JPH062917A - Control method for air conditioner - Google Patents

Abstract

(57) [Summary] [Purpose] To accurately detect the input current of an air conditioner and control the input current. [Composition] An air conditioner detects an input current and controls the compressor by an inverter so that the input current does not exceed a predetermined input current. If the detected value of the input current is not accurate, the input current cannot be controlled accurately. FIG. 1 shows an inverter device for controlling the compressor 4 by an inverter and its control system. Reference numeral 1 is a power supply, and 5 is an input current instantaneous value detection circuit having a current sensor 6 for detecting an input current. In order to obtain an accurate input current, the microcomputer 9 detects the instantaneous value of the input current at the timing when at least a half cycle of the input AC is divided into equal parts, and calculates the value corresponding to the input current from this instantaneous value. Then, based on the calculated value, the microcomputer 9 generates a PWM waveform signal for controlling the drive circuit 8 of the inverter unit 3, and inverter-controls the compressor 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air conditioner control method, and more particularly to an input current detection method for controlling an input current.

[0002]

2. Description of the Related Art An air conditioner is provided with a control circuit as shown in FIG. This control circuit is for inverter control of the compressor 14, 11 is a power supply, 12 is a converter unit for converting the input AC from the power supply 11 into a predetermined DC voltage,
Reference numeral 13 is an inverter unit that supplies electric power to the compressor 14. By the way, when the air conditioner is used in ordinary households,
The input current is the power supply because the power for the 11 current capacity is large.
In order to prevent the current capacity of 11 from being exceeded, the input current is detected and the compressor 14 is controlled by an inverter so that the input current becomes equal to or lower than a predetermined input current. For example, when using power supply A,
For example, if an input current of 10 A flows in the control circuit of the air conditioner and the input current waveform is as shown in FIG. 5 (A), the output of the input current detection circuit 15 is as shown in FIG. 5 (B). On the other hand, the zero-cross detection circuit 17 outputs a zero-cross detection signal of the input AC and inputs this to the microcomputer 19. The microcomputer 19 detects a zero-cross from this signal and uses it for timing of signal transmission / reception between the indoor unit and the outdoor unit, as well as the microcomputer.
The output of the input current detection circuit 15 shown in FIG.
A / D conversion is performed inside the device 19, and the analog voltage Va is converted into digital data I corresponding to the input current to detect the input current. The microcomputer 19 compares the digital data Imax corresponding to the preset maximum value of the input current with the digital data I corresponding to the detected input current, and calculates I
When> Imax, the PWM signal for controlling the inverter unit 13 output from the microcomputer 19 to the drive circuit 18 is adjusted to reduce the capacity of the compressor 14 and reduce the input current so that the input current is It is controlled so that the current capacity is not exceeded.

[0003]

However, for example, the power supply A
When a different power supply B is used, the input current is the same, for example, 10 A
In this case, the input current waveform is as shown in FIG. 5C, and the output of the input current detection circuit 15 is as shown in FIG. 5D. When the output of the input current detection circuit 15 is A / D converted at the same zero-cross timing to detect the input current, Va in the case of the power supply A and Vb in the case of the power supply B are A / D.
It will be D converted. However, as shown in the figure, Va and Vb are not equal, Va <Vb, and even if the input current is 10 A, the digital data IA and IB corresponding to the A / D converted input current are not equal and IA <
IB occurs, the input current is not accurately detected, and an error due to the power supply used is likely included. Therefore, depending on the power supply used, the input current may flow beyond the current capacity of the power supply, or conversely, the input current may not reach the current capacity of the power supply, but the capacity of the compressor may be reduced. In some cases, the capacity of the harmony machine cannot be fully utilized. Further, since the maximum current value is set to be small in consideration of the error, there is a problem that the capacity of the air conditioner becomes small. Therefore, it is an object of the present invention to provide an air conditioner control method that does not cause the above-mentioned problems.

[0004]

The present invention has been made to solve the above problems, and detects an input current,
In a control method of an air conditioner for controlling a compressor by an inverter device so that an input current is equal to or less than a predetermined input current, at least a half cycle of an input alternating current, an instantaneous value of the input current is detected at a predetermined number of points, A value corresponding to the input current is calculated from this instantaneous value, and the input current is controlled based on this calculated value.

