JP3116882B2 - Micro overload current monitoring circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a micro-overload current monitoring circuit, and more particularly to a micro-overload current monitoring circuit for monitoring an overload abnormal current for each load in an apparatus employing a centralized power supply system. .

[0002]

2. Description of the Related Art FIG. 6A is a block diagram of a conventional automatic positioning apparatus abnormality monitoring apparatus disclosed in Japanese Patent Application Laid-Open No. 61-147791 as a first conventional example.

In the case of the first conventional example, each time a positioning control operation (one cycle) is performed by the automatic positioning device, a device for monitoring the average load current integrates the load current until the completion of the positioning control cycle. The integrated value is divided by the integration time T to obtain the average load current Ia, the current average load current Ian is calculated by the arithmetic and comparison device 24a, and the same is obtained and stored in the memory device 23 until the previous time. Is compared with the average load current Ian-1, and its deviation value (referred to as a difference value in the present invention) ΔIa = Ian−Ian−1 is compared with a preset deviation limit value DL.

Here, if ΔIa ≦ DL, it is determined that the current average load current Ian is normal, and the average load current Ian up to the previous time is normal.
-1 is stored after updating, and in the case of △ Ia> DL, this average load current Ian is determined to be abnormal and a warning signal is output. The current (FIG. 7A) has a drawback that an abnormality cannot be detected.

FIG. 6B is a circuit diagram of a conventional overload detector disclosed in Japanese Patent Application Laid-Open No. 63-283419, which is a second conventional example.

In FIG. 6B, first, a current detector 24
Converts the current value I detected by the analog / digital converter 2
After conversion into a digital quantity by 5 and addition of M data by the first averaging processor 26, the added value is divided by the number of additions M to obtain an average current IA.

The average current IA obtained in this way is compared with a judgment reference value I0 stored in advance in a memory in the arithmetic unit 27. If IA> I0 is judged, an overload state is judged and the overload relay 35 is turned on. Activate.

When it is determined that IA ≦ I0,
The square value IA ² of the average current IA is obtained by the calculator 29, and the load resistance R (armature circuit resistance) is multiplied by IA ² to obtain I
A ² R is obtained, and the temperature rise θ corresponding to IA ² R is calculated by the primary delay calculator 31. Temperature rise θ thus obtained
Is compared with the reference temperature θo specified as the rating item and the comparator 3
2, and when it is determined that θ> θo, the square value IA ² of the average load current IA is obtained by the calculator 37.
The square value IA ² is sampled and added M during a predetermined time T, and the added value is divided by the number N of additions, and the average value 1 / N (ΣIA ² ) during the time T is calculated by the average processor 38. The load resistance (armature circuit resistance) R
Is multiplied by the average value 1 / N (ΣIA ² ) to obtain R / N (Σ
The temperature rise corresponding to IA ² ) is compared with a reference temperature θo specified as a rating item by the comparator 4, and when it is determined that θ> θo, the overload relay 35 is operated to operate the overload relay 35. Is detected.

When it is determined that θ ≦ θo, it is a conventional technique to determine that the vehicle is in a normal operation state. The comparison and determination method includes a method of setting a reference value Io with respect to a direct average current value; Calculating the temperature rise θ during the predetermined time T delays the detection of abnormalities, and cannot prevent accidents such as burnout of parts (FIG. 7B).

[0010]

However, the first and second prior arts described above have the following drawbacks.

A first problem is that in the first conventional example,
The abnormality monitoring device of the type that compares and determines only the deviation value of the average load current this time from the deviation value (difference value) of the previous average load current, monitors an abnormal current that continues to rise instantaneously with a load current with a large load fluctuation. There is a problem of difficulty.

The reason for this is that, for a load current that fluctuates as shown in FIG. 7A, the difference between the previously obtained integrated average load current value Ian-1 and the currently obtained integrated average load current value Ian (difference value 7) In the case of the load current shown in FIG. 7A, the calculated deviation value ΔIa = Ian−Ian−1 is compared with the preset deviation limit value DL.
This is because an abnormality cannot be detected because the value as Ia does not change (in this case, a constant value).

The second problem is that, as shown in the second conventional example, in the conventional overload detecting device in which the comparison determination value directly sets the current value, the detection of the abnormal current is delayed, There is a problem that it is difficult to prevent accidents such as burnout of parts.

