Temperature rise adjusting method of dv / dt amplitude reduction filter

Abstract

The invention relates to the technical field of temperature rise adjustment, and particularly discloses a temperature rise adjustment method of a dv / dt amplitude reduction filter, which comprises the following steps: S1, setting a voltage range of the filter, and setting an environment temperature range; obtaining the temperature rise of the filter under the same environment temperature and different voltages, and obtaining a curve that the temperature rise of the filter changes along with the voltage and the environment temperature through nonlinear regression analysis; s2, when the temperature rise of the filter is greater than or equal to a preset value, setting an ideal temperature rise value of the filter, obtaining a real-time environment temperature, and substituting the real-time environment temperature into a curve that the temperature rise of the filter changes along with the voltage and the environment temperature to obtain a target voltage; and S3, when the Upeak value of the filter is greater than or equal to a preset value, adjusting the load at a preset fixed load interval until the Upeak value is less than the preset value, and reducing the temperature rise of the filter and the Upeak value. According to the invention, the relationship between the temperature rise of the filter and the Upeak value can be balanced, the service life of equipment is prolonged, and the system performance and reliability are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of temperature rise regulation, and particularly relates to a method for regulating the temperature rise of a dv / dt reduction filter. Background Art

[0002] A filter is an electronic circuit or device used to selectively pass or block signals of different frequencies. Its core functions include but are not limited to the following: 1. Frequency selection: allowing signals within a specific frequency range to pass through while blocking (or greatly attenuating) signals of other frequencies; 2. Interference elimination: in power lines or other signal lines, a filter can effectively reduce or eliminate unwanted frequency components, such as high-frequency interference, thereby protecting devices from its harm.

[0003] The temperature rise of a filter refers to the phenomenon that its internal temperature rises due to the passage of current during operation. When the filter is working, due to the existence of internal resistance and other factors, energy loss will occur, and this part of the energy is ultimately converted into heat, resulting in an increase in the temperature of the device. The magnitude of this temperature rise is one of the important indicators for measuring the performance of the filter because it is directly related to the reliability and stability of the filter. For example, the temperature drift characteristic: the operating frequency of the filter will drift with the change of temperature, and this phenomenon is called temperature drift. Temperature drift will cause the passband of the filter to shift, thereby affecting the insertion loss of the passband, especially the loss at the edge position of the passband, and the suppression ratio outside the band, which is particularly crucial for application scenarios requiring precise frequency response.

[0004] In the chemical industry, the temperature rise requirement for filters is generally less than about 70°C. This is because too high a temperature rise of the filter will lead to a decline in its performance or even damage. The Upeak value refers to the peak-to-peak voltage that the filter can reach during operation. The Upeak value and the temperature rise of the filter are in an opposing relationship, that is, a lower temperature rise requirement means a larger actual Upeak value. This means that if a lower temperature rise of the filter is required, its Upeak value will increase accordingly, and vice versa, and it is not easy to balance the two. Based on this, a method for regulating the temperature rise of a dv / dt reduction filter is provided to balance the relationship between the temperature rise and the Upeak value of the filter, extend the service life of the device, and improve the system performance and reliability. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for regulating the temperature rise of a dv / dt reduction filter to solve the above technical problems.

[0006] The purpose of the present invention can be achieved by the following technical solutions: A method for regulating the temperature rise of a dv / dt reduction filter includes the following steps: S1: Set the voltage range of the filter [V min ,Vmax , and set the environmental temperature range [K min , K max ; While keeping the environmental temperature constant, adjust the voltage of the filter from low to high at a preset fixed voltage interval, and obtain the temperature rise of the filter after a preset time interval; Adjust the environmental temperature from low to high at a preset environmental temperature interval, and after each adjustment of the environmental temperature, repeat the above steps to obtain the temperature rise of the filter at the same environmental temperature but different voltages, and obtain the curve f(V, K) of the temperature rise of the filter varying with voltage and environmental temperature through non-linear regression analysis; S2: Collect the temperature rise T of the filter in real time rea , set the temperature rise threshold T of the filter thr , when there is a temperature rise T of the filter rea ≥T thr , set the ideal temperature rise value T of the filter ide , and obtain the real-time environmental temperature K rea , and substitute it into the curve f(V, K) of the temperature rise of the filter varying with voltage and environmental temperature to obtain the target voltage V goa , and adjust the voltage of the filter to the target voltage V goa ; S3: Obtain the Upeak value of the filter in real time. When the Upeak value of the filter is greater than or equal to the preset value, adjust the load at a preset fixed load interval until the Upeak value is less than the preset value.

