinder to achieve electrical contact between the primary terminal measuring electric claws of the crimping device and the primary terminal of the mutual inductor, thereby completing the electrical connection for measuring the DC resistance of the primary winding; the secondary terminal crimping device is connected to the side of the conveying device and is driven by a crimping cylinder to achieve electrical contact between the secondary terminal measuring electric claws of the crimping device and the secondary terminal of the mutual inductor, thereby completing the electrical connection for measuring the DC resistance of the secondary winding. The present invention realizes redundant multi-point flexible contact of the electrical contact surface and sampling of four-wire resistance measurement signals through the honeycomb-shaped double-arc arrangement of the primary terminal measuring electric claws and the sleeve-type structure of the secondary terminal measuring electric claws, solves the problem of reliability of high-precision measurement, and solves the problem of influencing quantities of high-precision measurement through the simulation of mutual inductors and contact resistance calibration technology, thereby realizing precise and automatic measurement.

Description

Technical Field

[0001] The present invention discloses an automatic measuring device for the DC resistance of a mutual inductor, which relates to the technical fields of industrial automation and automatic measurement. Background Art

[0002] At present, the product detection assembly lines of power mutual inductor manufacturing enterprises all adopt the manual operation mode, which has high labor costs, high labor intensity, low efficiency, and high personal safety risks. Therefore, it is very necessary to realize the unmanned automation of the product detection assembly line. And the measurement of the DC resistance of the mutual inductor winding is an important part of the automatic detection project, which has an important impact on the performance and reliability of the mutual inductor.

[0003] On the other hand, the DC resistance measurement is based on Ohm's law, that is, by outputting a constant current and then measuring the voltage of the conductor under test, and then calculating the corresponding resistance value through Ohm's law. For current mutual inductors, the number of turns of the primary winding is small, the resistance is in the micro-ohm level, the resistance sampling voltage signal is less than 1 mV, and the self-resistance of the measurement loop conductor, the contact resistance of the measurement probe contact, and the influence of the ambient temperature are very likely to have a great impact on the correctness of the measurement result.

[0004] To cooperate with the automatic detection of mutual inductors, it is urgent to invent an automatic DC resistance measuring device with automation, high reliability, and high measurement accuracy to fill the gaps in the corresponding technologies and devices. And the automation of electrical connection and the reliability of electrical connection are the key points. Summary of the Invention

[0005] The present invention aims at the defects in the above-mentioned background art and provides an automatic measuring device for the DC resistance of a mutual inductor, which solves the requirements for accurate electrical contact positioning and small contact resistance for high-precision measurement.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows: an automatic measuring device for the DC resistance of a mutual inductor, comprising: a bracket, a conveying device, a primary terminal crimping device, a secondary terminal crimping device, and a DC resistance measuring unit; the primary terminal crimping device is connected to the upper bracket of the conveying device to realize the automatic electrical connection between the primary terminal of the mutual inductor under test and the DC resistance measuring unit; the secondary terminal crimping device is connected to the side of the conveying device to realize the automatic electrical connection between the secondary terminal of the mutual inductor under test and the DC resistance measuring unit.

[0007] For the above-mentioned automatic measuring device for the DC resistance of a mutual inductor, the conveying device includes: a roller conveyor and a tooling tray. The roller conveyor is used to convey the tooling tray, and the tooling tray is used to hold the mutual inductor under test and for tooling positioning.

[0008] The aforementioned automatic measuring device for the DC resistance of the mutual inductor, wherein the primary terminal crimping device includes: a first crimping cylinder, a translation mechanism, and primary terminal measuring electric claws; the first crimping cylinder realizes power drive in the vertical direction to generate the pressure required for electrical contact; the translation mechanism realizes the forward and backward movement of the electric claws in the horizontal direction, the positioning and crimping of the terminals of the mutual inductor for measurement;

[0009] The upper end of the first crimping cylinder is connected to a bracket, and the lower end is connected to the translation mechanism. The lower end of the translation mechanism is slidably connected to two primary terminal measuring electric claws to realize the synchronous crimping of a pair of terminals of the mutual inductor;

