JP2005227073A - Phase interruption detection device and pump system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a phase interruption detection device capable of easily and surely detecting the generation of the phase interruption at a low cost by constructing the phase interruption detection means with a soft wear utilizing the conventional current detection means and the operation process means. <P>SOLUTION: The phase interruption detection system comprises three phase AC power source; the current detectors 13, 14 interlinked with two phases between the power source and the three phase load receiving power therefrom; the detection means 16 for detecting current wave form from the detection signals of the current detectors; the means 16 for detecting the effective current value, current maximum value, and the zero cross time current value at the time the other phase is zero cross from the current wave forms; and the comparison means 16 for comparing these detection values. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a phase loss detection device, and more particularly to a phase loss detection device capable of detecting a phase loss in power supplied from a three-phase AC power source to a load device such as a pump with a two-phase current detector. Moreover, it is related with the pump system provided with the said phase loss detection apparatus.

Conventionally, most pump systems used for deep wells and water supply devices are equipped with three-phase motors, and there is a phase loss due to some cause in the power supplied from the three-phase AC power supply to these pumps. If this occurs, inconvenience occurs in the operation of the pump. For this reason, a phase loss detection device that detects that phase loss has occurred in power supplied from a three-phase AC power supply has been known (see, for example, Patent Documents 1 and 2).
Japanese Patent Laid-Open No. 7-134154 JP-A-62-102166

  For example, in Patent Document 1, current detectors are arranged in two of the three phases, and from the relationship between the detected current and a predetermined current, an open phase of any phase in which the current detector is arranged is detected. There has been proposed a phase loss detection device that detects a phase loss of a phase in which no current detector is arranged by comparing a current before a predetermined time (for example, 1 second) with a current current. According to this phase loss detection device, if a phase failure occurs in a phase that does not have a current detector, the current greatly increases from the phase current to the line current before and after the phase loss, so a change in current is detected. By doing so, it is possible to detect an open phase of a phase in which no current detector is arranged.

  Further, in Patent Document 2, a current detector is arranged for each of the three phases, the detected current of each phase is sampled every 30 °, and one cycle is stored in the RAM. There has been proposed an open phase detection method in which a partial current is calculated, an unbalance rate is calculated, and a phase failure is determined when the unbalance rate exceeds a predetermined value.

  However, in the phase loss detection device described in Patent Document 1, when phase loss occurs in the power supplied to the three-phase motor that drives the pump, the current does not necessarily increase from the phase current to the line current. Absent. For this reason, there is a problem that an open phase cannot always be detected accurately.

  Further, in the phase loss detection device described in Patent Document 2, it is necessary to arrange current detectors in all three phases, and complex calculation processing is performed using the detection results of the respective current detectors. is required. For this reason, the phase loss detection apparatus of Patent Document 2 has a problem that the cost is high and the calculation process also takes time.

  The present invention has been made in view of the above-described circumstances. By using the existing current detection means and arithmetic processing means and constructing the phase loss detection means with software, it is easy and reliable at low cost. An object of the present invention is to provide a phase loss detection device capable of detecting the occurrence of phase loss. Moreover, it aims at providing the pump system provided with the said phase loss detection apparatus.

  The phase loss detection device of the present invention that solves the above problems detects a current of two phases of the three phases interposed between a three-phase AC power source and a three-phase load that receives power supply from the power source. A current detector, a detecting means for detecting a current waveform from a detection signal of the current detector, and a current effective value, a maximum current value, and a current waveform of the other phase from the current waveform at a point where the zero point intersects. It is characterized by comprising means for detecting a current value at zero crossing at a certain zero crossing timing, and comparison means for comparing these detected values.

  According to the present invention, the phase loss detection means can be constructed only by software using the existing current detection means and arithmetic processing means in the pump system and the like. That is, in general, in a pump system, current detection means is provided in two of the three phases to detect an overcurrent or to control the operation of the pump. For this reason, the pump system generally includes an arithmetic processing unit including a CPU and a memory for performing arithmetic processing on the detected current. According to the present invention, it is possible to easily and surely detect the occurrence of a phase loss at low cost by constructing the phase loss detection unit only with software using the existing current detection unit and arithmetic processing unit. Therefore, it is possible to provide a phase loss detection device capable of achieving the above.

