Internal resistor of resistance type bias magnetic treatment device and design method thereof

Mode of execution

, The present invention will be described in detail with reference to the accompanying drawings.

As 1 shows, the maximum resistance of the resistor of I model is 2 Ω, and the maximum resistance value of the resistor II model is 10 Ω, and the maximum resistance value of the resistor of the type II is the resistor. Through simulation analysis, a resistor made of which resistance sheet is adopted can meet the standard requirement.

The heat conduction equation is:

The specific heat capacity of the material c - (J/(kgg·K)).

q- Microelement internal heat source generation rate (J/(s·m)³ )).

Due to the fact that convection heat exchange and radiation heat exchange conditions of resistors are not considered, only the internal heat conduction is considered, first types of boundary conditions are required to be set.

T ＝ 20 °C (On resistive surface)

Because each of the resistor pieces in the resistor is connected in series, the material of each resistance piece is the same, and the flowing current is equal. The cross-sectional area of each part of the resistance sheet is substantially the same, and therefore, the same rectangular resistance sheet with the same cross-sectional area can be replaced by the same cross-sectional area in consideration of the heating problem. First, the I model resistance sheet is verified, and the resistor disc thickness 1.5 mm, the width 20 mm, and the current flowing in the length direction thereof are equal, and therefore, a section of 3 cm long is intercepted, as shown 2. As the resistance sheet material is an iron-clad aluminum alloy, reference data can be found to have a specific resistance ρ^-6 Ω ·m (Ω ·m) The thermal stability after the correction is satisfied by 10 kA current 1s, and when the current passing through the resistive sheet is 10 kA, the amount of heat generated per unit volume of the resistive sheet is increased.

Cross-sectional area (m) of s - resistance sheet in the formula² ).

Heating power (Q-) W/m resistance unit volume³ ).

This is applied to a finite element model to obtain a temperature profile shown 3. As can be seen from the figure, when 10 kA current is applied, the highest point temperature inside resistance 1s is 3676 (degree) C or more, the resistor disc can be blown at the moment, 10 kA current can not be borne. Then, the current is reduced, and the simulation images at the values 5 kA, 4kA, 3kA, 2 kA and 1 kA are obtained respectively, and the data shown in Table 1 are obtained by collating.

Table 1 I model resistance chip different current value lower resistance temperature data

It is known from the table that when the current passing through the resistor is 3 kA hours, the highest resistance temperature is reduced to 347 (degree) C, this temperature resistance can be safely borne, but the current to withstand the individual resistor is controlled below 3 kA in order to prevent the simulation error from causing high actual temperature bias.

The resistance value of the resistor chip can reach 2 Ω, so that the total resistance value 3 Ω is obtained, and the current through the single resistor is not more than 3 kA, and the resistor is designed in a series-parallel mode. As shown 4, a single resistor resistance 2 Ω is connected in series 4 resistors, the resistance of each group of resistors is 0.5 Ω, 6 groups are connected in series to obtain the resistance of the total resistance 3 Ω, and when 6 current is applied to all resistances, the resistance heating condition after 1s is 4 through 10 kA current when the current size of the single resistor is 2. 5kA. 5. When current is applied to all the resistors, as shown 248.5 (degree) C 2.5 kA. , The design requirement can be met by adopting the arrangement mode, and the number of the chip resistors required by the scheme is 24.

The simulation process of the model resistance piece of FIG. 1 II is similar to the I model process, II model resistance piece is 1mm×15mm in cross-section dimension, and compared I model resistance piece cross section, the calorific value is higher when the same current, and the simulation calculates it through 3 kA, 2 kA and 1 kA current temperature data, arranges the data of Table 2.

Table 2 II type resistance sheet resistance temperature data at different current values

Series connection enables the total resistance value 2 kA to, so that the resistor temperature can be controlled to be about when current is applied to all resistors, and the resistor temperature can be 6 controlled to be within the range of about equal to or less than 10 Ω the range. 10. The simulation result shows that the resistor 3 temperature can be controlled to be within 3 Ω a range of 3 about sup .1. 10 .sup. 10 kA-beta.times.10.sup.beta.times.10.sup.beta.times.10.sup. 1 kA-sup.times.10.sup.sup. 30 100 (degree) C.

Considering that the selected chip resistor is manufactured by welding, the welding resistance is present at the welding position, so that the resistivity of the part is relatively large relative to the rest part, and the temperature rise of the part is higher than the rest part when the current is applied. , It is assumed that there is a weld on the resistive sheet, as shown 7 as a model of the weld, and the middle black portion of the resistive sheet is a weld seam having a higher resistivity. Since the magnitude of the resistivity at the weld is difficult to calculate, it is assumed that the resistivity of the weld site is twice the resistance sheet, that is ρ^-6 Ω · m. The simulation analysis of the current 1s was performed on resistors of two models I and II respectively to obtain a resistance temperature distribution as shown 8. 8a and 8b show the temperature distribution of the resistance chip I in 2.5 kA current and the temperature distribution of II model resistance sheets at 1 kA currents, I model resistance sheets are 2.5 kA at the highest temperature through 477 °C currents and II model resistance pieces are 1 kA in maximum point temperature when the II model resistance sheets pass 186 °C currents.

The simulation results of the resistance pieces of the two types and the arrangement manner of the resistors are collated as shown 3.

Table 3 shows two resistance sheets from each other.

It can be seen from the table that although II model resistance tiles are smaller in cross-sectional area, a single resistor throughflow capability is weak, but the current through a single resistor can be made smaller after multiple resistors are connected in parallel, and the highest temperature of the resistance at large currents is lower. When 3 series 10 parallel arrangement mode is adopted, the current inlet end is designed on the same 4 side, and if the current inlet end is arranged on the same side, the resistance is difficult to realize after 6 6 strings are arranged on the same side; after resistance after welding is taken into consideration, the heat stability of the II model resistor is more excellent; therefore, the II model resistor is selected as the resistor used in the device. As 9 of II model resistors 3 and 10 are arranged in parallel, the single resistors are provided with two outlet terminals at the same side, and two vertical copper plates are used for connecting a group of resistors in parallel.

Effects

1, The resistance sheet with two different models is considered, the total resistance value is 3 Ω, and the resistor structure can be given when 10kA/s current can be borne.

2, To the invention, the influence of the resistance of the resistance chip is considered, the temperature distribution condition of the two resistor structures is compared, and a more reasonable resistor design scheme is selected.

3, The invention takes into consideration the device current input end setting, the manufacturing, transportation and field installation difficulty of the cabinet body and the thermal stability performance of the resistor, and provides a more suitable resistor design method.