JP2009296806A - Monitor of ac motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a monitor of an AC motor which is unlikely to be affected by the current amplitude and has high detection accuracy. <P>SOLUTION: The monitor of the AC motor includes: an individual current detecting means, for example, an individual current detector 5 which detects an individual current flowing through a plurality of hysteresis motors 3 from an AC power supply 2, respectively; a total current detecting means, for example, a total current detector 4 which detects a total current flowing through the whole AC motors 3 from the AC power supply 2; and a determination means, for example, a monitoring circuit 7 which determines that one or more the hysteresis motors 3 are abnormal when a current phase difference from an individual current detection value exceeds an abnormal determination level (specified value) determined by the hysteresis motors 3 with a total current detection value as a reference, out of current detection values simultaneously detected by the total current detector 4 and the individual current detector 5. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a monitoring apparatus for an AC motor that monitors an operating state of an AC motor of a synchronous motor such as a hysteresis motor or an asynchronous motor such as an induction motor.

  Conventionally, in a system in which a plurality of hysteresis motors are connected in parallel to a common AC power source and a load is driven, the state of each hysteresis motor is monitored, and the abnormal hysteresis motor is disconnected to continue the operation.

  As shown in FIG. 10, the average vector difference method used conventionally detects the current of each hysteresis motor, and the difference between the averaged reference (average current vector) and each current vector is preset. When the specified value (circular portion) is exceeded, it is determined that the motor is abnormal (see Patent Document 1).

The abnormality detection level is set so that an abnormality is not judged even though it is normal due to variations in the characteristics of each hysteresis motor. In order to improve the detection accuracy, the average current vector difference method corrects the reference vector for each monitoring group (see Patent Document 2) and adjusts the level for detecting an abnormality (see Patent Document 3) according to the number of units to be monitored. is doing.
JP 2000-092894 A JP2000-092895 JP2000-253695A

  Hysteresis motors have large current value fluctuations due to individual motor variations and aging, and the abnormality detection level cannot be set small. When the abnormal value detection level is set to a small value, it is determined that a normal hysteresis motor is abnormal.

  In the average current vector difference method, an abnormality detection level is set based on a difference in current amplitude. In general, the variation in current amplitude is larger than the variation in power factor (phase), so it has been difficult to improve the accuracy of the average current vector difference method.

  An object of the present invention is to provide a monitoring device for an AC motor that is not easily affected by current amplitude and has high detection accuracy.

In order to achieve the above object, an invention corresponding to claim 1 is an AC motor monitoring device for monitoring an abnormality of a plurality of AC motors connected in parallel to a common AC power source. Simultaneously by individual current detection means for detecting individual currents flowing through the AC motor, total current detection means for detecting total current flowing from the AC power source to the entire AC motor, the total current detection means and the individual current detection means simultaneously. Of the detected current detection values, the AC motor is determined to be abnormal when the current phase difference from the individual current detection value exceeds an abnormality determination level determined by the AC motor, with the total current detection value as a reference. Determination means to perform,
It is the monitoring apparatus of the alternating current motor provided with.

  In order to achieve the object, an invention corresponding to claim 2 is an AC motor monitoring device that monitors abnormalities of a plurality of AC motors connected in parallel to a common AC power source. Individual current detection means for detecting individual currents flowing through the AC motors, average calculation means for obtaining an average value of individual current detection values detected by the individual current detection means, and an average value obtained by the average calculation means as a reference And an AC motor monitoring device comprising: determination means for determining that the AC motor is abnormal when a current phase difference from the individual current detection value exceeds an abnormality determination level determined by the AC motor.

  In order to achieve the object, an invention corresponding to claim 4 is an AC motor monitoring device that monitors abnormalities of a plurality of AC motors connected in parallel to a common AC power source. With reference to the individual current detection means for detecting the individual current flowing through each AC motor, the voltage detection means for detecting the voltage applied to the entire AC motor from the AC power source, and the voltage detected by the voltage detection means, AC motor monitoring comprising: a determination unit that determines that the AC motor is abnormal when a current phase difference from an individual current detection value detected by the individual current detection unit exceeds an abnormality determination level determined by the AC motor Device.

  According to the present invention, it is possible to provide a monitoring device for an AC motor that is not easily affected by the current amplitude and that has high detection accuracy.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of an AC motor monitoring device of the present invention will be described with reference to the drawings. In the following description, a synchronous motor such as a hysteresis motor will be described as an example of an AC motor. However, the present invention is not limited to this and can be similarly applied to an asynchronous motor such as an induction motor.

