Calculation method for evaluating current-carrying capacity of bus

Abstract

The invention discloses a calculation method for evaluating the current-carrying capacity of a bus, and relates to the technical field of new energy automobiles, and the method comprises the steps: 1, obtaining parameters, 2, obtaining continuous current, 3, obtaining a temperature correction coefficient, and 4, calculating the current-carrying capacity of the bus. According to the method, a relative calculation formula of the bus current-carrying capacity is deduced through a heat balance theory, a group of bus current-carrying capacity values closest to the cross section size of a target bus are found out from a current-carrying capacity table of the bus in a standard environment, a temperature correction coefficient is selected from a temperature correction coefficient curve graph, and the current-carrying capacity of the bus is calculated. And substituting into a relative calculation formula to calculate the current-carrying capacity value of the target bus, thereby improving the calculation accuracy of the current-carrying capacity of the bus.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy vehicles, and in particular to a calculation method for evaluating the current carrying capacity of a busbar. Background Art

[0002] There are no specific standards or design specifications for the current carrying capacity of the busbar in the power battery and new energy vehicle industries. The busbar is a key device for collecting and distributing electric energy in the power system. If the current carrying capacity of the busbar is insufficient, it will generate heat due to overload when passing a large current, accelerate insulation aging, and may even cause serious faults such as busbar short circuit and burning, affecting the normal power supply of the entire power system. Evaluating the current carrying capacity of the busbar can detect and avoid such problems in advance, and provide a reliable basis for the planning, design and operation of the power system, ensuring that the busbar can safely and stably transmit electric energy under various operating conditions, reducing power outages caused by busbar failures, and improving the power supply reliability of the power system. Therefore, it is particularly important to invent a calculation method for evaluating the current carrying capacity of the busbar.

[0003] The existing technology also has the following defects, which are specifically reflected in the following: In the existing technology, the more commonly used calculation method is to estimate the current carrying capacity of the busbar by multiplying the cross-sectional area of ​​the busbar by the current coefficient. However, there is no exact basis for the specific value, and the estimates of different engineers vary greatly. Another relatively accurate method is to refer to standard copper busbars and aluminum busbars. These two standards have large deviations in actual applications through actual tests and need to be corrected through specific algorithms. This type of algorithm also has no unified standard, relies on the personal experience of engineers, and lacks rigorous theoretical support. Summary of the invention

[0004] The purpose of the present invention is to provide a calculation method for evaluating the current carrying capacity of a busbar, which solves the problems existing in the background technology.

[0005] To solve the above technical problems, the present invention adopts the following technical solution: The present invention provides a calculation method for evaluating the current-carrying capacity of a busbar, comprising: step one, obtaining parameters to determine the width and thickness of the busbar cross section, the ambient temperature of the busbar, and the maximum allowable temperature of the busbar.

[0006] Step 2: Obtain the continuous current. Based on the busbar current carrying capacity table under standard environment, combined with the width and thickness data of the busbar cross section, select the continuous current value according to the actual application of the busbar.

[0007] Step 3: Obtain the temperature correction coefficient. Based on the temperature correction coefficient curve, the temperature correction coefficient is selected in combination with the ambient temperature of the bus and the maximum temperature allowed by the bus.

[0008] Step 4: Calculate the busbar current carrying capacity based on the busbar current carrying capacity calculation formula.

[0009] Preferably, the busbar current carrying capacity calculation formula is specifically analyzed as follows: If the current is constant, the busbar temperature satisfies the formula when it reaches a thermal equilibrium state: I 2 ×R=Kt×A×Δt, where I represents the rated current, R represents the busbar resistance, A represents the busbar heat dissipation surface area, Δt represents the difference between the busbar surface temperature and the ambient temperature, and Kt represents the comprehensive heat dissipation coefficient.

[0010] Decompose the formula and insert And A=2×(w+h)×l, we get the formula: Where ρ0 represents the resistivity of the conductor at 0°C, a represents the coefficient of change of the conductor resistivity with temperature, T0 represents the ambient temperature, and T c It represents the surface temperature of the busbar when it reaches thermal equilibrium, w represents the width of the busbar, and h represents the thickness of the busbar.

