Design Method of Sectional AC Inductive Adjustable Load

Abstract

The present invention is a design method for a segmented AC inductive adjustable load. The method includes using a resistor and an inductor in series. Within the impedance adjustment range, the resistor and the inductor are segmented, and a method combining positions and grades is used. Band switches are used for selection to meet the requirements of current and power factor. The present invention is divided into different positions and grades, and combined with reference resistors and reference inductors, so that the load becomes adjustable. The present invention has flexibility and adaptability, and breaks through the limitation of the traditional redesign of the load due to the non-adjustable load, which causes waste of manpower and material resources.

Description

Technical Field

[0001] The technical solution of the present invention relates to the technical field of low-voltage electrical appliance reliability life test, and specifically to a design method for a segmented AC inductive adjustable load. Background Art

[0002] The reliability of electrical products refers to the ability of products to complete specified functions under specified conditions and within specified time. Its reliability is an important part of product quality. Strictly speaking, the quality of a product should include two aspects: performance and reliability. Even if a product has high performance indicators, it cannot be considered a good quality product if its reliability is not high. The reliability of an automatic control system basically depends on the reliability of the components used in the system. At the same time, the reliability of the system generally decreases with the increase in the number of components used in the system. As the system develops towards large-scale, the number of components used in an automatic control system is increasing. As long as one of the components fails, it will generally cause the entire automatic control system to fail, resulting in significant economic losses. Therefore, the reliability of electrical components used in automatic control systems is becoming more and more important.

[0003] Low-voltage electrical appliances play an important role in control and protection in the power system, ensuring the safe and reliable operation of the power system. Under normal working conditions, low-voltage electrical appliances will be damaged by different external factors. As the lifespan increases, the material continues to age and the strength continues to decrease, eventually causing damage to the low-voltage electrical appliances. The key life indicators of low-voltage electrical appliances are divided into two categories: mechanical life and electrical life. Mechanical life refers to the number of no-load operations that low-voltage switching electrical appliances can withstand without the need for repair or replacement of parts; electrical life refers to the number of load operations that low-voltage electrical appliances can withstand under specified working conditions without the need for repair or replacement of parts. For this reason, the reliability of low-voltage electrical appliances is a characteristic that deserves special attention, and life tests on them are also essential.

[0004] Nowadays, more and more scientific research institutions, universities or other electrical enterprises need to use AC adjustable loads in scientific research, technology development and reliability life tests. In order to study the various characteristics of the product, it is necessary to simulate various load conditions, and it is necessary to use a variety of loads to evaluate the performance of the product. Some need to be connected in parallel, some need to be connected in series; some need to adjust the load properties (resistance, inductance and capacitance, etc.); some need to adjust the load size; some need to adjust the load current size at a constant voltage; some need to adjust the load voltage size at a constant current; some need to adjust the load current or voltage size at a constant power factor. This requirement of constantly changing load parameters has brought great difficulties to the configuration of the test and R&D site. In order to improve the test efficiency, resistors and reactors are used to simulate the motor load. Resistors and reactors use step-by-step adjustment with very small divisions, but with voltage adjustment within the allowable error, the change of the test current is stepless.

[0005] At present, most of the loads used in the reliability life tests of low-voltage electrical appliances are single fixed loads. For example, Ma Yue (Ma Yue. Research on the failure mechanism and life prediction method of aerospace relays [D]. Harbin Institute of Technology, 2013.) adopted a single fixed load in the design of the simulated load in the test. This method is relatively limited for the need to replace the load, and it is slightly wasteful in terms of materials and space. The tester is often required to have load capacity in the commissioning test of electrical equipment, and an adjustable load is required at this time. Summary of the invention

[0006] The problem of the present invention is to provide a design method for a segmented AC inductive adjustable load in view of the shortcomings in the current technology. In the design method of the present invention, a resistor and an inductor are connected in series. Within the impedance adjustment range, the resistor and the inductor are segmented. The segmentation can be combined with a position and a grade, and a band switch is used to select to meet the requirements of current and power factor. The present invention is divided into different positions and grades, and cooperates with a reference resistor and a reference inductor to make the load adjustable.

