Method and device for determining optimal installation torque of fuse link

Abstract

The present invention relates to the field of electrical component assembly, in particular to a method and device for determining the optimal installation torque of a fuse piece. The method of the present invention comprises the following steps: selecting a fuse piece to be tested and a control fuse piece; respectively fixedly connecting the fuse piece to be tested and the control fuse piece to a fuse group through nuts; connecting the fuse group to a test circuit; setting a critical rule; adjusting the torque of the nut in combination with the critical rule; measuring the temperature change of the fuse piece to be tested when the torque of the nut changes, and obtaining the optimal installation torque of the fuse piece to be tested through the temperature change. When the installation torque of the fuse piece is the optimal installation torque, the influence of the axial stress generated by the deformation caused by the fixed constraint on the fuse piece is minimized. The method of the present invention is simple, fast, easy to operate, and has strong application value and commercial value in practical applications.

Description

Technical Field

[0001] The present invention relates to the field of electrical component assembly, and in particular to a method and device for determining the optimal installation torque of a fuse link. Background Art

[0002] The low-voltage fuse link is the simplest protector in the medium and low voltage distribution network. It is connected in series in the circuit and will melt itself when passing through a short-circuit current or a long-term overload current, thereby protecting the low-voltage equipment. Due to its simple structure, convenient maintenance, and low price, it has good overload effect and short-circuit protection function. However, according to the report of the Power Distribution Equipment Quality Inspection Center of Guangzhou Power Supply Bureau, the overload capacity of commonly used fuse links fails to meet the national requirements, specifically manifested as not meeting the verification of the rated fusing current. Through in-depth research on the fusing mechanism of the fuse link, it is found that due to the fixed constraints at both ends of the fuse link during operation, the thermal stress generated during its temperature rise causes its deformation, thereby weakening the overload capacity of the fuse link, that is, this factor is not fully considered in the design of this product; at the same time, there is no clear specification for the fixed constraints for installing the fuse link at present, so that the installation of the fuse link in actual application mostly depends on the experience of the installer, which further promotes the increase of the unqualified rate when using this product. Therefore, the present invention proposes an installation method and a corresponding device that can minimize the influence of thermal stress on the fuse link during normal operation. Summary of the Invention

[0003] In view of the defects and deficiencies in the prior art, on the first aspect, the present invention provides a method for determining the optimal installation torque of a fuse link, including the following steps: selecting a fuse link to be tested and a reference fuse link, where at least one end of the fuse link to be tested has no fixed constraint during assembly and application; respectively fixedly connecting the fuse link to be tested and the reference fuse link to a fuse group through nuts, and the fuse groups are respectively adapted to the fuse link to be tested and the reference fuse link; connecting the fuse groups to a test circuit; setting a critical rule, which is used to determine the contact condition between the fuse link to be tested and the fuse group; adjusting the torque of the nut in combination with the critical rule; measuring the temperature change of the fuse link to be tested when the torque of the nut changes, and obtaining the optimal installation torque of the fuse link to be tested through the temperature change. By setting a reference fuse link and a critical rule, and combining the temperature change of the fuse link to be tested at different torques, the present invention obtains the optimal installation torque suitable for itself. The fuse link installed at the optimal installation torque is minimally affected by the axial stress generated by deformation due to fixed restraint in the installation axis direction, enabling the fuse link to transfer heat better, thereby improving the overload capacity of the fuse link, and further improving the qualification rate when using the product. The method of the present invention is simple, fast, easy to operate, and has strong application value and commercial value in actual application.

[0004] Optionally, the setting of the critical rule includes the following steps: setting a force boundary according to the axial stress between the nut and the fuse to be measured ; using the temperature at the contact position between the fuse to be measured and the fuse group , combined with the temperature at the center position of the fuse to be measured to set a first tolerance , where ; using the temperature at the center position of the fuse to be measured , combined with the temperature at the center position of the reference fuse to set a second tolerance , where . The method of the present invention sets a critical rule applicable to the actual installation application situation, improving the applicability of the method of the present invention.

