Remaining life prediction device and remaining life prediction method for fuse

Abstract

To provide a remaining life prediction device capable of predicting the remaining life of a fuse with high precision.SOLUTION: A remaining life prediction device 1 for a fuse comprises a current sensor 10 which always detects a current flowing in a fuse H, an electric conduction determination part 30, and a damage calculation part 40. The electric conduction determination part 30 determines whether a current value detected by the current sensor 10 is equal to or larger than a first threshold. The damage calculation part 40 integrates a deterioration amount based upon an electric conduction time and the current value when the current value increase to the first threshold or larger, and does not integrate the deterioration amount when the current value is less than the first threshold.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an apparatus and method for predicting the remaining life of a fuse. [Background technology]

[0002] Conventionally, fuses are provided in power supply circuits of electrical equipment to protect the electrical equipment from overcurrent. A fuse has the property that it thermally expands due to Joule heat generated when electricity is applied, and thermally contracts without generating Joule heat when electricity is not applied. When such thermal expansion and thermal contraction are repeated, the fuse element deteriorates due to metal fatigue and may break. In particular, when an overcurrent exceeding a specified value flows when electricity is applied, the difference between thermal expansion and thermal contraction becomes large, making the fuse more likely to break.

[0003] When a fuse blows, electrical equipment cannot operate normally. For this reason, there is known a technique for determining the deterioration of a fuse and predicting the remaining life of the fuse before the fuse blows.

[0004] For example, a fuse deterioration determination device in Patent Document 1 calculates the amount of damage to a fuse per unit time, and integrates the amount of damage by approximating the maximum amount of damage among multiple amounts of damage within a predetermined period of time as the amount of damage for that predetermined period of time. If the integrated value of the amount of damage exceeds a threshold, the deterioration determination device outputs an alert regarding the remaining life of the fuse. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2018-155591 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the fuse deterioration determination device disclosed in Patent Document 1, the maximum amount of damage among multiple amounts of damage within a predetermined period is approximated as the amount of damage for that predetermined period, so there is a possibility that the amount of damage may be overestimated. Therefore, there is a demand for a remaining life prediction device that can predict the remaining life of fuses with higher accuracy.

[0007] SUMMARY OF THE PRESENT EMBODIMENTS Accordingly, an object of the present invention is to provide a remaining life predicting device that can predict the remaining life of a fuse with high accuracy. [Means for solving the problem]

[0008] According to one aspect of the present embodiment, a remaining life prediction device for a fuse includes: a current sensor that constantly detects a current flowing through the fuse; A current flow determination unit; A damage calculation unit; Equipped with The energization determination unit determines whether a current value detected by the current sensor is equal to or greater than a first threshold value, The damage calculation unit: When the current value becomes equal to or greater than the first threshold value, an amount of deterioration is calculated based on a current-flow time and the current value; When the current value is less than the first threshold value, the deterioration amount is not integrated. Effect of the Invention

[0009] According to the present invention, by not integrating the deterioration amount when the current value is less than a predetermined value, the deterioration amount of the fuse can be accurately evaluated and the remaining life of the fuse can be predicted with high accuracy. [Brief description of the drawings]

[0010] [Figure 1] 1 is a block diagram of a remaining life prediction device according to a first embodiment of the present invention. [Diagram 2] FIG. 4 is an internal block diagram of a deterioration amount calculation unit. [Diagram 3] 6 is a graph illustrating waveform data of a fuse current and internal processing of a current flow determination unit. [Figure 4] 11 is a flowchart relating to a process for calculating a current flow time and an integrated value of the square of the absolute value of a fuse current. [Diagram 5] 1 is a graph showing the fusing current characteristics of a fuse. [Figure 6] 1 is a graph showing characteristics of the number of repeated energizations of a fuse and a load factor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, the present embodiment will be described with reference to the drawings. For the sake of convenience, the description of the members having the same reference numbers as those already described in the description of the embodiment will be omitted. Also, for the sake of convenience, the dimensions of each member shown in the drawings may differ from the actual dimensions of each member.

