JP4321712B2 - Fuse blow time simulation circuit and simulation method - Google Patents

Description

  The present invention relates to a simulation circuit and a simulation method for calculating a fusing time of a fuse incorporated in an apparatus. In particular, the fusing time of a fuse incorporated in the apparatus is calculated in advance, and the apparatus is continuously driven within that time. As a result, the fuse can be used for a long period of time, and maintenance of the apparatus in which the fuse is incorporated is facilitated.

  Conventional fuse models for simulation have been modeled by measuring while flowing current until the fuse is actually blown. That is, the temporal change of the fuse resistance is calculated from the change in current and voltage during measurement. The fuse was modeled as a resistance that changes with time and incorporated into the simulator.

  FIG. 14 shows an example of the resistance change of the fuse calculated from the current and voltage waveform that has passed through the fuse. Such data is obtained by experiment. In other words, it is necessary to conduct an experiment each time the rated capacity of the fuse, the composition and structure of the metal change, and obtain data on resistance change when the fuse is blown.

ここでＲはヒューズ抵抗を含む回路抵抗、Ｌはケーブルインダクタンス、Ｅは電源電圧である。(1)式をi(t)について解くと、(2)式になる。

(2)式を用いることより、熱量積分値Ｗ₁ は(3)式で表される。

Regarding the calculation of the fusing time, the current flowing through the fuse is calculated using the fuse test circuit of FIG. There is a method of setting the fusing time when the energy accumulated in the fuse, that is, the integrated value of heat reaches the reference energy (allowable energy).
First, an integral value of heat W ₁ that is energy stored in the fuse is obtained. The time when the shorting switch is turned on is set to t = 0. The current i (t) after t seconds is expressed by equation (1).

Here, R is a circuit resistance including a fuse resistance, L is a cable inductance, and E is a power supply voltage. When equation (1) is solved for i (t), equation (2) is obtained.

By using the equation (2), the heat integration value W ₁ is expressed by the equation (3).

On the other hand, the allowable energy value W ₂ often uses a part of the catalog value provided by the manufacturer. When a fuse used for communication has a current large enough to cut off within about 10 ms, the allowable energy value is often constant regardless of the fusing time. Therefore, W ₂ can be regarded as a constant.

The time t when W ₁ = W ₂ is the fusing time. FIG. 16 shows a graph for explaining the fuse blowing time. This graph shows the change over time in the heat energy integrated value obtained by substituting the allowable energy value, a certain inductance value, and resistance value into the right side of Equation (3). The intersection of the allowable energy value and the calorific integral value obtained by calculation is the fusing time.

  The above solution is valid only when the fuse has a large passing current that blows within about 10 ms. When the passing current to the fuse is small, that is, when the fusing time is lengthened, the allowable energy value changes with time, and the calculation becomes complicated. Also, whenever the circuit constant changes, the calorific value and fusing time are derived. Then, it becomes necessary to build a simulation circuit by inputting this value into the fuse switch.

  Further, when the fuse is incorporated in a large-scale power supply system circuit as shown in FIG. 17B, the interaction between the plurality of circuit elements becomes strong. Therefore, the fuse blow time cannot be analyzed using the parameters of the simple circuit shown in FIG.

  FIG. 18 shows the difference in current passing through the fuse between the simple circuit (FIG. 17A) and the large-scale power feeding system circuit (FIG. 17B). In FIG. 17, it can be seen that even if the inductance value and the resistance value included in the short circuit are the same, the current increase rate of the large-scale power feeding circuit is small and the steady-state current value is also small compared to the simple circuit. Therefore, the time for reaching the allowable energy value, that is, the fusing time and the passing current immediately before fusing differ between the simple circuit and the large-scale power feeding system circuit.

  An object of the present invention is to solve the above-described problems in the prior art. Provided is a simulation circuit and method for easily and accurately determining a fuse blow time even when a current passing through a fuse is small or when a fuse is incorporated in a complicated circuit.