[0010] The translation mechanism includes: a cross beam, an electric cylinder mounting plate and an electric cylinder, an electric cylinder push plate, a guide rail mounting plate and a guide rail, a moving slider and a sliding plate, a sensor induction piece and a sensor;

[0011] Both ends of the cross beam are respectively connected to the electric cylinder mounting plates. Each electric cylinder mounting plate is connected to an electric cylinder. The push rod of the electric cylinder is connected to the corresponding push plate and fixedly connected to the sliding plate; a pair of guide rail mounting plates are connected to the bottom of the cross beam. Guide rails are connected to the guide rail mounting plates. Sliders are connected to the guide rails. The sliders are connected to the sliding plate. The sliding plate is connected to the primary terminal measuring electric claws below; the sensor induction piece is connected to the rear end of the sliding plate, and the sensor is installed at a predetermined position on the cross beam.

[0012] The aforementioned automatic measuring device for the DC resistance of the mutual inductor, wherein the primary terminal measuring electric claws are honeycomb-shaped, and the components include: a bushing, a first crimping spring, a current sampling plate, a voltage sampling plate, an insulating cylinder, a primary terminal sampling probe group, a first crimping spring shaft, and a positioning pin; the current sampling plate and the voltage sampling plate are two curved copper bars. The current sampling plate is connected to an 8-bit probe socket, and the voltage sampling plate is connected to a 4-bit probe socket.

[0013] The first crimping spring shaft passes through the insulating cylinder and the current and voltage sampling plates from bottom to top and is connected to the upper bushing. The lower part of the spring shaft is connected to the bottom of the insulating cylinder through two positioning pins; a compressed first crimping spring is sleeved between the positioning pins and the bushing;

[0014] The primary terminal sampling probe group includes an 8-bit current sampling probe group and a 4-bit voltage sampling probe group; the voltage and current sampling probe groups are arranged in an arc shape. The 8-bit current sampling probes are distributed on the outer arc, and the 4-bit voltage sampling probes are distributed on the inner arc. There is complete electrical isolation between the voltage and current probe groups and between the corresponding sampling plates, ensuring that the voltage signal is sampled from the root of the measured component, avoiding the influence of probe sharing on the measurement result, and realizing accurate four-wire resistance measurement;

[0015] The aforementioned automatic measuring device for the DC resistance of the mutual inductor, wherein the primary terminal sampling probe group is inserted into the wall of the insulating cylinder from below the fixed insulating column, welded to the sampling plate probe seats of each of the upper parts of the insulating cylinder to form a structure body, and a honeycomb-shaped probe group is formed at the bottom of the insulating cylinder; the current sampling plate and the voltage sampling plate are connected to the primary terminal DC resistance measuring instrument of the DC resistance measuring unit through shielded flexible wires.

[0016] The aforementioned automatic measuring device for the DC resistance of the mutual inductor, wherein the secondary terminal crimping device includes: a positioning bracket, a second crimping cylinder, and a secondary terminal measuring electric claw; the positioning bracket is connected to the side of the conveying device, and the upper end of the positioning bracket is connected to the secondary terminal measuring electric claw through the second crimping cylinder.

[0017] The aforementioned automatic measuring device for the DC resistance of the mutual inductor, wherein the secondary terminal measuring electric claw is of a sleeve type structure, including: a crimping plate, a current sampling copper tube base, a current sampling copper tube, a voltage sampling probe base, a voltage sampling probe, and a second crimping spring assembly;

[0018] The current sampling copper tube base is a 4-hole insulating insert, embedded in the corresponding square hole of the crimping plate; 4 voltage sampling probe bases are sleeved into the corresponding current sampling copper tube bases and connected to the 4 voltage sampling probes on the lower side; 4 current sampling copper tubes are embedded in the corresponding copper tube bases and sleeved with corresponding second crimping springs on the lower side, and nuts are used to fix the bottoms of the copper tubes to make the springs in a partially compressed state; 4 voltage sampling probes pass through the inner cavities of the corresponding current sampling copper tubes and are connected to the corresponding probe seats; the current copper tube base and the voltage probe base are connected to the secondary terminal switching device of the DC resistance measuring unit through shielded flexible wires.

