Apparatus and method for detecting phase loss and interruption in three-phase AC power supply

Abstract

To provide a motor drive device with quicker response of detection of phase interruption and blockage of a three-phase AC power source as compared with a conventional device without changing a circuit arrangement responding to a power source voltage, and a method of detecting the phase interruption and the blockage.SOLUTION: An apparatus according to the present invention has photo couplers having light receiving elements that are set so as to be brought into their on-state if a voltage is a predetermined threshold voltage or higher and that are connected to between a L1 phase of the three-phase AC power supply 1 and a L2 phase thereof, between the L2 phase and a L3 phase thereof, and between the L3 phase and the L1 phase, respectively, converting voltages between the L1 phase of the three-phase AC power source and the L2 phase thereof, between the L2 phase and the L3 phase thereof, and between the L3 phase and the L1 phase into pulse detection signals, and a control unit for subjecting the respective pulse detection signals to AND operation to generate an AND operation pulse. Based on the respective pulse detection signals and the AND operation pulse, it is determined that any phase interruption occurs, whether or not any blockage occurs, and which phase among the L1 phase, the L2 phase and the L3 phase was interrupted.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an apparatus and method for detecting a loss or interruption of a phase in a three-phase AC power supply. [Background technology]

[0002] Conventionally, methods for detecting a loss of a phase or interruption of a three-phase AC power supply are known.

[0003] For example, in JP 2008-187874 A (Patent Document 1), a photocoupler is connected between each of the lines of a three-phase AC power supply, between the first and second phases, between the second and third phases, and between the third and first phases. The light-emitting element of this photocoupler emits light when a normal voltage is being supplied. Meanwhile, when the light-receiving element of the photocoupler is turned on, a pulse detection signal is output. Then, a missing phase of each phase is detected based on the presence or absence of this pulse detection signal (normal: pulse present, missing phase: no pulse).

[0004] For example, in JP 2012-42316 A (Patent Document 2), two phases of a three-phase AC power supply are connected to an electromagnetic contactor (R phase and T phase in the example). This allows detection of the presence or absence of excitation of the coil of the electromagnetic contactor to detect a missing phase of one of the two phases connected to the electromagnetic contactor. In addition, two phases other than the electromagnetic contactor (R phase and S phase in the example) are connected to a single-phase detection circuit. The light receiving element of the photocoupler in the single-phase detection circuit outputs a pulse detection signal by turning on. With this configuration, it is possible to detect a missing phase of one of the two phases by detecting the presence or absence of a pulse detection signal. Thus, Patent Document 2 discloses a method for detecting which phase is missing by combining the missing phase results obtained by the electromagnetic contactor and the single-phase detection circuit. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2008-187874 A [Patent Document 2] JP 2012-42316 A Summary of the Invention [Problem to be solved by the invention]

[0006] In Patent Document 1, in order to turn on the light receiving element of the photocoupler of only the missing phase in accordance with the power supply voltage, it is necessary to adjust the resistance value and the threshold value of the photocoupler, etc., and adjusting the circuit elements in accordance with the power supply voltage is time-consuming and laborious.

[0007] In Patent Document 2, a cutoff is detected using the DC voltage after a three-phase AC power supply is rectified by a rectifier circuit. However, a smoothing capacitor is connected in parallel to the rectifier circuit, and cutoff cannot be detected until the voltage of this capacitor becomes zero, resulting in a delayed detection response.

[0008] Therefore, an object of the present invention is to provide a detection device that can reduce the time and effort required for tasks such as adjusting circuit elements in accordance with the power supply voltage, or that can detect a phase loss or interruption of a three-phase AC power supply in a short period of time. [Means for solving the problem]

[0009] The three-phase AC power supply loss and interruption detection device of the present invention includes three photocouplers and a control unit. Each of these photocouplers includes a light receiving element that turns on at a predetermined threshold voltage or higher. In addition, these three photocouplers are connected between the lines of the L1 phase and L2 phase, the L2 phase and L3 phase, and the L3 phase and L1 phase of the three-phase AC power supply, respectively, and convert the line voltages between the L1 phase and L2 phase, the L2 phase and L3 phase, and the L3 phase and L1 phase into three detection signals. The control unit obtains three pulse detection signals or three inverted pulse detection signals from the three detection signals output from the three photocouplers. The inverted pulse detection signal is a signal obtained by inverting the three pulse detection signals. In this configuration, the control unit performs an AND operation on the three pulse detection signals, or inverts and performs an AND operation on the three inverted pulse detection signals to generate an AND operation pulse. Furthermore, the control unit determines the normal state or the presence or absence of a loss of phase or interruption based on the AND operation pulse. In addition, three pulse detection signals or three inverted pulse detection signals obtained by inverting the three pulse detection signals are obtained from three photocouplers connected between the L1 phase and the L2 phase, between the L2 phase and the L3 phase, and between the L3 phase and the L1 phase. An AND operation pulse is generated by performing an AND operation on the three pulse detection signals or by inverting and ANDing the three inverted pulse detection signals. The normal state or the presence or absence of a missing phase or interruption of the AC voltage is determined by the AND operation pulse. moreover, The control unit sequentially changes the first counter in a fixed direction while the value of the AND operation pulse remains "0," determines that the state is normal when the first counter exceeds a predetermined first value, returns the first counter to 0 when the value of the AND operation pulse switches from 0 to 1, and sequentially changes the second counter in a fixed direction while the AND operation pulse remains "1."The control unit then determines that an interruption has occurred when it determines that the second counter is equal to or exceeds a predetermined second value, and determines that an open phase has occurred when it determines that the second counter is equal to or exceeds a third value smaller than the second value after reaching "1."