The fuse blow time simulation circuit according to the present invention squares and accumulates a measured current value by squaring a fuse switch that replaces the fuse of the target device, a current measuring unit that measures the current flowing through the fuse switch, and the like. by the stored energy calculator for calculating the energy stored in the fuse switch, the stored energy values with said stored energy calculation unit is constituted by a comparator for comparing the allowable energy of the fuse, the interest device After the operation, the measurement by the current measurement unit, the calculation by the stored energy calculation unit, and the comparison by the comparison unit are repeatedly executed, and the energy value stored by the stored energy calculation unit is the allowable energy value of the fuse. The time elapsed since the target device was operated is And said that you have a function of the time.

The method for simulating the fuse blow time according to the present invention repeats the step of replacing the fuse switch with the fuse of the target device, and the current flowing through the fuse switch is measured, and the measured current value is squared and accumulated. Accordingly, during the time elapsed since by operating a step of determining the energy stored in the fuse switch between the elapsed time from operating the targeted device, the energy value and a target device to be stored the difference between the energy value is lost by heat dissipation from the fuse is characterized in that a step of the time reaches the allowable energy value of the fuse and fuse blowing time.

According to the first and third aspects, it is possible to accurately determine the fusing time of the fuse by simulation without flowing an electric current to each fuse and conducting an experiment.
Claims 2 and 4 take into account the energy lost due to heat dissipation from the fuse when the target device is operated. That is, the reliability of the fusing time of the fuse obtained by the present invention can be improved.
When the target device is driven, the continuous driving is performed within the simulated fusing time. As a result, the fuse can be used for a long period of time, and maintenance of the target device becomes easy.

(Simulation circuit)
FIG. 1 shows a circuit example in which the fuse blow time simulation circuit according to the first embodiment of the present invention is incorporated in a target apparatus. The target device is composed of a DC power source, a resistor, an inductance, a short-circuit switch, and a fuse. The resistance value and inductance value of the entire device including the fuse are collected in one block of resistance and inductance, respectively. In addition, the fuse blow time simulation circuit according to this embodiment includes a fuse switch, a current measurement unit, a stored energy calculation unit, and a comparison unit. In the circuit shown in FIG. 1, the fuse of the target device is replaced with a series circuit including a fuse switch and a current measuring unit. Then, the current flowing through the fuse, that is, the replaced fuse switch, is measured.

(Simulation method)
FIG. 2 shows the flow of analysis according to this embodiment. Initially, the short circuit switch is off and the fuse switch is on. By turning on the short-circuit switch (short-circuit start), a current is passed through the circuit shown in FIG. Thereafter, the current flowing through the fuse switch is measured by the current measuring unit (fuse current measurement). In stored energy calculating unit obtains the amount of heat and the measured current value squared (heat calculation), we obtain the energy P ₁ stored in the fuse switch by accumulating. The stored energy is compared with the allowable energy of the fuse described in the catalog (comparison). If the stored energy P ₁ is smaller than the allowable energy is judged that the blown fuse. Then, returning to “fuse current measurement”, measurement and calculation are repeated. If the stored energy P ₁ exceeds the allowable energy, measured in the off fuse switch and terminates the operation. The time elapsed since turning on the short-circuit switch is taken as the fuse blow time.

(simulation result)
FIG. 3 shows a graph analyzed using the fuse blow time simulation circuit according to this embodiment. The left side is a graph when the target device does not have an inductance component, and the right side is a graph when there is an inductance component.

When there is no inductance component, the current flowing through the circuit changes rapidly as soon as the short-circuit switch is turned on. And in proportion to the time elapsed from when turning on the short-circuit switch is stored energy P ₁ increases. Storable energy P ₃ that the allowable energy minus the accumulated energy P ₁ is gradually decreased with time. When storable energy P ₃ goes to zero or below a value, no current flows in the circuit, it can be seen that a fuse switch is turned off. The time that has elapsed since turning on the short-circuit switch is the fuse blow time.

When there is an inductance component, the current increases with a time constant determined by the inductance value and the resistance value after the short-circuit switch is turned on. Stored energy P ₁ also rises with time. However, it can be seen that it rises more gently than when there is no inductance component. Accordingly, the storable energy P ₃ is decreases gently. Again, when the storable energy P ₃ goes to zero or below a value, no current flows in the circuit, it can be seen that a fuse switch is turned off. However, it can be seen that the fuse fusing time is longer than when there is no inductance component.

