JP2006238577A - Three-phase phase interruption detection circuit of air conditioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a three-phase phase failure detection circuit capable of detecting a phase interruption in three-phase alternating-current power supply with reliability and controlling and protecting a three-phase load. <P>SOLUTION: The three-phase phase failure detection circuit includes: an R-phase current detection circuit 4 that detects a current in R phase; a S-phase and T-phase current detection circuit 5 that detects currents in S phase and T phase in opposite phase; and a R-phase current value rectifying and smoothing circuit 6 and a S-phase and T-phase current value rectifying and smoothing circuit 7 that rectify and smooth the outputs of the respective detection circuits. When the output of the R-phase current value rectifying and smoothing circuit equal to or lower than a predetermined value is detected, or when the difference in output voltage between the R-phase current value rectifying and smoothing circuit 6 and the S-phase and T-phase current value rectifying and smoothing circuit 7 is equal to or lower than a certain value, it is determined that an open phase is present. Then, power supply to a three-phase load 3 is interrupted by a switch 2 to protect equipment. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a three-phase open phase detection circuit that performs phase loss detection of a three-phase AC power source in a device that uses a three-phase AC power source as a power source and protects the device.

  Conventionally, this type of three-phase phase loss detection circuit detects the voltage between each phase and neutral phase of a three-phase AC power source, and determines the phase loss based on the phase of each phase. 1).

  FIG. 5 shows a conventional three-phase phase loss detection circuit described in Patent Document 1, and FIG. 6 shows its signal waveform. As shown in FIG. 5, as means for detecting the voltage between each phase of the three-phase AC power supply 1 and the neutral phase, a phase detection circuit 10 using a photocoupler 101 and each phase output from the phase detection circuit 10 It is comprised from the control part 9 which determines a missing phase based on a signal.

In this configuration, when the signal between each phase and the neutral phase detected by the phase detection circuit 10 is normal, the phase difference between each phase is t1 as shown in FIG. The control unit 9 determines that the phase difference t1 is normal if the phase difference t1 is within a predetermined range, and the phase is missing if the phase difference t1 is not within the predetermined range.
JP-A-8-126194

  However, in the conventional configuration, when the three-phase load 3 has a neutral point 31 like an electric motor, an open phase occurs in, for example, the R phase of the three-phase AC power source 1 while the three-phase load 3 is energized. Then, an R-phase load terminal voltage having the same potential as the neutral point 31 is generated at the R-phase load terminal 32 of the three-phase load 3 and applied to the photocoupler 101 disposed between the R-phase and N.

  The R-phase load terminal voltage applied to the photocoupler 101 is approximately a half of the power supply voltage, but when the three-phase AC power supply 1 is intended to correspond to a wide range of power supply voltages, for example, rated ± 15%, Considering the component variation, the photocoupler 101 is erroneously detected, and a detection signal similar to that shown in FIG. 6 is input to the control unit 9 and the control unit 9 determines that the phase is normal, and phase loss detection cannot be performed. It was.

  In addition, it is necessary to add a dedicated circuit for three-phase phase loss detection, and in order to detect the power supply voltage, a problem that requires an insulation distance and a large mounting area in the circuit mounting design, and There was a problem of cost increase.

  The present invention solves the above-described conventional problems. Even when a phase failure of a three-phase AC power source occurs due to disconnection of a wire or disconnection of a connection line during energization of a three-phase load, the present invention can be detected without erroneous detection. The purpose is to ensure phase detection and protect the equipment.

  Another object of the present invention is to reduce the influence on the mounting area and reduce the cost increase.

In order to solve the conventional problems, a three-phase open phase detection circuit according to the present invention includes a three-phase AC power source, a three-phase load connected to the three-phase AC power source via a switch, and the switch A control unit that controls opening and closing; a first current detection circuit that detects a current of a first phase of the three-phase AC power source; a second phase current of a three-phase AC power source; A second current detection circuit that simultaneously detects the current of the phase in the opposite phase is provided, and outputs from the first rectification smoothing means, the second rectification comparison means that rectify and smooth the respective outputs, and the respective rectification smoothing means Voltage comparison means for comparing voltages is provided, and the voltage comparison means detects when the output of the first rectifying / smoothing means is a predetermined value or less, or the output voltage of the first rectifying / smoothing means and the second rectifying / smoothing means The switch is opened by the control unit when the difference in the output voltage is less than a certain value It is.

  The first phase missing phase is a decrease in output from the first rectifying and smoothing means, and the second phase and third phase missing phases are the output voltage of the first rectifying and smoothing means and the output of the second rectifying and smoothing means. By detecting the voltage difference with the voltage comparison means, it is possible to reliably detect the phase failure even when the three-phase load is energized, and the power to the three-phase load can be shut off by the switch. Can protect.