[0010] These configurations can solve the desired problems. Effect of the Invention

[0011] In a three-phase AC power supply loss / interruption detection device according to one aspect of the present disclosure, the time required to adjust circuit elements according to the power supply voltage or the time required to detect a loss of phase or interruption of the three-phase AC power supply can be shortened. [Brief description of the drawings]

[0012] [Figure 1]FIG. 1 is a block diagram showing the configuration of a three-phase AC power supply open-phase / interruption detection device according to the first embodiment. [Diagram 2] FIG. 2 is a schematic diagram of the detection circuit of the detection device. [Diagram 3] FIG. 3 is a schematic diagram of the detection circuit when L3 is missing a phase. [Figure 4] FIG. 4 is a waveform diagram illustrating the normal operation of the detection device. [Diagram 5] FIG. 5 is a waveform diagram illustrating the operation of the detection device when a phase is lost. [Figure 6] FIG. 6 is a waveform diagram illustrating the operation of the detection device at the time of interruption. [Figure 7] FIG. 7 is a waveform diagram illustrating a method for determining whether a phase is missing. [Figure 8] FIG. 8 is a waveform diagram illustrating a method for determining whether a signal is blocked. [Figure 9] FIG. 9 is a waveform diagram for explaining a method for determining a missing phase and an interruption. [Figure 10] FIG. 10 is a flow chart showing a method for determining a missing phase and an interruption. [Figure 11] FIG. 11 is a flowchart showing a method for determining a loss of a phase in the device for detecting loss of a phase and interruption of a three-phase AC power supply according to the second embodiment. [Figure 12] FIG. 12 is a diagram summarizing the determination method in step S60. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] (How one aspect of the present disclosure was achieved) First, similarly to Patent Document 1, a photocoupler is connected between each of the lines of the L1 phase and the L2 phase, the L2 phase and the L3 phase, and the L3 phase and the L1 phase of the three-phase AC power supply. The photocoupler converts each of the line voltages between the L1 phase and the L2 phase, the L2 phase and the L3 phase, and the L3 phase and the L1 phase of the three-phase AC power supply into a pulse detection signal. The light receiving element of each photocoupler is configured to be turned on at a predetermined threshold voltage or higher. Furthermore, the control unit obtains the detection signal output from the photocoupler as a pulse detection signal. Alternatively, the control unit is configured to generate a pulse detection signal based on the detection signal output from the photocoupler.

[0014] However, in the configuration of Patent Document 1, when determining whether a phase is lost or interrupted in a three-phase AC power supply, as described above, it is necessary to change the circuit elements according to the power supply voltage.On the other hand, when determining whether a phase is lost or interrupted in a three-phase AC power supply as disclosed in Patent Document 2, the interruption cannot be detected until the voltage of the smoothing capacitor connected in parallel to the rectifier circuit becomes zero, so the detection response is delayed.

[0015] Therefore, the inventors improved the configuration of Patent Document 1 and, through repeated intensive investigations and experiments, came up with the idea that the following three-phase AC power supply phase loss and interruption detection device can effectively detect phase loss and interruption. That is, the control unit performs an AND operation on each pulse detection signal to generate an AND operation pulse. With this configuration, the control unit can determine the presence or absence of a phase loss or interruption based on each pulse detection signal and the AND operation pulse. Furthermore, the inventors discovered that when the control unit determines that a phase is lost, the control unit can determine which of the L1 phase, L2 phase, and L3 phase is lost.

[0016] A specific example of a three-phase AC power supply loss and interruption detection device according to one embodiment of the present disclosure will be described below with reference to the drawings. Note that the embodiments described below all show comprehensive or specific examples. The numerical values, components, arrangement positions and connection forms of the components shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Furthermore, among the components in the following embodiments, components that are not described in an independent claim showing a superordinate concept will be described as optional components.

[0017] Note that each drawing is a schematic diagram and is not necessarily a precise illustration. In addition, in each drawing, the same reference numerals are used for substantially the same configurations, and duplicated explanations may be omitted or simplified.

[0018] (Embodiment 1) Hereinafter, a three-phase AC power supply open-phase / interruption detection device according to a first embodiment will be described with reference to the drawings.

[0019] FIG. 1 is a block diagram showing the configuration of a three-phase AC power supply open-phase / interruption detection device according to the first embodiment.

[0020] In Fig. 1, a three-phase AC power supply 1 is connected to a motor 6 via an inverter device 2. The three-phase AC power supply 1 is also directly connected to a detection circuit 7a. The three-phase AC power supply 1 outputs AC voltages in a first phase (L1 phase), a second phase (L2 phase), and a third phase (L3 phase), each of which has a phase difference of 2 / 3π.

[0021] The inverter device 2 includes a rectifier circuit (forward converter) 3, a smoothing capacitor 4, an inverse conversion circuit 5, and a detection device 7 for detecting phase loss and interruption of the three-phase AC power supply. The inverter device 2 is powered by the three-phase AC power supply 1, and supplies AC power of variable voltage and variable frequency to the motor 6.

