JP2012197998A - Air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air conditioner that prevents a stop of the air conditioner by an undercharge of DC voltage and a burnout of a current-limiting resistor.SOLUTION: The air conditioner includes: a diode for rectification that rectifies a voltage of AC power supply 1 to DC voltage; a smoothing capacitor 8; a current-limiting resistor 2 which limits an incoming current at the timing of initial charging of the smoothing capacitor 8; a charging relay 3 which is parallely-connected to the current-limiting resistor 2 and which can be switched between open and short; a control part 10 which controls switching between open and short of the charging relay 3; a load 9 which is driven by inverter control of DC power; a zero cross detection means 11 which detects a zero cross point of voltage of AC power supply wherein driving of the load is stopped and the charging relay is opened when the load stops if the zero cross detection means can not detect continuously the zero cross point at predetermined times.

Description

  The present invention relates to an air conditioner having an inrush current suppression circuit.

  In a conventional air conditioner, a converter device that rectifies the voltage of an AC power supply into a DC voltage prevents the rectifier circuit such as a rectifier diode from being damaged due to a large inrush current during the initial charging of the smoothing capacitor at startup. In order to do this, a charging relay that can switch between a current limiting resistor and a short circuit and an open circuit is connected in parallel to the charging circuit. FIG. 5 is a configuration diagram of a power supply circuit of a conventional air conditioner.

  At startup, the charging relay is opened to charge the smoothing capacitor via the current limiting resistor to prevent the rectifier circuit from being damaged, and the smoothing capacitor is charged with a sufficient DC voltage to generate an inrush current. When there was no risk of damage to the rectifier circuit, the charging relay was short-circuited to perform normal operation.

  In addition, when an instantaneous power failure or instantaneous low voltage (hereinafter referred to as an instantaneous power failure) occurs, the DC voltage is a smoothing capacitor, and a compressor or fan motor that drives the DC voltage charged in the smoothing capacitor by inverter control. Because it discharges with a time constant due to a load such as DC, a DC voltage is detected, and when the DC voltage drops to a predetermined value, the charging relay is opened to make a large rush without going through a current limiting resistor at the time of instantaneous power failure recovery The current was prevented from flowing.

  Also, by detecting the set differential value instead of the absolute value of the DC voltage, a large inrush current is prevented from flowing by opening the charging relay when the differential value is large (for example, Patent Document 1).

JP 2007-74884 A

  However, in the inverter-type air conditioner that drives a load such as a compressor or a fan motor using a smoothed DC voltage as in the conventional configuration, the charging relay is opened while the load is being driven. However, when the power supply voltage recovers from an instantaneous power failure, a large current flows through the current limiting resistor in order to cover the power consumption of the load. There was a problem that burnout would occur.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and an object thereof is to provide an air conditioner that prevents the air conditioner from being stopped and the current limiting resistance from being burned out due to insufficient charging of DC voltage.

In order to solve the above-described conventional problems, the air conditioner of the present invention limits the inrush current at the initial charging of the rectifier diode, the smoothing capacitor, and the smoothing capacitor that rectifies the voltage of the AC power source to the DC voltage. A current limiting resistor that flows in parallel, a charging relay that is connected in parallel to the current limiting resistor and that can be switched between a short circuit and an open circuit, a control unit that controls switching between a short circuit and an open circuit of the charging relay, and a DC voltage by inverter control If the zero cross point cannot be detected continuously for a preset number of times by the zero cross detection means, the drive of the load is stopped and the load is Opening the charging relay after stopping stops charging the smoothing capacitor without burning out the current limiting resistance when the charging relay is open or via the current limiting resistance. Stable start-up of the air conditioner by suppressing inrush current at the time of instantaneous power failure recovery and preventing imbalance in the refrigeration cycle at restart Make it possible.

  INDUSTRIAL APPLICABILITY The present invention can provide an air conditioner that prevents the air conditioner from being stopped and the current limiting resistance from being burned out due to insufficient charging of DC voltage.

Configuration diagram of a power supply circuit of an air conditioner in Embodiment 1 of the present invention Flow chart of control in the first embodiment Flow chart of control in Embodiment 2 of the present invention Flow chart of control in Embodiment 3 of the present invention Configuration diagram of power supply circuit of conventional air conditioner

  An air conditioner according to a first aspect of the present invention includes a rectifying diode that rectifies an AC power supply voltage into a DC voltage, a smoothing capacitor, a current limiting resistor that limits an inrush current during initial charging of the smoothing capacitor, and a limiter. A charging relay that can be switched between a short circuit and an open circuit in parallel with the current resistor, a control unit that controls switching between a short circuit and an open circuit of the charging relay, a load that drives a DC voltage by inverter control, and an AC power supply Zero cross detection means that detects the zero cross point of the voltage, and when the zero cross point cannot be detected continuously by the zero cross detection means for a preset number of times, the drive of the load is stopped and the charging relay is opened after the load stops By doing so, the charging current that is generated by charging the smoothing capacitor without burning out the current limiting resistance when the charging relay is opened or through the current limiting resistance is reduced. Without causing shutdown due to suppress the rush current at the time of recovery from power loss that also prevent imbalance of the refrigeration cycle at the time of restarting further allows the activation of stable air conditioner.

