JPH08275544A - Monitor for inverter - Google Patents

Abstract

PURPOSE: To monitor the operation of an inverter and to interrupt power supply to a load upon detection of abnormal operation. CONSTITUTION: The monitor 3 for an inverter comprises means 4 for full-wave rectifying the AC output from an inverter 2 to produce an output, means 5 for detecting an abnormal waveform caused by the abnormality in the waveform of AC output among the output waveforms from the means 4 and delivering an abnormal waveform detection signal, and means 6 tar making a decision that the waveform of AC output from the inverter 2 is abnormal based on the abnormal waveform detection signal and delivering an abnormality decision signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter monitoring device for monitoring a half-wave output from an inverter.

[0002]

2. Description of the Related Art A voltage output type inverter for converting a DC voltage into an AC voltage having a desired frequency and outputting the AC voltage is well known. Then, although an alternating waveform of the desired frequency is usually output from such an inverter, a half-wave waveform may be output due to malfunction of some switching elements, for example.

[0003]

However, when such a half-wave waveform is output from the inverter, when the motor is driven by using the inverter as a power source, the motor startup failure or its abnormal waveform is generated. This will result in burnout of the stator coil. Also, if you connect an inverter with an inductive load such as a motor or transformer, an excessive short-circuit current flows in the inductive load due to the half-wave waveform from the inverter, and at worst,
In some cases, the windings were burned out. The present invention has been proposed in view of the above, and an object thereof is to provide an inverter monitoring device capable of monitoring a malfunction of an inverter and stopping power supply to a load when the malfunction is detected.

[0004]

In order to achieve the above object, the inverter monitoring apparatus of the present invention is a rectified waveform output means for full-wave rectifying an AC output waveform output from an inverter and outputting the rectified waveform. Of the output waveforms from the output means, an abnormality detection means for detecting an abnormal waveform generated due to the abnormality of the AC output waveform and outputting it as an abnormal waveform detection signal, and from the inverter based on the abnormal waveform detection signal And an abnormality determining unit that determines that the AC output waveform is abnormal and outputs an abnormality determination signal.

[0005]

As described above, in the inverter monitoring device of the present invention, the rectified waveform output means performs full-wave rectification on the AC output waveform output from the inverter, and the abnormality detection means outputs the rectified waveform. An abnormal waveform generated due to an abnormal AC output waveform is detected and output as an abnormal waveform detection signal. Then, based on the abnormal waveform detection signal, the abnormality determination means determines that the AC output waveform from the inverter is abnormal and outputs the abnormality determination signal.

[0006]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing the overall configuration of the inverter monitoring device of the present invention. In the figure, an inverter 2 is used in a vehicle generator 1 that the applicant has already commercialized, and the three-phase alternating current supplied from the generator 1 is once rectified into a direct current and then converted into an alternating voltage of a predetermined frequency. To do. The AC voltage is output as a power supply voltage to a load not shown here via the two power supply lines 21a and 21b. Further, it is output to the inverter monitoring device 3 through the two power supply lines 21a and 21b as shown in the figure.

The inverter monitoring device 3 is a device that receives an AC output from the inverter 2 and monitors the operation of the inverter 2. The rectified waveform output is a full-wave rectified output of the AC output waveform output from the inverter 2. Means 4 and an abnormality detecting means 5 for detecting an abnormal waveform generated from an abnormality of the AC output waveform of the inverter 2 among the output waveforms from the rectified waveform output means 4 and outputting it as an abnormal waveform detection signal; An abnormality determination unit 6 that determines that the AC output waveform from the inverter 2 is abnormal based on the abnormal waveform detection signal and outputs an abnormality determination signal is provided.

The abnormality detecting means 5 detects an abnormal waveform based on the output waveform (full-wave rectified waveform) of the rectified waveform output means 4 and the base inverted waveform. Here, the base inverted waveform is a synchronizing signal of an AC output waveform in the inverter 2, and is generated by inverting the base waveform output from the base waveform generating means 23 in the inverter 2.