[0007] The technical solution adopted by the present invention to solve the technical problem is:

[0008] A design method for a segmented AC inductive adjustable load, the method comprising the following steps:

[0009] The first step is the structural design of the load;

[0010] Select resistors, inductors, and band switches for circuit connection design. Each reference resistor unit and reference inductor unit is loaded with a band switch. The maximum power factor is A. max Take 0.95;

[0011] The second step is to calculate the load range: determine U according to the required voltage and current range max , Umin , I max and I min , and then calculate the maximum impedance Z according to formulas (1) and (2) respectively max and minimum impedance Z min ;

[0012]

[0013]

[0014] The third step is to calculate the resistance range. Combined with the power factor required by the design, the maximum and minimum resistance R are calculated according to formulas (3) and (4) respectively. max and minimum resistance R min ,

[0015] R max =Z max A max (3)

[0016] R min =Z min A min (4)

[0017] When the power factor is 1, take the maximum power factor A max is 0.95; minimum power factor A min is 0, the resistance is 0;

[0018] The fourth step is to calculate the inductance range. Combined with the impedance range and power factor obtained in the second step, the maximum inductance L is designed according to formulas (5) and (6). max and minimum inductance L min :

[0019]

[0020]

[0021] Where, ω = 2πf, f is the frequency of the alternating current, which is 50 Hz;

[0022] Step 5: The segmentation adopts the method of combining position and binning; firstly, select the appropriate bin d;

[0023] First take d = 10;

[0024] The d represents the bin, and w represents the percentile;

[0025] Step 6: After determining the value of the bin d, calculate the bit w according to the impedance range obtained in step 2 according to formula (7);

[0026]

[0027] Step 7: Perform accuracy check based on the value of bin d and the calculated bit w;

[0028] The conditions for meeting the accuracy requirements of the minimum current are:

[0029] If the obtained accuracy meets the accuracy requirement of the minimum current, proceed to step 8; if the obtained accuracy does not meet the accuracy requirement of the minimum current, return to step 5 and change the d value; the change step length of the d value is 1;

[0030] Step 8. If the accuracy requirement of the minimum current is met, take the step d and position w as an example to design a segmented AC adjustable load. The step on each position w can be different during the design. For the convenience of design, the same step d can be selected and the reference resistance on each position can be solved:

[0031] Assume the impedance range is Z min ~Z max , the corresponding resistance and inductance are R min ~R max and L min ~L max ; For the convenience of design, it can be greater than R max The smallest integer of , and record it as R; similarly, take a value greater than L max The smallest integer of , and record it as L.

[0032] First position: The reference resistor R1 is There are d files in total;

[0033] Second place: The reference resistor R2 is There are d files in total;

[0034] …

[0035] The wth position: reference resistance R w for There are d files in total;

[0036] Then solve for the reference inductance at each bit:

[0037] First position: The reference inductance L1 is There are d files in total;

[0038] Second place: The reference inductance L2 is There are d files in total;

[0039] …

[0040] The wth position: reference inductance L w for There are d files in total;

[0041] Thus, the reference resistance and reference inductance on each bit are obtained;

[0042] Then, the resistance R and inductance L that meet the design requirements are obtained, and the inductance and resistance are connected in series to complete the design of the segmented AC inductive adjustable load.

[0043] Each of the reference resistor units includes d reference resistors connected in series;

[0044] Each of the reference inductance units includes d reference inductors connected in series;

[0045] Each reference resistance unit and reference inductance unit is connected in series with a band switch;

[0046] The d≤20; the w≤20; both are natural numbers.

[0047] The outstanding essential features of the present invention are:

[0048] The present invention adopts the idea of ​​segmentation, combines the gradation with the position, utilizes the coordination of resistors and inductors of different specifications, and utilizes the band switch to select the load, thereby realizing more precise control. By reasonably adjusting the specifications of the resistors and inductors, and coordinating the voltage within the allowable error range, a more precise current can be obtained. The segmentation idea of ​​the present invention breaks the single fixed load in the traditional sense, realizes that a set of loads can be used for multiple tests, and saves resources to the maximum extent. Taking the AC contactor as an example to highlight the advantages of this invention, there are 4 usage categories of the AC contactor, AC-1 to AC-4. Each usage mode has different rated voltage and rated current requirements. Therefore, when testing the AC contactor under multiple usage modes, loads of multiple specifications are required. The segmented inductive adjustable load in the present invention has the advantage that a set of loads can adapt to multiple test modes.