The reason is that, since the judgment reference value I0 in the comparison judgment is a direct comparison with the current value, it is necessary to consider the maximum value of the load current and the rush current (to prevent malfunction in detection). The criterion value I0 needs to be set to have a relatively large margin (FIG. 7B), and the criterion value I0 cannot be lowered to a point to be originally detected.

Therefore, the detection of the abnormality is delayed (α1 hour) as shown in FIG.

In the process of calculating the temperature rise θ,
In order to calculate the average value 1 / N (ΣIA ² ) during the predetermined time T, it is necessary to measure the current for a relatively long time (T time) in order to calculate the accurate temperature rise. 7 (B) -1) cannot be detected, and therefore the detection of abnormality is delayed (α2 hours) as shown in FIG. 7 (B) -1.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional circumstances, and has been made to solve the above-mentioned drawbacks inherent in the conventional technology. The new overload abnormal current can be detected, and the overload abnormal current can be monitored for each load unit to improve the reliability and safety of the equipment on which each load is mounted. An object of the present invention is to provide a minute overload current monitoring circuit.

[0018]

In order to achieve the above object, a minute overload current monitoring circuit according to the present invention compares and determines a difference addition value calculated from an average load current and monitors the load current. It is characterized by.

More specifically, the micro overload current monitoring circuit according to the present invention comprises: a load current measuring means for continuously measuring a load current of the load circuit; and a sample for sampling the measured load current at regular intervals. Converting means, A / D converting means for converting the sampled load current into a digital quantity, and dividing the load current value obtained by adding the number of outputs of the A / D converting means by the number of times of sampling by the number of times of sampling to obtain an average load. Average load current calculating means for calculating current, and deviation value calculating means for calculating a difference value by subtracting the average load current obtained this time from the average load current obtained last time,
The difference value and the previously obtained difference value are added to calculate a difference addition value, and the plus value of the difference value continuously exceeds a preset reset value at a normal load current. An addition deviation value calculating means for erasing the difference addition value abnormally accumulated when the difference addition value is compared with a preset allowable value, and if the difference addition value is smaller than the allowable value, it is determined that the load current is normal and the difference is determined. If the sum is greater than or equal to the permissible value, a comparison / judgment means for judging an overload abnormal current and generating a warning signal is provided.

[0020]

In the present invention, the value of the difference addition value calculated in the normal state is obtained by adding the difference values that change in the plus direction and the minus direction, so that the plus value and the minus value cancel each other, and a value within a certain value is obtained. Repeat the change.

On the other hand, at the time of an overload abnormal current, the value of the difference addition value increases rapidly (addition in the positive direction continues). It can be understood that the abnormal current can be detected instantaneously.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, preferred embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing a preferred embodiment according to the present invention.

Referring to FIG. 1, a load current I of a load circuit to which the present invention is connected is continuously measured by a load current measuring device 1, and sampling is performed by a sampler 2 at a constant period. Subsequently, the sampled load current value In is:
After being converted into a digital quantity by the A / D converter 3, a load current Dn obtained by adding N by the number of times of sampling N is obtained, and this load current Dn is divided by the number of times of sampling N, and the average load current Zn is averaged. It is calculated by the load current calculator 4.

Next, the deviation value calculator 5 calculates the average load current Z obtained this time from the average load current Zn-1 previously obtained.
n is subtracted (Zn-1 -Zn) to calculate a difference value Hn.

Further, the difference value Hn is added to the addition deviation value calculator 6.
To add the difference value Hn-1 obtained last time to calculate the difference addition value K. In addition, the addition deviation value calculator 6 performs the abnormal accumulation of the difference addition value described above (at a normal load current, the difference value H
In order to prevent the case where the positive value of n is continuous, if the difference value Hn of the plus directionality is added a predetermined number of times (reset setting value 9), the difference addition value that has accumulated abnormally Erase (reset) K.

Next, the difference addition value K calculated as described above is compared with an allowable value 8 set in advance by a comparison judging device 7, and if K <allowable value, it is judged that the load current is normal. Then, the above-mentioned average load current Zn-1 is updated to the average load current Zn acquired this time to calculate a new difference value, and the above-described operation is repeated.

If K ≧ permissible value, it is determined that an overload is abnormal, and a warning signal is output from the comparison / determination unit 7.

Next, the operation of the embodiment of the present invention will be described in detail with reference to FIGS.