The abnormality determination signal output from the abnormality detecting means 5 is input to the inverter operation stopping means 22,
The inverter operation stopping means 22 receives the abnormality determination signal and stops the operation of the inverter 2.

FIG. 2 is a schematic circuit diagram showing a specific example of the case where the inverter monitoring device 3 is assembled as an electronic circuit. In the figure, the rectified waveform output means 4 of the inverter monitoring device 3
Is composed of a rectifier 41 formed by connecting four switching elements in a bridge shape, and a photocoupler 42. An AC voltage of AC 100 V as shown in FIG. 3 is applied to the rectifier 41 from the inverter 2, and the rectifier 41 performs full-wave rectification on the AC voltage waveform and applies it to the light emitting diode of the photocoupler 42. A forward voltage is sequentially applied to the light emitting diode according to the full-wave rectified waveform, and the phototransistor of the photocoupler 42 correspondingly outputs a signal S2 (FIG. 3) having a pulse waveform. The signal S2 is sent to the abnormality detecting means 5.

The AC output of the inverter 2 and the signal S2 do not rise immediately even when the power switch of the inverter 2 is turned on, and a certain amount of time elapses before it rises.

Further, the AC output from the inverter 2 is shown in FIG.
When a half wave as shown in (1) is generated, the signal S2 is affected by the half wave and maintains 0 V (Lo level) in the portion corresponding to the half wave, and does not have a pulse waveform.

The abnormality detecting means 5 includes an OR circuit 52 and its O
It is composed of a NOT circuit 54 connected in series to the R circuit 52. To the OR circuit 52, the base inversion signal S3 and the power ON reset signal S1 are input together with the signal S2. The base inversion signal S3 is a signal generated by inverting the base signal S7, which is a synchronization signal of the AC output waveform in the inverter 2, in the NOT circuit 51, and Hi and Lo appear exactly opposite to the signal S2. It is like this.

The power-ON reset signal S1 is a signal for securing a time until the AC output from the inverter 2 rises when the power switch of the inverter 2 is turned ON.

When these three signals S1, S2, S3 are input to the OR circuit 52 when the AC output from the inverter 2 is normal, the OR circuit 52 continuously outputs the H signal.
The signal S4 at the i level is output. The signal S4 is held at the Hi level at the same time as the power switch of the inverter 2 is turned on because the power ON reset signal S1 is continuously input until the AC output from the inverter 2 rises as described above, and during that time, the base is turned on. This is because the pulse of the inverted signal S3 is not output from the OR circuit 52 as it is.

On the other hand, when the AC output from the inverter 2 includes a half wave, the signal S4 output from the OR circuit 52 is output.
Is a pulse wave that is at the Lo level only for the time period obtained by subtracting the time width at which the base inversion signal S3 is at the Hi level from the time width at which the signal S2 is at the Lo level.

The signal S4 from the OR circuit 52 is then inverted by the NOT circuit 54, so that the H level corresponding to only the half-wave portion in the AC output of the inverter 2 appears.
The half-wave detection signal S5 at the i level is sent to the abnormality determination means 6. Note that the signal S4 output from the OR circuit 52 is a base-shaped signal S4 having a whisker-shaped signal of about 70 μsec in order to prevent short circuit of the arm of the bridge in the rectifier 41.
Since it appears in synchronism with 7, the OR circuit 52 and the NOT circuit 5
4 and a CR circuit 53 is provided between them and the CR circuit 52 removes them.

The abnormality determining means 6 comprises a counting circuit 61 and a NOT circuit 62 connected in series with the counting circuit 61. When the half-wave detection signal S5 is input to the count circuit 61, the count circuit 61 counts the number of pulses of the half-wave detection signal S5 and counts a predetermined number or more of pulses, for example, 20 or more pulses. At this time, the abnormality determination signal S6 is sent via the NOT circuit 62.
Is output.