[0022] The phase loss / interruption detection device 7 includes a detection circuit 7a and a control unit 7b. The detection circuit 7a detects the voltages between the L1 and L2 phases, between the L2 and L3 phases, and between the L3 and L1 phases of the three-phase AC power supply 1, and outputs a phase loss detection signal corresponding to each phase. The output of the detection circuit 7a is supplied to the control unit 7b. The control unit 7b judges whether a phase has been lost or interrupted based on the output of the detection circuit 7a, and sends the result to the display unit 9.

[0023] FIG. 2 is a schematic diagram of a detection circuit 7a in the three-phase AC power supply according to the first embodiment.

[0024] As shown in FIG. 2, the detection circuit 7a includes resistor 11a, resistor 11b, bias resistor 12, capacitor 13, diode 14a, photocoupler 14, resistor 21a, resistor 21b, bias resistor 22, capacitor 23, diode 24a, photocoupler 24, resistor 31a, resistor 31b, bias resistor 32, capacitor 33, diode 34a, and photocoupler 34.

[0025] Between the lines of the L1 phase and the L2 phase of the three-phase AC power supply 1, resistors 11a and 11b for current limiting are connected to the L1 phase and the L2 phase, respectively. Between the lines of the L1 phase and the L2 phase, a bias resistor 12, a capacitor 13, a diode 14a, and a photocoupler 14 are connected. The photocoupler 14 has a light-emitting element 14b and a light-receiving element 14c. That is, between the lines of the L1 phase and the L2 phase, the bias resistor 12, the capacitor 13, the diode 14a, and the light-emitting element 14b are connected in parallel. Meanwhile, the resistors 11a and 11b and the bias resistor 12 are connected in series.

[0026] Between the lines of the L2 phase and the L3 phase, resistors 21a and 21b for current limiting are connected to the L2 phase and the L3 phase, respectively, in the same manner as between the L1 phase and the L2 phase. Between the lines of the L2 phase and the L3 phase, a bias resistor 22, a capacitor 23, a diode 24a, and a photocoupler 24 are connected. The photocoupler 24 includes a light-emitting element 24b and a light-receiving element 24c. That is, between the lines of the L2 phase and the L3 phase, the bias resistor 22, the capacitor 23, the diode 24a, and the light-emitting element 24b are connected in parallel. Meanwhile, the resistors 21a, 21b, and the bias resistor 22 are connected in series.

[0027] Furthermore, between the L3 phase and the L1 phase, resistors 31a and 31b for current limiting are connected to the L3 phase and the L1 phase, respectively, in the same manner as the L1 phase and the L2 phase. Between the L3 phase and the L1 phase, a bias resistor 32, a capacitor 33, a diode 34a, and a photocoupler 34 are connected. The photocoupler 34 includes a light-emitting element 34b and a light-receiving element 34c. That is, between the L3 phase and the L1 phase, the bias resistor 32, the capacitor 33, the diode 34a, and the light-emitting element 34b are connected in parallel. Meanwhile, the resistors 31a, 31b, and the bias resistor 32 are connected in series.

[0028] The photocouplers 14, 24, 34 are turned on / off according to the voltage V1 between the L1 phase and the L2 phase, the voltage V2 between the L2 phase and the L3 phase, and the voltage V3 between the L3 phase and the L1 phase. That is, the photocouplers 14, 24, 34 are turned on when the voltages V1, V2, V3 are greater than the threshold voltage V_ON. On the other hand, the photocouplers 14, 24, 34 are turned off when the voltages V1, V2, V3 are less than the threshold voltage V_ON.

[0029] Photocouplers 14, 24, and 34 output detection signals by turning on and off. Photocoupler 14 generates a pulse detection signal (ACOFF1) as the detection signal. Photocoupler 24 generates a pulse detection signal (ACOFF2) as the detection signal. Photocoupler 34 generates a pulse detection signal (ACOFF3) as the detection signal. Control unit 7b acquires these three pulse detection signals and determines whether the circuit is normal, has an open phase, or is shut off based on these three pulse detection signals.

[0030] 2, a pull-up resistor is connected to the light receiving element 14c, 24c, 34c side of each of the photocouplers 14, 24, 34. The photocouplers 14, 24, 34 output a high detection signal when they are off, and maintain a low state when they are on.

[0031] Although the photocouplers 14, 24, and 34 shown in FIG. 2 are turned on only when a current flows in one direction, they may be turned on for currents flowing in both directions.

[0032] FIG. 3 is a schematic diagram of the detection circuit 7a when L3 is missing a phase.

[0033] Next, the interphase voltages V1 to V3 will be described in a normal state where the three-phase AC power supply 1 has no phase loss or interruption, in a state where the three-phase AC power supply 1 has a phase loss, and in a state where the three-phase AC power supply 1 is interrupted. V1 is the voltage between the L1 phase and the L2 phase, V2 is the voltage between the L2 phase and the L3 phase, and V3 is the voltage between the L3 phase and the L1 phase. In the following description, the three-phase AC power supply 1 has a phase loss of the L3 phase, and the interruption of the three-phase AC power supply 1 is a phase loss of two or more of the three phases. The resistance values ​​of the resistors 11a, 11b, 21a, 21b, 31a, and 31b are the same.

[0034] The normal interphase voltages in the three-phase AC power supply 1 are V0 = effective voltage × √2, V1 = V0 sin(ωt), V2 = V0 sin(ωt + 2π / 3), and V3 = V0 sin(ωt + 4π / 3).