[Embodiment 1]
FIG. 1 is a diagram showing a schematic configuration of the first embodiment. The monitoring device of the present invention supplies power to the hysteresis motor 3 from the AC power source 2 via the hysteresis motor monitoring device 1.

  The monitoring apparatus according to the first embodiment includes individual current detection means for detecting individual currents flowing from the AC power supply 2 to the plurality of hysteresis motors 3, for example, an individual current detector 5, and the total current flowing from the AC power supply 2 to the entire AC motor 3. Current detection means, for example, the total current detector 4, and among the current detection values simultaneously detected by the total current detector 4 and the individual current detector 5, the total current detection value is used as a reference and the individual current detection value When the current phase difference exceeds an abnormality determination level (specified value) determined by the hysteresis motor 3, determination means for determining that the hysteresis motor 3 is abnormal, for example, a monitoring circuit 7 is provided.

The monitoring circuit 7 is configured as follows. The individual currents Iun and Iwn of the hysteresis motors HMn (n is 1 to k) selected by the total currents Iua and Iwa and the switching circuit 71 are balanced sine waves as shown in (1) to (4). The phase θs is
θs = ωt (ω = 2πf: f is the frequency of the AC power supply 2).

Iua = Asin (θs + θa) (1)
Iwa = Asin (θs + θa − 4π / 3) (2)
Iun = Bsin (θs + θn) (3)
Iwn = Bsin (θs + θn−4π / 3) (4)
(A: total current amplitude, B: individual current amplitude, θa: phase difference from phase θs of total current,
θn: phase difference from the phase θs of the hysteresis motor HMn)
The total currents Iua and Iwa and the individual currents Iun and Iwn of the motor n selected by the switching circuit 71 are held by a holding circuit 72, and sampling times tn1, tn2,..., Tni,. (In the case of FIG. 2, t11, t12,..., T1i,..., T1m (HM1 selection)) detected value iua,
Expressions (5) to (8) are obtained by iwa, iun, and iwn.

iua = Iua (t = tni) (5)
iwa = Iwa (t = tni) (6)
iun = Iun (t = tni) (7)
iwn = Iwn (t = tni) (8)
(where n is the HM number and i is the number of samplings)
FIG. 2 shows a current waveform input to the monitoring circuit 7. A solid line indicates a current waveform obtained by averaging all currents per unit, and a broken line indicates an individual current of the hysteresis motor HM1 selected by the switching circuit 71. The black circles in FIG. 2 are all currents iua and iwa, and the circles are individual currents iu1 and iw1 (FIG. 2 selects HM1).

The total currents iua and iwa and the individual currents iun and iwn are subjected to three-phase to two-phase conversion by the coordinate conversion circuit 74 using the reference θ of the phase reference circuit 78, and the total currents ida and iqa ((9)) Equation), individual currents idn, iqn (Equation (10)) are calculated.

In the derivation of the equations (17) and (18), the AC power supply 2 and the coordinate conversion reference θ are the same (θs = θ), but Δθ = θa−θn = −tan ⁻ as in the equation (23). ¹ (iqa / ida) + tan ⁻¹ (iqn / idn), and since the phase difference Δθn does not depend on θs, θ can be set to an arbitrary value.

    Although current detection is performed by two-phase current detection, it can be similarly applied to three-phase current detection.

  According to the first embodiment described above, by detecting an abnormality of the hysteresis motor 3 based on the current phase, it is possible to provide a monitoring apparatus for a hysteresis motor with a high degree of abnormality detection accuracy by reducing the influence of variations in the absolute current value.

[Embodiment 2]
As shown in FIG. 4, the second embodiment is different from the first embodiment described above in terms of the characteristics of the hysteresis motor 3 and correction means for correcting the individual current phase difference caused by the variation in the detector, for example, a phase correction circuit 712, Setting correction means for adjusting an abnormality determination level (specified value) according to the number of hysteresis motors 3, for example, a setting correction circuit 713 is newly added.

  As shown in FIG. 3, when there is variation in the current and power factor of each hysteresis motor, a phase difference Δθn occurs even during normal operation. When the normal operation of the hysteresis motor is confirmed, Δθn is stored as Δθ0n, and the output Δθ0n of the phase correction circuit 712 is subtracted from the phase difference Δθn, so that each hysteresis motor can be matched with the reference.