[0019] The aforementioned automatic measuring device for the DC resistance of the mutual inductor, wherein the DC resistance measuring unit includes: a DC resistance measuring instrument, a secondary terminal switching device, and a contact resistance calibrator.

[0020] The DC resistance measuring instrument includes a primary terminal DC resistance measuring instrument and a secondary terminal DC resistance measuring instrument, which respectively measure the DC resistance of the primary winding and the secondary winding of the mutual inductor. The DC resistance measuring instrument is of a four-wire system and has a pair of current measuring terminals and a pair of voltage measuring terminals;

[0021] The current measuring terminals of the primary terminal DC resistance measuring instrument are connected to the current sampling plate of the primary terminal measuring electric claw, and the voltage measuring terminals are connected to the current sampling plate of the primary terminal measuring electric claw; the current measuring terminals and voltage measuring terminals of the secondary terminal DC resistance measuring instrument are connected to the secondary terminal switching device through shielded flexible wires.

[0022] The secondary terminal switching device is an automatic / manual multi-position changeover switch, which is connected to the current sampling copper tube base of the secondary terminal measurement electric claw, the voltage sampling probe base, the current measurement terminal of the secondary terminal DC resistance measuring instrument, and the voltage measurement terminal through shielded flexible wires respectively. According to the number of secondary windings of the mutual inductor and the difference in terminal polarities, the corresponding secondary measurement circuit is switched;

[0023] The contact resistance calibrator is a zero DC resistance simulation mutual inductor. The primary terminal and secondary terminal of the zero DC resistance simulation mutual inductor are short-circuit copper bars. The zero DC resistance winding of the simulation mutual inductor is used for zero position calibration of DC resistance measurement to eliminate the influence of contact resistance on measurement.

[0024] The beneficial effects achieved by the present invention: For an automatic DC resistance measuring device of a mutual inductor of the present invention, before the DC resistance measurement operation of the mutual inductor, the primary terminal and secondary terminal DC resistances of the contact resistance calibrator are measured first, and the measured values are used as the contact resistance values in the DC resistance measurement of the measured mutual inductor. This value is subtracted from the DC resistance measurement result of the measured mutual inductor, thereby eliminating the influence of contact resistance on DC resistance measurement and achieving precision measurement at the micro-ohm level; when different batches of mutual inductors or the ambient temperature changes greatly, a calibration measurement is carried out again to ensure the real-time nature of calibration.

[0025] At the same time, through the voltage and current sampling probe group arranged in a honeycomb shape on the primary measurement electric claw, redundant multi-point flexible point contact with the electrical contact surface is realized, which can effectively avoid poor electrical contact caused by slight misalignment, uneven end face, local defects, dirt, etc. of the primary terminal of the measured mutual inductor, and solves the requirements for accurate electrical contact positioning and small contact resistance in high-precision measurement; through the measurement probe in the four-wire structure form of the primary terminal measurement electric claw and the secondary terminal measurement electric claw, the problem of accurate signal sampling in the four-wire resistance measurement method is solved; further, through the zero contact resistance calibrator and the real-time calibration method, the problems of the influence of contact resistance and ambient temperature change on the measurement result are solved. Description of the Drawings

[0026] Figure 1 is a structural schematic diagram of the present invention;

[0027] Figure 2 is an internal structural schematic diagram of the present invention;

[0028] Figure 3 is a schematic diagram of the primary terminal crimping device of the present invention;

[0029] Figure 4 is an exploded schematic diagram of the translation mechanism of the present invention;

[0030] Figure 5 is an exploded schematic diagram of the measurement electric claw of the primary terminal crimping device of the present invention;

[0031] Figure 6 is a schematic diagram of the insulating cylinder of the present invention;

[0032] Figure 7 Schematic diagram of the secondary terminal crimping device of the present invention;

[0033] Figure 8 Schematic diagram of the explosion of the measuring electric claw of the secondary terminal crimping device of the present invention;

[0034] Figure 9 Flow chart of the automatic measurement of the DC resistance of the present invention. Embodiment

[0035] The implementation of the technical solution will be further described in detail below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention and cannot be used to limit the protection scope of the present invention.