[0012] FIG. 1 is a block diagram of a remaining life prediction device 1 according to the present embodiment. As shown in FIG. 1, the remaining life prediction device 1 includes a current sensor 10, an A / D conversion unit 20, a current conduction determination unit 30, a damage calculation unit 40, a remaining life calculation unit 50, a temperature sensor 60, and a display unit 70. The current conduction determination unit 30 includes a threshold determination unit 31 and a current value integration unit 32. The damage calculation unit 40 includes a current conduction time calculation unit 41, an effective value calculation unit 42, a melting current value calculation unit 43, and a deterioration amount calculation unit 44. The current conduction determination unit 30, the damage calculation unit 40, and the remaining life calculation unit 50 include a memory and a processor. The memory is configured to store computer-readable instructions (programs). For example, the memory is configured with a ROM and a RAM. The processor is configured with at least one of a CPU, an MPU, and a GPU.

[0013] The current sensor 10 is connected in series to a fuse H arranged between a three-phase AC power supply 100 and a power conversion device 200 that converts AC into power, and constantly detects the current value of the AC (hereinafter also referred to as fuse current I) flowing through the fuse H. The A / D conversion unit 20 A / D converts the current value of the fuse current I detected by the current sensor 10. The temperature sensor 60 constantly detects the ambient temperature Th of the fuse H. The display unit 70 is composed of a liquid crystal panel or an organic EL panel, and displays an alert regarding the remaining life of the fuse H outputted by the remaining life calculation unit 50. The AC power supply 100 may be single-phase.

[0014] The threshold determination unit 31 determines whether the absolute value of the A / D converted current value (hereinafter also referred to as the fuse current absolute value Ia) is equal to or greater than a first threshold value Th1. If the maximum value of the fuse current absolute value Ia is equal to or greater than the first threshold value Th1, the threshold determination unit 31 determines that the fuse H is energized, and if the maximum value of the fuse current absolute value Ia is less than the first threshold value Th1, the threshold determination unit 31 determines that the fuse H is not energized. A detailed determination method will be described later.

[0015] The current value integrator 32 integrates the square value of the fuse current absolute value Ia during the period during which the threshold value determiner 31 determines that the fuse H is energized.

[0016] The current-carrying time calculation unit 41 calculates the current-carrying time Ton shown in the waveform data of the fuse current absolute value Ia in Fig. 3. The effective value calculation unit 42 calculates the fuse current effective value Irms, which is the effective value of the fuse current absolute value Ia, based on the integrated value of the squared value of the fuse current absolute value Ia calculated by the current value integrator 32 during the current-carrying time Ton. The fusing current value calculation unit 43 calculates the fusing current value If, ​​which is the minimum current value at which the fuse H is estimated to deteriorate and melt if a current is applied to the fuse H for the current-carrying time Ton. Furthermore, based on the ambient temperature of the fuse H detected by the temperature sensor 60, the fusing current value If' after temperature correction of the fusing current value If is calculated. The deterioration amount calculation unit 44 calculates the deterioration amount D of the fuse H based on the fuse current effective value Irms calculated by the effective value calculation unit 42 and the corrected fusing current value If' calculated by the fusing current value calculation unit 43. The detailed calculation methods for each will be described later.

[0017] 2 is an internal block diagram of the deterioration amount calculation unit 44. The deterioration amount calculation unit 44 includes a load factor calculation unit 45 and a deterioration amount integration unit 46.

[0018] The load factor calculation unit 45 calculates the load factor S from the fuse current effective value Irms calculated by the effective value calculation unit 42 and the corrected fusing current value If'.

[0019] The deterioration amount integrating unit 46 identifies the number of repeated energizations N from the load factor S calculated by the load factor calculating unit 45 and the load factor-current-passing-count characteristics shown in FIG. 6, and calculates the deterioration amount D of the fuse H from the maximum number of energizations Nmax of the fuse H set for each fuse and the number of repeated energizations N. <How to determine if power is on>

[0020] A detailed method for determining whether fuse H is energized will be described with reference to Fig. 3. Fig. 3 is a graph illustrating waveform data of the fuse current and internal processing of the energization determination unit. The fuse current I is an AC current flowing through the fuse H, and is waveform data of a current value detected by the current sensor 10 when the rotation speed of the motor M shown in Fig. 1 is increased. The fuse current absolute value Ia is waveform data representing the absolute value of the fuse current I.