That is, if the AC output of the inverter 2 is normal, the half-wave detection signal S5 is continuously at the Lo level, so the counting circuit 61 does not count and the abnormality determination signal S6 is not output. On the other hand, when a half wave appears in the AC output of the inverter 2, the half wave detection signal S5 as a clock pulse is output corresponding to the half wave.
The counting circuit 61 counts the clock pulse,
When 20 pulses or more are counted, the NOT circuit 62 outputs the abnormality determination signal S6.

A count reset signal S8 is sent from the count circuit 7 to the count circuit 61. That is, the count circuit 7 receives the above-mentioned base signal S7 (synchronization signal of the AC output waveform in the inverter 2) and counts the pulse, and 99 pulses corresponding to about 1 second (when the output frequency is 50 Hz). When you count
The count reset signal S8 is output to the count circuit 61. The count circuit 61 counts the half-wave detection signal S5 within about 1 second after the count reset signal S8 is received until the next count reset signal S8 arrives, during which 20 pulses or more are counted. At this time, the abnormality determination signal S6 is output.

In this way, the count of the half-wave detection signal S5 is reset when the predetermined time exceeds about 1 second. That is, even if the half-wave detection signal S5 is output, 20 pulses are output within the predetermined time. This is because if the frequency of occurrence is such that minutes are not counted, there is no problem even if the inverter 2 is used as a power source.

The reason why the abnormality determination signal S6 is not output unless 20 or more pulses are counted is that the inverter 2 is completely started up depending on the use condition when the power switch of the inverter 2 is turned on. It may take a time longer than that secured by the power-on reset signal S1. In that case, the AC output waveform at the time of rising is still present.
Three pulses will be output as the half-wave detection signal S5. Therefore, 20 pulses that sufficiently clear these 13 pulses are counted so as to avoid an erroneous determination that a normal rising edge is a half-wave output.

The inverter 2 is normally turned on by a power switch, but it may be turned on by a reset switch when the AC output trips for some reason during operation. In such a case, the power ON reset signal S1 is output.
Is not output, this power ON reset signal S1
Instead of the reset switch signal S9,
To enter. Reset switch signal S9 is power ON
Like the reset signal S1, it is a signal that holds the Hi level for a sufficient time to ensure the rising of the inverter 2. The count circuit 61 prohibits the count mode while the reset switch signal S9 is output. Thus, the erroneous determination at the time of rising with the reset switch can be avoided.

As described above, the abnormality determination signal S6 is generated by the inverter operation stopping means 22 provided in the inverter 2.
The inverter operation stopping means 22 receives the abnormality determination signal S6 and shuts off the operation of the inverter 2. The inverter operation stopping means 22 may be, for example, the inverter 2
There is a configuration in which the abnormality determination signal S6 is input to each switching element forming the H-bridge and the respective switching elements are turned off. In addition, the inverter monitoring device 3
As shown in FIG. 2, the photocoupler 42, the count circuit 61, and the count circuit 7 of FIG.
Is supplied.

As described above, in this embodiment, the AC output waveform output from the inverter 2 is full-wave rectified, and an abnormal waveform in the full-wave rectified waveform is detected to determine that the AC output waveform is abnormal. Since the determination is made and the abnormality determination signal is output, even if the switching element of the inverter 2 malfunctions and a half-wave waveform is output, the generation of the half-wave waveform can be accurately detected. The operation of the inverter 2 can be stopped in response to the detection of the half-wave waveform, and a situation in which a load such as a motor has a start failure or the stator coil is burned due to being restricted by an abnormal power source is prevented in advance. be able to.

The main part of the inverter monitoring device 3 is
Since it is composed of a rectifier, an OR circuit, and a count circuit,
The inverter monitoring device 3 can be simply configured with a small number of components and component types, and a space is not required so much. Therefore, it can be housed in a printed circuit board, can be used by being built in the inverter system without externally mounting the inverter monitoring device 3, and the inverter system itself can be constructed in a space-saving manner. In addition, the user can save the trouble of externally attaching and it becomes easy to use.