Δθ0n = θav_a−θav_n (24)
(Δθ0n is Δθn = θav_a−θav_n at normal time)
The setting correction circuit 713 calculates a correction value Δθlref for abnormality detection level setting for abnormality determination. Since all the reference currents include abnormal hysteresis motors, the abnormality detection level Δθl in equation (8) varies depending on the number of hysteresis motors 3 to be monitored. The smaller the number of monitored units, the greater the change in the reference when an abnormality occurs. For example, the output Δθlref of the setting correction circuit 713 is expressed by the equation (24) obtained by dividing the specified value Δθl by the number of operating units k.

Δθlref = Δθl / k (24)
(K is the number of operating hysteresis motors)
The abnormality determination equation (22) of the hysteresis motor 3 is the equation (22) that is obtained by adding the outputs of the phase correction circuit 712 and the setting correction circuit 713.

| Δθn − Δθ0n |> Δθl − Δθlref (25)
In the abnormality determination (25) equation, the current, power factor and detector variations of each hysteresis motor 3 are corrected on the right side, and the abnormality determination level corresponding to the change in the number is corrected on the left side, and the accuracy of the hysteresis motor abnormality determination level is corrected. Will improve.

  According to the second embodiment described above, a hysteresis motor monitoring device with high detection accuracy is provided by adjusting the abnormality determination level according to the number of AC motors to be corrected and monitored by the hysteresis motor 3 and detectors. it can.

[Embodiment 3]
In the third embodiment, as shown in FIG. 5, individual current detection means for detecting individual currents flowing from the AC power source 2 to the hysteresis motors 3, for example, individual current detectors 5, and individual current detectors 5 detect individual currents. An average calculation means for obtaining an average value of the current detection values, for example, an average circuit 79, and an abnormality determination level at which the current phase difference from the individual current detection values is determined by the hysteresis motor 3 based on the average value obtained by the average circuit 79. When it exceeds, a judging means for judging that the hysteresis motor 3 is abnormal, for example, a monitoring circuit 7 is provided.

  In the above-described embodiment, the detection value of the total current detector 4 of the hysteresis motor 3 is used as a reference. In this embodiment, the abnormality determination of the hysteresis motor 3 is performed using the average value of the current detected by the individual current detector 5 as a reference. It is what I do.

Iu_av ＝ （Iu1 + Iu2 + Iu3 + ・ ・ ・ ・ ・ + Iuk） / k (26)
Iw_av ＝ （Iw1 + Iw2 + Iw3 + ・ ・ ・ ・ ・ + Iwk) / k (27)
However, k is the number of operating units. Therefore, the difference between the first embodiment and the third embodiment is that the first embodiment is based on the total current, but the third embodiment is based on the average value of the individual currents. Are the same. In the third embodiment, the total current detector 4 of the hysteresis motor is not necessary and is omitted.

    In the first and second embodiments, since two types of current detectors (the total current detector 4 and the individual current detector 5) are used, a detection error occurs due to a difference in the rating of the current detector. In this case, since there is only one type of current detector 5, it is effective when the detection error due to the type of current detector is large.

[Embodiment 4]
As shown in FIG. 6, the fourth embodiment includes an AC motor selection unit, for example, an HM selection circuit 711, which newly selects the hysteresis motor 3 to be monitored among the plurality of hysteresis motors 3 in the embodiment of FIG. 5. The monitoring circuit 7 uses the average value of the individual current detection values of the hysteresis motor 3 not selected by the HM selection circuit 711 as a reference, and the phase difference of the individual current detection values of the hysteresis motor 3 selected by the HM selection circuit 711 indicates the abnormality determination level. When it exceeds, the hysteresis motor 3 is determined to be abnormal.

    Specifically, in the third embodiment, the average value of the individual hysteresis motors 3 is used as a reference, but in the fourth embodiment, the average current of a hysteresis motor other than one hysteresis motor that is the target of abnormality determination is used as a reference. The abnormality judgment of one judgment object hysteresis motor is performed.

    For example, the case where the first hysteresis motor is targeted is shown below.

Iu_av ＝ （Iu2 + Iu3 + ・ ・ ・ ・ ・ + Iuk) / (k-1) (28)
Iw_av ＝ （Iw2 + Iw3 + ・ ・ ・ ・ ・ + Iwk) / (k-1) (29)
However, k is the number of operating units. Therefore, the difference between the third and fourth embodiments is that the third embodiment is based on the current of all hysteresis motors, but the fourth embodiment is an average value of individual currents excluding the monitored hysteresis motor. Therefore, an HM selection circuit 711 is added to FIG. The hysteresis motor (HM) selected by the HM selection circuit 711 is excluded from the average target by the averaging circuit 710 and is selected as the switching target by the switching circuit 71.