[0021] Here, if the maximum value of the fuse current absolute value Ia is equal to or greater than the first threshold value Th1, the fuse H is determined to be energized, and if it is less than the first threshold value Th1, the fuse H is determined to be de-energized. This prevents overestimation of the degradation amount D by not using the fuse current absolute value Ia less than the first threshold value Th1, which does not affect the degradation of the fuse H, in calculating the degradation amount D of the fuse H. The first threshold value Th1 may be a value calculated by the product of the rated current, steady-state derating, and temperature derating of the fuse H. <How to calculate the power-on time>

[0022] A detailed calculation method for the current-flow time Ton of the fuse H will be described with reference to Fig. 4. Fig. 4 is a flowchart relating to a calculation process for the current-flow time and the integrated value of the square of the absolute value of the fuse current.

[0023] After the calculation process starts (S100), if the maximum value of the fuse current absolute value Ia is equal to or greater than the first threshold value Th1 (Yes in S101), it is determined that the fuse H is energized and the energization flag is set to Hi (S102). Furthermore, during the period in which it is determined that the fuse H is energized, the energization count value n1 is counted up (S103).

[0024] Furthermore, if the maximum value of the fuse current absolute value Ia is less than the first threshold value Th1 in the calculation process, it is determined that the fuse H is not energized (No in S101). Next, it is determined whether the energized flag is Hi (S104). During the period in which it is determined that the fuse H is not energized and the energized flag is Hi (Yes in S104), the non-energized count value n2 is counted up (S105). The calculation process is performed every software update period (for example, 125 μs).

[0025] The reason why the first threshold value Th1 is set for the fuse current absolute value Ia in this way is that when the fuse current absolute value Ia is equal to or greater than the first threshold value Th1, the fuse H is more likely to deteriorate, but when the fuse current absolute value Ia is less than the first threshold value Th1, the fuse H generates less Joule heat and deterioration is less likely to progress. In this way, when the fuse current absolute value Ia is less than the first threshold value Th1, it is determined that no current is flowing and the deterioration amount is not accumulated. This makes it possible to accurately evaluate the deterioration amount of the fuse H and predict the remaining life with high accuracy.

[0026] Thereafter, when the non-energized count value n2 becomes larger than 100 (Yes in S106), the non-energized count value n2 is set to an initial value of 0, and the energized flag is set to Low (S107). At this time, taking into consideration the delay time of the internal processing of the current sensor 10 and the energization determination unit 30, for example, 100 may be subtracted from the energized count value n1 when the energized flag is set to Low (S107). Note that even if it is determined that the fuse H is not energized, the energized count value n1 is counted up (S103) during the period when the energized flag is Hi, that is, during the period when the non-energized count value n2 is 100 or less (No in S106). In this way, even if it is determined that the fuse H is not energized, the energized flag is not immediately set to Low because, depending on the timing, due to the characteristics of the AC waveform, the fuse H may be determined to be non-energized in a certain software update period T, and the fuse H may be determined to be energized before and after that period T. In such a case, it is preferable to determine that the fuse H is energized both before and after the period T.

[0027] In this way, the energization time Ton of fuse H is defined as the period from when the maximum value of the fuse current absolute value Ia becomes equal to or greater than the first threshold value Th1 until when the predetermined time has elapsed since the maximum value becomes less than the first threshold value Th1 (the non-energized count value n2 becomes greater than 100). During the energization time Ton, the energized flag is Hi and the energized count value n1 is counted up.