[0007] As a further solution of the present invention: In the step S1, the voltage range [V min , V max is determined by the type and model of the filter. For example, a filter for a 50Hz single-phase power supply may have a rated voltage of 250V, while a filter for a three-phase power supply may have a rated voltage of 440V. This rated voltage ensures that the filter operates under safe working conditions and prevents internal components from being damaged due to excessive voltage.

[0008] As a further solution of the present invention: In the step S1, the process of setting the environmental temperature range specifically includes: Set m monitoring cycles, where m is a preset value, set the monitoring area, obtain the minimum value of the environmental temperature in the monitoring area within m monitoring cycles, and use it as the lower limit K of the environmental temperature range min ; Similarly, obtain the upper limit K of the environmental temperature range max .

[0009] As a further solution of the present invention: In the step S1, the process of obtaining the temperature rise of the filter specifically includes: Set a number of acquisition points on the filter at a preset fixed distance interval, obtain the temperature rise of the filter at each acquisition point, and calculate the average value as the temperature rise of the filter.

[0010] As a further solution of the present invention: In the process of calculating the average value, the following steps are further included: Calculate the evaluation difference ΔC = |Ci - C'|, where Ci represents the temperature rise measured at the i-th acquisition point, and C' is the average value. When there is an evaluation difference ΔC greater than or equal to a preset value, discard Ci and recalculate the average value.

[0011] As a further solution of the present invention: In the step S2, the ideal value T of the filter temperature rise ide The setting process specifically includes: Obtain the voltage V at the current time rea and the ambient temperature K rea , set the voltage range [V rea - V', V rea + V'], where V' is a preset value, set the ambient temperature range [K rea - K', K rea + K'], where K' is a preset value; Set n evaluation cycles, n is a preset value, obtain the ambient temperature in the evaluation cycles, screen out the ambient temperature within the ambient temperature range defined above, and define it as the initial temperature; Obtain the voltage of the filter when the ambient temperature is the to-be-determined temperature, and screen out the voltage within the voltage range defined above, and define it as the data voltage. Take the ambient temperature corresponding to the target voltage as the data temperature; Obtain the temperature rise of the filter corresponding to both the data voltage and the data temperature, and calculate the average value as the ideal value of the filter temperature rise.

[0012] As a further solution of the present invention: In the process of adjusting the filter voltage in the step S2, when the target voltage is outside the preset voltage adjustment range, the following steps are executed: Define the voltage within the voltage adjustment range as the to-be-determined voltage; Calculate the difference between the target voltage and the to-be-determined voltage, and obtain the minimum value among them. Adjust the voltage to the voltage corresponding to the minimum value.

[0013] As a further solution of the present invention: in step S3, during the process of adjusting the load, a load adjustment range is set. When there is a load within the load adjustment range that cannot make the Upeak value less than the preset value, record the Upeak value after each load adjustment, and obtain the load corresponding to the minimum value among them, which is defined as the first load, and adjust the load to the first load.

