JP2006180649A - Three-phase power supply unbalance detector and air conditioner using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect unbalance in three-phase power supply by an inexpensive method that does not call for any dedicated circuit. <P>SOLUTION: A three-phase power supply unbalance detector includes a rectification unit 2 that rectifies three-phase alternating-current power supply 1 into direct-current voltage, a smoothing unit 3 that smooths the direct-current voltage rectified at the rectification unit, an inverter 4 that uses the smoothed direct-current voltage as power supply, a three-phase motor 5 driven by the inverter, a voltage detecting means 6 that detects smoothed direct-current voltage, and a control unit 7 that computes the amount of ripples in the voltage detected by the voltage detecting means. When the amount of ripples detected at the control unit 7 becomes equal to or larger than a predetermined value and a predetermined time has passed after the three-phase motor 5 is started, the control unit determines that the three-phase power supply has been unbalanced. Then, it transmits a stop signal to the inverter 4 to stop the three-phase motor 5. Thus, when unbalancing occurs, it is quickly and reliably detected to protect the inverter 4. Such troubles as damage is thereby prevented from occurring in a controller due to operation in unbalanced state. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a three-phase power supply unbalance detection device that detects unbalance of a three-phase AC power supply in a device that uses a three-phase AC power supply as a power source and protects the device.

Conventionally, as shown in FIG. 3, when the voltages of the R, S, and T phases of the three-phase AC power supply 22 are in an equilibrium state, the output voltage Vout of the current detector 15 is approximately 0 [V]. . However, if an imbalance occurs due to some cause, such as poor power quality, the current detector 15 is arranged on a three-phase power line, so the output voltage Vout of the current detector 15 is 0 [V]. Instead, the output voltage Vout determined by the vector synthesis of the R, S, and T phases is generated according to the unbalanced state. When the magnitude of the output voltage Vout exceeds a predetermined value, the microcomputer 18 detects that an unbalanced state has occurred. When the unbalanced state is detected, the magnetic switch driving means 21 turns off the magnetic switches 12, 13, and 14 to stop the power supply to the three-phase induction motor 5, and the display unit 20 of the remote controller 19 is abnormal. Inform. Thus, by monitoring the current amount of the three-phase power supply line, the power supply abnormality of the air conditioner is detected, the power supply is stopped, and the power supply abnormality is notified.
Japanese Patent Laid-Open No. 9-9487

  However, since the conventional configuration requires a dedicated circuit such as a current detector, the hardware circuit configuration is complicated and the component area is enlarged, which is difficult to realize. In addition, the cost increases.

  The present invention solves the above-described conventional problems, and the purpose thereof is to eliminate the need for a dedicated circuit, and to detect an unbalance of a three-phase AC power supply quickly and reliably with a simple hardware configuration. An object of the present invention is to provide a three-phase power supply imbalance detection device that can be used.

  In order to solve the above-described conventional problems, a three-phase power supply unbalance detection device of the present invention smoothes a rectifying unit that rectifies a three-phase AC power source into a DC voltage, and a pulsating voltage rectified by the rectifying unit. A smoothing unit, an inverter using the smoothed DC voltage as a power source, a three-phase motor driven by the inverter, a voltage detecting means for detecting the smoothed DC voltage, and detected by the voltage detecting means A control unit for calculating a voltage ripple amount, and when the ripple amount detected by the control unit from the start of the three-phase motor is not less than a predetermined value and a predetermined time has elapsed, a three-phase power supply It is determined to be unbalanced, and the control unit transmits a stop signal to the inverter to stop the three-phase motor.

  The three-phase power supply unbalance detection device of the present invention avoids damage to the control device from malfunction due to operation in an unbalanced state by detecting the unbalance quickly and surely and applying a protective operation to the inverter when the unbalance occurs. can do. 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 ripple amount detected by the control unit after starting is greater than or equal to a predetermined value and after a predetermined time has elapsed, it is determined that the three-phase power supply is unbalanced and a stop signal is transmitted from the control unit to the inverter. If an unbalance occurs by stopping the three-phase motor, the unbalance is detected quickly and surely, and the inverter is protected to prevent the controller from being damaged due to the malfunction caused by the unbalanced operation. Avoid It is possible.

  In addition, since the amount of ripple is directly calculated by a control unit, that is, a microcomputer, and a predetermined value and a predetermined time are stored in advance, a hardware dedicated circuit is not required, so that the cost can be reduced.