[0028] Next, the energization time Ton is calculated from the energization count value n1 when the energization flag is set to Low and the software update period T using the following formula. (Formula 1) Ton = n1 × T <How to calculate the effective fuse current>

[0029] A detailed method for calculating the fuse current effective value Irms will be described with reference to FIG. While the energized flag is Hi, the squared value of the fuse current absolute value Ia is integrated (S103). While the energized flag is Low (No in S104) or while the de-energized count value n2 is greater than 100 (Yes in S106), the squared value of the fuse current absolute value Ia is not integrated. When the de-energized count value n2 becomes greater than 100 (Yes in S106) and the energized count value n1 is greater than 28 (Yes in S108), the calculation timing flag is set to Hi (S109), and the integrated value ΣIa 2 is used to calculate the fuse current effective value Irms. If the current count n1 is less than 28 (No in S108), the integrated value ΣIa 2 is small and does not affect the deterioration of the fuse H. In such a case, the current count value n1 and the integrated value ΣIa 2 Set the initial value to 0, and calculate the integral of the squared absolute fuse current Ia up to that point ΣIa 2 is not used in the calculation of the fuse current effective value Irms (S110), thereby preventing overestimation of the deterioration amount D. After steps S103, S109, and S110, the calculation process ends (S111). The calculation timing flag is set to 0 when the integration process, such as the integration of the squared value of the fuse current absolute value Ia, is completed and the integration value ΣIa 2 This indicates that the fuse current effective value Irms is calculated based on the

[0030] Next, the integrated value ΣIa of the square of the absolute fuse current Ia 2 From the energization count value n1 and the power supply count value n2, the fuse current effective value Irms is calculated using the following formula. (Formula 2) Irms = (ΣIa 2 / n1) 1 / 2 Regarding the fuse current effective value Irms calculated by the above formula, it can be considered that the Joule heat generated when the fuse current Ia, which is an AC current shown in Fig. 3, flows through the fuse H is equivalent to the Joule heat generated when a DC current with the same value as the fuse current effective value Irms flows through the fuse H. Therefore, by using the fuse current effective value Irms, it is possible to calculate the amount of deterioration of the fuse H when an AC current flows through it and to predict the remaining life with high accuracy. <How to calculate fusing current>

[0031] A method for calculating the fusing current value If of fuse H will be described with reference to FIG. 5. FIG. 5 is a graph showing the fusing current characteristics of fuse H. The vertical axis shows the fusing current value If, ​​and the horizontal axis shows the current flow time Ton. The fusing current value If is the minimum current value at which fuse H melts when a direct current is passed through fuse H for the current flow time Ton. The fusing current characteristics are characteristics specific to the fuse and are determined by the material of the fuse, etc. Based on the fusing current characteristics, the corresponding fusing current value If can be calculated from the current flow time Ton in the graph of FIG. 5.

[0032] Furthermore, a correction coefficient K for temperature correction of the fusing current value If is calculated based on the ambient temperature of the fuse H detected by the temperature sensor 60, and the fusing current value If is multiplied by the correction coefficient K to calculate the corrected fusing current value If'. Such temperature correction is performed because the ambient temperature of the fuse H affects the speed at which Joule heat generated in the fuse H is released to the outside of the fuse H. By using the corrected fusing current value If', it is possible to predict the remaining life with high accuracy, taking into account the ambient temperature of the fuse H. <How to calculate the load factor>

[0033] The load factor S is calculated from the fuse current effective value Irms and the corrected fusing current value If' using the following formula. (Formula 3) S=Irms / If' <How to calculate the number of repeated energizations>

[0034] A method for calculating the number of repeated energizations N of fuse H will be described with reference to Fig. 6. Fig. 6 is a graph showing the characteristics of the number of repeated energizations and the load factor of fuse H. The vertical axis shows the number of repeated energizations N, and the horizontal axis shows the load factor S. The characteristic graph of fuse H shown in Fig. 6 is expressed by the following formula. (Formula 4) N=S -22 The number of repeated energizations N is calculated using the load factor S calculated by the load factor calculation method, using the above formula. Note that the above characteristic graph and formula differ for each fuse. <How to calculate the amount of deterioration>

[0035] The deterioration amount D is calculated using the following formula from the maximum number of energization times Nmax and the number of repeated energization times N that are preset for the fuse H. The maximum number of energization times Nmax is, for example, 5.25 million times. (Formula 5) D=Nmax / N <How to calculate remaining life>

[0036] The remaining life RL is calculated as a percentage using the following formula based on the integrated value of the possible number of energization times Nmax and the deterioration amount D. (Formula 6) RL=100-ΣD / Nmax If the calculated remaining life RL is smaller than the second threshold value Th2, an alert regarding the remaining life is output to the display unit 70 shown in FIG.