If the current through the fuse is small, it is slowly heated until the melting point is reached. Therefore, the heat dissipation to the surroundings cannot be ignored. That is, the time until the fuse is blown becomes longer, and the change in allowable energy during that time cannot be ignored.
FIG. 6 shows a graph for explaining that the change in allowable energy cannot be ignored. When the current through the fuse is large, the fusing time is reached quickly. In the meantime, the allowable energy hardly changes, so that the allowable energy can be obtained as a constant value B. On the other hand, when the current flowing through the fuse is small, the fusing time becomes long. Meanwhile, the allowable energy changes as shown by curve A. Assuming that the allowable energy is constant, the fuse blow time cannot be determined accurately. Under the influence of heat dissipation from the fuse, the allowable energy increases as the energization time increases.

FIG. 7 shows a graph for explaining a method for accurately obtaining the fuse blowing time. Let the allowable energy change time be t ₁ , t ₂ , t ₃ ,. Also during the simulation start allowable energy changing time, the accumulated value of the energy lost by heat dissipation from the fuse and P _2. That is, the point (B + P ₂ = P ₁ ) where the value obtained by adding the accumulated value P _{2 of} energy lost due to heat dissipation to the constant value B intersects with the accumulated energy P ₁ is defined as the fuse melting time.

(Simulation circuit)
FIG. 4 shows a circuit example in which the fuse blow time simulation circuit according to the second embodiment of the present invention is incorporated in a target apparatus. The fuse blow time simulation circuit according to the present embodiment adds a dissipated energy calculation unit to the first embodiment. Here, the energy lost from heat dissipation from the fuse is accumulated.

(Simulation method)
FIG. 5 shows the flow of analysis according to this embodiment. The difference from the flowchart of FIG. 2 is a first embodiment, after measuring the fuse current is that which is adapted to accumulate seeking energy P ₂ lost by heat dissipation from the fuse. Then, for example, the sum of the allowable energy of the fuse described in the catalog and the energy P ₂ lost due to heat dissipation is compared with the stored energy P ₁ (comparison). As in Example 1, the case towards the stored energy P ₁ is small, it is determined that pre-blown fuse. Then, returning to “fuse current measurement”, measurement and calculation are repeated. If towards the stored energy P ₁ becomes large, measured in the off fuse switch and terminates the operation. The time elapsed since turning on the short-circuit switch is taken as the fuse blow time.

(simulation result)
FIG. 8 shows a graph analyzed in consideration of energy due to heat dissipation as in this embodiment and a graph analyzed without consideration. The left side is a graph analyzed without consideration, and the right side is a graph analyzed with consideration. However, both are measured in the absence of an inductance component.

In consideration of heat dissipation, the accumulated value P ₂ of the energy lost by it rises with a delay from the time of turning on the short-circuit switch. Therefore, storable energy P ₃ (= allowable energy + energy P ₂ lost due to heat dissipation−accumulated energy P ₁ ) has a gentle slope on the way. For this reason, the fuse blowing time becomes longer.
FIG. 9 shows a graph analyzed using the fuse blow time simulation circuit according to this embodiment. The left side is a graph when the target device does not have an inductance component, and the right side is a graph when there is an inductance component.

When there is an inductance component, the current increases with a time constant determined by the inductance value and the resistance value after the short-circuit switch is turned on. That is, the current flowing through the fuse is gently increased as compared with the case where there is no inductance component. Therefore storable energy P ₃ becomes time is delayed with a value of 0 or less, it can be seen that the fuse fusing time is prolonged.
FIG. 10 shows a graph obtained by analyzing a simple circuit and a large-scale power feeding system circuit by using the fuse blowing time simulation according to this embodiment. The graph on the left shows a simple circuit and the graph on the right shows an analysis of a large-scale power supply circuit. The inductance component and the resistance component included in the circuit for short-circuiting between the power source and the fuse are the same. Compared to the simple circuit, it can be seen that the current flowing through the fuse of the large-scale power supply system circuit is small, and the fuse blow time is long.

(Comparison between experiment and simulation)
FIG. 11 shows a comparison result between the fusing time measured by passing a current through the fuse and the fusing time obtained by the simulation of the present invention. In the case of simulations that do not consider heat dissipation, the results agree well with the experimental results when the current is large. However, they do not match as the current decreases. On the other hand, when heat dissipation is taken into account, it can be seen that even when the current is small, the experimental results are almost the same.