[0035] When the L3 phase is missing, the interphase voltages of the three-phase AC power supply 1 are V0 = effective voltage × √2, V1 = V0 sin(ωt), V2 = -V1 / 2, and V3 = -V1 / 2.

[0036] When the three-phase AC power supply 1 is cut off, the interphase voltages of the three-phase AC power supply 1 are V0=effective voltage×√2, V1=0, V2=0, and V3=0.

[0037] When the three-phase AC power supply 1 is operating normally, with V"1" as the reference, the phase of V2 leads V1 by (2 / 3)π, and the phase of V3 leads V1 by (4 / 3)π.

[0038] When L3 phase is lost, V2 and V3 are divided with V"1" as the reference. However, V2 and V3 are in opposite phase to V1. If the resistance values ​​of resistors 11a, 11b, 21a, 21b, 31a, and 31b are the same, V2 and V3 will be half the voltage of V1.

[0039] When the circuit is cut off, there is no closed circuit, so V1, V2, and V3 are 0.

[0040] FIG. 4 is a waveform diagram for explaining the normal operation of the detection device 7 for detecting a loss of phase and interruption according to the first embodiment. V1, V2, and V3 are waveforms of the voltages of the phases when the three-phase AC power source 1 is operating normally. The voltage V_ON is a threshold voltage at which the photocouplers 14, 24, and 34 are turned on. The detection signals of the photocouplers 14, 24, and 34 become low when V1, V2, and V3 exceed the voltage V_ON, and become high when V1, V2, and V3 fall below the voltage V_ON. The control unit 7b performs digital calculations using two values, 1 and 0. Therefore, the control unit 7b processes the high state as a pulse detection signal of 1 and the low state as a pulse detection signal of 0. The control unit 7b shown in FIG. 1 performs an AND operation on ACCOFF1 to 3 to obtain an AND operation pulse waveform. As shown in FIG. 4, the value of the AND operation pulse in the normal state is 0 and is constant. Therefore, the control unit 7b monitors the AND operation pulse, and when it detects that the value of the AND operation pulse is maintained at "0" for a predetermined time or more, it can determine that the three-phase AC power supply 1 is operating normally. Therefore, a normality determination time T_J is set in the control unit 7b. When the control unit 7b determines that the value of the AND operation pulse is maintained at "0" for a time longer than the normality determination time T_J, it determines that the three-phase AC power supply 1 is operating normally. As will be described later, when a phase is lost, the AND operation pulse repeats "1" and "0". Therefore, the normality determination time T_J is longer than the time during which the AND operation pulse maintains "0" when a phase is lost. Note that the voltages V1, V2, and V3 may be full waves instead of half waves.

[0041] FIG. 5 is a waveform diagram for explaining the operation of the detection device 7 for detecting a phase loss and interruption when a phase is lost. FIG. 5 shows the relationship between the waveforms of the voltages V1, V2, and V3, the pulse waveforms of the threshold voltages V_ON and ACCOFF1 to 3, and the AND operation pulse waveform when the L3 phase is lost as shown in FIG. 3. As shown in FIG. 5, in a state where a phase is lost, the AND operation pulse repeats 0 and "1". Therefore, the control unit 7b can determine that the three-phase AC power supply 1 is operating normally when it monitors the AND operation pulse and detects that the value of the AND operation pulse maintains "0" for a predetermined time or more. Therefore, the control unit 7b sets a phase loss determination time T_PL. When it is determined that the value of the AND operation pulse maintains "1" for a time longer than the phase loss determination time T_PL, the control unit 7b determines that one of the L1 phase, L2 phase, and L3 phase is lost.

[0042] The control unit 7b may determine that a phase is missing based on the time during which the value of the AND operation pulse is maintained at "0". In this case, when the control unit 7b determines that the value of the AND operation pulse is maintained at "0" for a time longer than the phase-missing determination time T_PL, the control unit 7b determines that the three-phase AC power supply 1 is missing a phase. In this case, the phase-missing determination time T_PL is set to be equal to or shorter than the normal determination time T_J. Alternatively, the control unit 7b may use the normal determination time T_J instead of the phase-missing determination time T_PL. In this case, the control unit 7b determines that a phase is missing when the time during which the value of the AND operation pulse is maintained at "0" exceeds "0" and is shorter than the normal determination time T_J.

[0043] The AND operation pulse waveform is the same when the L1 or L2 phase is missing as when the L3 phase is missing. However, ACOFF1-3 when the L1 or L2 phase is missing is different from ACOFF1-3 when the L3 phase is missing. Therefore, the control unit 7b can determine which of the L1, L2, and L3 phases is missing by detecting the ACOFF1-3 states.

[0044] FIG. 6 is a waveform diagram for explaining the operation of the detection device 7 for detecting a loss of phase and interruption during interruption. FIG. 6 shows the relationship between the waveforms of the voltages V1, V2, and V3 during interruption, the pulse waveforms of the threshold voltages V_ON, ACCOFF1 to ACCOFF3, and the AND operation pulse waveform. As shown in FIG. 6, in the interruption state, the value of the AND operation pulse is maintained at "1". Therefore, the control unit 7b can determine that the three-phase AC power source 1 is interrupted when it detects that the value of the AND operation pulse is maintained at "1" for a predetermined time or more by monitoring the AND operation pulse. Therefore, the control unit 7b sets an interruption determination time T_PF. When the control unit 7b determines that the value of the AND operation pulse is maintained at "1" for a time longer than the interruption determination time T_PF, it determines that the three-phase AC power source 1 is interrupted. Note that the interruption determination time T_PF is longer than the time during which the AND operation pulse is maintained at "1" during a loss of phase. Therefore, the interruption determination time T_PF is longer than the loss of phase determination time T_PL.