[0049] The beneficial effects of the present invention are:

[0050] (1) Compared with other single fixed loads, the present invention adopts the idea of ​​segmentation and the method of combining grade and position, which has certain flexibility and adaptability, and breaks through the limitation of traditional redesign of load due to non-adjustable load, resulting in waste of manpower and material resources.

[0051] (2) The resistor and reactor in the present invention adopt a step-by-step adjustment with very small divisions, which has the advantages of small adjustment fineness and large adjustment range. Combined with the voltage adjustment within the allowable error, the change of the test current is made stepless.

[0052] (3) Due to the adjustability of the load, the present invention can be applicable to tests under a variety of different modes and can be flexibly adjusted according to the requirements of different test modes, so as to give full play to its practical value. For example, for the test of AC1-AC4 of the AC contactor, the present invention fully demonstrates the advantages of the adjustable load.

[0053] (4) Compared with non-adjustable loads, the present invention increases flexibility, so that the present invention can be applied to a variety of test modes. In addition, since the load is designed by combining the step-by-step and position-by-position method, the resistor and inductor that can achieve the same function and have a small volume and less energy loss can be selected according to the actual situation, which achieves the advantages of saving space and materials to a certain extent and greatly reduces the test cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0055] Figure 1 This is the main circuit diagram of the segmented AC inductive adjustable load.

[0056] Figure 2 The figure is a workflow diagram of the design method of segmented AC inductive adjustable load. DETAILED DESCRIPTION

[0057] The main circuit of the segmented AC inductive adjustable load of the present invention is as follows Figure 1 As shown, it comprises a band switch, a reference resistance module and a reference inductance module; wherein the reference resistance module and the reference inductance module are connected in series;

[0058] The reference resistance module includes n reference resistance units, each of which is d reference resistances connected in series;

[0059] The reference inductor module includes n reference inductor units, each of which is d inductors and resistors connected in series;

[0060] The d is ≤ 20; the n is ≤ 20;

[0061] like Figure 1 As shown, each reference resistance unit and reference inductance unit is connected in series with a band switch;

[0062] The main function of the band switch is to select the resistance and inductance positions.

[0063] Figure 1This design mainly includes a reference resistance module and a reference inductance module, wherein the reference resistance module is divided into n reference resistance units, each of which represents a digit (i.e., units, tens, hundreds, etc., in this patent, it is the 1st, 2nd, ..., wth digit), and w and n can be considered equal in value, but n represents the number of reference resistance units, and w represents the digit; and each reference resistance unit contains d resistors, i.e., it is divided into d gears. The understanding of the reference inductance module is similar.

[0064] The design method of the segmented AC inductive adjustable load described in the present invention comprises the following specific steps:

[0065] The first step is the structural design of the load;

[0066] Select resistors, inductors, and band switches for circuit connection design. Each reference resistor unit and reference inductor unit is loaded with a band switch. The actual error is taken into account during the design process. The maximum power factor A max Take 0.95;

[0067] Usually, in actual experiments, the maximum power factor usually does not reach its theoretical value of 1, and the general error is 5%. Therefore, in the design process, the maximum power factor A is taken. max is 0.95;

[0068] Resistors and inductors are connected in series. Within the impedance adjustment range, the resistors and inductors are segmented and selected by band switches to meet the requirements of current and power factor.

[0069] The second step is to calculate the load range: determine U according to the required voltage and current range max , U min , I max and I min , and then calculate the maximum impedance Z according to formulas (1) and (2) respectively max and minimum impedance Z min :

[0070]

[0071]

[0072] The U max , U min , I max and I min this The ranges of the four parameters are generally given directly according to the corresponding standards based on actual design needs.

[0073] The third step is to calculate the resistance range. Combined with the power factor required by the design, the maximum and minimum resistance R are calculated according to formulas (3) and (4) respectively.max and minimum resistance R min :

[0074] R max =Z max A max (3)

[0075] R min =Z min A min (4)

[0076] When the power factor is 1, considering the allowable error, take the maximum power factor A max is 0.95; minimum power factor A min is 0, the resistance is 0;

[0077] The fourth step is to calculate the inductance range. Combined with the impedance range and power factor obtained in the second step, the maximum inductance L is designed according to formulas (5) and (6). max and minimum inductance L min :

[0078]

[0079]

[0080] Where, ω = 2πf, f is the frequency of the alternating current, which is 50 Hz;

[0081] Step 5: The segmentation adopts the method of combining position and binning; firstly, select the appropriate bin d;

[0082] First take d = 10;

[0083] Usually, according to the actual test process, d<20. If d is too large, there will be too many gears, and the adjustment of the gears will be too complicated. If d is too small, the gears will not reach the expected minimum range value and the stepless current cannot be achieved. Usually, d=10 is taken for subsequent design. If necessary, the value of d can be appropriately increased or decreased.

