JP2006087186A - Open-phase detector and air conditioner using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect an open phase in a three-phase power source by an inexpensive method which does not need an exclusive circuit. <P>SOLUTION: This open-phase detector is equipped with a rectifier which rectifies three-phase AC power into DC voltage, a smoother which smoothes the DC voltage rectified in the above rectifier, an inverter which uses the smoothed DC voltage as a power source, a three-phase motor which is driven by the above inverter, a voltage detecting means which detects the smoothed DC voltage, and a controller which calculates the amount of ripple of the voltage detected by the above voltage detecting means. In case that the amount of ripple detected by the controller is at or over a given value within a given time after start of the above three-phase motor, this determines it to be open-phase, and issues a stop signal to the above inverter by the above controller so as to stop the above three-phase motor. Hereby, in case that the open phase occurs, this detects the open phase quickly, and takes a protective action to the inverter, whereby this can avoid something wrong such as the damage or the like of the controller caused by the operation in an open-phase state. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a three-phase phase loss detection device that detects a phase loss 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, as shown in FIG. 3, a three-phase AC voltage is input to the rectifying unit 8 and the automatic setting detection level circuit 13. The rectifying unit 8 rectifies the input voltage into a DC voltage, but a ripple voltage is generated on the output side. This ripple voltage is detected by the ripple voltage detection circuit 11 and input to the input abnormality detection circuit 14. The ripple voltage is smoothed by the smoothing unit 12 and supplied to the load 9. On the other hand, in the automatic setting detection level circuit 13, after the input AC voltage is detected by the input voltage detection circuit 15, the highest voltage among the detected voltages of each phase is determined by the OR circuit 16, and based on the result. Thus, the detection level of the input abnormality detection circuit 14 is automatically set. The input abnormality detection circuit 14 detects an input abnormality by comparing the ripple voltage with a detection level, and outputs a detection pulse. The detection pulse is determined by the control unit 10 to detect an input phase loss (one phase is a power failure) and output an alarm (see Patent Document 1).
JP-A-5-3621

  However, since the conventional configuration requires a dedicated circuit such as an automatic setting detection level circuit and a comparator for comparing the detected ripple voltage with the automatic setting detection level, the hardware circuit configuration becomes complicated, and the components Since the area is enlarged, it is difficult to realize. In addition, there is a possibility of increasing costs. In addition, since phase loss detection is always performed, the comparator may malfunction due to the effects of noise, etc., and phase loss may be erroneously detected, or the amount of ripple changes depending on the load on the inverter side, resulting in false detection of phase loss. There is a fear.

  The present invention solves the above-described conventional problems, and the object thereof is not to require a dedicated circuit, and a simple hardware configuration can detect an open phase of a three-phase power supply quickly and reliably. An object of the present invention is to provide a phase loss detection device.

  In order to solve the above-described conventional problems, the phase loss detection device of the present invention includes a rectifying unit that rectifies a three-phase AC power source into a DC voltage, and a smoothing unit that smoothes a pulsating voltage rectified by the rectifying unit. An inverter that uses the smoothed DC voltage as a power source, a three-phase motor that is driven by the inverter, a voltage detection means that detects the smoothed DC voltage, and a ripple of the voltage detected by the voltage detection means A control unit for calculating the amount, and if the ripple amount detected by the control unit within a predetermined time after the start of the three-phase motor is greater than or equal to a predetermined value, it is determined that the phase is missing and the control unit The stop signal is transmitted to the inverter to stop the three-phase motor.

  The phase loss detection device of the present invention can prevent damage to the control device from malfunctions due to operation in the phase loss state by detecting phase loss early and reliably and applying a protective operation to the inverter when phase loss occurs. it can. Further, since the amount of ripple is directly calculated by a control unit, that is, a microcomputer, and a predetermined value is stored in advance, a hardware dedicated circuit is not required, so that the cost can be reduced.

  A first invention includes a rectifying unit that rectifies a three-phase AC power source into a DC voltage, a smoothing unit that smoothes a pulsating voltage rectified by the rectifying unit, and an inverter that uses the smoothed DC voltage as a power source. A three-phase motor driven by the inverter; a voltage detection means for detecting the smoothed DC voltage; and a control unit for calculating a ripple amount of the voltage detected by the voltage detection means. If the amount of ripple detected by the control unit within a predetermined time after starting is greater than or equal to a predetermined value, the control unit determines that the phase is missing and sends a stop signal to the inverter from the control unit. By stopping the electric motor, it is possible to prevent damage to the control device from malfunctions due to operation in the phase loss state by detecting the phase loss quickly and reliably when the phase loss occurs and applying a protective operation to the inverter.

  Further, since the amount of ripple is directly calculated by a control unit, that is, a microcomputer, and a predetermined value is stored in advance, a hardware dedicated circuit is not required, so that the cost can be reduced. Further, by detecting each time for a predetermined time after the start of the three-phase motor, it is possible to reliably detect the phase loss without being influenced by the influence of the magnitude of the load or noise during normal operation.

  According to the second aspect of the present invention, after the operation of the three-phase motor is stopped in the first aspect of the invention, the user is informed that any one of the phases of the three-phase power source is in a phase failure, and thus the user is notified. It is possible to reliably notify the phase loss of the material and improve the maintainability.