[0005] Optionally, the adjusting of the torque of the nut in combination with the critical rule includes the following steps: obtaining the lowest tightening torque range of the nut through engineering standards ; measuring the initial tightening torque of the nut ; respectively obtaining , and the working conditions of the fuse to be measured corresponding thereto, where the working conditions include the axial stress of the fuse to be measured , the first tolerance and the second tolerance ; when , and the corresponding working conditions meet the critical rule, reducing the torque of the nut sequentially by 2 starting from ; when , and the corresponding working conditions meet the critical rule, reducing the torque of the nut sequentially by 2 starting from ; when , , and and the corresponding working conditions meet the critical rule, the corresponding working conditions do not meet the critical rule, starting from , as the end point, adjusting the torque of the nut through the binary selection principle; when , , and and the corresponding working conditions meet the critical rule, the corresponding working conditions do not meet the critical rule, starting from starting from as the end point, adjust the torque of the nut through the binary selection principle; when does not meet the critical rule, re-determine the minimum tightening torque range and the initial tightening torque . The torque selection method of the present invention has a clear operation idea, is simple and convenient, and has strong operability and applicability in practical applications.

[0006] Optionally, when measuring the temperature change of the fuse link to be measured when measuring the torque change of the nut, obtain the optimum installation torque of the fuse link to be measured through the temperature change, including the following steps: obtain the temperature change of the fuse link to be measured under different torques; judge the critical torque that meets the critical rule according to the temperature change ; Define the critical torque as the optimum installation torque of the fuse link to be measured.

[0007] In a second aspect, the present invention also provides a device for determining the optimum installation torque of a fuse link. The device for determining the optimum installation torque of a fuse link implements the method for determining the optimum installation torque of a fuse link described in the first aspect, and is characterized in that it includes: a fuse link to be measured; a reference fuse link; a nut for fixing the fuse link to be measured and the reference fuse link; a fuse group fixedly connected to the fuse link to be measured and the reference fuse link respectively through the nut; a torque wrench for adjusting the torque of the nut; a power supply electrically connected to the fuse group through a wire; an ammeter electrically connected to the fuse group and the power supply respectively through a wire; a thermometer for measuring the temperatures of the fuse link to be measured and the reference fuse link. The device for determining the optimum installation torque of a fuse link of the present invention can efficiently implement the method for determining the optimum installation torque of a fuse link proposed in the first aspect, has strong stability, a wide applicable environment, and has practical operation significance and commercial value.

[0008] Optionally, the device for determining the optimum installation torque of a fuse link further includes a terminal controller communicatively connected to the power supply. The device for determining the optimum installation torque of a fuse link of the present invention can control the power supply through the terminal controller, so as to obtain a power supply combination device that meets the design requirements and has a stable output.

[0009] Optionally, both the fuse link to be measured and the reference fuse link include HR20 Guangdong type fuse links. The HR20 Guangdong type fuse link, as a commonly used fuse link, has low cost and is easy to obtain.

[0010] Optionally, the torque wrench includes an electronic digital display torque wrench, which can accurately quantify the torque value of the nut during installation. By using the electronic digital display torque wrench, the torque value of the installed nut can be accurately quantified to two decimal places, which can improve the accuracy of the optimal installation torque obtained by the present invention.

[0011] Optionally, the power supply can provide an alternating current of 50 Hz. The stable 50 Hz alternating current of the present invention ensures the circuit requirements when the fuse link to be measured and the reference fuse link are working properly, reduces the influencing variables of the method for determining the optimal installation torque of the fuse link, and further improves the stability and reliability of the method and device for determining the optimal installation torque of the fuse link.

[0012] Optionally, the thermometer includes an infrared thermometer. By using the infrared thermometer in the present invention, more accurate temperature values of the fuse link to be measured and the reference fuse link can be obtained, and the temperature changes of the fuse link to be measured and the reference fuse link can also be more intuitive. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a flowchart of the method for determining the optimal installation torque of the fuse link according to the present invention;

[0014] Figure 2 is the HR20 Guangdong type fuse link of the present invention;

[0015] Figure 3 is a schematic diagram of the modified HR20 Guangdong type fuse link of the present invention;

[0016] Figure 4 is a schematic diagram of the test circuit connection according to the present invention;

[0017] Figure 5 is a schematic diagram of the nut tightening operation on the fuse link according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] Specific embodiments of the present invention will be described in detail below. It should be noted that the embodiments described here are only for illustrative purposes and do not limit the present invention. In the following description, in order to provide a thorough understanding of the present invention, a large number of specific details are set forth. However, it is obvious to those of ordinary skill in the art that the present invention does not have to employ these specific details. In other instances, well-known circuits, software, or methods have not been specifically described to avoid obscuring the present invention.

