JP2663744B2 - Control device for air conditioner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air conditioner, and more particularly to a control device provided with an inverter device.

[0002]

2. Description of the Related Art FIG.
FIG. 1 shows a conventional failure detection device disclosed in Japanese Patent Application Laid-Open No. H10-209, in which 1 is a rectifier, and the output is input to an inverter 3 via a DC reactor 2. An induction motor 4 is driven by the output of the inverter 3. Reference numeral 5 denotes a speed detector for detecting the rotation speed of the induction motor 4, which inputs a deviation from the inverter output frequency 6 to a first comparator 7. A current detector 8 detects an input current to the inverter device. 9
Is a second comparator which receives the detection signal of the current detector 8 and compares it with a predetermined value or more. Reference numeral 10 denotes an AND circuit which receives the signals of the first comparator 7 and the second comparator 9 and
It is output as the failure signal 11 under the condition D.

Next, the operation will be described. The rotation speed of the induction motor 4 is detected by the speed detector 5 and the inverter output frequency 6
Is input to the first comparator 7.

For example, when the rectifier 1, the reactor 2, the inverter 3, and the induction motor 4 are all normal, the deviation between the inverter output frequency 6 and the speed detector 5 is only the slip frequency of the induction motor 4, and at most. It is about 10%.

However, for example, when the induction motor 4 is out of order in the locked state and malfunctions, the deviation between the inverter output frequency 6 and the speed detector 5 becomes very large. The difference between the speed deviations serves to determine the failure of the inverter device.

As a reference, Japanese Patent Application Laid-Open No. 57-206300 discloses a method in which a power factor is detected based on a phase difference between a current and a voltage of a compressor and compared with a reference value to control the power factor.

FIG. 6 shows, for example, Japanese Patent Application Laid-Open No. Hei 2-15755.
This is a control device for an air conditioner disclosed in Japanese Patent Application Publication No. 7-1995, in which a converter unit 12 and a smoothing capacitor 13 rectify an AC of an AC power supply 14 and convert it to a DC. Reference numeral 15 denotes a frequency variable device, which includes a converter unit 12 and a smoothing capacitor 13.
And an inverter unit 16. Reference numeral 8 denotes a current detector for detecting a current flowing into the frequency variable device 15. A control device for controlling the frequency of the inverter section 16 by using the detection signal as an input includes a first current value comparing means 17, a frequency change speed varying means 18 , A second current value comparing means 19 and a frequency changing means 20.

Next, the operation of the second conventional example will be described with reference to the flowchart of FIG. In step 1, the output of the current detector 8 is fetched, and in step 2, it is determined whether the current exceeds a first predetermined value which is a value one level lower than the stall point. At this time, if the value does not exceed the first predetermined value, the process proceeds to step 3, and the process proceeds to step 5 while keeping the frequency change speed high. If it is determined in step 2 that the value exceeds the first predetermined value, the process proceeds to step 4, the frequency change speed is switched to a low speed, and the process proceeds to step 5. In step 5, it is determined whether the current value exceeds a second predetermined value which is a stall point. If it does not exceed the second predetermined value, the process proceeds to step 6, where the operating frequency is increased to the frequency of the predetermined value, and the process returns to the main routine. If it exceeds the second predetermined value in step 5, control proceeds to step 7 to reduce the operating frequency and returns to the main routine.

[0009]

Since the conventional control device is constructed as described above, a speed detector is required, and expensive devices such as an encoder and a tachogenerator must be used. Cost was increased. As a method not using a speed detector, there is a method of making a determination based on an input current. However, there is a problem that the configuration is complicated and the detection speed is low.

In addition, the conventional control device has a problem that the control cannot follow the frequency change speed, which leads to the destruction of the frequency variable device, and that the current cannot be flowed to just below the rated power outlet.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem. In the first aspect, an inexpensive device is used to protect an air conditioner that accurately detects an abnormal condition of an inverter device (lock of a compressor). The aim is to get the device.

Another object of the present invention is to control the input current to just below the outlet rating, eliminate the overshoot of the current, and prevent the operation of the outlet breaker.