  Here, it is preferable that the comparison means is a means for comparing two-phase current effective values to be detected with each other. As a result, by comparing the current effective values of the two phases to be detected with each other, the current effective value of the phase to be detected becomes approximately zero when a phase failure occurs. Can be detected.

  The comparison means is preferably means for comparing the current maximum value of the two-phase current to be detected with the current value at the time of the other phase zero crossing. As a result, when a phase failure occurs in a phase other than the two phases provided with the current detector to be detected, the currents of the two phases to be detected are in phase with each other. The value is almost zero. For this reason, when the ratio between the current maximum value and the current value at the time of the other phase zero crossing is obtained, it becomes substantially zero, so that an open phase of a phase other than the two phases to be detected in which the current detector is arranged can be detected.

  Moreover, it is preferable to provide a memory for storing half a cycle or one cycle of the current waveform. Thereby, the current effective value, the current maximum value, and the current value at the time of other phase zero crossing can be easily detected from the current waveform.

  The pump system of the present invention is a pump system that receives power supply from a three-phase AC power source, and detects current of two phases of the three phases between the three-phase AC power source and the pump motor. , A detecting means for detecting a current waveform from a detection signal of the current detector, and a current effective value, a maximum current value, and a current value at the time of zero crossing at the timing when the other phase is zero crossed from the current waveform. And a phase loss detection device comprising means.

  Generally, according to the present invention, it is possible to provide an open phase detection device that can detect the occurrence of open phase easily and reliably at low cost. And in a pump system provided with this phase loss detection device, phase loss can be detected easily and reliably with almost no manufacturing cost.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1-3 is a figure which shows embodiment of the pump system carrying the phase loss detection apparatus based on this invention. In addition, in each figure, the same code | symbol is attached | subjected to the member or element which has the same effect | action or function, and the overlapping description is abbreviate | omitted.

  In FIG. 1, the pump system receives power supply from a three-phase AC power source through three-phase lines r, s, t, and a three-phase motor (three-phase load) 11 rotates to drive an impeller of the pump body 12. To supply and drain water. For example, in this pump system, the pump motor 11 is controlled to be turned on and off to accumulate water at a predetermined pressure in a tank (not shown), and water is supplied from the tank. For this reason, an arithmetic processing unit 15 including a CPU 16 is provided for operation control of the pump system. Further, it is necessary to detect the line current for overcurrent protection of the pump motor, etc. Therefore, CT13a, 14a and current detection circuits 13, 14 are provided in two of the three phases. For example, in order to detect overcurrent, the currents detected by the CTs 13a and 14a and the current detection circuits 13 and 14 are input to the arithmetic processing unit 15, and the overcurrent is detected by performing arithmetic processing there. And generating alarms. In FIG. 2, 18 is a display operation unit, 19a is a connection terminal with the display operation unit, and 19b is an external output terminal.

  In this pump system, an open phase detector 10 is connected to a line between three-phase AC power terminals R, S, T and a motor (three-phase load) 11. The current flowing through the line connected to the power source is detected by CTs 13a and 14a mounted on two phases of them. Then, two sets of current detection circuits 13 and 14 that convert the detected current into a voltage and output a detection signal corresponding to the current waveform, and perform calculation processing of the detection signals from the current detection circuits 13 and 14 to perform three-phase processing And an arithmetic processing unit 15 that detects the occurrence of phase loss in the current. Here, the phase loss detection device 10 of the present embodiment may attach the CTs 13a and 14a of the current detection circuits 13 and 14 to any two of the lines r to t from the three-phase AC power supply. In the embodiment, a case where CT 13a is attached to the R-phase line r and CT 14a is attached to the T-phase line t will be described.

  The CTs 13a and 14a, the current detection circuits 13 and 14 and the arithmetic processing unit 15 used in the phase loss detection device 10 can be used in combination with those used for operation control of the pump system described above. Therefore, in this phase loss detection device 10, it is possible to divert the existing system as it is by constructing only software for phase loss detection described below.

  As shown in FIG. 2A, the detection signals of the current detection circuits 13 and 14 are sinusoidal waveforms, and the current waveform from the three-phase AC power supply is 120 between the two phases of the R phase and the T phase at normal times. Detected as a sinusoidal waveform that is out of phase. When an open phase occurs in the R phase or the T phase from the three-phase AC power source, it is needless to say that the current waveform is only one of the R phase and the T phase. When an open phase occurs in the S phase from the three-phase AC power supply, the current waveforms of the R phase and the T phase are the same phase as shown in FIG.