[0014] Beneficial effects of the present invention: In the chemical industry, the temperature rise requirement of the filter is generally less than about 70°C. The Upeak value refers to the peak-to-peak voltage that the filter can reach during operation, and the temperature rise of the filter and the Upeak value are in an opposing relationship, and it is not easy to balance the two. In the present invention, first, the voltage range and the ambient temperature range of the filter are set; it can be understood that the voltage range is determined according to the model and type of the filter. Different models of filters have different rated voltages. Exceeding the rated voltage may cause damage to the filter, while a lower voltage will affect the normal operation of the equipment, thereby affecting the overall performance of the system. Therefore, it is necessary to determine the voltage range of the filter; setting the ambient temperature range is to reduce the amount of experiments, thereby reducing the amount of data and improving the data processing efficiency. Therefore, the temperature conditions in the past m years in the area where the filter works are selected, and the maximum and minimum values are determined, that is, the ambient temperature range; then, the temperature rise data of the filter at different ambient temperatures and voltages are obtained, and the curve f(V, K) of the temperature rise of the filter changing with voltage and ambient temperature is obtained through non-linear regression analysis; it can be understood that in actual situations, both the ambient temperature and the voltage will affect the temperature rise of the filter. The higher the voltage, the higher the temperature rise of the filter, and the higher the ambient temperature, the higher the temperature rise of the filter. Considering the two factors comprehensively improves the accuracy of the data. At the same time, in actual situations, there is also a potential mutual influence between the ambient temperature and the voltage. Therefore, the non-linear regression analysis method is used to obtain the curve f(V, K) of the temperature rise of the filter changing with voltage and ambient temperature. Non-linear regression analysis can accurately establish a complex relationship model between the temperature rise and the voltage, which helps to better control and predict the performance of the filter in the future. After that, the voltage of the filter is adjusted by obtaining the ambient temperature in real time and combining with the ideal value of the temperature rise of the filter, so as to achieve the purpose of controlling the temperature rise of the filter. It can be understood that when the temperature of the filter exceeds the set threshold, reducing the voltage can reduce heat generation and prevent the device from being damaged due to overheating. At the same time, the influence of the ambient temperature is considered, making the control of the temperature rise of the filter more accurate. Finally, the Upeak value of the filter is monitored in real time, and when the Upeak value is abnormal, the size of the load is adjusted to ensure that the Upeak value is within a reasonable range, while ensuring that the temperature rise of the filter does not exceed the limit and the Upeak value is reasonable. The present invention can balance the relationship between the temperature rise and the Upeak value of the filter, extend the service life of the equipment, and improve the performance and reliability of the system. Description of the Drawings

[0015] The present invention will be further described below with reference to the accompanying drawings.

[0016] Figure 1 It is a schematic flowchart of a method for adjusting the temperature rise of a dv / dt reduction filter according to the present invention. Detailed Embodiments

[0017] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0018] Please refer to Figure 1 As shown, the present invention is a method for adjusting the temperature rise of a dv / dt reduction filter, including the following steps: S1: Set the voltage range [V min , V max of the filter, and set the ambient temperature range [K min , K max ; Under the condition of keeping the ambient temperature unchanged, adjust the voltage of the filter from low to high at a preset fixed voltage interval, and obtain the temperature rise of the filter after a preset time interval; Adjust the ambient temperature from low to high at a preset ambient temperature interval, and after each adjustment of the ambient temperature, repeat the above steps to obtain the temperature rise of the filter at the same ambient temperature and different voltages, and obtain the curve f(V, K) of the temperature rise of the filter changing with voltage and ambient temperature through non-linear regression analysis; S2: Collect the temperature rise T rea of the filter in real time, set the temperature rise threshold T thr of the filter. When there is the temperature rise Trea ≥T thr When it is ≥T, set the ideal value T of the filter temperature rise ide , and obtain the real-time ambient temperature K rea , and substitute it into the curve f(V, K) of the filter temperature rise varying with voltage and ambient temperature to obtain the target voltage V goa , and adjust the voltage of the filter to the target voltage V goa ; S3: Obtain the Upeak value of the filter in real time. When the Upeak value of the filter is greater than or equal to the preset value, adjust the load at a preset fixed load interval until the Upeak value is less than the preset value.

