JPH04344192A - Controller of air conditioner - Google Patents

Abstract

PURPOSE:To obtain a controller of an air conditioner which can detect the abnormal condition (locking or open-phase of a compressor) of an inverter apparatus accurately through a low-cost apparatus. CONSTITUTION:A controller is constituted by a commercial power supply 14, AC/DC converter 12, DC/AC converter 13, induction motor 4, etc. The induction motor 4 is the power source of a compressor 4a for compressing and circulating a coolant. A power-factor detection circuit 21 is composed of a voltage-phase detection circuit 22 for detecting the phase of voltage applied to the induction motor 4 and a current-phase detection circuit 23 for detecting the phase of electric current flowing through the induction motor 4 and detects a power factor on the basis of the phase difference between the voltage and current by the output of the voltage-phase detection circuit 22 and current-phase detection circuit 23. The output of this power-factor detection circuit 21 is inputted to a comparison circuit 24 and compared with the output of a reference-value output circuit 25 for outputting a reference value so that the malfunction detection of the compressor 4a is conducted.

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 equipped with an inverter device.

0002

[Prior Art] FIG. 5 shows, for example, Japanese Patent Laid-Open No. 58-107089.
This is a conventional failure detection device disclosed in the above publication. In the figure, 1 is a rectifier, the output of which is input to an inverter 3 via a DC reactor 2. 4 is an induction motor, which is driven by the output of the inverter 3 mentioned above. A speed detector 5 detects the rotational speed of the induction motor 4, and inputs the deviation from the inverter output frequency 6 to a first comparator 7. A current detector 8 detects the input current to the inverter device. 9
is a second comparator which receives the detection signal from the current detector 8 and compares it to see if it is equal to or greater than a predetermined value. 10 is an AND circuit, into which the signals of the first comparator 7 and second comparator 9 are input;
It is output as a failure signal 11 under condition D.

Next, the operation will be explained. The rotational speed of the induction motor 4 is detected by the speed detector 5, and the inverter output frequency 6 is detected.
The deviation from this is input to the first comparator 7.

For example, when the rectifier 1, reactor 2, inverter 3, and 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 around 10%.

However, for example, if the induction motor 4 is locked and malfunctions, the deviation between the inverter output frequency 6 and the speed detector 5 becomes very large. This difference in speed deviation serves to determine a failure of the inverter device.

[0006] For reference, there is Japanese Patent Laid-Open No. 57-206300 which detects the power factor based on the phase difference between the current and voltage of the compressor and compares it with a reference value to control the power factor.

[0007] Also, FIG. 6 shows, for example,
This is a control device for an air conditioner shown in Publication No. 7, and in the figure, a converter section 12 and a smoothing capacitor 13 rectify alternating current from an alternating current power source 14 and convert it into direct current. 15 is a frequency variable device, which includes a converter section 12 and a smoothing capacitor 13;
and an inverter section 16. Reference numeral 8 denotes a current detector that detects the current flowing into the frequency variable device 15, and a control device that inputs the detection signal and controls the frequency of the inverter section 16 includes a first current value comparison means 17 and a frequency change speed variable means 18. , second current value comparison means 19, and frequency control means 20.

Next, the operation of this second conventional example will be explained using the flowchart shown in FIG. In step 1, the output of the current detector 8 is taken in, and in step 2, it is compared and determined whether the current exceeds a first predetermined value, which is a value one step lower than the stall point. At this time, if the first predetermined value is not exceeded, the process proceeds to step 3, and the frequency change speed remains high, and the process proceeds to step 5. If it exceeds the first predetermined value in step 2, the process proceeds to step 4, where the frequency change speed is switched to a low speed and the process proceeds to step 5. In step 5, it is compared and determined whether the current value exceeds a second predetermined value, which is the stall point. If the second predetermined value is not exceeded, the process proceeds to step 6, where the operating frequency is increased to the predetermined value, and the process returns to the main routine. If the second predetermined value is exceeded in step 5, the process proceeds to step 7, where control is performed to lower the operating frequency, and the process returns to the main routine.

[0009]

[Problems to be Solved by the Invention] Since the conventional control device is configured as described above, a speed detector is required, and expensive items such as encoders and tacho generators must be used, making the entire device This led to an increase in costs. Further, as a method that does not use a speed detector, there is a method of determining based on input current, but this method has problems such as a complicated configuration and a slow detection speed.

[0010]Furthermore, the conventional control device has the problem that the control cannot follow the frequency change speed, leading to damage to the frequency variable device, and the current cannot be passed up to the limit of the outlet rating.

The present invention has been made to solve the above-mentioned problems, and claim 1 provides a method for protecting an air conditioner by accurately detecting an abnormal state of an inverter device (compressor lock) using an inexpensive device. The purpose is to obtain equipment.

Another object of the present invention is to control the input current to the limit of the outlet rating, eliminate overshoot of the current, and prevent the outlet breaker from operating.

[0013]

[Means for Solving the Problems] A control device for an air conditioner according to claim 1 of the present invention has a DC/AC converter that converts an AC power source into an AC power source of arbitrary frequency and voltage. A voltage phase circuit detects the phase of the applied AC voltage, a current phase detection circuit detects the phase of the current flowing through the compressor, a power factor detection circuit detects the power factor from the phase difference between voltage and current, and a reference value output circuit that outputs a rate reference value;
It has a comparison circuit that compares the output of the power factor detection circuit and the output of a reference value output circuit that outputs a power factor reference value, and detects a locked state of the compressor based on the magnitude of the output of the power factor detection circuit. It is equipped with a detection circuit.