  According to the second aspect of the invention, after the operation of the three-phase motor is stopped in the first aspect of the invention, the fact that the three-phase power supply is unbalanced is transmitted to the user. Equilibrium can be surely informed and maintainability can be improved.

  3rd invention uses the three-phase power supply unbalance detection apparatus of 1st or 2nd invention for an air conditioner, and provides the air conditioner with good maintainability protected reliably at the time of unbalance. Can do.

  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 block diagram showing a configuration of an air conditioner using the three-phase power supply unbalance detection device according to Embodiment 1 of the present invention, and FIGS. It is a waveform diagram at the time of unbalance. In FIG. 1, 1 is a three-phase power source, 2 is a rectifying unit, 3 is a smoothing unit, 4 is an inverter, 5 is a three-phase motor, 6 is a voltage detection means, 7 is a control unit, and 8 is an abnormality display 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. In the present invention, the upper limit value and the lower limit value of the DC voltage detected by the voltage detection means 6 after starting the three-phase motor 5 are input to the control unit 7 to calculate the ripple amount. When the three-phase power source 1 is in an equilibrium state, the waveform is as shown in FIG. From experimental data, when the interphase voltage of the three-phase power source 1 is 380V, even if the load of the three-phase motor 5 increases, the ripple amount is about 5V. However, when only one phase of the three-phase power supply 1 occurs, for example, when a voltage change of ± 10% occurs and the three-phase power supply 1 is in an unbalanced state, a load starts to appear in the three-phase motor 5 as shown in FIG. The waveform becomes a ripple, and the ripple amount increases with the load to about 50 V at the maximum, and a difference of 40 V or more is generated. Further, when the load is light, even if the three-phase power supply is in an unbalanced state, the amount of ripple does not change because there is little discharge of the smoothing portion due to the load. Therefore, after the three-phase motor 5 starts to start, the unbalance detection of the three-phase power source 1 is performed by comparing the ripple amounts. Further, the predetermined value (A) as a comparison reference is a value obtained by adding a margin to the amount of ripple when no phase loss occurs, so that the three-phase power source 1 is caused by an increase in ripple accompanying an increase in load at equilibrium. Preventing false detection, and making the unbalanced abnormality after the predetermined amount of time (t) after the ripple amount exceeds the predetermined value (A) ensures that it will not be affected by noise or instantaneous power failure behavior. An unbalanced abnormality of the three-phase power source 1 can be detected.

Since the present invention detects the unbalance 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 It is not necessary to reset (A). When the amount of ripple calculated by the control unit 7 is equal to or greater than the predetermined value (A) and a predetermined time (t) has elapsed, it is determined that there is an imbalance, and a stop signal is transmitted from the control unit 7 to the inverter 4 to By stopping the electric motor 5, it is possible to avoid problems such as damage to the control device due to operation in an unbalanced state. Further, after the three-phase motor 5 is stopped, an unbalanced abnormality signal of the three-phase power source 1 is transmitted from the control unit 7 to the abnormality display unit 8 provided, for example, on the indoor side of the air conditioner, and displayed on the LED or the like to the user. By notifying abnormality, maintainability can be improved.

  As described above, since the three-phase power supply unbalance detection device according to the present invention can surely detect the unbalance of the three-phase power supply, the air conditioner that rectifies the three-phase power supply and supplies the power supply. Besides, it can also be applied to control devices such as refrigeration / freezing devices.

Configuration diagram of a three-phase power supply unbalance detection device in Embodiment 1 of the present invention Waveform diagram at the time of three-phase power supply equilibrium and unbalance in Embodiment 1 of the present invention Configuration diagram of unbalance 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 Abnormal display part 9, 10, 11 Three-phase power supply line 12, 13, 14 Magnetic switch 15 Current detector 16 Resistive element 17 Rectifier circuit 18 Microcomputer 19 Remote control 20 Display unit 21 Magnetic switch drive circuit 22 Three-phase AC power supply

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 Three-phase motor, 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, the control after the start of the three-phase motor If the ripple amount detected by the unit is greater than or equal to a predetermined value and after a predetermined time has elapsed, it is determined that the three-phase power supply is unbalanced and a stop signal is transmitted from the control unit to the inverter. A three-phase power supply unbalance detection device characterized by stopping an electric motor. An abnormality display section that displays an unbalanced abnormality is provided, and when it is determined that there is an unbalanced condition, the start operation of the three-phase motor is stopped, and then the user is notified that the three-phase AC power supply is unbalanced. The three-phase power supply unbalance detection apparatus according to claim 1. An air conditioner using the three-phase power supply unbalance detection device according to claim 1.

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