[0019] Throughout the specification, references to "an embodiment", "embodiments", "an example", or "examples" mean that the specific features, structures, or characteristics described in connection with the embodiment or example are included in at least one embodiment of the present invention. Thus, the phrases "in an embodiment", "in embodiments", "an example", or "examples" that appear throughout the specification do not necessarily all refer to the same embodiment or example. In addition, the specific features, structures, or characteristics may be combined in any suitable combination and / or sub-combination in one or more embodiments or examples. Furthermore, those of ordinary skill in the art should understand that the diagrams provided herein are for illustrative purposes only and are not necessarily drawn to scale.

[0020] Please refer to Figure 1 , in one embodiment, the present invention provides a method for determining the optimal installation torque of a fuse link, including the following steps:

[0021] S1. Select a fuse link to be tested and a reference fuse link.

[0022] At least one end of the selected fuse link to be tested has no fixed constraint during assembly and application, while the reference fuse link is a commonly used fuse link with fixed constraints at both ends. During the actual installation of the fuse link, due to the clamping action of the nut, both the axial and transverse directions of the fuse link are fixed under the clamping action, so that both ends of the fuse link are fixed and cannot move, thus generating thermal stress. Optionally, a commonly used fuse link can be selected as the reference fuse link and modified to obtain a fuse link to be tested with at least one end having no fixed constraint.

[0023] In an alternative embodiment, as Figure 2 shown, the reference fuse link is selected as the commonly used HR20 Guangdong type fuse link, and the HR20 Guangdong type fuse link is modified. The modified HR20 Guangdong type fuse link is as Figure 3 shown, that is, the port of a fixed end of the HR20 Guangdong type fuse link is enlarged, so as to release the fixed constraint of this port. This enables this port of the HR20 Guangdong type fuse link to move within the range of this port under the influence of human factors when the thermal stress is large enough while satisfying the fixation during installation, thereby releasing the transverse constraint of the modified HR20 Guangdong type fuse link.

[0024] S2. Fix the fuse link to be tested and the reference fuse link to the fuse group respectively through nuts.

[0025] The fuse group needs to be adapted to the fuse link to be tested and the reference fuse link respectively. There are specific fuse groups adapted to different types of fuse links. It is easy for those skilled in the art to select the appropriate fuse according to the set fuse link to be tested and the reference fuse link, so no detailed explanation will be given.

[0026] S3. Connect the fuse group to the test circuit.

[0027] The test circuit provides a stable current required for normal operation to the fuse link under test and the reference fuse link through the fuse group. Specifically, during the test, the test circuit is selected to provide a stable corresponding rated current to the fuse link under test and the reference fuse link to complete the subsequent steps.

[0028] In an optional embodiment, please refer to Figure 4 , Figure 4 which is a schematic diagram of the connection of the test circuit of the invention. Among them, 1 is the fuse link under test, 2 is the reference fuse link, 3 is the fuse group, 4 is the connecting wire, 5 is the power supply, 6 is the terminal controller for controlling the power supply, 7 is the thermometer which is used to measure the temperatures of the fuse link under test and the reference fuse link, and 8 is the ammeter which is used to measure the current in the wire.

[0029] S4. Set the critical rule.

[0030] The critical rule is used to determine the contact condition between the fuse link under test and the fuse group. Please refer to Figure 5 . When tightening the fuse link with a nut, the tightening of the fuse link mainly depends on the tightening force of the nut. The relationship between the tightening force P and the nut torque M is:

