JPH0732534B2 - Rectifier load abnormality detection method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a load abnormality detection method for a rectifier, and more particularly to a load abnormality detection method that detects both load short-circuit and load open abnormalities.

[Conventional technology]

For example, a rectifier for converting AC power into DC power is generally widely used as a DC power supply device in many fields utilizing DC power such as electrolysis or electroplating of steel strips.

FIG. 4 shows a basic configuration of a six-phase half-wave rectifying semiconductor type rectifier as a typical example, in which a three-phase alternating current input through an overcurrent breaker 1 has a thyristor 2. Device S, for converting a three-phase alternating current into a six-phase alternating current, for example, a double Y-connected rectifier transformer 3, a half-wave rectifying diode 4, and half-wave rectified. For example, if electroplating, 10,000 amperes (A) It is supplied to the plating equipment as a direct current of a high level. In addition, this rectifier is provided with a load abnormality detection circuit in order to detect a short circuit accident in a load to which direct current power should be supplied and to prevent the accident from spreading in a short time. That is, a current detector 5 is inserted in the primary side of the rectifier transformer 3 and a voltage detector 6 is inserted in the secondary side, and the current detection signal SI detected by the former and the current detection signal SI detected by the latter are inserted. The detected voltage detection signal SV is input to the calculator 7. Then, the upper limit voltage Va and the lower limit current Ia for load abnormality detection, which are preset by a load short-circuit abnormality detection rate setting device (not shown), are input to the calculator 7.

FIG. 5 shows the operation characteristics of the load abnormality detection circuit in the rectifier. In the figure, In and Vn represent the rated current value and the rated voltage value, respectively, and the chain line L ₁ represents the minimum voltage-current characteristic in the rectifier operation. Is represented.

When a short-circuit accident (external short-circuit) occurs on the load side of a plating device or the like, the current rapidly increases. As a result, the voltage SV and the current SI output from the rectifier are out of the range of the above-mentioned minimum voltage-current characteristic, and at a low voltage such as Va volt, for example.
A large current of Ia amperes or more will be output. Therefore, as the load abnormality determination condition, the upper limit voltage Va for load abnormality detection and the lower limit current Ia for load abnormality detection are set in advance, and the determination condition values and the detected voltage measured by the calculator 7 are set in advance. The value SV and the detected current value SI are constantly compared, and SI> Ia
When SV <Va, it is determined that there is a load abnormality, and the arc extinguishing signal G _OFF is output to the thyristor 2.

[Problems to be solved by the invention]

However, in the load abnormality detection method of such a conventional rectifier (for example, Japanese Patent Laid-Open No. 58-154322),
The upper limit of the output voltage Va when the short circuit is abnormal is regulated by the internal short circuit voltage of the rectifier. Then, the load abnormality detection lower limit current Ia is also inevitably specified according to the minimum voltage-current characteristic in the rectifier operation (see FIG. 5).

Therefore, (1) the abnormality cannot be detected in the range where the load current SI is smaller than the load abnormality detection lower limit current Ia specified by the rectifier internal short-circuit voltage. Moreover, (2) as the load current SI becomes larger than the load abnormality detection lower limit current Ia, the sensitivity of abnormality detection becomes dull, and as a result, only a very short range of load short circuit shown in FIG. 5 can be dealt with. was there.

It is an object of the present invention to provide a load abnormality detecting method capable of significantly expanding the detectable range of load abnormality as compared with the prior art, and being capable of handling not only short circuit abnormality but also open abnormality.

[Means for solving problems]

According to the present invention, which achieves the above-mentioned object, a load resistance is calculated from an input current and an output voltage of a rectifier by a calculation means, and the calculation result is a short circuit upper limit set in advance from a rated current and a short circuit upper limit voltage corresponding to the rated current. When it is smaller than the resistance or when it is larger than the open lower limit resistance set in advance from the rated voltage and the corresponding open upper limit current, it is judged that the load is abnormal and the rectifier output is made zero.