  The three-phase phase loss detection circuit of the present invention uses a three-phase load as a compressor and the first and second current detection circuits also serve as a compressor overcurrent protection current detection circuit.

  As a result, it is not necessary to add a dedicated circuit for detecting the three-phase phase loss, and the influence on the mounting area and cost increase can be reduced.

  The three-phase phase loss detection circuit of the present invention can reliably detect phase loss during energization of a three-phase load, can be realized with a small mounting area and low cost, and can protect equipment.

  A first invention includes a three-phase AC power source, a three-phase load connected to the three-phase AC power source via a switch, and a control unit that controls opening and closing of the switch. A first current detection circuit that detects the first phase current of the phase AC power supply and a second current that simultaneously detects the second phase current and the third phase current of the three phase AC power supply in opposite phases A detection circuit is provided, a first rectifying / smoothing means for rectifying and smoothing each output, a second rectifying / comparing means, and a voltage comparing means for comparing output voltages from the respective rectifying / smoothing means, and the voltage comparing means, When the output of the first rectifying / smoothing means is detected to be equal to or less than a predetermined value, or when the difference between the output voltage of the first rectifying / smoothing means and the output voltage of the second rectifying / smoothing means is a certain value or less, the control unit By opening the switch by means of the Phase loss can be detected, power to the three-phase load can be shut off by a switch, and equipment can be protected.

  In particular, the second aspect of the present invention uses a three-phase load according to the first aspect of the present invention as a compressor, and the first and second current detection circuits also serve as a current detection circuit for overcurrent protection of the compressor. There is no need to add a dedicated circuit for phase detection, and the effect on mounting area and cost increase can be reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a circuit diagram of a three-phase phase loss detection circuit according to the first embodiment of the present invention. In FIG. 1, a three-phase AC power source 1 is connected to a compressor 3 that is a three-phase load via a switch 2. An R-phase current detection circuit 4 that detects current of one phase (R-phase) of each phase (R-phase, S-phase, T-phase) from the three-phase AC power source 1 to the compressor 3 and the remaining two phases ( An S-phase T-phase current detection circuit 5 for simultaneously detecting currents in S-phase and T-phase in opposite phases is provided, and an R-phase current value rectification smoothing circuit 6 for rectifying and smoothing each output, and an S-phase T-phase current value rectification The output voltage V1 of the R-phase current value rectifying / smoothing circuit 6 and the output voltage V2 of the S-phase / T-phase current value rectifying / smoothing circuit 7 which are connected to the smoothing circuit 7 are input to the voltage comparison circuit 9 provided in the control unit 8, The control unit 8 is configured to control the switch 2 according to the input of the voltage comparison circuit 9.

  The operation and action of the three-phase phase loss detection circuit configured as described above will be described below. First, the operation when there is no phase loss will be described. The current flowing through the compressor 3 is detected by the R phase current detection circuit 4 and the S phase T phase current detection circuit 5. The R-phase, S-phase, and T-phase currents have waveforms that are 120 degrees out of phase as R1, S1, and T1 in FIG. 2, and the output of the R-phase current detection circuit 4 has the same waveform as that of R1, S-phase T The output of the phase current detection circuit 5 has a waveform of -S1 + T1, which is the sum of the reverse phase -S1 of the S phase current and the T phase current T1, and its peak value is √3 times R1, S1, and T1. R1 is rectified and smoothed by the R-phase current value rectifying and smoothing circuit 6, -S1 + T1 is rectified and smoothed by the S-phase and T-phase current value rectifying and smoothing circuit 7, and V2 is a value of √3 times V1. V1 and V2 are input to the voltage comparison circuit 9, and the magnitude of the output V1 of the R-phase current value rectifying and smoothing circuit 6 is not less than the first set value (A1) and not more than the second set value (A2), and V2 When the magnitude is equal to or smaller than the third set value (A3) and the voltage difference between V1 and V2 is equal to or greater than a certain value and V1 <V2, it is determined to be normal, and the control unit 8 controls the switch 2 to close. When V1 is equal to or greater than the second set value (A2) and V2 is equal to or greater than the third set value (A3), it is determined that an overcurrent occurs, and the switch 2 is controlled to open.

  For example, when the current of the compressor 3 becomes too large due to an abnormality in the refrigeration cycle of the air conditioner, the energization to the switch 2 is stopped, the switch 2 is opened, the energization to the compressor 3 is stopped, and the protection control is performed. Do. When there is no phase loss and no overcurrent as shown in FIG. 2, protection control is not performed.