[0031] ,

[0032] where K is the torque coefficient and D is the nominal thread diameter of the nut. For known model nuts and contact surfaces, K and D are determined values, and the tightening force P is proportional to the nut torque M. The friction force f between the fuse link and the gasket and the carrier is proportional to the tightening force P. Therefore, the value of the friction force f is also proportional to the tightening torque M. And the friction force f is the main factor generating thermal stress during temperature rise after eliminating the fixed constraints at both ends of the fuse link. By reducing the torque, the thermal stress in the direction of the friction force caused by the friction force during temperature rise can be reduced. However, the torque cannot be reduced indefinitely. When the tightening force is too small or the torque is too small, the installation of the fuse link may be loose and fall off, resulting in poor contact between the fuse link and the fuse group. Poor contact will lead to too large contact resistance, causing serious heating during operation, and may cause the fuse link to blow at a small load current, resulting in malfunction, and even damaging the equipment severely. Therefore, when installing the fuse link with different torque values and testing in a rated current environment, the minimum torque used to meet the condition of good contact is the most suitable installation torque for this specification of fuse link.

[0033] Therefore, according to the actual installation requirements, setting the critical rule includes the following steps: setting a force boundary according to the axial stress between the nut and the fuse link under test When the axial stress corresponding to the selected torque needs to be less than this boundary ; use the temperature at the contact position between the fuse to be measured and the fuse group , and combine it with the temperature at the center position of the fuse to be measured to set the first tolerance , where , that is, the first tolerance corresponding to the selected torque needs to be less than or equal to 90%; use the temperature at the center position of the fuse to be measured , and combine it with the temperature at the center position of the reference fuse to set the second tolerance , where , that is, the second tolerance corresponding to the selected torque needs to be less than or equal to 0.5%. The method of the present invention sets a critical rule for actual installation application, improving the applicability of the method of the present invention.

[0034] S5. Adjust the torque of the nut in combination with the critical rule.

[0035] The adjusting the torque of the nut in combination with the critical rule includes the following steps: obtaining the lowest tightening torque range of the nut through engineering standards ; measuring the initial tightening torque of the nut ; respectively obtaining , and corresponding working conditions of the fuse to be measured, and the working conditions include the axial stress of the fuse to be measured , the first tolerance and the second tolerance ; when , and the corresponding working conditions meet the critical rule, reduce the torque of the nut by 2 in sequence starting from ; when , and the corresponding working conditions meet the critical rule, reduce the torque of the nut by 2 in sequence starting from ; when , , and and the corresponding working conditions meet the critical rule, the corresponding working conditions do not meet the critical rule, starting from , as the end point, adjust the torque of the nut through the binary selection principle; when , and and the corresponding working condition satisfies the critical rule when the corresponding working condition does not satisfy the critical rule, starting from as the starting point as the end point, adjust the torque of the nut through the binary selection principle; when does not satisfy the critical rule, re-determine the lowest tightening torque range and the initial tightening torque . Determine whether it is necessary to select the next torque for testing according to the critical rule. If necessary, the device temperature must be restored to room temperature before operation can be carried out. Note that when testing with a new torque, it is necessary to calibrate the torque of the normal tablets in the control group. The torque selection method of the present invention has a clear operation idea, is simple and convenient, and has strong operability and applicability in practical applications.

[0036] In an alternative embodiment, when and the corresponding working condition satisfies the critical rule, starting from as the starting point, sequentially decrease the torque of the nut by 2 , and further include the following steps: sequentially obtain the working conditions corresponding to the torques with a decrease amount of 2 as the unit until the torque when the working condition does not satisfy the critical rule is obtained, and set this torque as the last torque selection value ; find the critical torque between the last torque selection value and the penultimate selection value through the bisection method until is accurate to two decimal places.

[0037] In another alternative embodiment, when and the corresponding working condition satisfies the critical rule, starting from as the starting point, sequentially decrease the torque of the nut by 2 , and further include the following steps: sequentially obtain the working conditions corresponding to the torques with a decrease amount of 2 as the unit until the torque when the working condition does not satisfy the critical rule is obtained, and set this torque as the last torque selection value ; find the critical torque between the last torque selection value and the penultimate selection value through the bisection method until is accurate to two decimal places.

[0038] In yet another alternative embodiment, when the critical rule is not satisfied, re-determine the minimum tightening torque range and the initial tightening torque , that is, when the three torque critical points do not satisfy the critical rule, check whether there is a problem with the test device until one or more of the test devices meet the requirements after correction, and then perform the subsequent steps.

[0039] S6. Measure the temperature change of the fuse to be tested when measuring the torque change of the nut, and obtain the optimum installation torque of the fuse to be tested through the temperature change.