[0036] As Figures 1 - 8 shown in an embodiment, an automatic DC resistance measuring device for an instrument transformer includes: a bracket 1, a conveying device 2, a primary terminal crimping device 3, a secondary terminal crimping device 4, and a DC resistance measuring unit 5.

[0037] The conveying device 2 includes: a roller conveyor 21 and a tooling tray 22. The roller conveyor 21 is used to convey the tooling tray 22, and the tooling tray 22 is used to hold the instrument transformer 6 to be measured.

[0038] The primary terminal crimping device 3 is connected to the upper part of the bracket 1 and crimps the primary terminal of the instrument transformer to be measured to form a primary terminal electrical connection; the secondary terminal crimping device 4 is connected to the side of the conveying device 2 and crimps the secondary terminal of the instrument transformer to be measured to form a secondary terminal electrical connection;

[0039] The primary terminal crimping device 3 includes: a first crimping cylinder 31, a translation mechanism 32, and a primary terminal measuring electric claw 33; the upper end of the first crimping cylinder 31 is connected to the bracket 1, and the lower end is connected to the translation mechanism 32. The translation mechanism 32 is connected to the primary terminal measuring electric claw 33 below;

[0040] The translation mechanism 32 of the primary terminal crimping device 3 includes: a cross beam 321, an electric cylinder mounting plate 322, an electric cylinder 323, a guide rail mounting plate 324, a guide rail 325, a slider 326, a push plate 327, a slide plate 328, a sensor induction piece 329, and a sensor 320;

[0041] Both ends of the cross beam 321 are respectively connected to the electric cylinder mounting plates 322. The electric cylinder mounting plates 322 are connected to the electric cylinders 323. The push rod of the electric cylinder 323 is connected to the push plate 327. The guide rail mounting plate 324 is connected to the bottom of the cross beam 321. The guide rail 325 is connected to the guide rail mounting plate 324. The slider 326 is connected to the guide rail 325. The push plate 327 is respectively connected to the push rod of the electric cylinder 323 and the left end of the sliding plate 328. The upper end of the sliding plate 328 is connected to the slider 326, the rear end is connected to the sensor sensing piece 329, and the lower end is connected to the primary end measuring electric claw 33. The sensor 320 is connected to the cross beam 321.

[0042] The primary end measuring electric claw 33 of the primary end crimping device 3 is honeycomb-shaped and includes 2 sets. The composition of each set includes: a bushing 331, a first crimping spring 332, a current sampling board 333, a current sampling board 334, an insulating cylinder 335, a primary end sampling probe group 336, a first crimping spring shaft 337, and a positioning pin 338.

[0043] The first crimping spring shaft 337 passes through the insulating cylinder 335, the current sampling board 334, and the current sampling board 333 from bottom to top and is connected to the upper bushing 331. The lower part of the first crimping spring shaft 337 is connected to the bottom of the insulating cylinder 335 through two positioning pins 338.

[0044] A compressed first crimping spring 332 is sleeved between the positioning pin 338 and the bushing 331.

[0045] The current sampling board 334 and the current sampling board 333 are two curved copper bars. The current sampling board 334 is connected to an 8-bit probe base, and the current sampling board 333 is connected to a 4-bit probe base.

[0046] Eight current sampling probes and four voltage sampling probes are respectively inserted into the wall of the insulating cylinder 335 from below the fixed insulating column and welded to the respective copper bar probe bases in the upper part of the insulating cylinder 335 to form an installation body, forming a honeycomb-shaped sampling probe group 336 with the bottom of the insulating cylinder 335. The primary end sampling probe group 336 is arranged in an arc shape. The probes for 8-bit current sampling are distributed on the outer arc, and the probes for 4-bit voltage sampling are distributed on the inner arc.