[0084] The d mentioned above represents the grade, and w represents the percentile, which is usually understood as the tenth place, hundredth place, unit place, tenth place, hundredth place, etc. The grade d refers to the change of the grade on each place. For example, if there are 10 grades on the unit place, it means that d=10 on the unit place. Each reference resistance unit and reference inductance unit is connected in series with a band switch. This switch is used to control the number of resistors and inductors that need to be connected to the circuit (for example, one resistor is connected to the first grade and two are connected to the second grade). Therefore, adjusting the grade refers to adjusting the grade of the band switch)

[0085] Step 6: After determining the value of the bin d, calculate the bit w according to the impedance range obtained in step 2 according to formula (7);

[0086]

[0087] Step 7: Perform accuracy check based on the value of bin d and the calculated bit w;

[0088] The conditions for meeting the accuracy requirements of the minimum current are:

[0089] If the obtained accuracy meets the accuracy requirement of the minimum current, proceed to step 8; if the obtained accuracy does not meet the accuracy requirement of the minimum current, return to step 5 and change the d value; the change step length of the d value is 1;

[0090] Step 8. If the accuracy requirement of the minimum current is met, take the design of bin d and position w as an example. The bins on each position w can be different during the design. For the convenience of design, the same bin d can be selected, and the reference resistance on each position can be solved:

[0091] Assume the impedance range is Z min ~Z max , the corresponding resistance and inductance are R min ~R max and L min ~L max For the convenience of design, it can be taken to be greater than R max The smallest integer of , and record it as R. Similarly, take a value greater than L max The smallest integer of , and record it as L;

[0092] First position: The reference resistor R1 is There are d files in total;

[0093] Second place: The reference resistor R2 is There are d files in total;

[0094] …

[0095] The wth position: reference resistance R w for There are d files in total;

[0096] Then solve for the reference inductance at each bit:

[0097] First position: The reference inductance L1 is There are d files in total;

[0098] Second place: The reference inductance L2 is There are d files in total;

[0099] …

[0100] The wth position: reference inductance Lw for There are d files in total;

[0101] Accuracy Guarantee:

[0102] When designing, the design current accuracy must also be considered. but General Requirements In order to meet the accuracy requirement of the minimum current, |dZ|≤0.02Z min In other words, The resistance and inductance can meet the above requirements respectively. If the accuracy requirement of the minimum current cannot be met, it is necessary to reselect the grade d and perform the accuracy test again. In addition, d is generally limited by the band switch. If the switch is divided into 10 grades, the calculation method of the bit is

[0103] The significance of satisfying the current accuracy is that the resistor and reactor can be adjusted in steps with very small divisions, which has the advantages of small adjustment fineness and large adjustment range. With the voltage adjustment within the allowable error, the test current can be changed steplessly. That is, according to the designed divisions and grades, the band switch is used at different divisions to adjust the gears of the resistor and inductor, so that the current reaches the minimum division value.

[0104] When designing a segmented AC adjustable load, assume that the resistance value to be adjusted is R and the inductance value is L. First, connect the d reference resistors R1 in the highest position (i.e. the first position) in series to form a reference resistor unit. The lead wire at the front end of the reference resistor unit serves as a terminal of the load, and the end is left hanging. Secondly, connect the reference resistors (R2, R3, ..., R w ) are also connected in series to form the reference resistance unit at each position, with the end left hanging. At the same time, a lead wire is connected to the end of each reference resistor at each position and connected to the band switch of the corresponding position, and the other end of the band switch is connected to the front end of the reference resistance unit at the next position. Finally, after the resistor R is designed, the inductor L is designed in a similar way, and the inductor and resistor are connected in series to complete the design of the segmented AC inductive adjustable load. Assume that the gear indications on each position of the current resistance gear are a1, a2, ..., a w The gear positions on the inductance gear are indicated as b1, b2, ..., b w Then the impedance Z=R+jωL, where R=R1*a1+R2*a2+…+R w *a w ; L=L1*b1+L2*b2+…+L w *b wAfter completing the design of the segmented AC inductive adjustable load, considering the safety issues in actual use, the shell is packaged, and finally the resistance and inductance are adjusted by using band switches at different positions to meet the experimental needs.