[0013]

A control device for an air conditioner according to the present invention converts an AC power supply into a DC power supply, converts the DC power supply into an AC power supply having an arbitrary frequency and voltage, and controls the induction motor. In an air conditioner equipped with an inverter that drives a compressor as a drive source, a voltage phase detection circuit that detects a phase of an AC voltage applied to the compressor, and a current phase detection that detects a phase of a current flowing through the compressor. A power factor detection circuit that detects a power factor from a phase difference between a voltage and a current; and a power factor that indicates a predetermined value set between a power factor value indicated during normal operation of the induction motor and a power factor value indicated during locking. A power factor reference value output circuit that outputs a reference value; and a comparison circuit that compares the outputs of the power factor detection circuit and the reference value output circuit. An abnormality detection circuit that detects the status It is intended to.

An air conditioner control device comprising a converter section and an inverter section for operating an induction motor at a discrete step-like operation frequency, wherein the operation frequency control section includes frequency comparison means and The frequency comparing means comprises a frequency changing width switching means, a current comparing means, and a frequency changing means, and the frequency comparing means receives a current operating frequency and a predetermined frequency that is a switching point of the frequency changing width, and the operating frequency is higher than the predetermined frequency. The frequency change width switching means switches the variable width of the frequency change means in a direction in which the variable width becomes smaller by a significant signal from the frequency comparison means. The current comparing means compares the detected current value of the converter unit with the rated current value of the outlet, and when the former is larger, the frequency is decreased, and the latter is larger. When the frequency increases, a significant signal for switching the frequency changing direction is generated, and the frequency changing means includes a current operating frequency, an output signal of the frequency changing width switching means, and the current comparing means. And outputs a value obtained by adding / subtracting the frequency of the selected change width to the current operation frequency to the inverter unit as a new operation frequency.

[0015]

According to a first aspect of the present invention, a control device for an air conditioner detects a power factor of a compressor from a phase difference between an AC voltage applied to the compressor and an AC current flowing through the compressor, and detects the detected power factor. The lock of the compressor is detected by comparing the value with a power factor reference value set between a power factor value indicated during normal operation of the induction motor and a power factor value indicated during locking.

According to a second aspect of the present invention, in the control device for an air conditioner, when the current operating frequency is higher than a predetermined frequency by the frequency comparing means, a significant signal is generated, and the frequency change width receiving the significant signal is generated. The switching means switches in a direction in which the variable width of the discretized frequency becomes smaller. The current comparing means compares the converter detection current value with the outlet rated current value.If the former is large, the frequency is decreased in the direction of decrease, and if the latter is large, the frequency is changed in the direction of increase in the frequency. Generate a significant signal to switch. Then, the frequency changing means receives these outputs and outputs a value obtained by adding or subtracting the frequency of the selected change width to the current operating frequency as a new operating frequency to the inverter section, so that the frequency near the outlet rated current value is obtained. The frequency change range is subdivided and the control area is set up to the very end of the outlet rated current value.

[0017]

【Example】

Embodiment 1 FIG. Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a control block diagram of the present invention, in which 14 is a commercial power supply, 12 is an AC / DC converter, 13 is a DC / AC converter, and 4 is an induction motor, which is a power source for a compressor 4a that pressurizes and circulates refrigerant. ing. 21 is a voltage phase detection circuit 22 for detecting the phase of the voltage applied to the induction motor 4
And a current phase detection circuit 23 for detecting the phase of the current flowing through the induction motor 4. The output of the voltage phase detection circuit 22 and the current phase detection circuit 23 detects the power factor based on the phase difference between the voltage and the current. It is a power factor detection circuit. Reference numeral 24 denotes a comparison circuit that receives the output of the power factor detection circuit 21 as an input, reference numeral 25 denotes a reference value output circuit that outputs a reference value, and reference numeral 26 denotes an abnormality detection circuit that detects a locked state of the compressor 4a. FIG. 2 shows the characteristics of a general induction motor.

Next, the operation will be described. In FIG. 1, the induction motor 4 of the compressor 4a converts a commercial power supply 14 into a three-phase AC power supply having a desired frequency and voltage by using the DC power supply once converted by the AC / DC converter 12 into a DC power. It is driven by the AC power converted to. The phase of the voltage applied to the induction motor 4 is detected by the voltage phase detection circuit 22, the phase of the current flowing through the induction motor 4 is detected by the current phase detection circuit 23, and the power factor is calculated from the phase difference between the voltage phase and the current phase. Detected by the power factor detection circuit 21. The output of the power factor detection circuit 21 is input to a comparison circuit 24, which compares the output with a reference value output circuit 25 that outputs a reference value.