[0047] To avoid electrical short circuits in the electric needle part, electrical isolation is performed between the current sampling board 334, the current sampling board 333, and the corresponding probe groups, ensuring that the voltage signal is sampled from the root of the measured component, and the current measurement loop wire only passes through the measured current, avoiding the series connection influence of the current sampling probe and the resistance of the measurement loop wire itself on the terminal resistance of the measured component, and realizing accurate four-wire resistance measurement.

[0048] The current sampling board 334 and the current sampling board 333 are connected to the primary end direct resistance measuring instrument 51 through shielded flexible wires.

[0049] The secondary terminal crimping device 4 includes: a positioning bracket 41, a second crimping cylinder 42, and a secondary terminal measuring electric claw 43; the positioning bracket 41 is installed on the side of the conveying device 2, and the upper end of the positioning bracket 41 is connected to the secondary terminal measuring electric claw 43 through the second crimping cylinder 42.

[0050] The secondary terminal measuring electric claw 43 of the secondary terminal crimping device 4 is of a sleeve type, and its components include: a crimping plate 431, a voltage sampling probe base 432, a voltage sampling probe 437, a current sampling copper tube base 433, a current sampling copper tube 434, a second crimping spring 435, and a connecting nut 436;

[0051] The current sampling copper tube base 433 is a 4-hole insulating insert, which is embedded in the corresponding square hole of the crimping plate 431; 4 voltage sampling probe bases 432 are sleeved into the corresponding holes of the current sampling copper tube base 433 and connected to the 4 voltage sampling probes on the lower side; 4 current sampling copper tubes are embedded in the corresponding bases and sleeved into the second crimping spring 435, and the second crimping spring 435 is fixed at the bottom of the copper tube with a nut 436 to make the second crimping spring 435 in a partially compressed state; 4 voltage sampling probes 437 pass through the inner cavity of the current sampling copper tube 434 and are connected to the corresponding probe bases 432; the current copper tube base 433 and the voltage probe base 432 are connected to the secondary terminal direct resistance measuring instrument 52 through test wires.

[0052] The direct resistance measuring unit 5 includes: a primary terminal direct resistance measuring instrument 51, a secondary terminal direct resistance measuring instrument 52, a secondary terminal switching device 53, and a contact resistance calibrator 54; the primary terminal direct resistance measuring instrument 51 measures the direct resistance of the primary winding of the transformer, and the secondary terminal direct resistance measuring instrument 52 measures the direct resistance of the secondary winding; the direct resistance measuring instrument is of a four-wire system and has a pair of current measuring terminals and a pair of voltage measuring terminals;

[0053] The current measuring terminals of the primary terminal direct resistance measuring instrument 51 are connected to the current sampling plate 334 of the primary terminal measuring electric claw, and the voltage measuring terminals are connected to the current sampling plate 333 of the primary terminal measuring electric claw; the current measuring terminals and voltage measuring terminals of the secondary terminal direct resistance measuring instrument 5 are connected to the secondary terminal switching device 53 through shielded flexible wires.

[0054] The secondary terminal switching device 53 is an automatic / manual multi-position changeover switch, which is connected to the current sampling copper tube, voltage sampling probe of the measuring electric claw 43 of the secondary terminal crimping device and the current measuring terminals, voltage measuring terminals of the secondary terminal direct resistance measuring instrument 52 through shielded flexible wires, and switches the corresponding secondary measurement circuits according to the number of secondary windings of the transformer and the difference in terminal polarities;

[0055] The contact resistance calibrator 54 is a zero direct resistance virtual transformer simulating the transformer, and its primary terminal and secondary terminal are short-circuit copper bars, which are used for zero position calibration of direct resistance measurement to eliminate the influence of contact resistance on measurement;

[0056] Before the DC resistance measurement, the DC resistance measurement unit first measures the primary and secondary contact resistances of the contact resistance calibrator 54 as the contact resistance value in the measurement of the current transformer to be measured. The DC resistance meter subtracts this value as the measurement result of the winding DC resistance, thereby eliminating the influence of the contact resistance in the measurement and achieving micro-ohm-level precision measurement. The calibration frequency depends on the batch of current transformers and the change of ambient temperature; for different batches of current transformers or large changes in ambient temperature, a new calibration needs to be carried out.