[0105] Each of the reference resistor units includes d reference resistors connected in series;

[0106] Each of the reference inductance units includes d reference inductors connected in series;

[0107] Each reference resistance unit and reference inductance unit is connected in series with a band switch;

[0108] The d is ≤ 20; the w is ≤ 20;

[0109] In Example 1, the design of the present invention enables the adjustment of the reference resistance and the reference inductance to achieve a relatively high precision, so that the present invention can be more widely used in actual experiments and adapt to various experimental modes.

[0110] Figure 2 It shows that the working process of the design method of the segmented AC inductive (resistive) adjustable load of the present invention is:

[0111] (1) Start → whether to start the experiment. If not, continue to wait. If the experiment is to start, proceed to step (2).

[0112] (2) Design the load structure, using resistors and inductors in series;

[0113] (3) Calculate the maximum and minimum impedances and find the impedance range Z;

[0114] (4) Calculate the maximum and minimum resistances and find the resistance range R;

[0115] (5) Calculate the maximum and minimum inductances and find the inductance range L;

[0116] (6) Select the appropriate bin d;

[0117] (7) Based on the selected grade d and the required load range, calculate the position w;

[0118] (8) Performing an accuracy test to determine whether the minimum current accuracy requirement is met. If so, combining the resistance R, the inductance L, the bin d, and the bit w, the reference resistance and the reference inductance for each bit are solved; if not, repeating step 6;

[0119] (9) Determine whether the next test is needed (if a new load needs to be designed, it can be designed according to the above steps. Usually, it is determined whether the adjustable load designed this time has met the requirements of this test and whether additional design is needed). If necessary, return to step (2); if not, exit directly.

[0120] Example 1

[0121] Design a segmented AC inductive load with the following technical parameters: external voltage U = 110-277V; current requirement I = 1-30A with 2% error; power factor requirement The error is 0.05. The specific design scheme is as follows.

[0122] (For this example, see step 8, "First position: the reference resistance is 30 ohms, with 10 positions", which means d = 10, i.e. 10 positions, and n is actually the number of positions. In this example, the result shows that w = 4, which means there are four reference resistance units and four reference inductance units, so n = 4. You can refer to Figure 1 to understand. )

[0123] The first step is to design the load structure. Use resistance and inductance in series. Within the impedance adjustment range, the resistance and inductance are segmented and selected by band switches to meet the requirements of current and power factor.

[0124] The second step is to calculate the load range. According to the voltage and current range given by the required design requirements, the maximum and minimum impedances are calculated according to formulas (1) and (2) respectively.

[0125]

[0126]

[0127] Required load range: Z = Z max ~Z min =277~3.67Ω

[0128] The third step is to calculate the resistance range, and combine the power factor required by the design to calculate the maximum and minimum resistances according to formulas (3) and (4) respectively;

[0129] R max =Z max A max (3)

[0130] R min =Z min A min (4)

[0131] Required resistance range: R = R max ~R min=263.15~1.1Ω

[0132] Step 4: Calculate the inductance range, combine the impedance range and power factor obtained in step 2, and design the maximum and minimum inductances according to formulas (5) and (6);

[0133]

[0134]

[0135] Assuming the power grid is industrial frequency, we know that f = 50Hz, and ω = 2πf, so the required inductance range L = L max ~L min =841.5~3.6mH.

[0136] The fifth step is to use a combination of position and binning to divide the segments. First, select a suitable bin d. In this design, we select bin d = 10;

[0137] Step 6: Select the appropriate grade d and the impedance range obtained in step 2 according to the actual situation, and calculate the bit w according to formula (7).

[0138]

[0139] Right now Therefore, w can choose 4 bits;

[0140] Step 7: Select the appropriate bin d and the calculated bit w based on the actual situation, and perform accuracy test. In order to meet the accuracy requirements of the minimum current, Right now It can be seen that this design meets the accuracy requirements of the minimum current.