  The third aspect of the invention uses the phase loss detection device of the first or second aspect of the invention in an air conditioner, and can provide an air conditioner with good maintainability that is reliably protected during phase loss.

  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 diagram illustrating a configuration of an air conditioner using the phase loss detection device according to the first embodiment of the present invention. In FIG. 1, 1 is a three-phase power source, 2 is a rectification unit, 3 is a smoothing unit, 4 is an inverter, 5 is a three-phase motor, 6 is a voltage detection means, and 7 is a control unit. The three-phase motor 5 is driven by the operation of the inverter 4 based on the operation instruction from the control unit 7. About the control apparatus comprised as mentioned above, the operation | movement and an effect | action are demonstrated below.

When the three-phase power source 1 is input and a sufficient voltage is charged in the smoothing unit 3, an operation instruction is given to the inverter 4 by the instruction of the control unit 7 and the three-phase motor 5 starts to start. The three-phase motor 5 performs a starting operation while maintaining a constant rotational speed for a predetermined time (t) after starting to start, and eventually approaches the target rotational speed according to an instruction from the control unit 7 after the predetermined time (t) has elapsed. . Such control is a control method that is widely used in air conditioners and the like. In the present invention, the upper limit value and the lower limit value of the DC voltage detected by the voltage detection means 6 during the predetermined time (t) are input to the control unit 7 to calculate the ripple amount. In a normal state in which no phase is present in any phase of the three-phase power source 1, the waveform is as shown in FIG. From experimental data, when the interphase voltage of the three-phase power supply 1 is 380V, the ripple amount is about 5V. However, when a phase failure occurs in any of the three-phase power supplies 1, a waveform as shown in FIG. 2B is obtained, and the ripple amount is about 18V, resulting in a difference of 10V or more. Also, when the load is light, there is no change in the amount of ripple because there is no discharge of the smooth part due to the load even if the three-phase power supply is open. Therefore, the phase loss of the three-phase power source 1 is detected by comparing the amount of ripple when the three-phase motor 5 starts to start and the load during a predetermined time (t) is stable. In addition, the predetermined value (a) as a comparison reference is set to a value obtained by adding a margin to the amount of ripple when no phase loss occurs, thereby preventing erroneous detection due to an increase in ripple due to an increase in load. When a phase failure occurs in any phase of the phase power supply 1, it is possible to reliably detect the phase loss.

  Since the present invention detects an open phase of the three-phase power source 1 based on the magnitude of the ripple amount, for example, even if the input voltage of the three-phase power source 1 fluctuates, if the load is within the range of the ripple amount margin, the predetermined value The resetting of (a) is unnecessary. When the amount of ripple calculated by the control unit 7 is equal to or greater than the predetermined value (a), it is determined that the phase is missing, a stop signal is transmitted from the control unit 7 to the inverter 4, and the three-phase motor 5 is stopped. It is possible to avoid problems such as damage to the control device due to the operation in the phase loss state. In addition, after the three-phase motor 5 is stopped, the control unit 7 transmits a phase failure signal to an abnormality display unit 17 provided, for example, on the indoor side of the air conditioner, and displays it with an LED or the like to notify the user of the abnormality. Maintenance performance can be improved.

  As described above, the phase loss detection device according to the present invention can reliably detect the phase loss of the three-phase power supply. Therefore, besides the air conditioner that rectifies the three-phase power supply and supplies power. It can also be applied to control devices such as refrigeration / freezing devices.

Configuration diagram of phase loss detection apparatus according to Embodiment 1 of the present invention Waveform diagrams at normal time and phase loss in Embodiment 1 of the present invention Configuration diagram of phase loss detection device in the prior art

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Three-phase power supply 2 Rectification part 3 Smoothing part 4 Inverter 5 Three-phase motor 6 Voltage detection means 7 Control part 8 Rectification part 9 Load 10 Control part 11 Ripple voltage detection circuit 12 Smoothing part 13 Automatic setting detection level circuit 14 Input abnormality detection circuit 15 Input voltage detection circuit 16 OR circuit 17 Abnormal display part

Claims (3)

A rectifier that rectifies a three-phase AC power source into a DC voltage, a smoother that smoothes the pulsating voltage rectified by the rectifier, an inverter that uses the smoothed DC voltage as a power source, and is driven by the inverter A three-phase motor, a voltage detecting means for detecting the smoothed DC voltage, and a control unit for calculating a ripple amount of the voltage detected by the voltage detecting means, and a predetermined time after starting the three-phase motor If the amount of ripple detected by the control unit is greater than or equal to a predetermined value, it is determined that the phase is missing and the control unit sends a stop signal to the inverter to stop the three-phase motor. A feature of phase loss detection device. An abnormality display section that displays a phase failure error is provided, and when it is determined that a phase failure has occurred, the restart operation of the three-phase motor is stopped, and then the user is notified that the three-phase AC power supply is in a phase failure error. The phase loss detection apparatus according to claim 1, wherein An air conditioner using the phase loss detection device according to claim 1 or 2.

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