  Next, a case where an open phase occurs in the R phase will be described. When the R phase is lost, the R phase current becomes zero. Therefore, as shown in FIG. 3, the output waveform R1 of the R phase current detection circuit 4 is zero, and the output V1 of the R phase current value rectifying and smoothing circuit 6 is zero. become. Since the output V1 of the R-phase current value rectifying and smoothing circuit 6 is equal to or less than the first set value (A1), it is determined that the R-phase is missing, the switch 2 is controlled to open, and the energization to the compressor 3 is stopped. Perform phase protection control.

  The case where a phase failure occurs in the S phase will be described with reference to FIG. When the S phase is open, the compressor 3 is driven by two phases, the R phase and the T phase, so that the single phase operation is performed. For this reason, the R-phase current and the T-phase current have alternating waveforms that are 180 degrees out of phase as R1 and T1. Since the S-phase current is zero, the waveform of -S1 + T1 is the same as T1. The output waveforms of the R-phase current value rectifying and smoothing circuit 6 and the S-phase and T-phase current value rectifying and smoothing circuit 7 are V1 and V2, and V1 = V2. The voltage comparison circuit 9 compares the voltages V1 and V2, and if the voltage difference is less than a certain value and V1 <V2, it is determined that the phase is missing, and the control unit 8 controls the opening of the switch 2 to energize the compressor 3. To stop phase loss protection control.

  Even when a phase loss occurs in the T phase, the phase loss protection control is performed by comparing the voltages V1 and V2 in the voltage comparison circuit 9 as in the case of the phase loss in the S phase.

  As described above, in the present embodiment, an R-phase current detection circuit that detects an R-phase current and an S-phase and T-phase current detection circuit that simultaneously detect S-phase and T-phase currents in opposite phases are provided. An R-phase rectifying / smoothing circuit for rectifying and smoothing the output of the S-phase, an S-phase / T-phase rectifying / comparing means, and a voltage comparing circuit for comparing the output voltages from the respective rectifying / smoothing circuits are provided, and the output of the R-phase rectifying / smoothing circuit is below a predetermined value. Is detected, or when the difference between the output voltage V1 of the R-phase rectifying / smoothing circuit and the output voltage V2 of the S-phase / T-phase rectifying / smoothing circuit is detected to be equal to or less than a predetermined value, the phase loss protection control is performed and the compressor is energized. The device can be protected by shutting off the switch with a switch.

  In addition, since the R-phase and S-phase T-phase current detection circuits are also used as the current detection circuit for overcurrent protection of the compressor, it is not necessary to add a dedicated circuit for detecting the three-phase phase loss, thus reducing the mounting area. Impact and cost increase can be reduced.

  As described above, the three-phase phase loss detection circuit of the air conditioner according to the present invention can realize the phase loss detection while energizing the three-phase load reliably, with a small mounting area and at a low cost, and can protect the equipment. Therefore, it can also be applied to the protection of equipment by detecting phase loss such as inverter equipment using a three-phase AC power supply as a power source.

Circuit diagram of a three-phase phase loss detection circuit according to Embodiment 1 of the present invention Output waveform diagram of each part at normal time in Embodiment 1 of the present invention Each part output waveform diagram at the time of R-phase phase loss in Embodiment 1 of the present invention Each part output waveform diagram at the time of S-phase loss in Embodiment 1 of the present invention Circuit diagram of conventional three-phase phase loss detection circuit Waveform diagram showing the input signal to the conventional control unit

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Three-phase alternating current power supply 2 Switch 3 Three-phase load 4 R phase current detection circuit 5 S phase T phase current detection circuit 6 R phase current value rectification smoothing circuit 7 S phase T phase current value rectification smoothing circuit 8 Control part 9 Voltage comparison circuit

Claims (2)

A three-phase AC power source, a three-phase load connected to the three-phase AC power source via a switch, and a control unit for controlling the opening and closing of the switch; The first current detection circuit that detects the current of the phase and the second current detection circuit that detects the current of the second phase and the current of the third phase of the three-phase AC power source simultaneously in opposite phases are provided. The first rectifying / smoothing means and the second rectifying / comparing means for rectifying and smoothing the output of the output voltage, and the voltage comparing means for comparing the output voltages from the respective rectifying and smoothing means are provided. When the output of the smoothing means is detected below a predetermined value, or when the difference between the output voltage of the first rectifying and smoothing means and the output voltage of the second rectifying and smoothing means is below a certain value, the control unit A three-phase phase loss detection circuit that opens the switch. The three-phase open phase of the air conditioner according to claim 1, wherein the three-phase load is a compressor, and the first and second current detection circuits are also used as a current detection circuit for overcurrent protection of the compressor. Detection circuit.

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