Further, when the AC output waveform from the inverter 2 is normal, the full wave rectified waveform of the signal S2 and the base inversion signal S3 are such that Hi and Lo appear exactly opposite to each other, so that the inverter If the AC output waveform from 2 has an abnormal portion even a little, the abnormality will appear in the output signal S4 of the OR circuit 52. Therefore, for example, even if a pseudo AC waveform is generated due to a back electromotive force generated when a half-wave output enters the transformer winding or the like, the pseudo AC waveform can be accurately detected, and the half-wave waveform can be detected with high accuracy. become.

In the above description, the pulse count number until the abnormality is detected is 20 pulses, but this pulse count number can be arbitrarily set as required.

[0029]

As described above, according to the inverter monitoring device of the present invention, the AC output waveform output from the inverter is full-wave rectified, and the abnormal waveform in the full-wave rectified waveform is detected to output the AC output. Since it is determined that the waveform is abnormal and an abnormality determination signal is output, even if the switching element of the inverter malfunctions and a half-wave waveform is output, it is possible to accurately detect the occurrence of the half-wave waveform. Can
In addition, the operation of the inverter can be stopped in response to the detection of this half-wave waveform, and the situation in which a start failure occurs in the load of the motor or the like, or the stator coil is burned due to being restricted by an abnormal power source is prevented. can do. Further, since the main part of the inverter monitoring device is composed of the rectifier, the OR circuit, and the counting circuit, the inverter monitoring device can be simply configured with a small number of parts and types of parts, and a space is not required so much. As a result, it can be stored on a printed circuit board, can be used by being built in the inverter system without externally installing the inverter monitoring device, and not only can the inverter system itself be constructed in a space-saving manner. , It is easy for the user to use because it can save the trouble of external attachment.
Furthermore, if there is any abnormal portion in the AC output waveform from the inverter, the abnormality appears as an abnormal waveform detection signal.For example, a pseudo AC waveform is generated by a counter electromotive voltage generated when a half-wave output enters the transformer winding. Even if occurs, the pseudo AC waveform can be accurately detected, and the half-wave waveform can be detected with high accuracy.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of an inverter monitoring device of the present invention.

FIG. 2 is a schematic circuit diagram as a specific example of an inverter monitoring device.

FIG. 3 is a time chart showing signals at respective points of the inverter monitoring device.

[Explanation of symbols]

 1 Generator 2 Inverter 3 Inverter Monitoring Device 4 Rectification Waveform Output Means 5 Abnormality Detection Means 6 Abnormality Judgment Means 7 Counting Circuit 22 Inverter Operation Stopping Means 23 Base Waveform Generating Means 41 Rectifier 42 Photocoupler 52 OR Circuit 61 Counting Circuit

Claims (4)

[Claims] 1. A rectified waveform output means for full-wave rectifying and outputting an AC output waveform output from an inverter, and an output waveform from the rectified waveform output means, which occurs due to an abnormality in the AC output waveform. Abnormality detecting means for detecting the abnormal waveform detected and outputting it as an abnormal waveform detection signal, and abnormality determining means for determining that the AC output waveform from the inverter is abnormal based on the abnormal waveform detection signal and outputting the abnormality determination signal An inverter monitoring device comprising: 2. The abnormality detecting means detects the abnormal waveform based on an output waveform of the rectified waveform output means and a base inverted waveform generated by inverting a base waveform which is a synchronizing signal of an AC output waveform in the inverter. The inverter monitoring device according to claim 1, wherein detection is performed. 3. The inverter monitor according to claim 1, wherein the abnormal waveform detection signal is a pulse wave, and the abnormality determination means outputs the abnormality determination signal when counting a predetermined number or more of pulse waves. apparatus. 4. The inverter monitoring device according to claim 1, further comprising an inverter operation stopping means for stopping the operation of the inverter in response to the abnormality determination signal.