  From this, the arithmetic processing unit 15 compares the detection signals (current waveforms) of the current detection circuits 13 and 14 according to a program stored in a memory (not shown) by the CPU 16, so that the R from the three-phase AC power supply is obtained. From the comparison result corresponding to the change in the detection signal due to the occurrence of the missing phase in any of the phase, the S phase, and the T phase, the phase in which the missing phase is generated can be detected.

  That is, the CPU 16 samples the detection signal of the half cycle or one cycle of the current detection circuits 13 and 14 every 0.5 mSec, for example, and stores it in the memory (RAM) 17. Then, by comparing these data while temporarily storing them in the RAM 17, the phase in which a phase failure has occurred is detected. Specifically, the CPU 16 can detect the occurrence of an open phase in the R phase or the T phase of the current waveform detection target by comparing the effective current values of the R phase and the T phase. Further, when the ratio of the current value at the time of other phase zero crossing to the maximum current value of the R phase and the T phase is equal to or less than a preset value, it can be determined (detected) that the S phase is missing.

  First, current effective values of the R phase and the T phase are obtained from the waveform data. The effective current value is obtained by integrating the current waveform data and calculating the area. When normal, the effective current values of the R phase and the T phase are equal. Therefore, when this ratio is taken, it becomes 1. However, when either the R phase or the T phase is missing, the effective current value of the missing phase is zero. Therefore, when the ratio with the phase that is not a phase that has been lost is taken, it becomes zero. For this reason, it can be easily detected that one of the R phase and the T phase is lost by comparing the effective values of both phases.

Also, the maximum current value Ipr in the R-phase current waveform, the zero-cross current value Izr at the zero-cross timing when the T-phase current value is zero, the maximum current Ipt in the T-phase current waveform, and the R-phase current value is zero. The current value Izt at zero crossing is obtained from the waveform data. At the normal time, as shown in FIG. 2A, the current waveforms of the R phase and the T phase are shifted by 120 °. For this reason,
Izr / Ipr = 0.86
Izt / Ipt = 0.86
It becomes. However, when the S phase is missing, the R phase and the T phase have the same phase as shown in FIG. 2B. For this reason,
Izr / Ipr = 0
Izt / Ipt = 0
It becomes. Therefore, the S phase phase loss can be easily detected by the above comparison.

  The current waveform data of each of the R phase and the T phase is stored in the RAM 17 (see FIG. 1) of the arithmetic processing unit 15 for 100 mSec. Then, for example, current value data is acquired every 0.5 mSec and overwritten and saved in the RAM 17. Then, by stopping the overwriting when the phase loss state is detected, the current waveform indicating the phase loss state can be saved. Then, by making this waveform accessible by the CPU 16, it is possible to observe the current waveform when the phase loss occurs on the personal computer by transmitting the current waveform data to another personal computer or the like by communication. it can. Therefore, by checking this current waveform, it can be used for maintenance work such as investigation of the cause of the phase loss.

  In addition, this current waveform data is always acquired, and even when an overcurrent or overload condition occurs, the current waveform in an overcurrent or overload condition can be obtained by stopping overwriting. It is possible to save. The current waveform data in such an abnormal state can be observed from a personal computer as described above, and can be used for various maintenance tasks as in the detection of the phase failure state. Further, by preparing, for example, 10 RAM areas of current waveform data for 100 mSec, it is possible to check the current waveform data at the time of detection for 10 times. In this case, when the number of detections is 11 times or more, it is preferable that the old data is sequentially overwritten and stored so that new 10 data can always be confirmed.

  Next, a specific procedure for phase loss detection will be described with reference to the flowchart of FIG. First, as shown in the flowchart of FIG. 3, the CPU 16 calculates the current effective value by integrating the R-phase current waveform, and similarly calculates and compares the T-phase current effective value (step S1). ).