[0019] It should be noted that in the chemical industry, the temperature rise requirement of the filter is generally less than about 70°C. The Upeak value refers to the peak-to-peak voltage that the filter can reach during operation, and the temperature rise of the filter and the Upeak value are in an opposing relationship, and it is not easy to balance the two. In the present invention, first, the voltage range and ambient temperature range of the filter are set; it can be understood that the voltage range is determined according to the model and type of the filter. Different models of filters have different rated voltages. Exceeding the rated voltage may cause damage to the filter, while a lower voltage will affect the normal operation of the equipment and thus the overall performance of the system. Therefore, it is necessary to determine the voltage range of the filter; setting the ambient temperature range is to reduce the amount of experiments, thereby reducing the amount of data and improving the data processing efficiency. Therefore, the temperature conditions in the past m years in the area where the filter operates are selected, and the maximum and minimum values are determined, that is, the ambient temperature range; then, the temperature rise data of the filter at different ambient temperatures and voltages are obtained, and the curve f(V, K) of the filter temperature rise varying with voltage and ambient temperature is obtained through nonlinear regression analysis; it can be understood that in actual situations, both the ambient temperature and voltage will affect the temperature rise of the filter. The higher the voltage, the higher the temperature rise of the filter, and the higher the ambient temperature, the higher the temperature rise of the filter. Considering the two factors comprehensively improves the accuracy of the data; At the same time, in actual situations, the ambient temperature and voltage also have a potential mutual influence. Therefore, the nonlinear regression analysis method is used to obtain the curve f(V, K) of the filter temperature rise varying with voltage and ambient temperature. Nonlinear regression analysis can accurately establish a complex relationship model between the temperature rise and voltage, which helps to better control and predict the performance of the filter subsequently; After that, the voltage of the filter is adjusted by obtaining the ambient temperature in real time and combining it with the ideal value of the filter temperature rise, so as to achieve the purpose of controlling the filter temperature rise. It can be understood that when the temperature of the filter exceeds the set threshold, reducing the voltage can reduce heat generation and prevent the device from being damaged due to overheating. At the same time, the influence of the ambient temperature is considered, making the control of the filter temperature rise more accurate. Finally, the Upeak value of the filter is monitored in real time, and when the Upeak value is abnormal, the size of the load is adjusted to ensure that the Upeak value is within a reasonable range, while ensuring that the filter temperature rise does not exceed the limit and the Upeak value is reasonable.

[0020] In another preferred embodiment of the present invention, in the step S1, the voltage range [V min , V max of the filter is determined by the type and model of the filter. For example, the rated voltage of a filter for a 50Hz single-phase power supply may be 250V, while the rated voltage of a filter for a three-phase power supply may be 440V. This rated voltage ensures that the filter operates under safe working conditions and prevents internal components from being damaged due to excessive voltage.

[0021] It should be noted that different models of filters have different rated voltages. Exceeding the rated voltage may cause damage to the filter, while a lower voltage will affect the normal operation of the equipment and thus the overall performance of the system. Therefore, it is necessary to determine the voltage range of the filter.

[0022] In another preferred embodiment of the present invention, in the step S1, the process of setting the ambient temperature range specifically includes: Set m monitoring cycles, where m is a preset value. Set the monitoring area, obtain the minimum value of the ambient temperature in the monitoring area within m monitoring cycles, and use it as the lower limit K min ; Similarly, obtain the upper limit K max of the ambient temperature range.

[0023] It can be understood that the duration of each monitoring cycle is one year, and the monitoring area is the area where the current filter is working. The ambient temperature range is determined by the maximum and minimum temperatures in the recent m years, that is, the ambient temperature range, which can reduce unnecessary time and thus reduce the amount of data to be processed subsequently, improving the overall processing efficiency of the system.

[0024] In another preferred embodiment of the present invention, in the step S1, the process of obtaining the filter temperature rise specifically includes: Set a number of acquisition points on the filter at a preset fixed distance interval, obtain the temperature rise of the filter at each acquisition point, and calculate the mean value as the temperature rise of the filter.

[0025] It should be noted that in actual situations, the temperature rises at different positions of the filter may be different. The reasons include: 1. Heat conduction path: The heat dissipation conditions at different positions may be different. Some areas may be closer to heat dissipation components or have better heat conduction paths, so the temperature rise is smaller. For those areas with poor heat dissipation conditions, the temperature rise may be higher due to heat accumulation; 2. Device layout: The layout of devices on the circuit board also affects the temperature rise. If there are more devices or they are arranged closely in a certain area, it may cause local hot spots, thus affecting the temperature rise in that area. Therefore, the acquisition points are selected and the average value of the temperature rises at the acquisition points is calculated to obtain the temperature rise of the filter, so as to improve the accuracy of the data. At the same time, the acquisition points are evenly distributed, which can reduce the probability of errors.

[0026] In another preferred embodiment of the present invention, during the process of calculating the average value, the following steps are further included: Calculate the evaluation difference ∆C = |Ci - C'|, where Ci represents the temperature rise measured at the i-th acquisition point, and C' is the average value of the temperature rise of the filter. When the evaluation difference ∆C is greater than or equal to the preset value, discard Ci and recalculate the average value.