    According to the fourth embodiment, by setting the reference to the average value of the individual currents of the hysteresis motor 3 that is not subject to abnormality determination, the abnormal AC motor can be excluded from the reference, and the detection accuracy is improved.

[Embodiment 5]
In the fifth embodiment, as shown in FIG. 7, individual current detection means for detecting individual currents flowing from the AC power supply 2 to each hysteresis motor 3, for example, the individual current detector 5, and the AC power supply 2 are applied to the entire AC motor. Voltage detection means for detecting the voltage to be detected, such as a voltage detector 714;
When the current phase difference from the individual current detection value detected by the individual current detector 5 exceeds the abnormality determination level determined by the hysteresis motor 3 with reference to the voltage detected by the voltage detector 714, the hysteresis motor 3 is abnormal. For example, a monitoring circuit 7 is provided.

  In the fifth embodiment, the first to fourth embodiments use the current detection value as a reference, while in the fifth embodiment, abnormality determination is performed using the voltage as a reference. In FIG. 7, the total current detector 4 and the setting correction circuit 713 are deleted from the system of FIG. 4, and a voltage detector 714 is added.

  The change from FIG. 4 will be described. The voltages Vu and Vw detected by the voltage detector 714 are balanced sine waves as shown in (30) and (31). The phase θs is θs = ωt (ω = 2πf: f is the frequency of the AC power supply 2).

  The individual currents Iun and Iwn are the same as the equations (3) and (4).

Vu = Csin (θs + θv) (30)
Vw = Csin (θs + θv − 4π / 3) (31)
(C: voltage amplitude, θv: phase difference from voltage phase θs)
The voltages Vu and Vw and the individual currents Iun and Iwn of the hysteresis motor n selected by the switching circuit 71 are held by the holding circuit 72, and sampling times tn1, tn2,... Tni,. (In the case of FIG. 8, t11, t12,..., T1i,..., T1m (HM1 selection)) detected value vu,
vw is expressed by equations (32) and (33), and iun and iwn are expressed by equations (7) and (8).

vu = Vu (t = tni) (32)
vw = Vw (t = tni) (33)
(I is the number of samplings)
FIG. 8 shows voltage and current waveforms input to the monitoring circuit 7. The solid line represents the voltage waveform, and the broken line represents the individual current of the hysteresis motor HM1 selected by the switching circuit 71. The black circles in FIG. 8 are the voltages Vu and Vw, and the circles are the individual currents iu1 and iw1 (FIG. 8 selects HM1).

In the derivation of equations (39) and (18), the AC power supply 2 and the coordinate conversion reference θ are the same (θs = θ), but Δθ = θv−θn = −tan ⁻ as in equation (43). ¹ (vq / vd) + tan ⁻¹ (iqn / idn), and the phase difference Δθn does not depend on θs, so that θ can be an arbitrary value.

    Since the phase difference between the voltage and the individual current does not reflect the detected value of the abnormal hysteresis motor as in the case of using the total current and the individual current, setting by the number of units in the setting correction circuit 713 Correction of the value Δθlref is not necessary. The discriminant of the abnormality determining circuit 77 is the equation (29).

| Δθn − Δθ0n |> Δθlv (29)
[Embodiment 6]
In the sixth embodiment, as shown in FIG. 9, the schematic individual current detector 5 can detect currents flowing through a plurality of hysteresis motors 3 forming a set among the hysteresis motors 3.

    In the first embodiment shown in FIG. 1, the number of hysteresis motors detected by the individual current detector 5 is one, but in the embodiment shown in FIG. 9, for example, two hysteresis motors are monitored. Since the detection based on the current phase difference can improve the accuracy compared to the detection based on the conventional absolute value, a plurality of units can be detected by passing the same-phase wires of the plurality of hysteresis motors through the individual current detector 5 in a lump. It has become possible.

    Although two units are shown in FIG. 9, two or more units can be detected if the individual current detector 5 can penetrate the electric wire.

  According to the sixth embodiment, by detecting the current of a plurality of hysteresis motors in the individual current detector 5 attached to each hysteresis motor, the hysteresis motor can be monitored without adding the current detector 5. The number can be increased.

[Modification]
4 includes a phase correction circuit 712 that corrects individual current phase differences generated due to variations in the characteristics of the hysteresis motor 3 and detectors, and a setting correction circuit 713 that adjusts the abnormality determination level according to the number of hysteresis motors 3. 5, FIG. 6, and FIG. 9 may be provided.