[0011] Based on the above formula, it is analyzed that when other conditions remain unchanged, the busbar current capacity is In direct proportion, if the current carrying capacity of a copper busbar with a width of w and a thickness of h in a certain environment is i, then the current carrying capacity I of a copper busbar with a width of W and a thickness of H in the same environment satisfies the equation: Right now Substitute the temperature correction coefficient k2 to obtain the calculation formula for the busbar current carrying capacity:

[0012] The beneficial effects of the present invention are as follows: the present invention provides a relatively reasonable and accurate calculation method for evaluating the current-carrying capacity of a busbar, and the calculation method is used to cross-check with the existing data in the current-carrying capacity table of copper busbars and aluminum busbars under standard environments. The deviation rate of adjacent data rows is less than 5%, and the limit deviation rate of the first row and the last row is less than 17%, which is much lower than the calculation method of multiplying the cross-sectional area by the current-carrying coefficient; and the algorithm is clear, which improves the accuracy of the calculation of the current-carrying capacity of the busbar. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0014] Figure 1 The present invention is a schematic flow chart of the steps for implementing the method.

[0015] Figure 2 This is the temperature correction coefficient curve.

[0016] Description of the drawings: Figure 2 The horizontal axis is the maximum temperature T allowed by the busbar c , the curve cluster is the ambient temperature T0, and the vertical axis is the temperature correction coefficient k2. DETAILED DESCRIPTION

[0017] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] Reference Figure 1 As shown, the present invention provides a calculation method for evaluating the current carrying capacity of a busbar, comprising: step one, obtaining parameters to determine the width and thickness of the busbar cross section, the ambient temperature of the busbar, and the maximum allowable temperature of the busbar.

[0019] It should be noted that the busbar refers to a copper busbar or an aluminum busbar.

[0020] Step 2: Obtain the continuous current. Refer to Table 1. Based on the current carrying capacity table of the busbar under standard conditions, combined with the width and thickness data of the busbar cross section, select the continuous current value according to the actual application of the busbar.

[0021] It should be noted that the actual application of the busbar is divided into busbars with coatings, insulation layers or bare bars, placed horizontally or vertically, and a set of w and h closest to the width W and thickness H of the busbar cross section are found in the table, and the continuous current value i is selected.

[0022] Table 1

[0023]

[0024]

[0025] It should be noted that the data in the table are for copper busbar and aluminum busbar at ambient temperature T0 = 35°C and busbar temperature T c = Current carrying capacity at 65°C.

[0026] Step 3: Get the temperature correction coefficient, refer to Figure 2 , based on the temperature correction coefficient curve, combined with the ambient temperature of the busbar and the maximum temperature allowed by the busbar, select the temperature correction coefficient.

[0027] It should be noted that according to the ambient temperature T0, the maximum allowable busbar temperature T c , search directly in the diagram, for example, if the ambient temperature T0 = 35°C and the maximum allowable bus temperature T0 = 65°C, then the coefficient k2 = 1; if the ambient temperature T0 = 5°C and the maximum allowable bus temperature T0 = 105°C, then the coefficient k2 = 1.95.

[0028] Step 4: Calculate the busbar current carrying capacity based on the busbar current carrying capacity calculation formula.

[0029] In a specific embodiment, the busbar current-carrying capacity calculation formula and the specific analysis process are as follows: On a theoretical level, the busbar current-carrying capacity is the ability of the busbar to continuously pass current under limited ambient temperature and surface temperature rise conditions. When current passes through the conductor, Joule heat is generated, causing the temperature of the conductor to rise. After the temperature of the conductor rises, it will dissipate heat to the surrounding environment through air convection and radiation emission. If the current and ambient temperature are constant, in the initial stage of current flow, the heat generation power is greater than the heat dissipation power, the temperature of the conductor will continue to rise, and the heat dissipation power will also increase accordingly, until the heat generation power is equal to the heat dissipation power, the conductor will enter a thermal equilibrium state, that is, the temperature of the conductor will no longer rise and the heat dissipation power will no longer increase. At this time, the current is the current-carrying capacity of the ambient temperature and limited temperature rise conditions.