[0027] It should be noted that the purpose of doing this is to reduce errors. When the evaluation difference is greater than or equal to the preset value, it indicates that the difference between the temperature rise at the corresponding acquisition point and the average value is too large, which may be caused by measurement errors or other reasons. Therefore, discard the temperature rise at this acquisition point and recalculate the average value to improve the accuracy of subsequent processing.

[0028] In another preferred embodiment of the present invention, in step S2, the ideal value T of the temperature rise of the filter ide The setting process specifically includes: Obtain the voltage Vrea and the ambient temperature Krea at the current time, set the voltage range [Vrea - V', Vrea + V'], where V' is a preset value, and set the ambient temperature range [Krea - K', Krea + K'], where K' is a preset value; Set n evaluation periods, n is a preset value, obtain the ambient temperatures in the evaluation periods, and screen out the ambient temperatures that belong to the ambient temperature range defined above, and define them as the initial temperatures; Obtain the voltage of the filter when the ambient temperature is the pending temperature, and screen out the voltages that belong to the voltage range defined above, and define them as the data voltages. Take the ambient temperature corresponding to the target voltage as the data temperature; Obtain the temperature rise corresponding to the filter that is both the data voltage and the data temperature, and calculate the average value as the ideal value of the temperature rise of the filter.

[0029] It can be understood that the purpose of doing this is to ensure the normal operation of the filter while reducing the temperature rise. Although a low temperature rise can ensure the service life of the equipment, when adjusting the temperature rise of the filter by adjusting the voltage in this solution, blindly pursuing a low temperature rise may lead to too low voltage, which in turn may cause the equipment to malfunction and affect the overall performance of the system. Therefore, an evaluation period is set, where each evaluation period is one day, and the temperature rise at the same voltage and ambient temperature as the current time in the past n days is obtained as the ideal temperature rise value, which can ensure the performance of the equipment while adjusting the temperature rise.

[0030] In another preferred embodiment of the present invention, in step S2, during the process of adjusting the filter voltage, when the target voltage is outside the preset voltage adjustment range, the following steps are executed: Define the voltage within the voltage adjustment range as the undetermined voltage; Calculate the difference between the target voltage and the undetermined voltage, and obtain the minimum value among them, and adjust the voltage to the voltage corresponding to the minimum value.

[0031] It is worth noting that too low filter voltage may cause the system to malfunction or the working performance to decline; too high voltage may cause the system to generate too much heat, increase energy consumption and may damage circuit components. Therefore, it is set that during the process of adjusting the voltage, the voltage should be maintained within the set voltage adjustment range. When the target voltage does not exist within the voltage range, the voltage closest to the target voltage is selected to ensure the system performance and the service life of the equipment as much as possible.

[0032] In another preferred embodiment of the present invention, in step S3, during the process of adjusting the load, a load adjustment range is set. When the load within the load adjustment range cannot make the Upeak value less than the preset value, record the Upeak value after each load adjustment, and obtain the load corresponding to the minimum value among them, and define it as the first load, and adjust the load to the first load.

[0033] It is worth noting that by setting the load range, the adjustment amplitude can be limited to ensure adjustment within a controllable range and avoid exceeding the range that the system can withstand; selecting the load corresponding to the minimum value as the first load is because this load can make the Upeak value as close as possible to the preset value, ensuring that the system is as close as possible to the best working state under the condition of meeting the preset conditions.

[0034] The above has described a detailed description of an embodiment of the present invention, but the content described above is only the preferred embodiment of the present invention and cannot be considered as limiting the scope of implementation of the present invention. All equivalent changes and improvements made according to the scope of the present invention application should still fall within the scope covered by the patent of the present invention.