[0057] As Figure 9 shown, the automatic measurement process of the DC resistance of the current transformer is as follows:

[0058] I) Primary terminal DC resistance measurement:

[0059] 1) Transport the tooling current transformer tray to the measurement station;

[0060] 2) The verification system downloads the current transformer information in the MES according to the current transformer barcode. The PLC controller drives the sliding mechanism of the translation mechanism through the electric cylinder according to the current transformer information. When the moving skate magnetic induction piece moves to the corresponding magnetic induction sensor position, the electric cylinder is braked and the primary terminal measurement electric claw is positioned;

[0061] 3) The PLC controller drives the first crimping cylinder to move downward, and the two primary terminal measurement electric claws press down. The primary signal sampling probe group of the electric claws makes electrical contact with the primary terminals of the current transformer;

[0062] 4) The current sampling probe groups of the two primary terminal measurement electric claws form a loop with the primary terminal windings of the current transformer. The DC resistance measurement unit injects a constant measurement current through the current loop; the voltage sampling probe groups of the two primary terminal measurement electric claws sample the voltage across the current transformer terminals;

[0063] 5) The primary terminal DC resistance meter automatically measures and passes the calibration, and calculates the measured DC resistance value of the winding; the sliding average value of the latest 20 qualified test data of the same type of current transformer is used as the standard value. If the deviation between the measured value of the DC resistance meter and the standard value is within ±3%, it is qualified; otherwise, it is unqualified;

[0064] 6) The qualified data is uploaded to the EMS, and the unqualified current transformers are measured again. If they are unqualified twice, they are judged unqualified.

[0065] II) Secondary terminal DC resistance measurement:

[0066] The secondary terminal DC resistance measurement is carried out after the primary terminal DC resistance measurement:

[0067] 1) The PLC controller receives the control instructions issued by the system, controls the intake solenoid valve of the second crimping cylinder of the secondary terminal crimping device to open, drives the cylinder to move downward, and drives the crimping plate and the secondary terminal measuring electric claws to press down. Two adjacent ones of the 4 current sampling copper tubes / voltage sampling probe kits of the secondary terminal measuring electric claws are grouped into a pair, divided into 2 pairs, and are simultaneously crimped with 2 pairs of secondary terminals of the mutual inductor;

[0068] 2) The DC resistance measurement unit injects a constant measurement current through the current loop, and forms the first measurement loop with a pair of current sampling copper tubes of the secondary terminal measuring electric claws and the voltage sampling probes inside the copper tubes and the windings of a pair of secondary terminals of the mutual inductor; another pair of current sampling copper tubes and the voltage sampling probes inside the copper tubes form the second measurement loop with the secondary terminals of the other pair of windings;

[0069] 3) The measurement system reads the parameters of the mutual inductor in the control system through the Ethernet, and changes the measurement loop through the secondary switching device according to the mutual inductor model in the parameters to adapt to the DC resistance measurement of different models of mutual inductors;

[0070] 4) The secondary terminal DC resistance measuring instrument automatically measures and calibrates, calculates the measured DC resistance value of the winding; takes the sliding average value of the latest 20 qualified detection data of the same model of mutual inductor as the standard value. If the deviation between the measured value of the DC resistance measuring instrument and the standard value is within ±3%, it is qualified; otherwise, it is unqualified, and the data is uploaded to the EMS system.

[0071] 5) Repeat 3) and 4) to complete the measurement of the other pair of terminals.