[0045] Here, we will explain how to determine the value of the threshold voltage V_ON. As shown in Figures 4 to 6, the time during which the pulse waveforms of ACCOFF1 to 3 and the AND operation pulse waveform maintain a value of 1 changes depending on the value of V_ON. When a phase is lost, the voltage is divided as described above. Therefore, the value of V_ON is set to half or less of the maximum value of the three-phase AC power supply voltage. As a result, the waveform of the AND operation pulse is always 0 under normal conditions as shown in Figure 4, repeats "1" and "0" during a phase loss as shown in Figure 5, and is always "1" during interruption as shown in Figure 6.

[0046] The larger the value of V_ON, the longer the time that "1" is maintained in the pulse waveforms of ACCOFF1 to 3 and the AND operation pulse waveform. In other words, the smaller the value of V_ON, the shorter the time that "1" is maintained in the pulse waveforms of ACCOFF1 to 3 and the AND operation pulse waveform.

[0047] As shown in FIG. 4 to FIG. 6, the waveform of the AND operation pulse is different in normal, phase loss, and cut-off. Therefore, the control unit 7b can determine whether the three-phase AC power source 1 is in a phase loss or cut-off state by using the AND operation pulse. Furthermore, the control unit 7b can determine which phase of the three-phase AC power source 1 is in a phase loss state by detecting the waveforms of ACOFF1 to 3. That is, the control unit 7b detects ACOFF1 to 3, and the AND operation pulse calculated from these values ​​can determine whether the three-phase AC power source 1 is in a normal, phase loss, or cut-off state, so that the control unit 7b can easily determine whether the three-phase AC power source 1 is in a phase loss or cut-off state without changing the circuit elements as in the past. Furthermore, the control unit 7b requires the voltage of the smoothing capacitor 4 to generate the AND operation pulse, so that the delay in the response until the AND operation pulse is generated can be suppressed. Therefore, the control unit 7b can detect whether the three-phase AC power source 1 is in a phase loss or cut-off state in a short time. By setting the threshold voltage V_ON to a desired value, the AND operation pulse is output in both the phase loss and cut-off states. Therefore, the control unit 7b can reliably determine whether the three-phase AC power source 1 is in a phase loss or cut-off state.

[0048] In the detection circuit 7a, the value of the threshold voltage V_ON may be adjusted by the above-mentioned method to generate ACOFF1 to 3. Therefore, the same circuit may be used for the circuits (11a to 14c) that generate ACOFF “1”, the circuits (21a to 24c) that generate ACOFF2, and the circuits (31a to 34c) that generate ACOFF3.

[0049] Next, the determination of the loss and interruption of a phase of the three-phase AC power supply 1 in the control unit 7b will be specifically described.

[0050] Fig. 7 is a waveform diagram for explaining a method for determining a missing phase, Fig. 8 is a waveform diagram for explaining a method for determining an interruption, and Fig. 9 is a waveform diagram for explaining a method for determining a missing phase and an interruption.

[0051] FIG. 7 shows the relationship between the AND operation pulse waveform (ACCOFF_AND), the open-phase / interrupt detection counter, the open-phase determination counter, the normal determination time T_J, the open-phase determination time T_PL, and the open-phase determination result.

[0052] FIG. 8 shows the relationship between ACCOFF_AND, the open-phase / interruption detection counter, the open-phase determination counter, the interruption determination time T_PF, and the interruption determination result.

[0053] FIG. 9 shows the relationship between ACCOFF_AND, normal judgment counter, open-phase / interruption detection counter, open-phase judgment counter, interruption judgment time T_PF, normal judgment time T_J, open-phase judgment time T_PL, open-phase judgment result, and interruption judgment result. The open-phase determination time T_PL is shorter than the interruption determination time T_PF and the normality determination time T_J.

[0054] Fig. 10 is a flow chart showing a method for determining whether a phase is missing or interrupted. The determination of whether a phase is missing or interrupted in the three-phase AC power supply 1 by the control unit 7b will be specifically described with reference to Fig. 10. The control unit 7b can be configured by, for example, a CPU (Central Processing Unit). In this case, the subsequent processing can be executed by, for example, a program stored in the CPU.

[0055] Although not shown in Fig. 10, in the initial step, preparations are made in advance for the step of determining whether the power is normal, an open phase, or is cut off. In the initial step, ACOFF1 to 3 are obtained from the photocouplers 14, 24, and 34, or are generated from the outputs of the photocouplers 14, 24, and 34. Furthermore, an AND operation is performed on these ACOFF1 to 3 to generate ACOFF_AND.

[0056] In step S41, it is determined whether the current value of ACCOFF_AND is 1. If the current value of ACCOFF_AND is 1 (YES in step S41), the process proceeds to step S42. If the current value of ACCOFF_AND is not 1 (NO in step S41), the process proceeds to step S47.

[0057] In step S42, it is determined whether the previous value of ACCOFF_AND is 1. If the previous value of ACCOFF_AND is 1 (YES in step S42), the process proceeds to step S44. This step makes it possible to detect that the value of ACCOFF_AND has switched from "1" to "0." If the previous value of ACCOFF_AND is not 1 (NO in step S42), the normality determination counter is set to 0 (step S43), and the process proceeds to step S44.

