JPH01313681A - Control method for air conditioner - Google Patents

Abstract

PURPOSE:To permit a boost of voltage to be contrived reducing a load for an AC power source by decreasing operational power of a compressor when the voltage, supplied to an air conditioner, of the AC power source decreases to a predetermined value or less. CONSTITUTION:A three-phase AC power source 13 applies its voltage to one terminal of a comparator 23 through a rectifier circuit 19, smoothing capacitor 20 and voltage divider resistors 21, 22. While reference voltage, determined by resistors 24, 25, is applied to the other terminal of the comparator 23. When the voltage of the three-phase AC power source 13 decreases to the reference voltage or less, the comparator 23 gives an output to a terminal R of a control part 3, thus it decreases a frequency applied to a compressor 1 through an inverter circuit part 2. Accordingly, because the compressor 1 decreases its ability and consumption power, a boost of the voltage of the three-phase AC power source 13 is contrived.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to control of changing the capacity of an air conditioner having a compressor whose operating capacity can be changed.

(Example) Conventional Technology In general, there is a conventional technology that deals with the drop in power supply voltage as described in Japanese Patent Publication No. 3538/1983. The system described in this publication is one that issues a voltage drop alarm when the power supply voltage falls below a predetermined voltage. This alarm was used to prevent malfunctions and malfunctions due to voltage drops.

(c) Problems to be Solved by the Invention In the conventional technology configured as described above, the predetermined voltage at which the alarm is activated is set to the lowest voltage at which the equipment becomes almost inoperable. This was consistent with the inability to operate. However, in devices that can change the capacity, that is, the power consumption, when the power supply voltage drops, the power supply voltage may increase if the capacity is reduced to reduce power consumption, but conventional technology does not address this issue. No consideration was given to

In view of these problems, the present invention provides a control method that increases the power supply voltage by reducing the power consumption of equipment when the power supply voltage decreases.

(D) Means for Solving the Problems The present invention provides an air conditioner having a refrigeration cycle using a compressor whose operating capacity can be changed, and in which the operating capacity of the compressor is changed based on the air conditioning load. In the control method, an operation is performed to reduce the operating capacity of the compressor when the voltage of the AC power supply that can be fully supplied to the air conditioner falls below a predetermined voltage.

(*) Effect If the control method configured as described above is used, when the heavy pressure of the AC power supply that can be supplied to the air conditioner falls below a predetermined value, the capacity of the compressor will be reduced and the power consumption of the compressor will be reduced. This is intended to boost the voltage of the AC power supply.

(f) Examples Examples of the present invention will now be described based on the drawings. FIG. 1 is a main part control circuit diagram for operating a compressor 1 used in an air conditioner. A three-phase induction motor is used to drive the compressor 1, and this motor is supplied with the output of an inverter circuit 2 that converts DC voltage into three-phase AC.

Therefore, by changing the frequency of the three-phase alternating current output from this inverter circuit WJ2, the rotation speed of the electric motor, that is, the capacity of the compressor 1 can be changed. In the inverter circuit section 2, switching elements are connected in a three-phase bridge configuration, and 0N10FF of each switching element is performed by a signal based on the PWM theory output from the control section 3. Based on the frequency signal given to the terminal f, the control unit 3 uses the PWM theory to
Generate a signal. Therefore, the capacity of the compressor 1 can be fully controlled by the frequency signal applied to the terminal r of the control section 3.

Note that this frequency signal is output from the temperature control section of the air conditioner.

In addition, 4 is a resistor for detecting the DC current flowing through the inverter circuit section 2, 5 is a smoothing capacitor, and 6 is a constant voltage +
A constant voltage circuit that supplies vcc, 7 is a noise filter, 8
9 is a reactor, 9 is a rectifier circuit composed of a plurality of rectifier diodes, 10 is a current transformer that detects the alternating current flowing through the rectifier circuit 9, 11 is a noise filter, and 12 is a power relay, which supplies and cuts off the AC power supply 13. It has normally open contact pieces 14, 15, 16 for controlling. 17 and 18 are positive characteristic thermistors, which are used to prevent inrush current. Furthermore, when the DC current value detected using the resistor 4 or the AC current value detected using the current transformer 10 exceeds a predetermined value, the control unit 3 stops increasing the frequency or lowers the frequency. The detected DC current value and AC current value are controlled so as not to exceed a predetermined value.