In order to be able to compare with a preset ratio (set value), when an open phase occurs in the R phase and the current effective value is smaller than the current effective value of the T phase, the small value of the R phase is The numerator ratio A is calculated by the following formula. (Step S2)
Ratio A = (R phase effective current value / T phase effective current value) × 100 (%)

On the other hand, if the current effective value of the R phase is equal to or greater than the current effective value of the T phase, similarly, the ratio A that makes the value of the T phase a numerator is calculated by the following equation (step S3).
Ratio A = (effective current value of T phase / effective current value of R phase) × 100 (%)

  When the ratio A of the effective current value of the R phase / the effective current value of the T phase is smaller than the set ratio (step S4), it is determined that an open phase abnormality has occurred in the R phase (step S22).

  Similarly, when the ratio A of the effective current value of the T phase / the effective current value of the R phase is smaller than the set ratio (step S5), it is determined that an open phase abnormality has occurred in the T phase (step S23).

On the other hand, if the calculated ratio A is not smaller than the set ratio, the R-phase current maximum value, the T-phase current maximum value, the R-phase current value when the T-phase is zero-crossing, and the R-phase zero-crossing The current value of the T phase at the time is calculated (step S11), and the ratios B and C of the current value at the time of other phase zero crossing with respect to the maximum current values of the R phase and the T phase are calculated (steps S12 and S13).
Ratio B = (R-phase current value at T-phase zero crossing / R-phase current maximum value) × 100 (%)
Ratio C = (T-phase current value at R-phase zero crossing / T-phase current maximum value) × 100 (%)

  Next, the calculated ratios B and C are compared with the set ratio (step S14), and if any one of the ratios B and C is equal to or greater than the set ratio, it is assumed that no phase loss abnormality has occurred. Judgment is made (step S19). On the other hand, if both of the ratios B and C are smaller than the set ratio, it is determined that a phase failure abnormality has occurred in the S phase (step S20).

  In the above steps, when a phase loss abnormality occurs, the phase loss state is immediately displayed on the display operation unit 18 (see FIG. 1). That is, the phase in which the phase failure has occurred and the data such as the ratios A, B, and C, the occurrence time, etc. are displayed as necessary, and an alarm is generated. Therefore, since the occurrence of phase loss, particularly the phase that has lost phase, can be displayed, the cause of phase loss can be found at an early stage by intensively investigating the phase where phase loss has occurred. For this reason, the effect that the time concerning a maintenance can be shortened arises. Further, as described above, these pieces of information are sent to a personal computer or the like and used as maintenance data together with current waveform data.

  Here, although one embodiment of the present invention has been described so far, it is needless to say that the present invention is not limited to the above-described embodiment, and may be implemented in various forms within the scope of the technical idea. For example, the phase loss detection device can be applied not only to a pump system but also to various systems including a three-phase load that receives power supply from a three-phase AC power source.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows embodiment of the pump system carrying the phase loss detection apparatus based on this invention, and is a block diagram which shows the schematic whole structure. It is a figure which shows the detected electric current waveform, (a) is a wave form diagram which shows the electric current waveform at the time of normality, (b) is a wave form diagram which shows the electric current waveform at the time of abnormality (at the time of S phase missing). It is a flowchart explaining the detection process of the phase loss.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Phase loss detection apparatus 11 Three-phase motor 12 Pump main body 13a, 14a Current detector (CT)
13, 14 Current detection circuit 15 Arithmetic processor 16 CPU
17 RAM
18 Display operation section

Claims (5)

A current detector that detects a current of two phases of the three phases interposed between a three-phase AC power source and a three-phase load that receives power from the power source;
Detecting means for detecting a current waveform from a detection signal of the current detector;
It comprises means for detecting a current effective value, a current maximum value, and a current value at zero crossing at the timing when the other phase zero crosses from the current waveform, and a comparison means for comparing these detected values. Open phase detector.   2. The phase loss detection apparatus according to claim 1, wherein the comparison unit is a unit that compares the effective current values of the two phases to be detected with each other.   2. The phase loss detection device according to claim 1, wherein the comparison means is a means for comparing the current maximum value of the two-phase current to be detected with the current value at the time of the other phase zero crossing.   2. The phase loss detection apparatus according to claim 1, further comprising a memory for storing a half cycle or one cycle of the current waveform. A pump system that receives power supply from a three-phase AC power source, a current detector that detects a current of two phases of the three phases between the three-phase AC power source and the pump motor;
Detecting means for detecting a current waveform from a detection signal of the current detector;
A pump system comprising: a phase failure detection device including a current effective value, a current maximum value, and a zero crossing current value at a timing at which the other phase zero crosses from the current waveform.

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