[0141] Step 8. Take the resistor R, bin d, and position w as an example for design. The bins at each position can be different. For the convenience of design, the same bin d can be selected and the reference resistance at each position can be solved:

[0142] Designed resistance range R min ~R max 1.1~263.15Ω, inductance range L min ~L max The maximum value of the resistance is 300Ω and the maximum value of the inductance is 900mH.

[0143] First position: The base resistance is 30 ohms, with 10 levels (0 to 9).

[0144] Second position: The base resistance is 3 ohms, with 10 levels;

[0145] The third position: the base resistance is 0.3 ohms, with 10 levels;

[0146] Fourth position: The base resistance is 0.03 ohms, with 10 levels;

[0147] Then solve for the reference inductance at each bit:

[0148] First position: The base resistance is 90 millihenries, with 10 levels in total;

[0149] Second position: The base resistance is 9 millihenry, with 10 levels;

[0150] The third position: the base resistance is 0.9 millihenry, with 10 levels;

[0151] Fourth digit: The base resistance is 0.09 millihenry, with a total of 10 levels.

[0152] On the basis of obtaining the reference resistance and reference inductance, the adjustment range of the segmented AC inductive adjustable load can be obtained. The maximum adjustable resistance and inductance values ​​are when all the gears on all positions are adjusted to the maximum position (i.e., the position of '9'), and the minimum is when all the gears on all positions are adjusted to the minimum position (i.e., the position of '0'). For Example 1, the adjustable range of resistance is 0-299.27, and the minimum adjustment accuracy is 0.03Ω. The inductance adjustment range is 0-899.91mH, and the minimum adjustment accuracy is 0.09mH. The resistance and inductance adjustment ranges both meet the design requirements.

[0153] When actually designing a segmented AC adjustable load, first connect the 9 reference resistors R1 (R1=30Ω) of the highest position (i.e. the first position) in series to form a reference resistor unit, and the lead wire at the front end of the reference resistor unit serves as a terminal of the load, with the end hanging. Secondly, connect the reference resistors R2, R3, and R4 (R2=3Ω, R3=0.3Ω, and R4=0.03Ω) of the remaining positions in series to form reference resistor units on each position, with the ends hanging. At the same time, connect a lead wire to the end of each reference resistor on each position and connect it to the band switch of the corresponding position, and the other end of the band switch is connected to the front end of the reference resistor unit on the next position. Finally, after designing the resistor R, design the inductor L in a similar way, and connect the inductor and the resistor in series to complete the design of the segmented AC inductive adjustable load. Assume that the resistance value to be adjusted is 187Ω and the inductance value is 762mH. When adjusting the resistance level, start from the first level. If the first level is 6, the resistance of the circuit connected to this level is 180Ω (30*6); if the second level is 2, the resistance of the circuit connected to this level is 6Ω (3*2); if the third level is 3, the resistance of the circuit connected to this level is 0.9Ω (0.3*3); if the fourth level is 3, the resistance of the circuit connected to this level is 0.09Ω (0.03*3). The total resistance value is 187≈30*6+3*2+0.3*3+0.03*3. Similarly, for the inductor. If the first position is 8, the inductance of the circuit connected to this position is 720mH (90*8); if the second position is 4, the inductance of the circuit connected to this position is 36mH (9*4); if the third position is 6, the inductance of the circuit connected to this position is 5.4mH (0.9*6); if the fourth position is 3, the inductance of the circuit connected to this position is 0.54 (0.09*6). The total resistance value is 762≈90*8+9*4+0.9*6+0.09*6.

[0154] It is worth noting that, in combination with the actual selection of appropriate grading and the calculated position, the accuracy test is carried out. If the minimum current accuracy requirement cannot be met, the number of gradings is continued to be increased on the basis of the original grading until the design can meet the minimum current accuracy requirement. At present, the loads used in the reliability life test of most low-voltage electrical appliances are single fixed loads, and can only be tested in a single mode. This method is relatively limited for the need to replace the load, and there is waste in materials and space. As for Example 1, there are not only voltage and current requirements, but also power factor restrictions. In order to facilitate industrial production, the reference resistance and reference inductance are taken as close to the integer of the adjustment range as possible. In this way, not only can the waste of materials and space be reduced as much as possible in industrial production, but also production is more economical. And it is convenient to manufacture and design resistors and inductors, and reduce the generation batch. At the same time, it is convenient to adjust the required impedance, adopt a step adjustment with very small division, and cooperate with the voltage adjustment within the allowable error, so that the change of the test current is stepless.

