JP2004286239A - Method of controlling cooling device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of controlling a cooling device capable of properly controlling if abnormal voltage occurs. <P>SOLUTION: In the control circuit 1 of an inverter air conditioner, a common dc voltage Vc is inputted into a compressor inverter 12 supplying power to a compressor drive motor 14 and a fan inverter 16 supplying power to a fan drive motor 18. As voltage threshold values for determining the occurrence of undervoltage, a threshold value Vct1 is set for the compressor and a threshold valve Vft1 is set for the fan. Also, as voltage threshold values for determining the occurrence of overvoltage, a threshold value Vct2 is set for the compressor and a threshold valve Vft2 is set for the fan. In a normal state, there is a relation of Vft1<Vct1<Vc<Vft2<Vct2. When the dc voltage Vc reaches the threshold Vft1 or Vft2, the fan is stopped, and when the dc voltage Vc reaches the threshold Vct1 or Vct2, the compressor is stopped. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an abnormal voltage protection technique for a plurality of inverters, and can be applied, for example, when protecting a compressor inverter and a fan inverter of a cooling device.
[0002]
[Prior art]
Conventionally, a compressor driven by a compressor drive motor and a fan driven by a fan drive motor are provided, and the compressor drive motor and the fan drive motor generate power from the compressor inverter and the fan inverter, respectively. The supplied cooling device has been proposed, for example, as an air conditioner.
[0003]
For example, Patent Literature 1 discloses a technology in which these two inverters are connected in parallel to a DC power supply and inputs a DC voltage supplied from the DC power supply and converts the DC voltage into an AC.
[0004]
[Patent Document 1]
JP-A-62-141450 [0005]
[Problems to be solved by the invention]
In general, voltage abnormalities may occur such that overvoltage is applied to both inverters for various reasons, or conversely, the voltage drops and an undervoltage occurs. In such a case, for example, it is desirable to stop the motor.
[0006]
However, since the purpose of use is different between the fan drive motor and the compressor drive motor, it is not necessary to stop the fan drive motor and the compressor drive motor at the same time, and the operation of the cooling device may be continued. is there.
[0007]
The present invention has been made in view of the above problems, and has as its object to provide a method of controlling an inverter when a voltage abnormality occurs.
[0008]
[Means for Solving the Problems]
A first aspect of the present invention provides a compressor inverter (12) for supplying electric power to a compressor drive motor (14) for driving a compressor for compressing a refrigerant, and a fan drive motor (18) for driving a fan. A method of controlling a cooling device including a fan inverter (16) for supplying electric power, wherein a common DC voltage (Vc) is input to the compressor inverter and the fan inverter. When the DC voltage is higher than the high voltage threshold for the fan (Vft2), the inverter for the fan is stopped (102), and when the DC voltage is higher than the high voltage threshold for the compressor (Vct2). Then, the compressor inverter is stopped (104). The high voltage threshold for the fan is lower than the high voltage threshold for the compressor.
[0009]
According to a second aspect of the present invention, a compressor inverter (12) for supplying electric power to a compressor drive motor (14) for driving a compressor for compressing a refrigerant and a fan drive motor (18) for driving a fan are provided. A method of controlling a cooling device including a fan inverter (16) for supplying electric power, wherein a common DC voltage (Vc) is input to the compressor inverter and the fan inverter. When the DC voltage becomes lower than the compressor low voltage threshold (Vct1), the compressor inverter is stopped (106), and the DC voltage becomes lower than the fan low voltage threshold (Vft1). In this case, the fan inverter is stopped (108). The fan low voltage threshold is lower than the compressor low voltage threshold.