[0058] In step S44, the open-phase / interruption detection counter is changed in one direction (FIGS. 7 to 9), and the process proceeds to step S45. For example, the open-phase / interruption detection counter value starts from an initial value (for example, "0") and changes so as to increase sequentially each time step S44 is passed. As a result, the value of the open-phase / interruption detection counter increases in proportion to the time that the photocouplers 14, 24, and 34 are on, and thus has a timekeeping function. Since the open-phase / interruption detection counter increases in proportion to the time that ACCOFF_AND is maintained at "1", the control unit 7b can measure the time that the photocouplers 14, 24, and 34 are on based on the value of the open-phase / interruption detection counter. Note that the initial value is not limited to "0". In addition, the open-phase / interruption detection counter is not limited to a configuration in which the open-phase / interruption detection counter value increases sequentially from the initial value each time step S44 is passed, and may start from the initial value and change so as to decrease sequentially each time step S44 is passed.

[0059] In step S45, the open-phase / interruption detection counter is compared with the interruption judgment time value T_PF. As a result, if it is determined that the value of the open-phase / interruption detection counter is equal to or exceeds the interruption judgment time value T_PF (YES in step S45 in Figs. 8 and 9), it is determined that an interruption has occurred (step S46). If the value of the open-phase / interruption detection counter does not exceed the interruption judgment time value T_PF (NO in step S45), the process returns to the initial step S41.

[0060] In step S47, it is determined whether the previous value of ACCOFF_AND is "1". If the previous value of ACCOFF_AND is "1" (step S47: YES), the process proceeds to step S48. This step 47 detects that the value of ACCOFF_AND has switched from "1" to "0". If the previous value of ACCOFF_AND is not "1" (step S47: NO), the process proceeds to step S53.

[0061] In step S48, the open-phase / interruption detection counter is compared with the open-phase determination time value T_PL. If the open-phase / interruption detection counter is equal to or exceeds the open-phase determination time value T_PL (YES in step S48), the process proceeds to step S49. If the open-phase / interruption detection counter is not equal to or greater than the open-phase determination time value T_PL (NO in step S48), the process proceeds to S52.

[0062] In step S49, the phase loss determination counter is changed and increased in one direction (FIGS. 7 and 9), and the process proceeds to step S50. For example, the phase loss determination counter starts from an initial value (0), and is changed so as to increase successively each time step S49 is passed. As a result, the value of the phase loss determination counter increases in proportion to the duration and number of times a phase is lost. Therefore, the control unit 7b can detect the duration or number of times a phase is lost based on the value of the phase loss determination counter. The initial value of the phase loss determination counter is not limited to starting from "0", and may start from a specified value. Also, the phase loss determination counter may start from a specified value, and is changed so as to decrease successively each time step S49 is passed.

[0063] In step S50, the loss phase determination counter is compared with the loss phase determination value C_J. In step S50, it is determined whether the loss phase determination counter is equal to or exceeds the loss phase determination value C_J. If it is determined that the loss phase determination counter is equal to or exceeds the loss phase determination value C_J (FIGS. 7 and 9, YES in step S50), it is determined that one of the phases is missing (step S51). If it is determined that the loss phase determination counter does not exceed the loss phase determination value C_J (NO in step S50), the process proceeds to step 52. Note that in step S50, the value of the loss phase determination counter and the loss phase determination value C_J are determined as the number of times.

[0064] In step S52, the open-phase / interruption detection counter is set to an initial value (0), and the process proceeds to step S53.

[0065] In step S53, the normality determination counter is changed in one direction (FIG. 9), and the process proceeds to step S54. In step S53, the normality determination counter is changed in an increasing direction. For example, the normality determination counter starts from an initial value (0), and is changed so as to increase successively each time step S53 is passed. As a result, the normality determination counter value increases in proportion to the time during which the three-phase AC power supply 1 is operating normally. Therefore, the control unit 7b can detect that the three-phase AC power supply 1 is operating normally based on the normality determination counter value. In addition, the initial value of the normality determination counter is not limited to starting from "0", and may be started from a specified value. In addition, the normality determination counter may be changed so as to start from an initial value, and is changed so as to decrease successively each time step S49 is passed. In step S54, the normality determination counter is compared with the normality determination time value T_J. If it is determined that the normality determination counter is equal to or exceeds the normality determination time value T_J (YES in step S54 in FIG. 9), the open-phase determination counter is reset to the initial value (step S55), it is determined to be normal (step S56), and the process returns to the initial step S41. If the normality determination counter does not exceed the normality determination time T_J (NO in step S54), the process returns to the initial step S41.

[0066] By repeating the processes of steps S41 to S56, it is possible to determine whether a phase of the three-phase AC power supply 1 is lost or interrupted.

[0067] In the first embodiment, when it is detected that the value of ACOFF_AND has switched from "1" to "0" (NO in step S41, YES in step S47), the open-phase determination process (steps S48 to S51) is performed. By doing so, open-phase determination is not performed during the cut-off state, and it is possible to exclusively determine whether a phase is open or cut off in the three-phase AC power supply 1. On the other hand, the open-phase determination process (steps S48 to S51) may be performed after step S45. The open-phase determination can be performed more quickly by performing the open-phase determination process (steps S48 to S51) after step S45.