FIGS. 2A to 2D are waveform diagrams showing a process for calculating the difference addition value K from the load current described above.

First, in FIG. 2A, the load current I continuously measured is sampled (N
1 to Nx), and the sampling load currents I1 to Ix
Find x. Next, the sampling load currents I1 to Ix are converted into digital quantities D1 to Dx.
ＤDx are sequentially added, and then divided by the number of times of sampling Nx, and the average load current Zn shown in FIG. 2B is calculated at regular intervals (example: Z1, Z2,... Zx).

Next, the average load current Zn-1 calculated this time is subtracted from the average load current Zn calculated last time (example: Z2-Z1).
) And calculate the difference value Hn shown in FIG. 2C (example: H2
= Z2-Z1). Then, in the plus direction component (eg:
H1, H2) or a difference value Hn having a minus direction component (eg, -Hx) is added to the previous difference value Hn-1, and a difference addition value K (eg, H1 + () shown in FIG. -Hx)).

The above is the process of calculating the difference addition value K from the load current I that is continuously measured. Next, the comparison judgment process based on the difference addition value K, which is a feature of the present invention, will be described in more detail. .

FIGS. 3A to 3G are waveform charts for explaining the operation of the process of calculating the difference addition value according to the present invention.

3 (A) to 3 (G), FIG. 3 (A) is a waveform diagram showing an average load current with a large load fluctuation, which cannot detect an abnormal current with the conventional technique. It is. First, by the above-described operation, the average load current Zn is calculated as shown in FIG. 3A, and then the difference value Hn shown in FIG. 3B is calculated.

Here, the difference value Hn is considered with a deviation value (absolute amount) which is a comparison determination amount in the conventional technology (FIG. 3B). ,
Abnormality cannot be detected because there is no change (constant amount) in the deviation value (absolute amount) at normal time The difference addition value K shown in FIG. 3C is calculated by the above-described operation.

The difference addition value K repeatedly increases and decreases within a certain value as shown in FIG. 3C in a normal state, and the difference value Hn of the plus direction component in an overload abnormal current. The addition is continued, and the difference addition value K sharply increases ((C) in FIG. 3), and the overload abnormal current can be detected instantaneously (small value).

In the prior art, the waveform diagram of the load current for which the detection of the abnormality is delayed is also shown in FIG. 3D. As shown in FIG. 3 (G) -2), the instantaneous detection (small value) of the overload abnormal current can be easily performed as described above.
In the case of the average load current shown in (E) -1 of FIG. 3, since the normal load current value gradually rises, a small plus value of the difference value Hn is continuously added, so that the plus value is added forever. Is repeated, and the difference addition value K may be abnormally accumulated.

Therefore, in the present invention, when the addition of the plus difference value Hn is repeated with a preset reset setting value (eg, 5 times), the accumulated difference addition value K is deleted (reset). . Therefore, the above-described abnormal accumulation of the difference addition value K is eliminated ((G) -1 in FIG. 3), and at the time of an overload abnormal current, the difference addition value K sharply increases within the reset setting value (FIG. 3). (G) -2), the overload abnormal current is detected instantaneously (small value) and a warning signal is output.

Next, another embodiment of the present invention will be described with reference to FIG.

FIGS. 4A to 4D are waveform charts for explaining another embodiment of the present invention.

In the waveform diagram shown in FIG. 4A, after calculating the difference addition value K, the vector amount Bn (FIG. 4B) is further obtained, and the number of times that the plus vector of the vector amount Bn continues is calculated. Set an allowable value (weighting), compare with a preset allowable value, and if + Bn times ≧ allowable value,
It is detected as an overload abnormal current, and if + Bn count <allowable value, it is determined as a normal current, and a difference value H for calculating a new difference addition value is calculated.
This is a micro overload current monitoring circuit that updates n. For reference, the vector quantity Bn is given by the equation

[0043]

Is obtained.

The set value of the allowable value of the difference addition value K is
By setting also in the minus direction ((C) in FIG. 4), a failure due to component deterioration (a circuit that normally operates) is detected by a sharp decrease in the difference addition value, and early detection of the failure becomes possible. A micro underload current monitoring circuit is provided.

As still another modification, the sampling cycle for calculating the average load current as shown in FIG. 4D is made dependent on an externally input clock, and the sampling cycle is varied according to the variation of the load current. In addition, there is provided a minute overload current monitoring circuit that allows a more accurate average load current value to be calculated and monitors a minute abnormal current.