Next, the characteristics of the induction motor will be described with reference to FIG. As shown in the graph, the power factor value for slip of the induction motor increases as the slip increases and the power factor becomes 0 [%] at slip = 0. However, depending on the operating frequency, the power factor value may be maximized on the way as shown in FIG. 2 and thereafter decrease. Here, when the induction motor 4 is rotating normally, as shown in FIG.
８０80 [%]. When the induction motor 4 is in the locked state, that is, when the slip = 1, the power factor value increases to 90.
[%] Rank.

Therefore, the output of the reference value output 25 is set to an intermediate value between the power factor when the induction motor 4 is operating normally and the power factor value when the induction motor 4 is locked. Input to the circuit 24. If the detected power factor of the power factor detection circuit 21 is smaller than the output of the reference value output circuit 25, the induction motor 4 is operating normally, and conversely, the output of the reference value output circuit 25 is smaller than the output of the reference value output circuit 25. When the detected power factor of the power factor detection circuit 21 is larger, it is understood that the induction motor 4 is locked.

Embodiment 2 FIG. Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. FIG.
FIG. 1 is a block diagram showing an embodiment of the present invention.
2 and the smoothing capacitor 13 rectify the AC of the AC power supply 14 and convert it to DC. Using this DC as a power supply, the inverter 16 converts the AC into an AC having an arbitrary commanded frequency, supplies the AC to the compressor 4a, and controls the operating frequency of the compressor 4a.
As described above, the frequency variable device 15 includes the converter unit 12,
It comprises a smoothing capacitor 13 and an inverter section 16. Reference numeral 8 denotes a current detector for detecting the magnitude of a current input to the frequency variable device 15. An operation frequency control unit for controlling the frequency of the inverter unit 16 by using the result as an input includes a frequency comparison unit 27, a frequency change width switching unit. 28, a current value comparing means 17 and a frequency changing means 20.

Next, the operation will be described with reference to the flowchart of FIG. In step 201, it is determined whether the operating frequency exceeds a predetermined frequency. The predetermined frequency is set to a frequency at which the current flowing into the frequency variable device does not reach the predetermined value. If the comparison result shows that the frequency does not exceed the predetermined frequency, the process proceeds to step 202, where the frequency change width is normally set to, for example, 1 [Hz].
Proceed to 4. If the operation frequency exceeds the predetermined frequency in step 201, the process proceeds to step 203, where the frequency change width is set to a small value (for example, 0.5 [Hz]), and the process proceeds to step 204. In step 204, the current value is read and the process proceeds to step 205. In step 205, it is determined whether the current exceeds a predetermined value. If the frequency does not exceed the predetermined value, the process proceeds to step 206, where the frequency is increased to the predetermined frequency, and the process returns to the main routine. Step 2
If the predetermined value is exceeded in step 05, the process proceeds to step 207, in which the operation frequency is reduced, and the process returns to the main routine.

By controlling as described above, when the operating frequency of the frequency variable device is high, the frequency change width is reduced to suppress the change in the current value per frequency step to reduce the overshoot of the current. Controlled.

[0024]

As described above, according to the first aspect of the present invention,
According to the air conditioner equipped with an inverter that converts an AC power supply into a DC power supply, converts the DC power supply into an AC power supply having an arbitrary frequency and voltage, and drives a compressor that uses an induction motor as a driving source. A voltage phase detection circuit for detecting a phase of an AC voltage applied to the compressor, a current phase detection circuit for detecting a phase of a current flowing through the compressor, and a power factor for detecting a power factor from a phase difference between the voltage and the current A detection circuit, a power factor reference value output circuit that outputs a predetermined value set between a power factor value indicated during normal operation of the induction motor and a power factor value indicated during locking as a power factor reference value, and the power factor detection. A comparison circuit for comparing the output of the circuit and the reference value output circuit, and an abnormality detection circuit for detecting a locked state of the compressor according to the magnitude of the output of the power factor detection circuit. Detection of indirect power factor (phase difference) By substituting, it is possible to detect the abnormal state of accurately inverter inexpensive (lock of the compressor).