[0068] As shown in FIG. 1, the output of the control unit 7b is supplied to a display 9 (e.g., an LED lamp). After determining whether the three-phase AC power supply 1 is missing or cut off, the control unit 7b outputs the determination result to the display unit 9. This allows the display unit 9 to notify the outside of the missing phase or cut off state, making inspection easier and improving safety. FIG. 11 is a flowchart showing a method for determining whether a phase is missing in a three-phase AC power supply. Step S60 is provided between steps 51 and 52 shown in FIG. 10 when determining which of the L1 to L3 phases is missing. Note that, except for the configuration in which step S60 is inserted between steps 51 and 52, the process is the same as that shown in FIG. 10, and therefore will not be described.

[0069] Fig. 12 is a summary diagram of the determination method in step S60. As shown in Fig. 12, it is possible to determine which of the L1 to L3 phases is missing, based on the values ​​of ACOFF1 to ACOFF3 when the AND operation pulse is 0. Therefore, in step S60, it is determined which of the conditions in Fig. 12 the AND operation pulse and ACOFF1 to ACOFF3 match.

[0070] Since step S60 has passed the determination in step S41 shown in FIG.

[0071] In step S61, it is determined whether ACCOFF1 is 1. If ACCOFF1 is 1 (YES in step S61), it is determined that the L3 phase is missing (step S62) (FIG. 5), and the process proceeds to step S52. If ACCOFF1 is not 1, the process proceeds to step S63.

[0072] In step S63, it is determined whether ACCOFF2 is 1. If ACCOFF2 is 1 (YES in step S63), it is determined that the L1 phase is missing (step S64), and the process proceeds to step S52. If ACCOFF2 is not 1, the process proceeds to step S65.

[0073] In step S65, it is determined whether ACCOFF3 is 1. If ACCOFF3 is 1 (YES in step S65), it is determined that the L2 phase is missing (step S66), and the process proceeds to step S52. If ACCOFF3 is not 1, the process proceeds to step S52.

[0074] In each determination step in FIG. 10 and FIG. 11, the determination condition value may be inverted between 0 and 1, and the determination condition results may be interchanged between YES and NO.

[0075] (Variation 1) Next, a method for determining whether a phase is lost or interrupted when the voltage or frequency of the three-phase AC power supply 1 changes will be described.

[0076] The control unit 7b can set a cutoff determination time T_B, a loss-of-phase determination time T_PL, a normality determination time T_J, and a loss-of-phase determination time C_J.

[0077] If the threshold voltage V_ON at which the photocouplers 14, 24, and 34 turn on remains the same, and the voltage of the three-phase AC power supply 1 increases, the time that the AND operation pulse maintains "1" becomes shorter. Conversely, if the voltage of the three-phase AC power supply 1 decreases, the time that the AND operation pulse maintains "1" becomes longer. If the frequency of the three-phase AC power supply 1 increases, the number of times that the AND operation pulse is 1 per period increases. If the frequency of the three-phase AC power supply 1 decreases, the number of times that the AND operation pulse is 1 per period decreases.

[0078] Therefore, the above-mentioned waveform can be obtained by adjusting the above set values ​​in response to changes in the voltage and frequency of the three-phase AC power supply 1, so there is no need to particularly change the circuit elements, and it is possible to determine whether a phase is missing or interrupted in the three-phase AC power supply 1 for various voltages and frequencies.

[0079] (Variation 2) The photocouplers 14, 24, and 34 may be in an ON state and output a low signal. In this case, the control unit 7b takes in values ​​obtained by inverting the output signals of the photocouplers 14, 24, and 34 as ACCOFF1 to 3. Alternatively, a NOT circuit that inverts a signal may be inserted between the photocouplers 14, 24, and 34 and the control unit 7b. In these cases, when the photocouplers 14, 24, and 34 are in an ON state, the values ​​of ACCOFF1 to 3 are 1. Therefore, the control unit 7b makes a determination in accordance with the processes shown in Figs. 4 to 12.

[0080] (Variation 3) Photocouplers 14, 24, 34 are configured to output a low signal when they are on, and control unit 7b generates inverted ACCOFF1-3 by directly acquiring the outputs of photocouplers 14, 24, 34. Alternatively, when photocouplers 14, 24, 34 are on and output a high signal, a NOT circuit that inverts the signal is inserted between photocouplers 14, 24, 34 and control unit 7b, or control unit 7b inverts the output signals of photocouplers 14, 24, 34 to generate inverted ACCOFF1-3.

[0081] In this example, the inverted ACCOFF1 to 3 are signals obtained by inverting the ACCOFF1 to 3 shown in Fig. 4 to Fig. 6. That is, when the photocouplers 14, 24, and 34 are in the on state, the values ​​of the inverted ACCOFF1 to 3 are 0.

[0082] The control unit 7b inverts the inverted ACCOFF1 to 3 and performs an AND operation to obtain ACCOFF_AND.

[0083] In this case, in the judgment steps (steps S61, S63, S65) in Fig. 11 and in Fig. 12, judgment may be made by inverted ACCOFF1-3 instead of ACCOFF1-3. In this case, the value of the judgment condition in these steps is changed from 1 to 0. In Fig. 12, when judgment is made by replacing ACCOFF1-3 with inverted ACCOFF1-3, the value of the judgment condition for each phase is changed from 1 to 0. However, the value of ACCOFF_AND remains 0.