[0037] As described above, the remaining life prediction device according to the embodiment of the present invention can predict the remaining life of a fuse with high accuracy by not integrating the deterioration amount when the absolute value of the fuse current and the integrated value of the square of the absolute value of the fuse current are less than a predetermined value. Also, by temperature-correcting the fusing current value based on the ambient temperature of the fuse detected by a temperature sensor, it becomes possible to predict the remaining life of the fuse with high accuracy, taking into account the ambient temperature of the fuse.

[0038] Although the embodiment of the present invention has been described above, it goes without saying that the technical scope of the present invention should not be interpreted as being limited by the description of the embodiment. The embodiment is merely an example, and it is understood by those skilled in the art that various modifications of the embodiment are possible within the scope of the invention described in the claims. The technical scope of the present invention should be determined based on the scope of the invention described in the claims and its equivalents. [Explanation of symbols]

[0039] 1: Remaining life prediction device 10: Current sensor 20: A / D conversion section 30: Energization determination section 31: Threshold judgment unit 32: Current value integrator 40: Damage calculation section 41: Current flow time calculation unit 42: Effective value calculation section 43: Fusing current value calculation section 44: Deterioration amount calculation section 45: Load factor calculation section 46: Deterioration amount calculation unit 50: Remaining life calculation part 60: Temperature sensor 70: Display section 100: Three-phase AC power supply 200: Power conversion device H: Fuse M: Motor

Claims

1. A fuse remaining life predictor, comprising: a current sensor that constantly detects a current flowing through the fuse; A current flow determination unit; A damage calculation unit; Equipped with The energization determination unit determines whether a current value detected by the current sensor is equal to or greater than a first threshold value, The damage calculation unit: When the current value becomes equal to or greater than the first threshold value, an amount of deterioration is calculated based on a current-flow time and the current value; The remaining life prediction device does not integrate the deterioration amount when the current value is less than the first threshold value.

2. The remaining life prediction device includes: a remaining life calculation unit that calculates a remaining life of the fuse from the accumulated deterioration amount, The remaining life prediction device according to claim 1 , wherein the remaining life calculation unit outputs an alert regarding the remaining life of the fuse when the remaining life is smaller than a second threshold value.

3. The remaining life prediction device includes: a temperature sensor for detecting an ambient temperature of the fuse; The damage calculation unit: Calculate the current application time, Calculating an effective value of the current value during the energization time; calculating a fusing current value, which is a minimum current value at which the fuse melts when a current is passed through the fuse for the current passing time, from the current passing time; correcting the fusing current value by multiplying it by a correction coefficient based on the ambient temperature; Calculating a load factor from the effective value of the current value and the corrected fusing current value; Calculating the number of repeated energizations from the load factor and the load factor-energization number characteristics; 2. The remaining life predicting device according to claim 1, further comprising: an accumulation step for accumulating the amount of deterioration calculated by dividing a number of times that the fuse can be energized, the number of times the fuse can be repeatedly energized.

4. The remaining life prediction device according to claim 1 , wherein the first threshold value is a product of a rated current, a steady-state derating, and a temperature derating of the fuse.

5. 2 . The remaining life prediction device according to claim 1 , wherein the current flow time is a period from when the current value becomes equal to or greater than the first threshold value until a predetermined time has elapsed since the current value becomes less than the first threshold value.

6. 1. An electronic device having a fuse, comprising: The remaining life prediction device according to claim 2 ; A display unit that displays the alert output by the remaining life calculation unit.

7. A method for predicting a remaining life of a fuse, comprising: causing a processing device having a processor to execute a computer program recorded in a non-volatile memory, the method comprising: When a current value flowing through the fuse is equal to or greater than a first threshold value, an amount of deterioration is calculated based on a current flow time and the current value, and the amount of deterioration is stored in the non-volatile memory; The remaining life prediction method includes not integrating the deterioration amount when the current value is less than the first threshold value.

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