[0047]

The present invention is constructed and operates as described above. According to the present invention, the following effects can be obtained.

The first effect is to detect a sign of an overload abnormal current due to component deterioration by catching a minute change in load current, thereby preventing accidents such as component burnout. Becomes

The reason is as shown in FIG.
Since the difference addition value for judgment comparison is sequentially calculated from the average load current that is sequentially consumed, the value of the difference addition value at the time of normal current repeatedly changes within a small constant value. It can be set to an extremely small value, and at the time of an overload abnormal current, the value of the difference addition value increases sharply and instantaneously exceeds the allowable value (small value) described above. Therefore, the sign of the overload abnormal current such as component burnout can be instantaneously (small value) detected by comparing the difference addition value with the above-mentioned allowable value.

The second effect is that in a device employing the centralized power supply system (FIG. 5B), the overload abnormal current can be monitored for each load unit, and a simple device self-diagnosis function can be performed. And it is easy to distinguish between an abnormal load and a normal load.

The reason is as follows, referring to FIG.
The load in which an abnormality has occurred is only the load circuit 2. Since an overload abnormal current due to component deterioration can be detected in the sign period before an accident such as component burnout according to the present invention, a subsequent load (part deterioration occurrence) unit. This is because it is possible to detect (warning signal) in the previous symptom period similarly to the above, and to constantly monitor during the operation of the load circuit, so that it can be used as a simple self-diagnosis function.

Further, it is possible to monitor the abnormality of the load current in units of load in the same manner as described above. In the device in which the load circuit is mounted, the warning signal output by the detection of the overload abnormal current of the present invention is used to make it normal. This is because an operation such as power-off can be avoided for a load during operation, so that an abnormal load and a normal load can be easily separated.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment according to the present invention.

FIGS. 2A to 2D are waveform diagrams illustrating the operation of a process of calculating a difference addition value according to the present invention.

FIGS. 3A to 3G are waveform charts for explaining a comparison judgment operation of the present invention.

FIGS. 4A to 4D are diagrams for explaining the operation of another embodiment according to the present invention;

FIGS. 5A and 5B are diagrams showing the effect of the present invention.

FIG. 6A is a block diagram showing a first conventional example;
(B) is a block diagram showing a second conventional example.

7A is a waveform diagram showing the operation of a first conventional example (FIG. 6A), and FIG. 7B is a second conventional example (FIG. 6B).
FIG. 6 is a waveform chart showing the operation of FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 load current measuring device 2 sampler 3 A / D converter 4 average load current calculator 5 difference value calculator 6 difference addition value calculator 7 comparison comparator

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI H02H 3/02 H02H 3/02 G

Claims (4)

(57) [Claims] 1. A load current measuring means for continuously measuring a load current of a load circuit, a sampling means for sampling the measured load current at a constant period, and converting the sampled load current into a digital quantity. A / D conversion means, average load current calculation means for calculating an average load current by dividing a load current value obtained by adding the output of the A / D conversion means by the number of times of sampling by the number of times of sampling, and A deviation value calculating means for calculating a difference value by subtracting the average load current obtained this time from the load current, and calculating a difference addition value by adding the difference value and the previously obtained difference value to obtain a normal load current And an addition deviation value calculating means for erasing the difference addition value abnormally accumulated when the difference addition value continuously exceeds a preset reset setting value when the plus value of the difference value continues. The difference addition value is compared with a preset allowable value. If the difference addition value is smaller than the allowable value, it is determined that the load current is normal. A minute overload current monitoring circuit, comprising: a comparing and judging means for generating the current. 2. If the relation between the difference addition value and the permissible value is a difference addition value <permissible value, the comparison determination means calculates the previous average load current value for calculating a new difference value. 2. The minute overload current monitoring circuit according to claim 1, further comprising updating the average load current value acquired this time. 3. A system employing a centralized power supply system, wherein a plurality of minute overload current monitoring circuits according to claim 1 are installed, and each of the monitoring circuits independently monitors an overload abnormal current in each load unit. And a simple overload current monitoring circuit characterized by a simple device self-diagnosis function. 4. The apparatus according to claim 1, wherein a sampling period of the sampling means for sampling the measured load current at a constant period is made dependent on a clock input from the outside, and is varied in accordance with a change in the load current. 3. The minute overload current monitoring circuit according to any one of 1 and 2.