JPH06101895A - Inverter control device for air conditioner - Google Patents

Abstract

(57) [Summary] [Purpose] The upper and lower reference values of the input current are temperature-compensated, and the input current is variably controlled by comparing the temperature-corrected reference value with the input current. The purpose is to prevent the control from changing depending on the usage environment. [Structure] A detection signal detected by an input current detection unit (an input current detector 5 and an input current detection circuit 17) that detects an input current from a power source 1 to an inverter unit 3, and an outside air temperature detection unit that detects an outside air temperature. The detection signal detected by 15 and the control unit 1
4 and input the upper and lower reference values of the input current set in the reference value setting unit 16 by the control unit 14 to the outside air temperature detection unit 15
Is corrected by the detection signal from the input current detecting means and the control signal is output by the input current detecting means. The operating frequency of the electric motor 4 driving the motor (not shown) is variably controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter control device for an air conditioner. In recent years, more and more air conditioners have adopted an inverter system. In an air conditioner that employs this inverter system, the input current is limited and the breaker of the commercial power source to which the air conditioner is connected is limited. Protective devices such as are not working.

[0002]

2. Description of the Related Art In a conventional air conditioner, an upper limit reference value A and a lower limit reference value B of an input current are set, and when the input current exceeds the reference value A, the operating frequency of a motor driving a compressor. When the input current falls below the reference value B, the operating frequency of the motor is increased to control the input current so that it falls within a certain range, and the reference values A and B are set to the operation modes (cooling and (Heating) or, depending on the difference in the frequency of the commercial power source, different values are set to protect the electric circuit components inside the air conditioner.

[0003]

However, the detected value of the input current changes in the environment where the air conditioner is used due to the temperature characteristics of the electric circuit parts used in the input current detection circuit and the like. However, there is a problem that an error occurs between the input current to the air conditioner and the detected value of the input current, and the control of the input current becomes unstable. The present invention uses the standard value A
And B are temperature-corrected according to the environment in which the air conditioner is used, the input value is compared with the temperature-corrected reference value, and the operating frequency of the electric motor is variably controlled to stabilize the control of the input current. With the goal.

[0004]

FIG. 1 is an electric circuit block diagram of an inverter control device for an air conditioner showing an embodiment of the present invention. As shown in FIG. 1, the operating frequency is variable by an inverter unit 3. In an inverter control device for an air conditioner in which a compressor (not shown) is driven by an electric motor 4 to be controlled, an input current detection unit (in the figure, an input current detection unit that detects an input current from a commercial power source 1 to an inverter unit 3 is shown. , An input current detector 5 and an input current detection circuit 17), a control unit 14 for controlling the inverter unit 3, and a reference value setting unit 16 for setting the upper and lower reference values of the input current provided in the control unit 14. And an outside air temperature detection unit 15 for detecting the outside air temperature,
The detection signal detected by the input current detection means and the detection signal detected by the outside air temperature detection unit 15 are input to the control unit 14, and the reference value is corrected by the detection signal detected by the outside air temperature detection unit 15 by the control unit 14. At the same time, the corrected reference value is compared with the detection signal detected by the input current detecting means to output a control signal and input it to the inverter section 3 to variably control the operating frequency of the electric motor 4. There is.

[0005]

According to the present invention, even if the input current detection value changes due to the temperature characteristics of the electric circuit components used in the input current detection circuit 17 and the like, the detected temperature detected by the outside air temperature detection unit 15 The upper and lower reference values of the input current set in the reference value setting unit 16 are corrected to cancel the change in the input current detection value due to the temperature characteristics of the electric circuit components, and the input current detection value and the input current detection value are input under substantially the same conditions. It is possible to compare with the reference value of the electric current, and therefore, even if the ambient temperature in which the air conditioner is used changes, the input current to the air conditioner is controlled to stay within a certain range, and It becomes possible to protect the electric circuit components inside the air conditioner.