[0030] Based on the above theory, if the current is constant, the busbar temperature reaches a thermal equilibrium state and satisfies the formula: I 2 ×R=Kt×A×Δt, where I represents the rated current, R represents the busbar resistance, A represents the busbar heat dissipation surface area, Δt represents the difference between the busbar surface temperature and the ambient temperature, and Kt represents the comprehensive heat dissipation coefficient.

[0031] Decompose the formula and insert And A=2×(w+h)×l, we get the formula: Where ρ0 represents the resistivity of the conductor at 0°C, a represents the coefficient of change of the conductor resistivity with temperature, T0 represents the ambient temperature, and T c It represents the surface temperature of the busbar when it reaches thermal equilibrium, w represents the width of the busbar, and h represents the thickness of the busbar.

[0032] Based on the above formula, it is analyzed that when other conditions remain unchanged, the busbar current capacity is In direct proportion, if the current carrying capacity of a copper busbar with a width of w and a thickness of h in a certain environment is i, then the current carrying capacity I of a copper busbar with a width of W and a thickness of H in the same environment satisfies the equation: Right now Substitute the temperature correction coefficient k2 to obtain the calculation formula for the busbar current carrying capacity:

[0033] The present invention provides a relatively reasonable and accurate calculation method for evaluating the current carrying capacity of a busbar. The calculation method is used to perform cross-checking with existing data in a current carrying capacity table of a copper busbar and an aluminum busbar under a standard environment. The deviation rate of adjacent data rows is less than 5%, and the limit deviation rate of the first row and the last row is less than 17%. The deviation rate is much lower than the calculation method of multiplying the cross-sectional area by the current carrying coefficient. In addition, the algorithm is clear, thereby improving the accuracy of the calculation of the current carrying capacity of the busbar.

[0034] The above contents are merely examples and explanations of the concept of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the scope defined by the present invention, they shall all fall within the protection scope of the present invention.

Claims

1. A calculation method for evaluating the current carrying capacity of a busbar, characterized in that: include: Step 1: Obtain parameters to determine the width and thickness of the busbar cross section, the ambient temperature of the busbar, and the maximum allowable temperature of the busbar; Step 2: Obtain the continuous current. Based on the current carrying capacity table of the busbar under standard environment, combined with the width and thickness data of the busbar cross section, select the continuous current value according to the actual application of the busbar; Step 3: Obtain the temperature correction coefficient. Based on the temperature correction coefficient curve, the temperature correction coefficient is selected in combination with the ambient temperature of the busbar and the maximum temperature allowed by the busbar. Step 4: Calculate the busbar current carrying capacity based on the busbar current carrying capacity calculation formula.

2. A calculation method for evaluating busbar current carrying capacity according to claim 1, characterized in that: The busbar current carrying capacity calculation formula and the specific analysis process are as follows: If the current is constant, the busbar temperature reaches thermal equilibrium and satisfies the formula: I 2 ×R=Kt×A×Δt, where I represents the rated current, R represents the busbar resistance, A represents the busbar heat dissipation surface area, Δt represents the difference between the busbar surface temperature and the ambient temperature, and Kt represents the comprehensive heat dissipation coefficient; Decompose the formula and insert And A=2×(w+h)×l, we get the formula: Where ρ0 represents the resistivity of the conductor at 0°C, a represents the coefficient of change of the conductor resistivity with temperature, T0 represents the ambient temperature, and T c It represents the surface temperature of the busbar when it reaches thermal equilibrium, w represents the width of the busbar, and h represents the thickness of the busbar; Based on the above formula, it is analyzed that when other conditions remain unchanged, the busbar current capacity is In direct proportion, if the current carrying capacity of a copper busbar with a width of w and a thickness of h in a certain environment is i, then the current carrying capacity I of a copper busbar with a width of W and a thickness of H in the same environment satisfies the equation: Right now Substitute the temperature correction coefficient k2 to obtain the calculation formula for the busbar current carrying capacity:

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