According to a second aspect of the present invention, there is provided a control device for an air conditioner, comprising a converter section and an inverter section, for operating an induction motor at a step-like discrete operating frequency, The operating frequency control unit includes frequency comparing means, frequency changing width switching means, current comparing means, and frequency changing means, and the frequency comparing means includes a predetermined frequency serving as a switching point between the current operating frequency and the frequency changing width. Is input, and a significant signal is generated when the operating frequency is higher than a predetermined frequency.The frequency change width switching means uses the significant signal from the frequency comparison means to change the variable width of the frequency change means. The variable width is switched in a direction in which the variable width becomes smaller. The current comparing means compares the detected current value of the converter unit with the rated current value of the outlet. The frequency changing means generates a significant signal for switching the frequency changing direction in the direction of decreasing the number, and in the case of the latter increasing the frequency in the increasing direction. An output signal of the switching means and an output signal of the current comparing means are input,
A value obtained by adding or subtracting the frequency of the selected change width from the current operation frequency is output to the inverter unit as a new operation frequency. Therefore, when the operation frequency of the compressor is high, that is, a large amount of current flows into the frequency variable device. In this case, by reducing the frequency change width, the current change width per one frequency step can be reduced, so that it is possible to control without overshooting of the current at a value just below the outlet rating, so that the outlet breaker does not operate. There is an effect that a control device for an air conditioner can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a control device for an air conditioner according to Embodiment 1 of the present invention.

FIG. 2 is a characteristic diagram showing electric characteristics of the induction motor of the present invention.

FIG. 3 is a block diagram showing a control device for an air conditioner according to Embodiment 2 of the present invention.

FIG. 4 is a control flowchart according to a second embodiment of the present invention.

FIG. 5 is a block diagram showing a conventional control device for an air conditioner.

FIG. 6 is a block diagram of a control device showing a second conventional example.

FIG. 7 is a control flowchart of FIG.

[Explanation of symbols]

 Reference Signs List 4 induction motor 4a compressor 17 current comparing means 20 frequency changing means 21 power factor detecting circuit 22 voltage phase detecting circuit 23 current phase detecting circuit 24 comparing circuit 25 reference value output circuit 26 abnormality detecting circuit 27 frequency comparing means 28 frequency changing width switching means

Claims (2)

(57) [Claims] 1. An air conditioner equipped with an inverter that converts an AC power supply into a DC power supply, converts the DC power supply into an AC power supply having an arbitrary frequency and voltage, and drives a compressor driven by an induction motor. A voltage phase detection circuit for detecting a phase of an AC voltage applied to the compressor, a current phase detection circuit for detecting a phase of a current flowing through the compressor, and a force for detecting a power factor from a phase difference between the voltage and the current. Rate detection circuit and induction
Power factor value during normal operation of motive and power factor value during lock
Outputs the predetermined value set between as the power factor reference value
A power factor reference value output circuit, and a comparator circuit for comparing the output of the power factor detection circuit and the reference value output circuit, and detecting an abnormality in the lock state of the compressor based on the magnitude of the output of the power factor detection circuit. A control device for an air conditioner, comprising a detection circuit. 2. A system comprising a converter section and an inverter section.
The induction motor to a step-like discrete operating frequency.
Control device for an air conditioner that is operated
The control unit includes a frequency comparison unit, a frequency change width switching unit, and a power supply.
Current comparing means and frequency changing means.
The number comparison means switches between the current operating frequency and the frequency change width.
The predetermined frequency to be a point is input, and the operating frequency is
A significant signal is generated when the wave number is larger than the wave number.
The frequency change width switching means is provided from the frequency comparison means.
Signal, the variable width of the frequency changing means
The direction of the current comparison
The column shows the detected current value of the converter and the rated current of the outlet.
Value, and if the former is larger, decrease the frequency.
If the latter is large, increase the frequency
Signal to switch the direction of change
In addition, the frequency changing means determines the current operating frequency and the frequency.
The output signal of the wave number change width switching means and the output of the current comparing means
The force signal is input and the current operating frequency is selected.
The value obtained by adding or subtracting the frequency of the change width is used as the new operating frequency.
And output it to the inverter section.
The control device of the air conditioner that.