  FIG. 12 shows a result of comparison in which the allowable energy change time is set finely in a simulation considering heat dissipation. It can be seen that the simulation considering heat dissipation is in good agreement with the experimental results.

  FIG. 13 shows a comparison result of energy stored in the fuse or fuse switch during the fusing time. When the fusing time is short, the stored energy is constant and the three results agree. As the fusing time increases, the simulation results that take heat dissipation into account increase the energy. This is consistent with the experimental results.

It is a circuit example which incorporated the fuse blow time simulation circuit by Example 1 of this invention in the apparatus used as object. It is a flowchart which shows the fuse blow time simulation method by Example 1 of this invention. It is the graph which analyzed the apparatus and inductance which do not have an inductance component using Example 1 of the present invention. It is a circuit example which incorporated the fuse blow time simulation circuit by Example 2 of this invention in the apparatus made into object. It is a flowchart which shows the fuse fusing time simulation method by Example 2 of this invention. It is a graph explaining that the change of the allowable energy of a fuse cannot be disregarded by the energy dissipated from the fuse. It is a graph explaining the method of calculating | requiring the fuse fusing time correctly in consideration of the energy dissipated from the fuse. It is a graph which compares the case where the case where the energy by heat dissipation is considered and the case where it is not considered. It is the graph which analyzed the apparatus and inductance which do not have an inductance component using Example 2 of the present invention. It is the graph which analyzed the simple circuit and the large-scale electric power feeding system circuit using Example 2 of this invention. It is a graph which shows the comparison result of the fusing time measured by sending an electric current through a fuse, and the fusing time calculated | required by the simulation of this invention. It is a graph which shows the comparison result of the fusing time measured by sending an electric current through a fuse, and the fusing time calculated | required by the simulation of this invention. It is a graph which shows the comparison result of the energy accumulate | stored in the fuse or fuse switch in the fusing time in experiment and simulation. It is a graph which shows an example of the resistance change of the fuse computed from the electric current and voltage waveform which passed through the fuse. This is a fuse test circuit for obtaining a fuse blow time by a conventional method. It is a graph explaining fuse fusing time. It is a circuit diagram explaining that fuse fusing time differs when a simple circuit and a fuse are attached and when a fuse is attached to a large-scale power feeding system circuit. It is a graph explaining that the electric current which flows through a fuse differs in the two circuits shown in FIG.

Claims (4)

A fuse switch that replaces the fuse of the target device, a current measurement unit that measures the current flowing through the fuse switch, and the energy accumulated in the fuse switch by accumulating the measured current value squared A storage energy calculation unit to calculate, and a comparison unit that compares the energy value stored in the storage energy calculation unit with the allowable energy value of the fuse ,
After operating the target device, the measurement in the current measurement unit, the calculation in the stored energy calculation unit, and the comparison in the comparison unit are repeatedly executed, and the energy value stored in the stored energy calculation unit is upon reaching the allowable energy of the fuse, the fuse blowing time simulation circuit, characterized in Rukoto the time elapsed since by operating the targeted equipment until have the ability to fuse fusing time. A dissipated energy calculating unit that calculates energy lost due to heat dissipation from the fuse during the elapsed time after the target device is operated, and the energy value stored in the stored energy calculating unit and the dissipated energy When the difference from the energy value lost by heat dissipation from the fuse calculated by the calculation unit reaches the allowable energy value of the fuse, the time elapsed since the target device was operated is the fuse blow time fuse time simulation circuit according to claim 1, characterized in that a function of a. The process of substituting the fuse switch with the fuse of the target device, and measuring the current flowing through the fuse switch, repeating the accumulation of the measured current value to the square, and operating the target device And a step of obtaining energy stored in the fuse switch during an elapsed time from the time when the stored energy value reaches an allowable energy value of the fuse, and a step of setting a fuse blow time. Fuse blow time simulation method. The process of substituting the fuse switch with the fuse of the target device, and measuring the current flowing through the fuse switch, repeating the accumulation of the measured current value to the square, and operating the target device A process for obtaining energy stored in the fuse switch during the elapsed time since the operation of the fuse, energy value stored and energy lost due to heat dissipation from the fuse during the elapsed time since the target device was operated And a step of setting a fuse blow time as a time when a difference from the value reaches an allowable energy value of the fuse.

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