[0155] After completing the design of the segmented AC inductive adjustable load, considering the safety issues in actual use, the shell is packaged, and finally the resistance and inductance are adjusted by using band switches at different positions to meet the experimental needs.

[0156] On this basis, the reference resistance, reference inductance and band switch at each position are connected in series. Considering the safety issues in actual use, the outer shell is packaged, and finally the band switch is used to adjust the resistance and inductance at different positions to meet the experimental needs.

[0157] The above design examples show that the present invention adopts the idea of ​​segmentation, as well as the method of combining grading and position, which can be flexibly adjusted according to the needs of different test modes and has strong practicality. The reference resistor and reference inductor designed in the example have achieved very high accuracy, which largely meets the various ranges of adjustment in actual tests, thereby realizing stepless changes in test current. In addition, when designing, for resistors and inductors of different specifications, devices with the same functions, small size and low energy loss can be selected to save space and materials to the greatest extent, thereby reducing test costs.

[0158] Matters not covered by the present invention are known technologies.

Claims

1. A design method for a segmented AC inductive adjustable load. The method is characterized in that it comprises the following steps: The first step is the structural design of the load; Select resistors, inductors, and band switches for circuit connection design. Each reference resistor unit and reference inductor unit is loaded with a band switch. The maximum power factor is A. max Take 0.95; The second step is to calculate the load range: determine U according to the required voltage and current range max , U min , I max and I min , and then calculate the maximum impedance Z according to formulas (1) and (2) respectively max and minimum impedance Z min ; The third step is to calculate the resistance range. Combined with the power factor required by the design, the maximum and minimum resistance R are calculated according to formulas (3) and (4) respectively. max and minimum resistance R min , R max =Z max A max (3) R min =Z min A min (4) When the power factor is 1, take the maximum power factor A max is 0.95; minimum power factor A min is 0, the resistance is 0; The fourth step is to calculate the inductance range. Combined with the impedance range and power factor obtained in the second step, the maximum inductance L is designed according to formulas (5) and (6). max and minimum inductance L min : Where, ω = 2πf, f is the frequency of the alternating current, which is 50 Hz; Step 5: The segmentation adopts the method of combining position and binning; firstly, select the appropriate bin d; First take d = 10; The d represents the bin, and w represents the percentile; Step 6: After determining the value of the bin d, calculate the bit w according to the impedance range obtained in step 2 according to formula (7); Step 7: Perform accuracy check based on the value of bin d and the calculated bit w; The conditions for meeting the accuracy requirements of the minimum current are: If the obtained accuracy meets the accuracy requirement of the minimum current, proceed to step 8; if the obtained accuracy does not meet the accuracy requirement of the minimum current, return to step 5 and change the d value; the change step length of the d value is 1; Step 8. If the accuracy requirement of the minimum current is met, take the step d and position w as an example to design a segmented AC adjustable load. The step on each position w can be different during the design. For the convenience of design, the same step d can be selected and the reference resistance on each position can be solved: Assume the impedance range is Z min ~Z max , the corresponding resistance and inductance are R min ~R max and L min ~L max ; Take greater than R max The smallest integer of , and record it as R; take a value greater than L max The smallest integer of , and record it as L; First position: The reference resistor R1 is There are d files in total; Second place: The reference resistor R2 is There are d files in total; … The wth position: reference resistance R w for There are d files in total; Then solve for the reference inductance at each bit: First position: The reference inductance L1 is There are d files in total; Second place: The reference inductance L2 is There are d files in total; … The wth position: reference inductance L w for There are d files in total; Thus, the reference resistance and reference inductance on each bit are obtained; Then, the resistance R and inductance L that meet the design requirements are obtained, and the inductance and resistance are connected in series to complete the design of the segmented AC inductive adjustable load.

2. The design method of the segmented AC inductive adjustable load as claimed in claim 1, It is characterized in that each reference resistor unit comprises d reference resistors connected in series; Each of the reference inductance units includes d reference inductors connected in series; Each reference resistance unit and reference inductance unit is connected in series with a band switch; The d is ≤ 20; the w is ≤ 20; both are natural numbers.

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