[0072] The present invention provides a device for automatically measuring the DC resistance of a mutual inductor. By arranging the voltage and current sampling probe groups in a honeycomb shape on the primary terminal measuring electric claws, redundant multi-point flexible point contact with the electrical contact surface can be realized, which can effectively avoid the poor electrical contact phenomenon caused by the slight misalignment of the primary terminals of the measured mutual inductor and local defects and dirt on the end face, and solves the requirements for accurate electrical contact positioning and small contact resistance in high-precision measurement; the four-wire structure of the primary terminal measuring electric claws and the secondary terminal measuring electric claws solves the problem of accurate sampling of measurement signals in the four-wire resistance measurement method; the zero-contact resistance calibrator and the real-time calibration method solve the problems of the influence of the contact resistance and the uncertain change of the ambient temperature on the measurement result, etc.

[0073] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and deformations can still be made, and these improvements and deformations should also be regarded as the protection scope of the present invention.

Claims

1. An automatic measuring device for the DC resistance of a mutual inductor, characterized in that, Including: A bracket, a conveying device, a primary terminal crimping device, a secondary terminal crimping device, and a DC resistance measurement unit; the primary terminal crimping device is connected to the upper bracket of the conveying device to realize the automatic electrical connection between the primary terminal of the transformer under test and the DC resistance measurement unit; the secondary terminal crimping device is connected to the side of the conveying device to realize the automatic electrical connection between the secondary terminal of the transformer under test and the DC resistance measurement unit. The primary terminal crimping device includes: a first crimping cylinder, a translation mechanism, and primary terminal measurement electric claws. The upper end of the first crimping cylinder is connected to the bracket, and the lower end is connected to the translation mechanism. The lower end of the translation mechanism is slidably connected to two primary terminal measurement electric claws to realize the synchronous crimping of a pair of terminals of the transformer. The primary terminal measurement electric claws are honeycomb-shaped and are composed of: a bushing, a first crimping spring, a current sampling plate, a voltage sampling plate, an insulating cylinder, a primary terminal sampling probe group, a first crimping spring shaft, and a positioning pin; the current sampling plate and the voltage sampling plate are two curved copper bars. The current sampling plate is connected to an 8-bit probe socket, and the voltage sampling plate is connected to a 4-bit probe socket. The first crimping spring shaft passes through the insulating cylinder and the current and voltage sampling plates from bottom to top and is connected to the upper bushing. The lower part of the spring shaft is connected to the bottom of the insulating cylinder through two positioning pins; a compressed first crimping spring is sleeved between the positioning pin and the bushing. The primary terminal sampling probe group includes an 8-bit current sampling probe group and a 4-bit voltage sampling probe group; the voltage and current sampling probe groups are arranged in an arc shape. The 8-bit current sampling probes are distributed on the outer arc, and the 4-bit voltage sampling probes are distributed on the inner arc. The primary terminal sampling probe group is inserted into the wall of the insulating cylinder from below the fixed insulating column and welded to the respective sampling plate probe sockets on the upper part of the insulating cylinder to form a structure body, forming a honeycomb-shaped probe group at the bottom of the insulating cylinder.

2. The automatic measuring device for the DC resistance of the mutual inductor according to claim 1, characterized in that The conveying device includes: a roller conveyor and a tooling tray. The roller conveyor is used to convey the tooling tray, and the tooling tray is used to hold the transformer under test and tooling positioning.

3. The automatic measuring device for the DC resistance of the mutual inductor according to claim 1, wherein The first crimping cylinder realizes the power drive in the vertical direction to generate the pressure required for electrical contact; the translation mechanism realizes the forward and backward movement of the electric claws in the horizontal direction, the positioning and crimping of the transformer terminals for measurement. The translation mechanism includes: a cross beam, an electric cylinder mounting plate and an electric cylinder, an electric cylinder push plate, a guide rail mounting plate and a guide rail, a moving slider and a sliding plate, a sensor sensing piece and a sensor. The two ends of the cross beam are respectively connected to the electric cylinder mounting plates. Each electric cylinder mounting plate is connected to an electric cylinder. The push rod of the electric cylinder is connected to the corresponding push plate and fixedly connected to the sliding plate; the bottom of the cross beam is connected to a pair of guide rail mounting plates. The guide rails are connected to the guide rail mounting plates, and the sliders are connected to the guide rails. The sliders are connected to the sliding plate, and the sliding plate is connected to the primary terminal measurement electric claws below; the sensor sensing piece is connected to the rear end of the sliding plate, and the sensor is installed at a predetermined position on the cross beam.