[Action]

The load resistance R is calculated by the calculating means from the input current and the output voltage of the rectifier. On the other hand, the load short-circuit upper limit resistance Ru is set from the upper limit voltage of the load short-circuit abnormality detection and the rated current, and the load open lower limit resistance Rl is set from the upper limit current and the rated voltage of the load open abnormality detection. Then, the above resistors are constantly compared during the operation of the rectifier, and when the load resistance R is equal to or less than the short circuit upper limit resistance Ru, it is determined that a large current of a predetermined value or more has flowed due to the load short circuit, while the load resistance R is the open lower limit resistance Rl. In the above cases, it is determined that only a current equal to or less than a predetermined value will flow when the load is released, and in any case, the rectifier output is immediately set to zero to prevent the accident from spreading.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an example of a load abnormality detection circuit for a rectifier to which the present invention is applied. In the figure, the same or corresponding parts as in the conventional case are designated by the same reference numerals.

The controller 10 includes an input / output port, an arithmetic processing unit (CP
U), a RAM, a microcomputer having a storage device such as a ROM, and a current detection signal SI obtained by the current detector 5 and a voltage detection signal VI obtained by the voltage detector 6 at its input port. While the thyristor 2 is firing,
It is always input. In addition, in accordance with the characteristics of the load and the specifications of the rectifier, the upper limit voltage signal V ₁ for load short circuit abnormality detection and the upper limit current I ₁ for load open abnormality detection that are preset by the load abnormality detection rate setting device (not shown) are Is entered. Furthermore, the rated voltage
Vn, rated current In, current detector 5 and voltage detector 6
The lower limit voltage V _{0 for} load open abnormality detection and the lower limit current I _{0 for} load short circuit abnormality detection, which are set to prevent malfunction due to each detector error and calculation error, are input as load abnormality detection information.

Based on the load abnormality detection information, the controller 10
Determines whether or not there is a load abnormality, and outputs a control signal having a logical value "1" or a logical value "0" from the output side port as a firing / extinguishing command signal of the thyristor 2. That is, for example, if it is judged that there is an abnormality, an arc-extinguishing signal having a logical value of "1" is output to the thyristor 2, whereby, for example, the thyristor is extinguished by short-circuiting its cathode and anode, and power is supplied to the load. Is cut off.

Hereinafter, the procedure of the load abnormality detecting method of the present invention performed according to the configuration of the load abnormality detecting device shown in FIG. 1 is stored in advance in the ROM of the storage device of the microcomputer.
Description will be made based on the program shown in FIG.

Now, the control signal of logical value "0" is output from the controller 10, so that the gate signal is supplied to the gate of the thyristor 2 and is in the ignition state, and a load (for example, an electroplating device) not shown in the drawing is It is assumed that a predetermined DC power is being supplied via the rectifier.

First, the initial setting is executed in step, and then the process proceeds to step, in which the current signal SI detected by the current detector 5 and
The analog signal of the voltage signal SV detected by the voltage detector 6
Convert to a digital signal with the A / D converter, read it, and move to the step. In step, the resistance R = SV / SI is calculated based on these detected values, and the calculated resistance R = SV / SI is temporarily stored in a predetermined area of the storage device.

Next, move to the step, and the rated current value In determined according to the characteristics of the load and the rectifier specifications, and the load short-circuit abnormality detection upper limit voltage V ₁ represented by the allowable minimum voltage when the rated current In flows Are read (see FIG. 3), and based on this, the resistance Ru = V ₁ / In is calculated, and the result is temporarily stored in a predetermined storage area as the load short-circuit upper limit resistance value Ru.

Next, the process proceeds to step, and the presence or absence of load short circuit abnormality is determined by comparing the current load resistance value R calculated in the above step with the load short circuit upper limit resistance value Ru calculated in step. That is, if there is a short circuit in the load, a large current flows at a lower voltage than in the normal state, so the load short circuit upper limit resistance value Ru should show a small value. Therefore, if the current load resistance value R> Ru, it is determined that there is no load short circuit, and the process proceeds to step. On the other hand, if R <Ru, it is considered that there is a high possibility that a short-circuit accident will occur, but there is also the possibility of current and voltage detection errors. Therefore, the process shifts to step, and it is determined whether or not the detected current value SI exceeds the load short circuit abnormality detection lower limit current set value I ₀ . If the result is SI> I ₀ , it is determined that there is a load short circuit abnormality because it is outside the above error range, and the process proceeds to the step, and the output port of the controller 10 is connected to the thyristor 2
The thyristor arc extinguishing signal G _OFF is output to, and as a result, the current to the load becomes zero, and the accident spread is prevented.

That is, according to this embodiment, when the voltage-current characteristic of FIG. 3 is within the range of trapezoid I ₀ , In, V ₁ , v ₀ , it can be determined that there is a short circuit abnormality.