  In the air conditioner of the second invention, in particular in the first invention, the preset number of times of detection of the zero cross point is changed according to the operating condition of the load, so that it is preset when the operating condition of the load is small. By setting a large number of zero cross point detections to be performed and setting the number of zero cross point detections to be small when the load operating condition is large, the load can be continued as much as possible when the load operating condition is small. When the driving situation is large, the driving can be stopped early. For example, the continuous number is set to be large when the compressor is rotating at a low speed, and the continuous number is set to be small when the compressor is at a high speed. Note that the judgment of when the load operating condition is small and large differs depending on the type of load, so it cannot be determined uniquely, but it depends on whether it is larger or smaller than the threshold that is the criterion for judgment in advance. to decide.

  In the air conditioner of the third invention, particularly in the first or second invention, when the zero cross point cannot be detected continuously for a preset number of times, the driving of the load is stopped, and the charging relay is stopped after the load is stopped. If the zero cross point is detected continuously for a preset number of times, the charging relay is short-circuited, and then the drive of the load is started. It is possible to suppress an inrush current at the time of instantaneous power failure recovery without causing burnout or without causing an operation stop due to insufficient charging caused by charging the smoothing capacitor via a current limiting resistor.

In the air conditioner of the fourth invention, particularly in the first or second invention, when the zero cross point cannot be detected continuously for a preset number of times, the driving of the load is stopped and the charging relay is stopped after the load is stopped. When the predetermined time has elapsed since the drive of the load was stopped and the detection of the zero cross point was continuously detected a predetermined number of times, the charging relay was short-circuited, and then the load was By starting the drive, the current limiting resistance when the charging relay is open is not burned out, or the operation is stopped due to insufficient charging caused by charging the smoothing capacitor through the current limiting resistance. By suppressing the inrush current at the time of return from stop and further preventing the imbalance of the refrigeration cycle at the time of restart, it is possible to start the air conditioner stably.

  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 configuration diagram of a power supply circuit of an air conditioner according to Embodiment 1 of the present invention.

  In FIG. 1, the voltage of the AC power source 1 is rectified to a DC voltage by the rectifying diodes 4 to 7, and the DC voltage is smoothed by the smoothing capacitor 8.

  Then, a load 9 such as a compressor or a fan motor is driven by inverter-controlling a smoothed DC voltage (hereinafter referred to as DC voltage).

  Further, in order to limit the inrush current during the initial charging of the smoothing capacitor 8, a current limiting resistor 2 and a charging relay 3 connected in parallel to the current limiting resistor 2 and capable of switching between short circuit and open circuit are provided in the charging circuit. By connecting and opening the charging relay 3 at startup, the smoothing capacitor 8 is charged via the current limiting resistor 2 to prevent the rectifier circuit from being damaged.

  When a sufficient DC voltage is charged in the smoothing capacitor 8 and there is no risk of damage to the rectifier circuit due to inrush current, the charging relay 3 is short-circuited and normal operation is performed. Moreover, it has the control part 10 which performs various controls.

  In addition, a zero cross detection unit 11 for detecting a zero cross point of an AC voltage supplied from the AC power source 1 is provided, and the number of zero cross points detected by the zero cross detection unit 11 by the control unit 10 is continuously detected. If it is not possible, a drop in the DC voltage is predicted. Therefore, the load 9 such as a compressor or a fan motor is stopped, and the charging relay is opened after the load stops.

  FIG. 2 is a flowchart of control for suppressing the inrush current at the momentary power failure in Embodiment 1 of the present invention.

  First, the zero-cross point is detected by the zero-cross detecting means 11 (S21), and it is determined whether the number of detection of the zero-cross point has been detected continuously in advance (S22). It should be noted that the preset number of times is variable according to the number of rotations of the compressor, and is set to be large at low speeds and set to be small at high speeds.

  If the number of detections of the zero cross point is continuously detected more than a preset number, it is determined whether or not a load such as a compressor or a fan motor is being driven (S23), and it is determined that the driving is not being performed. In this case, the charging relay 3 is opened (S25), and when it is determined that it is being driven, the load such as the compressor or the fan motor is stopped (S24), and the charging relay is stopped after the load is stopped. 3 is released (S25).