Moreover, 19 is a rectifier circuit, which is connected to the single-phase AC portion of the three-phase AC power supply 13. A smoothing capacitor 20 smoothes the output of the rectifier circuit 19. 21.
A voltage dividing resistor 22 divides the terminal voltage of the smoothing capacitor 20 and outputs the divided voltage to one terminal of the comparator 23. A reference voltage defined by a resistor 24.25 is applied to the other terminal of the comparator 23. This comparator 23 operates when the voltage applied to one terminal becomes less than the reference voltage applied to the other terminal, that is, when the voltage applied to one terminal becomes lower than the reference voltage applied to the other terminal, the comparator 23
When the voltage becomes equal to or less than a predetermined voltage corresponding to the reference voltage, an output is given to the control section 3.

Note that 26 is a positive feedback resistor that provides a differential to the operation of the comparator 23. Further, the control unit 3 lowers the frequency applied to the compressor 1 when the output of the comparator 23 is applied to the terminal R. FIG. 2 is an explanatory diagram showing the main operations of the control section 3 shown in FIG. 1. In this explanatory diagram, first, in step S1, it is determined whether an overcurrent condition exists, that is, whether the current flowing through the resistor 4 or the current detected by the current transformer 10 exceeds a predetermined value. Next, in step S, it is determined whether there is an output from the comparator 23, that is, whether the voltage of the AC power supply 13 is below a predetermined voltage. When steps S, , S, are established, the process proceeds to step S, and the currently set frequency F is newly set to "F-F-N".

Note that the value of N may be arbitrarily set based on the maximum capacity of the compressor 1, the resolution of the frequency output from the control unit 3, or the design philosophy of the air conditioner. In this example, it is N-5. In addition, when steps S, , S, do not hold, that is, when there is no current abnormality or voltage abnormality, a signal of frequency r is input in step S4, and then the currently set frequency F and the input frequency f are input in step S4. It compares the size with , and proceeds to step S6 or step S. Step S,
Then, "F-f II" is set, and in step S, "F=F+N+t", that is, the frequency is increased. Next, in step S, the inverter circuit section 2
The switching element 0N10FF is controlled. After this, in step S, this frequency F setting is maintained for one second, and then the process goes to step SI again to repeat the above operation. still,
The value of T is set to about 4 seconds in this embodiment.

With the configuration as described above, when the voltage of the AC power source falls below a predetermined value, the capacity of the compressor is reduced, thereby reducing the power consumption of the air conditioner.

Although this embodiment has been explained using an air conditioner, it can be similarly applied to refrigerators, showcases, and other refrigeration machines.

(G) Effects of the Invention The present invention provides a method for controlling an air conditioner that has a refrigeration cycle using a compressor whose operating capacity can be changed, and in which the operating capacity of the compressor is changed based on the air conditioning load. When the voltage of the AC power supply supplied to the air conditioner falls below a predetermined voltage, the operating capacity of the compressor is reduced, so when the voltage of the AC power supply decreases, the power consumption in the compressor is reduced. This reduces the load on the AC power supply and increases the voltage.

[Brief explanation of the drawing]

FIG. 1 is a schematic electrical circuit diagram of an air conditioner showing an embodiment of the present invention, and FIG. 2 is an explanatory diagram showing the main operations of the control section shown in FIG. 1. DESCRIPTION OF SYMBOLS 1... Compressor, 3... Control part, 19... Rectifier circuit.

Claims (1)

[Claims] (1) In a method for controlling an air conditioner, the air conditioner has a refrigeration cycle using a compressor whose operating capacity can be changed, and the operating capacity of the compressor is changed based on the air conditioning load. A method for controlling an air conditioner, comprising: performing an operation to reduce the operating capacity of the compressor when the voltage of the AC power supply becomes lower than a predetermined voltage.