[0040] The step of measuring the temperature change of the fuse to be tested when measuring the torque change of the nut and obtaining the optimum installation torque of the fuse to be tested through the temperature change includes the following steps: obtaining the temperature change of the fuse to be tested at different torques; judging the critical torque that satisfies the critical rule according to the temperature change ; taking the critical torque as the optimum installation torque of the fuse to be tested. To ensure the accuracy of the optimum installation torque, at least five groups of tests can be selected, and finally the measured results are averaged, and this value is the optimum installation torque of the fuse of this specification.

[0041] By setting a reference fuse and a critical rule, and combining the temperature change of the fuse to be tested at different torques, the present invention obtains the optimum installation torque suitable for itself. The fuse installed at the optimum installation torque is least affected by the axial stress generated by the deformation caused by the fixed restraint in the installation axial direction, so that the fuse can transfer heat better, thereby improving the overload capacity of the fuse, and further improving the qualification rate when the product is used. The method of the present invention is simple and fast, easy to operate, and has strong application value and commercial value in practical applications.

[0042] Please refer to Figure 4, the present invention also provides a device for determining the optimal installation torque of a fuse link. The device for determining the optimal installation torque of a fuse link is used to implement the method for determining the optimal installation torque of a fuse link, and is characterized by comprising: a fuse link to be tested; a reference fuse link; a nut for fixing the fuse link to be tested and the reference fuse link; a fuse group fixedly connected to the fuse link to be tested and the reference fuse link respectively through the nut; a torque wrench for adjusting the torque of the nut; a power supply electrically connected to the fuse group through a wire; an ammeter electrically connected to the fuse group and the power supply respectively through a wire; and a thermometer for measuring the temperatures of the fuse link to be tested and the reference fuse link. The device for determining the optimal installation torque of a fuse link according to the present invention can efficiently implement the method for determining the optimal installation torque of a fuse link proposed in the first aspect, has strong stability, a wide applicable environment, and has practical operational significance and commercial value.

[0043] In an optional embodiment, the device for determining the optimal installation torque of a fuse link further includes a terminal controller communicatively connected to the power supply. The device for determining the optimal installation torque of a fuse link according to the present invention can control the power supply through the terminal controller, so as to obtain a power supply combination device that meets the design requirements and has a stable output.

[0044] In an optional embodiment, both the fuse link to be tested and the reference fuse link include HR20 Guangdong type fuse links. Specifically, the reference fuse link is a commonly used HR20 Guangdong type fuse link, such as Figure 2 shown, and the fuse link to be tested is a modified HR20 Guangdong type fuse link, such as Figure 3 shown. As a commonly used fuse link, the HR20 Guangdong type fuse link has low cost and is easy to obtain.

[0045] In an optional embodiment, the nut selected is a nut of model M10, and its minimum tightening torque range is , with the unit being .

[0046] In an optional embodiment, the fuse group is selected as a GMHRW20 type isolator fuse group. This isolator group is easy to obtain and convenient to use.

[0047] In an optional embodiment, the torque wrench includes an electronic digital display torque wrench, and the electronic digital display torque wrench can accurately quantify the torque value of the nut during installation. By using the electronic digital display torque wrench, the torque value of the installed nut can be accurately quantified to two decimal places, which can improve the accuracy of the optimal installation torque obtained by the present invention.

[0048] In an alternative embodiment, the power supply can provide an alternating current of 50 Hz. The stable 50-Hz alternating current of the present invention ensures the circuit requirements when the fuse links under test and the reference fuse links are operating normally, reduces the influencing variables of the method for determining the optimum installation torque of the fuse links, and further improves the stability and reliability of the method and device for determining the optimum installation torque of the fuse links.

[0049] In an alternative embodiment, the ammeter is a clamp ammeter, which is convenient for installation and disassembly and facilitates experimental operation.

[0050] In an alternative embodiment, the thermometer includes an infrared thermometer. By using the infrared thermometer, the present invention can obtain more accurate temperature values of the fuse links under test and the reference fuse links, and at the same time, the temperature changes of the fuse links under test and the reference fuse links can be more intuitive.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the various embodiments of the present invention, and they should all be covered by the scope of the claims and the description of the present invention.