[0005]

According to the above control method, the input current is detected by detecting the instantaneous value of the input current at a predetermined number of points for at least a half cycle of the input AC, and detecting the value corresponding to the input current from the detected instantaneous value. Since the input current is calculated and the input current is controlled based on this calculated value, the input current can be accurately calculated even if the input current waveform is not constant due to the influence of the power source impedance of the power source used. Since the input current can be controlled based on the calculated value, it is possible to accurately control the input current with respect to the predetermined input current.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. An air conditioner has an inverter device for controlling the inverter of a compressor, and FIG. 1 shows a main part of the inverter device according to the present invention. In the figure, 1 is a power source, 2 is a converter unit for converting an input AC from the power source 1 into a predetermined DC voltage, and 3 is a converter unit 2.
Is an inverter unit that converts the DC input from the AC input into AC by the inverter control and supplies the AC to the compressor 4. Reference numeral 5 is an input current instantaneous value detection circuit that has an electric current sensor (CT) 6 to detect an instantaneous value of the input current, and 7 is a timing for determining the power supply frequency, detecting the input current, and transmitting / receiving between the indoor unit and the outdoor unit. Is a zero-cross detection circuit for detecting a zero-cross point, 8 is a drive circuit for driving the inverter unit 3, and 9 is a microcomputer for generating a PWM waveform signal for controlling the drive circuit 8. The microcomputer 9 is provided with an input current instantaneous value detection circuit 5
In addition to an A / D converter that converts the analog signal from the digital signal into a digital signal, a timer, a storage unit, and the like are incorporated.

The air conditioner has the zero-cross detection circuit 7 for detecting the zero-cross point of the input AC for the discrimination of the input frequency and the interrupt processing as described above, and the microcomputer 9 has an A / D converter and a timer. The present invention utilizes these, since it has a built-in storage unit, etc., detects the instantaneous value of the input current at a predetermined number of locations for at least a half cycle of the input AC, and responds to the input current from this instantaneous value. The value is calculated, and the input current is controlled based on the calculated value. Hereinafter, a specific example will be described with reference to FIGS. 2 shows the microcomputer 9
3 is a flowchart showing the operation of FIG. 3, and FIG. 3 shows the input current waveform and the timing of detecting its instantaneous value when the power supplies 1 used are different (power supply A, power supply B).

The instantaneous value of the input current is detected by inputting the output of the input current instantaneous value detection circuit 5 to the microcomputer 9. For example, when the power supply A is used and the input current is 10 A, the input current waveform is as shown in FIG. 3 (a), and the output of the input current instantaneous value detection circuit 5 is as shown in FIG. 3 (b). The microcomputer 9 is a zero cross detection circuit 7
Is input, the zero cross is detected (step ST1 in FIG. 2), and this time is set to t0 (step ST in FIG. 2).
2). At this time, the microcomputer 9 A / D-converts the input output of the input current instantaneous value detection circuit 5 to obtain digital data of the instantaneous value (step ST3 in FIG. 2). After that, the A / D conversion is repeated every t time by the timer inside the microcomputer 9 to obtain digital data of the instantaneous values of I0 to I9 from t0 to t9 (step ST3 of FIG. 2).
~ ST6).

The value I corresponding to the input current is, for example, I0,
I1, ..., I9 are each squared to obtain a sum, and this sum is then calculated as the number (10) of the digital data of the instantaneous values of I0 to I9.
(Step ST7 in FIG. 2). In the case of the present embodiment, these series of operations are repeated every time the zero cross is detected. The method of calculating the value I corresponding to the input current and the number of instantaneous values to be detected are not limited to the above example. Next, FIG. 3 shows an input current waveform when the same input current 10A using the power source B is used.
The output of the input current instantaneous value detection circuit 5 is shown in FIG.
It shows in (d). Similar to the case of the power supply A, the value I corresponding to the input current is obtained, but the result is equal to the value of the power supply A.

[0010]

According to the air conditioner controlled by the control method as described above, due to the influence of the power source impedance of the power source used, even if the input current waveform is not constant, the detection of the input current is erroneous. The input current exceeds the current capacity of the power supply depending on the power supply used, or conversely, the capacity of the compressor is reduced even when the input current does not reach the maximum current of the power supply. The input current can be effectively used up to the maximum of the current capacity of the power supply, and the capacity of the air conditioner is improved without setting the maximum current to a small value in consideration of an error.

[Brief description of drawings]

FIG. 1 is a circuit block diagram of a main part of an air conditioner showing an embodiment of the present invention.

FIG. 2 is a control flowchart showing an embodiment of the present invention.

FIG. 3 is a current waveform diagram for explaining an embodiment of the present invention.

FIG. 4 is a circuit block diagram of a main part of an air conditioner showing a conventional example.

FIG. 5 is a current waveform diagram for explaining a conventional example.

[Explanation of symbols]

 1 Power Supply 2 Converter Section 3 Inverter Section 4 Compressor 5 Input Current Instantaneous Value Detection Circuit 6 Current Sensor 7 Zero Cross Detection Circuit 8 Drive Circuit 9 Microcomputer

Claims (1)

[Claims] 1. An air conditioner control method for detecting an input current and controlling a compressor by an inverter device so that the input current becomes equal to or less than a predetermined input current. A method for controlling an air conditioner, comprising detecting an instantaneous value of an input current at a location, calculating a value corresponding to the input current from the instantaneous value, and controlling the input current based on the calculated value.