[0006]

1 is a block diagram of an electric circuit of an inverter control device for an air conditioner, showing an embodiment of the present invention.
Reference numeral 2 denotes an AC / DC converter, which converts the AC input from the commercial power supply 1 into DC, inputs the DC into the inverter unit 3, and converts the AC into a three-phase AC voltage having a desired frequency and voltage. It is input to the electric motor 4 that drives a compressor (not shown). Input current detector 5 and input current detection circuit 1
7 is provided with an input current detecting means, and a commercial power source 1
The input current detector 5 is inserted in the input circuit from the input circuit, the input current detector detects the input current, the input current detection circuit 17 converts the input current into a DC voltage, and the DC voltage is input to the control unit 14. The input current detection circuit 17 is a rectifier circuit including a resistor 6 that converts the input from the input current detector 5 into a voltage, a diode 7 that converts the voltage generated across the resistor 6 into a DC voltage, and a capacitor 8. , The resistors 9 and 10 for dividing the DC voltage output from the rectifier circuit, and the divided DC voltage are integrated by an integrating circuit including a resistor 11 and a capacitor 12,
By selecting the time constant of the same integrator circuit, the time constant is selected so that it is not influenced by noise and is output, and is input to the control unit 14.

Reference numeral 13 is a power supply frequency detection unit, one end of which is connected to the input circuit from the commercial power supply 1 and the other end of which is connected to the control unit 14. The power supply frequency detection unit 13 requires an insulating function in terms of circuit configuration. In that case, use a photo coupler to insulate,
The level is lowered so that it can be input to the control unit 14 and the level is input to the control unit 14, and a counter built in the control unit 14 counts to determine the power supply frequency.
Reference numeral 16 is a reference value setting unit that sets the upper and lower reference values of the input current, and may be provided inside the control unit 14 or outside the control unit 14. Further, the reference value setting unit 16 may use a memory to store a reference value set in advance in the memory, or may be configured by a switch circuit and switch the switch circuit between the upper and lower reference values. You may be able to output. Reference numeral 15 denotes an outside air temperature detection unit, which is provided, for example, in the outdoor unit portion of the air conditioner so as to detect the outside air temperature and input it to the control unit 14.
Based on the input, the temperature inside the outer box in which the input current detecting means of the air conditioner is stored is estimated, and the upper and lower reference values of the input current set in the reference value setting unit 16 by the control unit 14 are corrected. I am trying to do it.

FIG. 2 is a flow chart for explaining the operation of the control unit 14 shown in FIG. 1. Referring to FIG.
The operation of each part of the electric circuit block diagram shown in FIG. An operation signal is input to the control unit 14 using an operation unit or a remote controller provided in the air conditioner. Control unit 1
Reference numeral 4 captures an operation signal and determines whether the power supply frequency is 50 Hz based on the input from the power supply frequency detection unit 13. next,
The operation signal input to the control unit 14 determines whether it is the cooling mode, and when it is NO, the heating mode is set, and the outside air temperature zone is determined by the input from the outside air temperature detection unit 15 and set in the reference value setting unit 16. The upper limit reference value A and the lower limit reference value B of the input current are corrected to predetermined values, and if YES, the outside air temperature detection unit 1
The input from 5 determines the outside air temperature zone, and corrects the upper limit reference value A and the lower limit reference value B of the input current set in the reference value setting unit 16 to predetermined values.

Table 1 is a correction value table for A and B with respect to the outside air temperature. As shown in the table, the power supply frequency is 50 Hz.
The setting values of A and B are corrected depending on whether the operation mode is cooling operation or heating operation. Furthermore, due to the difference in outside temperature, A
The set values of B and B are corrected. For example, when the outside air temperature is -20 to 0 °, it is set to zone 1, when it is 0 to 20 °, it is set to zone 2, and when it is 20 to 40 °, zone 3 is set. As
Each of them has a different value. Therefore, A can be corrected to a value of A1 to 12 and B can be corrected to a value of B1 to 12 depending on the difference in the power supply frequency, the operation mode, and the outside temperature. It can be corrected to the value up to.