[0010]
A third aspect of the present invention is the cooling device control method according to the first aspect, wherein the fan inverter (16) is provided when the DC voltage becomes higher than a fan high voltage threshold (Vft2). ) Is stopped (102), and when the DC voltage becomes higher than the high voltage threshold for compressor (Vct2), the inverter (12) for compressor is stopped (104). The high voltage threshold for the fan is lower than the high voltage threshold for the compressor.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a circuit diagram illustrating an electrical configuration of an outdoor unit 1 of an inverter air conditioner to which a control method according to an embodiment of the present invention can be applied.
[0012]
The outdoor unit 1 is connected to a three-phase AC power supply 2 via a switch 4. The diode module 6 receives a three-phase alternating current through the switch 4 and performs full-wave rectification on the three-phase alternating current. The DC including the ripple output from the diode module 6 is smoothed by the low-pass filter 9.
[0013]
The low-pass filter 9 is, for example, a choke input type, and has a reactor 8 and a smoothing capacitor 10. The reactor 8 and the smoothing capacitor 10 are connected in series via one end thereof, and the other end of the reactor 8 is connected to the high voltage side of the diode module 6 (the cathode side of the diode constituting the diode module 6). Is connected to the low voltage side of the diode module 6 (the anode side of the diode constituting the diode module 6). The output of the low-pass filter 9 is obtained as a DC voltage Vc that appears at both ends of the smoothing capacitor 10.
[0014]
Each of the compressor inverter 12 and the fan inverter 16 receives a DC voltage Vc as an input, converts the DC voltage Vc into a three-phase AC, and outputs the converted AC voltage. Upon receiving these three-phase alternating currents, the compressor drive motor 14 and the fan drive motor 18 rotate.
[0015]
The DC voltage Vc is measured by the voltage measuring means 28, and the result is transmitted to the microcomputer 29 for refrigerant control. The refrigerant control microcomputer 29 individually instructs the inverter control microcomputers 31 and 33 to start / stop the compressor inverter 12 and the fan inverter 16 in accordance with the criteria described later.
[0016]
The inverter control microcomputer 31 controls the switching control circuit 30 in accordance with the instruction of the refrigerant control microcomputer 29, and the switching control circuit 30 controls on / off of a switching element (for example, a transistor) included in the fan inverter 12. The signal 24 is output. That is, the inverter control microcomputer 31 controls the operation (including the stop) of the fan inverter 12.
[0017]
The inverter control microcomputer 33 controls the switching control circuit 32 in accordance with the instruction of the refrigerant control microcomputer 29, and the switching control circuit 32 controls on / off of a switching element (for example, a transistor) included in the compressor inverter 16. A signal 26 is output. That is, the inverter control microcomputer 33 controls the operation (including the stop) of the compressor inverter 16.
[0018]
For example, the diode module 6, the low-pass filter 9, the compressor inverter 12, the switching control circuit 30, and the inverter control microcomputer 31 are provided on the compressor control board P1. The fan inverter 16, the switching control circuit 32, and the inverter control microcomputer 33 are provided on the fan control board P2. The voltage measuring means 28 and the refrigerant control microcomputer 29 are provided on the refrigerant control board P3.
[0019]
The refrigerant control microcomputer 29 includes a compressor low-voltage threshold Vct1 and a compressor high-voltage threshold as thresholds for protecting the compressor inverter 12 for determining undervoltage occurrence and overvoltage occurrence, respectively. The threshold value Vct2 (> Vct1) is stored. Further, as a threshold value for protecting the fan inverter 16, a low voltage threshold value Vft1 for the fan and a high voltage threshold value Vft2 (> Vft1) for the fan are stored for determination of occurrence of undervoltage and determination of occurrence of overvoltage, respectively. I have.
[0020]
Next, a specific protection procedure will be described. First, a control method when the DC voltage Vc becomes overvoltage will be described. One cause of the overvoltage is that the number of revolutions of the fan rises due to the amount of outside air. The regenerative voltage from the fan drive motor 18 to the inverter causes overvoltage. In such a case, it is considered that stopping the fan eliminates the overvoltage, and it is not necessary to stop the compressor, and it is desirable to continue the operation of the compressor.