[0084] (supplement) As described above, the first embodiment including the above-mentioned modified examples has been described as an example of the technology disclosed in the present application. However, the technology according to the present disclosure is not limited to these, and can be applied to the embodiments with appropriate changes, substitutions, additions, omissions, etc., or other modified examples other than those described above, without departing from the spirit of the present disclosure.

[0085] For example, in the first embodiment, the AND operation in the control unit 7b may be performed using an AND circuit. [Industrial Applicability]

[0086] INDUSTRIAL APPLICABILITY The detection device for loss of or interruption of a phase of a three-phase AC power supply according to the present disclosure can be widely used in devices such as motors that use three-phase AC power supplies. [Explanation of symbols]

[0087] 1 Three-phase AC power supply 2. Inverter device 3 Rectifier circuit 4 Smoothing capacitors 5. Reverse conversion circuit 6 Motor 7. Detection Equipment 7a Detection circuit 7b Control section 9 Display section 11a, 11b, 21a, 21b, 31a, 31b resistor 12, 22, 32 Bias resistors 13, 23, 33 Capacitor 14, 24, 34 Photocoupler 14a, 24a, 34a Diodes 14b, 24b, 34b Light-emitting element 14c, 24c, 34c Photodetector

Claims

1. three photocouplers each including a light receiving element which is turned on when the voltage is equal to or higher than a predetermined threshold voltage, each photocoupler being connected between the lines of an L1 phase and an L2 phase, an L2 phase and an L3 phase, and an L3 phase and an L1 phase of a three-phase AC power supply, and each photocoupler converts line voltages between the L1 phase and an L2 phase, an L2 phase and an L3 phase, and an L3 phase and an L1 phase of the three-phase AC power supply into three detection signals; a control unit that acquires three pulse detection signals or three inverted pulse detection signals obtained by inverting the three pulse detection signals from the three detection signals output from the three photocouplers, The control unit performs an AND operation on the three pulse detection signals, or inverts and ANDs the three inverted pulse detection signals to generate an AND operation pulse, and determines whether or not there is a normal state or a missing phase or an interruption based on the AND operation pulse. In a detection device for a three-phase AC power supply, The control unit is (a) sequentially changing a first counter in a certain direction during the time that the value of the AND operation pulse continues to be "0", and judging that the first counter is in a normal state when the first counter exceeds a predetermined first value; (b) resetting the first counter to 0 when the value of the AND operation pulse changes from 0 to 1, and sequentially changing the second counter in a certain direction during the time that the AND operation pulse continues to be "1"; determining that the second counter is interrupted when the second counter is equal to or exceeds a second predetermined value; When the second counter is called "1" and judged to be equal to or exceed a third value smaller than the second value, it is determined that a phase is missing. Detection device for three-phase AC power supplies.

2. The control unit is When determining whether a phase is missing, if the value of the AND operation pulse is 0, a phase having a value of 1 among the three pulse detection signals or a phase having a value of 0 among the three inverted pulse detection signals is determined to be missing.

2. A detection device for a three-phase AC power supply as claimed in claim 1.

3. the control unit adjusts at least one of the first to third values ​​in response to at least one of a voltage and a frequency of the three-phase AC power supply.

2. A detection device for a three-phase AC power supply as claimed in claim 1.

4. A three-phase AC power source outputs AC voltages at L1 phase, L2 phase, and L3 phase, and three pulse detection signals or three inverted pulse detection signals obtained by inverting the three pulse detection signals are obtained from three photocouplers respectively connected between the L1 phase and the L2 phase, between the L2 phase and the L3 phase, and between the L3 phase and the L1 phase; performing an AND operation on the three pulse detection signals, or performing an AND operation on the three inverted pulse detection signals to generate an AND operation pulse; The AND operation pulse is used to determine whether the AC voltage is in a normal state or has a phase loss or is interrupted. In a method for detecting a loss or interruption of a three-phase AC power supply, When determining whether or not there is a phase loss or interruption, (a) sequentially changing a first counter in a certain direction during the time that the value of the AND operation pulse continues to be "0", and judging that the first counter is normal when it is judged that the first counter is equal to or exceeds a predetermined first value; (b) resetting the first counter to 0 when the AND operation pulse changes from 0 to 1, and sequentially changing the second counter in a certain direction during the time when the AND operation pulse continues to have a value of "1"; determining that the second counter is interrupted when the second counter is equal to or exceeds a second predetermined value; When the second counter is determined to be equal to or exceeding a third value smaller than the second value, the phase is determined to be missing. A method for detecting phase loss or interruption in a three-phase AC power supply.

5. The determination of the missing phase is performed prior to the determination of the interruption.

5. The method for detecting a loss or interruption of a phase in a three-phase AC power supply according to claim 4.

6. The determination of the interruption is performed prior to the determination of the missing phase.

5. The method for detecting a loss or interruption of a phase in a three-phase AC power supply according to claim 4.

7. When determining whether a phase is missing, if the AND operation pulse is 0, it is determined that a phase having a value of 1 among the three pulse detection signals or a phase having a value of 0 among the three inversion pulse detection signals is missing.

5. The method for detecting a loss or interruption of a phase in a three-phase AC power supply according to claim 4.

8. Setting at least one of the first to third values ​​in a control unit; At least one of the first to third time periods is adjusted in response to at least one of the voltage and the frequency of the three-phase AC power supply.

5. The method for detecting a loss or interruption of a phase in a three-phase AC power supply according to claim 4.

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