As the control unit 14, for example, a microcomputer or the like is used, and the output of the input current detection circuit 17 is the A of the microcomputer.
/ D input port, and the same microcomputer corrects the upper limit reference value A of the input current according to the power supply frequency, the operation mode and the outside temperature to obtain the correction value A ', and the lower limit reference value B to correct the correction value B. ′, It is determined whether the input of the A / D input port is equal to or greater than the correction value A ′, and if YES, a control signal is input to the inverter unit 3 and the operating frequency of the electric motor 4 is lowered based on the input, and air conditioning is performed. If the input current to the machine is NO and NO, it is further judged whether the input of the A / D input port is less than or equal to the correction value B '. If YES, the control signal is input to the inverter unit 3 and the motor is driven based on the input. The operating frequency of 4 is increased to increase the input current to the air conditioner, and in the case of NO,
The operating frequency of the electric motor 4 is maintained so that the input current to the air conditioner does not change. Therefore, even if the input current detection value changes due to the temperature characteristics of the electric circuit components used in the input current detection circuit 17 and the like, the outside air temperature detection unit 15
The upper and lower reference values of the input current set in the reference value setting unit 16 are corrected based on the detected temperature detected in step 1, and the change in the input current detected value due to the temperature characteristics of the electric circuit components is canceled, and under almost the same conditions. The input current detection value and the reference value of the input current can be compared. Therefore, even if the ambient temperature in which the air conditioner is used changes, the input current to the air conditioner stays within a certain range. Can be controlled and the electric circuit components inside the air conditioner can be protected.

[0011]

As described above, according to the present invention,
Even if the input current detection value changes due to the temperature characteristics of the electric circuit components used for the input current detection means, etc., the reference values for the upper and lower limits of the input current are corrected by the detected temperature detected by the outside air temperature detection unit. Then, the change in the input current detection value due to the temperature characteristics of the electric circuit components is canceled, and the input current detection value and the reference value of the input current can be compared under almost the same conditions. Even if the ambient temperature used changes, the input current to the air conditioner can be controlled so that it stays within a certain range, and the electric circuit components inside the air conditioner can be protected. It greatly contributes to the improvement of machine performance.

[Brief description of drawings]

FIG. 1 is a block diagram of an electric circuit of an inverter control device for an air conditioner, showing an embodiment of the present invention.

FIG. 2 is a flowchart illustrating an operation of a control unit 14 shown in FIG.

[Explanation of symbols]

 1 Commercial Power Supply 2 AC / DC Converter 3 Inverter Section 4 Motor 5 Input Current Detector 6 Resistor 7 Diode 8 Capacitor 9 Resistor 10 Resistor 11 Resistor 12 Capacitor 13 Power Supply Detection Section 14 Control Section 15 Outside Air Temperature Detection Section 16 Standard Value setting section 17 Input current detection circuit

Claims (2)

[Claims] 1. In an inverter control device for an air conditioner in which a compressor is driven by an electric motor whose operating frequency is variably controlled by an inverter section, an input current detecting means for detecting an input current from a power source to the inverter section. A control unit for controlling the inverter unit, a reference value setting unit provided in the control unit for setting reference values for upper and lower limits of the input current, and an outside air temperature detecting unit for detecting an outside air temperature. The detection signal detected by the current detection means and the detection signal detected by the outside air temperature detection unit are input to the control unit, and the control unit corrects the reference value by the detection signal detected by the outside air temperature detection unit. Comparing the corrected reference value with the detection signal detected by the input current detection means, outputting a control signal and inputting it to the inverter section, the operating frequency of the electric motor is variably controlled. An inverter control device for an air conditioner, comprising: 2. When the detection signal detected by the input current detection unit is equal to or higher than the corrected upper limit value of the input current, the operating frequency of the electric motor is decreased based on the control signal output from the control unit. When the detection signal detected by the input current detection unit is equal to or lower than the corrected lower limit value of the input current, based on the control signal output from the control unit,
The inverter control device for an air conditioner according to claim 1, wherein the operating frequency of the electric motor is increased, and in other cases, control is performed so as to maintain the operating frequency of the electric motor.