[0021]
Therefore, when the DC voltage Vc tends to increase, control is performed to stop the fan drive motor 18 before stopping the compressor drive motor 14. Specifically, for example, the fan high voltage threshold Vft2 is set lower than the compressor high voltage threshold Vct2. When the DC voltage Vc is higher than the fan high voltage threshold Vft2, the refrigerant control microcomputer 29 controls the inverter control microcomputer 33 to stop the operation of the fan inverter 16. As a result, the fan drive motor 18 stops, and if there is no change in the air volume or the wind direction of the outside air, the state transits to a direction in which the overvoltage is eliminated.
[0022]
When the overvoltage is eliminated, that is, when the DC voltage Vc becomes equal to or less than the high voltage threshold value Vft2 for the fan, the refrigerant control microcomputer 29 causes the inverter control microcomputer 33 to restart the operation of the fan inverter 16. Perform control.
[0023]
When the DC voltage Vc is further higher than the compressor high voltage threshold value Vct2, the refrigerant control microcomputer 29 instructs the inverter control microcomputer 33 to stop the operation of the fan inverter 16, Control for stopping the operation of the inverter 12 is also performed.
[0024]
Next, a control method when the DC voltage Vc becomes an undervoltage will be described. One cause of the undervoltage is a voltage fluctuation of the AC power supply 2. In this case, it is desirable to stop the compressor. However, in order to prevent a rise in the pressure of the refrigerant due to the stop of the fan, it is desirable that the compressor is also stopped when the fan is stopped. Therefore, the fan high voltage threshold Vft1 is set lower than the compressor low voltage threshold Vct1, and when the DC voltage Vc is lower than the compressor low voltage threshold Vct1, the refrigerant control microcomputer 29 is switched to the inverter control microcomputer. 31 is controlled to stop the operation of the compressor inverter 12. As a result, when the compressor drive motor 14 is first stopped while the fan drive motor 18 is being driven, and then the voltage of the AC power supply 2 is restored, the state transitions in a direction to eliminate the undervoltage.
[0025]
Of course, when the DC voltage Vc is still lower and lower than the fan low voltage threshold Vft1, the refrigerant control microcomputer 29 controls the inverter control microcomputer 33 to stop the operation of the fan inverter 16. Do. As a result, the fan drive motor 18 stops.
[0026]
FIG. 2 is a flowchart illustrating the operation of the voltage protection in the outdoor unit 1 shown in FIG. 1, and shows the procedure of the above protection. In step 101, it is determined whether or not the DC voltage Vc is higher than the fan high voltage threshold Vft2. If it is determined that the voltage is large, it is determined that the DC voltage Vc is an overvoltage for the fan inverter 16, the process proceeds to step 102, and the fan inverter 16 stops (stops the fan). Then, the process proceeds to a step 103, wherein it is determined whether or not the DC voltage Vc is higher than a compressor high voltage threshold value Vct2. If it is determined that the voltage is large, it is determined that the DC voltage Vc is an overvoltage for the compressor inverter 12 as well, and the routine proceeds to step 104, where the compressor inverter 12 is stopped (stop of the compressor).
[0027]
If it is determined in step 103 that the DC voltage Vc is equal to or less than the compressor high voltage threshold value Vct2, a command to stop the compressor is not output from the refrigerant control microcomputer 29 again, and the process returns to step 101. .
[0028]
If it is determined in step 101 that the DC voltage Vc is equal to or lower than the fan high voltage threshold Vft2, the process proceeds to step 105, where it is determined whether the DC voltage Vc is lower than the compressor low voltage threshold Vct1. . If it is determined that the voltage is low, it is determined that the DC voltage Vc is an insufficient voltage for the compressor inverter 12, and the routine proceeds to step 106, where the compressor inverter 12 is stopped (compressor stop). Then, the process proceeds to a step 107, wherein it is determined whether or not the DC voltage Vc is smaller than a fan low voltage threshold value Vft1. If it is determined that the voltage is small, it is determined that the DC voltage Vc is insufficient for the fan inverter 16 as well, and the routine proceeds to step 108, where the fan inverter 16 stops (stops the fan). Thereafter, the process returns to step 101.