4. The automatic measuring device for the DC resistance of the mutual inductor according to claim 1, characterized in that, There is complete electrical isolation between the current and voltage sampling probe groups and between the corresponding sampling plates, ensuring that the voltage signal is sampled from the root of the measured component, avoiding the influence of probe sharing on the measurement result, and realizing accurate four-wire resistance measurement.

5. The automatic measuring device for the DC resistance of the mutual inductor according to claim 1, characterized in that The current sampling plate and the voltage sampling plate are connected to the primary terminal DC resistance measuring instrument of the DC resistance measurement unit through shielded flexible wires.

6. The automatic measuring device for the DC resistance of the mutual inductor according to claim 1, wherein, The secondary terminal crimping device includes: a positioning bracket, a second crimping cylinder, and a secondary terminal measuring electric claw; the positioning bracket is connected to the side of the conveying device, and the upper end of the positioning bracket is connected to the secondary terminal measuring electric claw through the second crimping cylinder.

7. The automatic measuring device for the DC resistance of the mutual inductor according to claim 6, wherein, The secondary terminal measuring electric claw is of a sleeve type structure and includes: a crimping plate, a current sampling copper tube base, a current sampling copper tube, a voltage sampling probe base, a voltage sampling probe, and a second crimping spring assembly; the current sampling copper tube base is a 4-hole insulating insert embedded in the corresponding square hole of the crimping plate; 4 voltage sampling probe bases are sleeved into the corresponding current sampling copper tube bases and connected to the 4 voltage sampling probes on the lower side; 4 current sampling copper tubes are embedded in the corresponding copper tube bases and sleeved with corresponding second crimping springs on the lower side, and nuts are used to fix the bottoms of the copper tubes so that the springs are in a partially compressed state; 4 voltage sampling probes pass through the inner cavities of the corresponding current sampling copper tubes and are connected to the corresponding probe seats; the current copper tube base and the voltage probe base are connected to the secondary terminal switching device of the DC resistance measuring unit through a shielded flexible wire.

8. The automatic measuring device for the DC resistance of the mutual inductor according to claim 1, characterized in that The DC resistance measuring unit includes: a DC resistance measuring instrument, a secondary terminal switching device, and a contact resistance calibrator; The DC resistance measuring instrument includes a primary terminal DC resistance measuring instrument and a secondary terminal DC resistance measuring instrument, which respectively measure the DC resistance of the primary winding and the secondary winding of the mutual inductor. The DC resistance measuring instrument is of a four-wire system and has a pair of current measuring terminals and a pair of voltage measuring terminals; The current measuring terminals of the primary terminal DC resistance measuring instrument are connected to the current sampling plate of the primary terminal measuring electric claw, and the voltage measuring terminals are connected to the current sampling plate of the primary terminal measuring electric claw; the current measuring terminals and voltage measuring terminals of the secondary terminal DC resistance measuring instrument are connected to the secondary terminal switching device through a shielded flexible wire; The secondary terminal switching device is an automatic / manual multi-functional change-over switch, which is respectively connected to the current sampling copper tube base, the voltage sampling probe base of the secondary terminal measuring electric claw, and the current measuring terminals and voltage measuring terminals of the secondary terminal DC resistance measuring instrument through a shielded flexible wire, and switches the corresponding secondary measurement circuit according to the number of secondary windings of the mutual inductor and the difference in terminal polarities; The contact resistance calibrator is a zero DC resistance simulation mutual inductor. The primary terminal and secondary terminal of the zero DC resistance simulation mutual inductor are short-circuit copper bars, and the zero DC resistance winding of the simulation mutual inductor is used for zero position calibration of DC resistance measurement to eliminate the influence of contact resistance on measurement.

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