Claims

1. A method for regulating the temperature rise of a dv / dt reduction filter, characterized in that: The following steps are involved: S1: Set the voltage range of the filter [V min , V max ], and set the ambient temperature range [K min , K max ]; Under the condition of keeping the ambient temperature constant, adjusting the voltage of the filter from low to high at a preset fixed voltage interval, and obtaining the temperature rise of the filter after a preset time interval; Adjust the ambient temperature from low to high at a preset ambient temperature interval, and repeat the above steps after each adjustment of the ambient temperature, obtain the temperature rise of the filter under the same ambient temperature and different voltages, and obtain the curve f(V, K) of the temperature rise of the filter as a function of voltage and ambient temperature through nonlinear regression analysis; S2: Real-time acquisition of filter temperature rise T rea , set the filter temperature rise threshold T thr , when there is a temperature rise of the filter T rea ≥T thr When the filter temperature rise is set to the ideal value T ide , and obtain the real-time ambient temperature K rea , and substitute the curve f(V, K) of the temperature rise of the filter with the change of voltage and ambient temperature to obtain the target voltage V goa , and adjust the filter voltage to the target voltage V goa ; S3: acquiring the Upeak value of the filter in real time, and when the Upeak value of the filter is greater than or equal to a preset value, adjusting the load at a preset fixed load interval until the Upeak value is less than the preset value.

2. The temperature rise adjustment method of a dv / dt reduction filter according to claim 1, characterized in that: In step S1, the voltage range of the filter [V min , V max ] Determined by the type and model of the filter. For example, a filter for a 50Hz single-phase power supply may have a rated voltage of 250V, while a filter for a three-phase power supply may have a rated voltage of 440V. This rated voltage ensures that the filter operates under safe working conditions and prevents damage to internal components due to excessive voltage.

3. The temperature rise adjustment method of a dv / dt reduction filter according to claim 1, characterized in that: In step S1, the process of setting the ambient temperature range specifically includes: Set m monitoring cycles, where m is a preset value, set a monitoring area, obtain the minimum value of the ambient temperature in the monitoring area within m monitoring cycles, and use it as the lower limit K of the ambient temperature range min ; Similarly, get the upper limit K of the ambient temperature range max .

4. The temperature rise adjustment method of a dv / dt reduction filter according to claim 1, characterized in that: In step S1, the process of obtaining the filter temperature rise specifically includes: A plurality of collection points are set on the filter at preset fixed distance intervals, and the temperature rise of the filter is obtained at each collection point, and the average is calculated as the temperature rise of the filter.

5. The temperature rise adjustment method of a dv / dt reduction filter according to claim 4, characterized in that: The process of calculating the mean also includes the following steps: Calculate the evaluation difference ∆C=|Ci-C'|, where Ci represents the temperature rise measured at the i-th collection point, and C' is the mean value. When the evaluation difference ∆C is greater than or equal to the preset value, remove and discard Ci and recalculate the mean value.

6. The temperature rise adjustment method of a dv / dt reduction filter according to claim 1, characterized in that: In step S2, the ideal filter temperature rise value T ide The setting process specifically includes: Get the voltage Vrea and ambient temperature Krea at the current time, set the voltage range [Vrea-V', Vrea+V'], where V' is the preset value, and set the ambient temperature range [Krea-K', Krea+K'], where K' is the preset value; Set n evaluation cycles, where n is a preset value, obtain the ambient temperature in the evaluation cycle, and select the ambient temperature that falls within the ambient temperature range, which is defined as the initial temperature; The voltage of the filter when the ambient temperature is the undetermined temperature is obtained, and the voltage belonging to the voltage range is screened out and defined as the data voltage, and the ambient temperature corresponding to the target voltage is used as the data temperature; The temperature rise corresponding to the filter which is both the data voltage and the data temperature is obtained, and the average is calculated as the ideal value of the filter temperature rise.

7. The temperature rise regulation method of a dv / dt reduction filter according to claim 1, characterized in that: In the step S2, during the process of adjusting the filter voltage, when the target voltage is outside the preset voltage adjustment range, the following steps are performed: The voltage within the voltage regulation range is defined as a pending voltage; The difference between the target voltage and the to-be-determined voltage is calculated, and the minimum value thereof is obtained, and the voltage is adjusted to the voltage corresponding to the minimum value.

8. The temperature rise adjustment method of a dv / dt reduction filter according to claim 1, characterized in that: In the step S3, during the process of adjusting the load, a load adjustment range is set. When there is a load within the load adjustment range that cannot make the Upeak value less than the preset value, the Upeak value after each load adjustment is recorded, and the load corresponding to the minimum value is obtained and defined as the first load, and the load is adjusted to the first load.

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