[0029]
If it is determined in step 107 that the DC voltage Vc is equal to or higher than the fan low voltage threshold value Vft1, a command to stop the fan is not output again from the refrigerant control microcomputer 29, and the process returns to step 101.
[0030]
As described above, steps 101, 102, 103, and 104 are controls for overvoltage, and steps 105, 106, 107, and 108 are controls for undervoltage. These can be performed independently. That is, different voltage thresholds may be set for the compressor inverter and the fan inverter only for the determination of the undervoltage, or different voltage thresholds may be set for the compressor inverter and the fan inverter only for the determination of the overvoltage.
[0031]
In the flowchart, it is not always necessary to precede the control for the overvoltage as shown in FIG. 2, and the control for the undervoltage may precede the control for the overvoltage as shown in FIG. 3.
[0032]
【The invention's effect】
According to the first aspect of the present invention, the state of the cooling device is shifted in a direction to eliminate the overvoltage without stopping the compression operation by first protecting the overvoltage caused by the regenerative voltage from the fan.
[0033]
According to the second aspect of the present invention, when the fan is stopped, the compressor is also stopped to prevent the pressure of the refrigerant from increasing due to the stop of the fan.
[0034]
According to the third aspect of the present invention, the state of the cooling device is shifted in a direction to eliminate the overvoltage without stopping the compression operation by first protecting the overvoltage caused by the regenerative voltage from the fan.
[Brief description of the drawings]
FIG. 1 is a circuit diagram illustrating an electrical configuration of an outdoor unit according to an embodiment of the present invention.
FIG. 2 is a flowchart illustrating an operation of the exemplary embodiment of the present invention.
FIG. 3 is a flowchart illustrating an operation of the exemplary embodiment of the present invention.
[Explanation of symbols]
12 Compressor inverter 14 Compressor drive motor 16 Fan inverter 18 Fan drive motor 29 Refrigerant control microcomputers 31, 33 Inverter control microcomputer Vc Voltage

Claims (3)

A compressor inverter (12) for supplying electric power to a compressor drive motor (14) for driving a compressor for compressing the refrigerant;
A fan inverter (16) for supplying power to a fan drive motor (18) for driving the fan;
A cooling device in which a common DC voltage (Vc) is input to the compressor inverter and the fan inverter,
When the DC voltage is higher than the fan high voltage threshold (Vft2), the fan inverter is stopped (102),
When the DC voltage becomes higher than the compressor high voltage threshold (Vct2), the compressor inverter is stopped (104),
The cooling device control method, wherein the fan high voltage threshold is lower than the compressor high voltage threshold. A compressor inverter (12) for supplying electric power to a compressor drive motor (14) for driving a compressor for compressing the refrigerant;
A fan inverter (16) for supplying power to a fan drive motor (18) for driving the fan;
A cooling device in which a common DC voltage (Vc) is input to the compressor inverter and the fan inverter,
When the DC voltage is lower than the compressor low voltage threshold (Vct1), the compressor inverter is stopped (106),
When the DC voltage becomes lower than the fan low voltage threshold (Vft1), the fan inverter is stopped (108),
The method of controlling a cooling device, wherein the low voltage threshold for the fan is lower than the low voltage threshold for the compressor. When the DC voltage is higher than the fan high voltage threshold (Vft2), the fan inverter (16) is stopped (102),
When the DC voltage becomes larger than the compressor high voltage threshold (Vct2), the compressor inverter (12) is stopped (104),
The control method for a cooling device according to claim 2, wherein the high voltage threshold for the fan is lower than the high voltage threshold for the compressor.

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