On the other hand, if SI <I ₀ in the step, on the other hand, it is determined that there is no load short circuit abnormality because it is within the above-described error range, and the load release abnormality determination in the step and subsequent steps is performed.

In the step, the rated voltage value Vn determined according to the characteristics of the load and the rectifier specifications is read, and the maximum current value that can flow when this rated voltage Vn is applied in the limit state where it should be judged that the load is released is the load release abnormality. Read as detection upper limit current I ₁ (see Fig. 3), and based on this, calculate resistance Rl = Vn / I ₁ in steps, and load the result as load release lower limit resistance value R
It is temporarily stored as l in a predetermined storage area.

Next, the process proceeds to step, and the presence or absence of load release abnormality is determined by comparing the current load resistance value R calculated in the above step with the load release lower limit resistance value Rl calculated in step. That is, if the load is open, the resistance value should be larger than the load open lower limit resistance value Rl.
Therefore, if the current load resistance value R <Rl, it is determined that the load is not released and the process returns to the step. On the other hand, if R> Rl, it is considered that there is a high possibility that the load will be released, but there is a possibility that there is a detection error. Therefore, the process proceeds to step, and it is determined whether or not the detected voltage value SV exceeds the load release abnormality detection lower limit voltage set value V ₀ . If the result is SV> V ₀ , it is determined that there is a load release abnormality, the process moves to step, the thyristor arc extinguishing signal G _OFF is output from the output port of the controller 10 to the thyristor 2, and the current to the load is increased. Is cut off. As a result, it is possible to prevent accidents such as insufficient plating due to insufficient current when the load is released.

That is, according to this embodiment, when the voltage-current characteristic shown in FIG. 3 is within the range of the trapezoids V ₀ , Vn, I ₁ , i ₀ , it can be determined that there is an open abnormality.

On the other hand, if SV <V ₀ , it is within the detection error range,
It is determined that there is no opening abnormality and the process returns to the step. Thus, by repeatedly executing the above steps to steps during the operation of the rectifier, the accidents caused by the short circuit abnormality and the open abnormality of the load are prevented.

According to this embodiment, not only an accident at the time of transformer burnout due to a load short circuit at the time of electroplating but also troubles such as insufficient plating due to load release can be prevented, and the detection range of these load abnormalities can be expanded. The detection sensitivity can also be kept good.

In the above embodiment, the case where the load is applied to the electroplating apparatus has been described, but the present invention is not limited to this and can be applied to various apparatuses using a rectifier such as electrolysis, electrodialysis, and charging.

Also, the present invention is not limited to the six-phase half-wave rectification, and the single-phase,
It can also be applied to rectifiers such as three-phase AC and full-wave rectification.

Furthermore, the set position of the current detector 5 may be on the secondary side of the rectifier transformer 3.

〔The invention's effect〕

As described above, according to the present invention, the load resistance is calculated by the calculating means from the input current and the output voltage of the rectifier, and the rectifier output is controlled by judging the presence or absence of the load abnormality according to the result. In addition to significantly expanding the load abnormality detection range, it is possible to easily and reliably detect not only short circuit faults but also open faults, and the content and range of load fault countermeasures for rectifiers will be significantly expanded. The effect is obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of an apparatus to which the present invention is applied, FIG. 2 is a flowchart explaining a load abnormality detecting procedure of the present invention, and FIG. 3 is an operation characteristic diagram of a load abnormality detecting circuit to which the present invention is applied. FIG. 4 is a block diagram of a conventional load abnormality detection device for a rectifier, and FIG. 5 is an operation characteristic diagram of a conventional load abnormality detection circuit. 2 is a thyristor, 3 is a rectifier transformer, 4 is a diode, 5 is a current detector, 6 is a voltage detector, and 10 is an arithmetic means (microcomputer).

Claims (1)

[Claims] 1. A load resistance is calculated by a calculation means from an input current and an output voltage of a rectifier, and when the calculation result is smaller than a short circuit upper limit resistance preset from a rated current and a corresponding short circuit upper limit voltage, Alternatively, a load abnormality detection method for a rectifier, which determines that the load is abnormal when the open lower limit resistance set in advance from a rated voltage and an open upper limit current corresponding to the rated voltage is exceeded, and sets the rectifier output to zero.