Claims

1. A method for determining the optimal installation torque of a fuse link, characterized in that, It includes the following steps: Select a fuse link to be tested and a reference fuse link, and at least one end of the fuse link to be tested has no fixed constraint during assembly and application; Fix and connect the fuse link to be tested and the reference fuse link to the fuse group respectively through nuts, and the fuse group is adapted to the fuse link to be tested and the reference fuse link respectively; Connect the fuse group to the test circuit; Set a critical rule, which is used to determine the contact condition between the fuse link to be tested and the fuse group; Adjust the torque of the nut in combination with the critical rule; Measure the temperature change of the fuse link to be tested when the torque of the nut changes, and obtain the optimum installation torque of the fuse link to be tested through the temperature change; The setting of the critical rule includes the following steps: Set a force boundary according to the axial stress between the nut and the fuse link to be measured ; Using the temperature of the contact position between the fuse link to be measured and the fuse group and combining with the temperature of the central position of the fuse link to be measured set a first tolerance , wherein ; Using the temperature at the central position of the fuse slice to be measured , combined with the temperature at the central position of the control fuse slice Set the second tolerance , where .

2. The method for determining the optimal installation torque of the fuse link according to claim 1, wherein The adjusting of the torque of the nut in combination with the critical rule includes the following steps: Obtain the minimum tightening torque range of the nut through engineering standards ; Measure the initial tightening torque of the nut ; Obtain separately , and the working conditions of the corresponding fuse links to be tested, where the working conditions include the axial stress of the fuse links to be tested , the first tolerance and the second tolerance ; At and when the corresponding working conditions satisfy the critical rule, the torque of the nut is sequentially decreased by 2 starting from ; ;​ At and when the corresponding working conditions satisfy the critical rule, reduce the torque of the nut successively by 2 starting from ; ; At , , and and the corresponding working conditions satisfy the critical rule, when the corresponding working conditions do not satisfy the critical rule, starting from as the starting point and as the ending point, adjust the torque of the nut through the binary selection principle; When , , and and the corresponding operating conditions meet the critical rules, when the corresponding operating conditions do not meet the critical rules, starting from as the starting point and as the ending point, adjust the torque of the nut by the binary selection principle; When the critical rule is not satisfied, re-determine the minimum tightening torque range and the initial tightening torque .

3. The method for determining the optimal installation torque of the fuse link according to claim 1, characterized in that The measuring of the temperature change of the fuse link to be tested when the torque of the nut changes and obtaining the optimum installation torque of the fuse link to be tested through the temperature change includes the following steps: Obtain the temperature change of the fuse link to be tested under different torques; Determine the critical torque that meets the critical rule according to the temperature change ; Define the critical torque as the optimum installation torque of the fuse link to be measured.

4. A device for determining the optimal installation torque of a fuse link, the device for determining the optimal installation torque of a fuse link being applicable to the method for determining the optimal installation torque of a fuse link according to any one of claims 1-3, characterized in that, It includes: Fuse link to be tested; Reference fuse link; Nuts, which are used to fix the fuse link to be tested and the reference fuse link; Fuse group, which is fixedly connected to the fuse link to be tested and the reference fuse link respectively through the nuts; Torque wrench, which is used to adjust the torque of the nut; Power supply, which is electrically connected to the fuse group through a wire; Ammeter, which is electrically connected to the fuse group and the power supply respectively through wires; Thermometer, which is used to measure the temperatures of the fuse link to be tested and the reference fuse link.

5. The device for determining the optimal installation torque of the fuse link according to claim 4, characterized in that, It further includes a terminal controller, which is communicatively connected to the power supply.

6. The device for determining the optimal installation torque of the fuse link according to claim 4, wherein Both the fuse link to be tested and the reference fuse link include HR20 Guangdong type fuse links.

7. The fuse piece optimal installation torque determination device according to claim 4, characterized in that The torque wrench includes an electronic digital display torque wrench, which can accurately quantify the torque value of the nut during installation.

8. The fuse piece optimal installation torque determination device according to claim 4, characterized in that The power supply can provide an alternating current of 50Hz.

9. The fuse piece optimal installation torque determination device according to claim 4, characterized in that, The thermometer includes an infrared thermometer.

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