  It goes without saying that an average value calculation circuit 76 that samples and averages the current phase difference shown in the first embodiment in FIG. 4 may be provided as shown in FIGS.

  The concept of the individual current detector shown in FIG. 9 may be applied to FIGS.

Schematic for demonstrating Embodiment 1 of the monitoring apparatus of the alternating current motor of this invention. The figure which shows the total current of U phase of FIG. 1, W phase, and an individual current waveform (when HM1 is selected). The figure which shows the electric current vector (when HM1 is selected) of FIG. Schematic for demonstrating Embodiment 2 of the monitoring apparatus of the alternating current motor of this invention. Schematic for demonstrating Embodiment 3 of the monitoring apparatus of the alternating current motor of this invention. Schematic for demonstrating Embodiment 4 of the monitoring apparatus of the alternating current motor of this invention. Schematic for demonstrating Embodiment 5 of the monitoring apparatus of the alternating current motor of this invention. The figure which shows the voltage of U phase of FIG. 7, W phase, and an individual current waveform (when HM1 is selected). Schematic for demonstrating Embodiment 6 of the monitoring apparatus of the alternating current motor of this invention. The figure for demonstrating the conventional monitoring method (average vector difference method).

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Hysteresis motor monitoring apparatus, 2 ... AC power supply, 3 ... Hysteresis motor, 4 ... Total current detector, 5 ... Individual current detector, 7 ... Monitoring circuit, 71 ... Switching circuit, 72 ... Holding circuit, 73 ... AD conversion Circuit 74 74 Coordinate conversion circuit 76 Average value calculation circuit 77 Abnormality determination circuit 78 Phase reference circuit 79 Average circuit 710 Average circuit 711 HM selection circuit 712 Phase correction circuit 713 ... setting correction circuit, 714 ... voltage detector.

Claims (7)

In an AC motor monitoring device that monitors abnormalities of a plurality of AC motors connected in parallel to a common AC power source,
Individual current detecting means for detecting individual currents flowing from the AC power source to the AC motors, respectively;
A total current detecting means for detecting a total current flowing from the AC power source to the entire AC motor;
Of the current detection values detected simultaneously by the total current detection means and the individual current detection means, the abnormality determination in which the current phase difference from the individual current detection value is determined by the AC motor based on the total current detection value A determination means for determining that the AC motor is abnormal when a level is exceeded;
An AC motor monitoring device comprising: In an AC motor monitoring device that monitors abnormalities of a plurality of AC motors connected in parallel to a common AC power source,
Individual current detecting means for detecting individual currents flowing from the AC power source to the AC motors, respectively;
An average calculation means for obtaining an average value of the individual current detection values detected by the individual current detection means;
Determination means for determining that the AC motor is abnormal when a current phase difference from the individual current detection value exceeds an abnormality determination level determined by the AC motor based on the average value obtained by the average calculation means;
An AC motor monitoring device comprising: In the monitoring apparatus of the alternating current motor according to claim 2,
AC motor selection means for selecting an AC motor to be monitored from among the plurality of AC motors, wherein the determination means is based on an average value of individual current detection values of AC motors not selected by the AC motor selection means, and the AC A monitoring apparatus for an AC motor, wherein the AC motor is determined to be abnormal when the phase difference between the individual current detection values of the AC motor selected by the motor selection means exceeds an abnormality determination level. In an AC motor monitoring device that monitors abnormalities of a plurality of AC motors connected in parallel to a common AC power source,
Individual current detecting means for detecting individual currents flowing from the AC power source to the AC motors, respectively;
Voltage detecting means for detecting a voltage applied to the entire AC motor from the AC power source;
When the current phase difference from the individual current detection value detected by the individual current detection unit exceeds the abnormality determination level determined by the AC motor, with the voltage detected by the voltage detection unit as a reference, the AC motor is abnormal Determining means for determining
An AC motor monitoring device comprising:   5. The monitoring apparatus for an AC motor according to claim 1, wherein individual current levels generated due to variations in characteristics of the AC motor, the total current detection means, the individual current detection means, and the voltage detection means. A monitoring apparatus for an AC motor having correction means for correcting a phase difference and setting correction means for adjusting the abnormality determination level according to the number of the AC motors. In the monitoring apparatus of the alternating current motor according to any one of claims 1 to 5,
The individual electric current detection means detects an electric current flowing in each of a plurality of AC motors forming a set among the AC motors. In the monitoring apparatus of the alternating current motor according to any one of claims 1 to 6,
The AC motor monitoring device further comprises means for sampling and averaging the current phase difference a plurality of times.

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