As a result, when the load 9 is driven when a momentary power failure occurs, the charging relay 3 is opened to suppress the charging current to the smoothing capacitor 8, and the load 9 It is possible to prevent a large current for covering the consumed power from flowing through the current limiting resistor 2 and to prevent the current limiting resistor 2 from being burned out.

(Embodiment 2)
FIG. 3 is a flowchart of control for suppressing the inrush current at the momentary power failure according to the second embodiment of the present invention. Since the configuration of the power supply circuit and a part of the control flow in the second embodiment are the same as those in the first embodiment, the same reference numerals as those in the first embodiment are given and the description thereof is omitted.

  In FIG. 3, after the load is stopped, the charging relay is opened (S25), and then the zero cross point is detected by the zero cross detecting means (S26). It is determined whether or not it has been detected (S27). If it is determined that it has not been detected, the charging relay is kept open. If it is determined that the zero-cross point has been detected, charging is first performed. When the relay 3 is short-circuited (S28) and then it is determined that the load 9 such as the compressor and the outdoor fan motor before the instantaneous power failure is being driven is determined to be driving (S23), The load 9 is driven (S29).

  This prevents a large current to cover the power consumed by the load 9 from flowing into the current limiting resistor 2 by returning and driving the load 9 with the charging relay 3 open after the instantaneous power failure recovery, It is possible to prevent the current limiting resistor 2 from being burned out.

(Embodiment 3)
FIG. 4 is a flowchart of control for suppressing the inrush current at the momentary power failure according to the third embodiment of the present invention. Since the configuration of the power supply circuit and a part of the control flow in the third embodiment are the same as those in the first and second embodiments, the same reference numerals as those in the first and second embodiments are attached and the description thereof is omitted. To do.

  In FIG. 4, after the load is stopped, the charging relay is opened (S25), and then the zero cross point is detected by the zero cross detecting means (S26), and the number of times that the detected zero cross point is set in advance can be detected continuously. It is determined whether a time longer than the set value has elapsed since the load 9 stopped (S37). If it is determined that the zero cross point has not been detected, or the zero cross point has been detected. If it is determined that the time longer than the set value has not elapsed since the load stop, the charging relay is kept open, the zero-cross point is detected, and the load 9 stops and the set value is exceeded. If it is determined that the time has elapsed, the charging relay 3 is first short-circuited (S28), and then it is determined whether the load 9 such as the compressor or the outdoor fan motor before the instantaneous power failure is being driven. S23) Sometimes, when it is determined to be in the drive drives the load 9 (S29) has a configuration.

  This prevents a large current to cover the power consumed by the load 9 from flowing into the current limiting resistor 2 by returning and driving the load 9 with the charging relay 3 open after the instantaneous power failure recovery, It is possible to prevent the current limiting resistor 2 from being burned out, and also to prevent imbalance of the refrigeration cycle at the time of restart due to the load 9 such as the compressor and the outdoor fan motor being stopped. Enable startup.

  As described above, the present invention can be applied to all air conditioners having an inrush current suppression circuit.

DESCRIPTION OF SYMBOLS 1 AC power supply 2 Current limiting resistance 3 Charging relay 4 Rectifying diode 5 Rectifying diode 6 Rectifying diode 7 Rectifying diode 8 Smoothing capacitor 9 Load 10 Control unit 11 Zero cross detection means

Claims (4)

A rectifying diode that rectifies the voltage of the AC power source into a DC voltage, a smoothing capacitor, a current limiting resistor that limits the inrush current during the initial charging of the smoothing capacitor, and a short circuit connected in parallel to the current limiting resistor Relay that can be switched between open and open, a control unit that controls switching between short circuit and open of the charging relay, a load that drives a DC voltage by inverter control, and a zero cross point of the voltage of the AC power supply is detected A zero-cross detecting means for stopping the driving of the load when the zero-cross point cannot be continuously detected by the zero-cross detecting means for a preset number of times, and opening the charging relay after the load is stopped. A featured air conditioner. 2. The air conditioner according to claim 1, wherein the preset number of times of detection of the zero-cross point is changed in accordance with an operation state of the load. If the zero cross point cannot be detected continuously for a preset number of times, the driving of the load is stopped, the charging relay is opened after the load stops, and then the zero cross point is continuously set for a predetermined number of times. 3. The air conditioner according to claim 1, wherein when detected, the charging relay is short-circuited, and then the driving of the load is started. 4. When the zero-cross point cannot be detected continuously for a preset number of times, the driving of the load is stopped, the charging relay is opened after the load stops, and then the driving of the load is stopped for a predetermined time. 3, and when the zero-cross point is detected continuously for a preset number of times, the charging relay is short-circuited, and then the driving of the load is started. Air conditioner as described in.

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