The air conditioner control device according to claim 2 of the present invention further includes a frequency comparison means for comparing the frequency of the inverter with a predetermined frequency, and a frequency comparison means for comparing the frequency of the inverter with a predetermined frequency, and a frequency comparison means for comparing the frequency of the inverter with a predetermined frequency. A frequency resolution variable means for changing the frequency resolution, a current detecting means for detecting the current of the converter section, a current comparing means for comparing the current detected by the current detecting means with a predetermined value, and a comparison result of the comparing means. A frequency control means is provided to control the frequency of the inverter section accordingly.

[0015]

[Operation] The control device according to claim 1 of the present invention detects the power factor of the compressor from the phase difference between the AC voltage applied to the compressor and the AC current flowing through the compressor, and detects the power factor of the compressor based on the magnitude of the detected power factor value. Detect compressor lock.

Further, in the control device according to claim 2 of the present invention, when the operating frequency of the compressor is in a high frequency range, the frequency resolution is increased and the change in the input current value per frequency step is reduced to improve accuracy. did.

[0017]

【Example】

Example 1. Embodiment 1 of the present invention will be described below with reference to the drawings. FIG. 1 is a control block diagram of the present invention, in which 14 is a commercial power source, 12 is an AC/DC converter, 13 is a DC/AC converter, and 4 is an induction motor, which serves as a power source for a compressor 4a that pressurizes and circulates refrigerant. ing. 21 is a voltage phase detection circuit 22 that detects the phase of the voltage applied to the induction motor 4;
and a current phase detection circuit 23 that detects the phase of the current flowing through the induction motor 4, and 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 voltage and current. This is a power factor detection circuit. 24 is a comparison circuit which receives the output of the power factor detection circuit 21, 25 is a reference value output circuit which outputs a reference value, and 26 is an abnormality detection circuit which detects the locked state of the compressor 4a. Note that FIG. 2 shows the characteristics of a general induction motor.

Next, the operation will be explained. In FIG. 1, the induction motor 4 of the compressor 4a converts a commercial power source 14 into a three-phase AC power source with a desired frequency and voltage by converting the DC power source 14 into DC power by the AC/DC converting means 3 again. It is driven by AC power converted into 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 determined from the phase difference between the voltage phase and the current phase. It is detected by the power factor detection circuit 21. The output of the power factor detection circuit 21 is input to a comparison circuit 24, where it is compared with the output of a reference value output circuit 25 that outputs a reference value.

Next, the characteristics of the induction motor will be explained using FIG. As shown in the graph, the power factor value for the slip of the induction motor is such that when the slip is 0 and the power factor is 0%, the power factor value increases as the slip increases. However, depending on the operating frequency, as shown in FIG. 2, the power factor value may reach a maximum midway and then decrease. Here, when the induction motor 4 is rotating normally, as shown in FIG. 2, it is operating with slip = near 0, so the power factor value is approximately 50.
~80[%]. When the induction motor 4 is in a locked state, that is, 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 when the induction motor 4 is locked. input to 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, it means that the induction motor 4 is operating normally; If the power factor detected by the power factor detection circuit 21 is larger, it can be seen that the induction motor 4 is locked.

Example 2. Embodiment 2 of the present invention will be described below with reference to the drawings. FIG. 3 is a block diagram showing an embodiment of the present invention, in which a converter section 12 and a smoothing capacitor 13 rectify alternating current from an alternating current power source 14 and convert it into direct current. Using this direct current as a power source, the inverter section 16 converts it into alternating current at an arbitrary commanded frequency and supplies it to the compressor 4a, thereby controlling the operating frequency of the compressor 4a. In this way, the frequency variable device 15
is composed of a converter section 12, a smoothing capacitor 13, and an inverter section 16. 8 is a frequency variable device 15
A current detector detects the magnitude of the current input to the current detector, and a control device that uses the result as input to control the frequency of the inverter section 16 includes a frequency comparison means 27 and a frequency resolution variable means 28.
Consisting of

Next, the operation will be explained using the flowchart shown in FIG. In step 201, it is compared and determined whether the operating frequency exceeds a predetermined frequency. This predetermined frequency is set to a frequency at which the current flowing into the frequency variable device does not reach a predetermined value. As a result of the comparison, if the predetermined frequency is not exceeded, the process proceeds to step 202, where the frequency resolution is normally set to, for example, 1 [Hz], and the process proceeds to step 20.
Proceed to step 4. If the operating frequency exceeds the predetermined frequency in step 201, the process proceeds to step 203, where the frequency resolution is set finely (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 compared and determined whether the current exceeds a predetermined value. If the predetermined value is not exceeded, the process proceeds to step 206, the frequency is increased to a 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, where control is performed to lower the operating frequency, 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 resolution is increased, the change in current value per frequency step is kept small, and current overshoot is eliminated. .

[0024]

[Effect of the invention] As described above, claim 1 according to this invention
According to the above, there is a voltage phase detection circuit that detects the phase of the AC voltage applied to the compressor, a current phase detection circuit that detects the phase of the current flowing through the compressor, and a power factor that is detected from the phase difference between voltage and current. It has a power factor detection circuit, a reference value output circuit that outputs a power factor reference value, and a comparison circuit that compares the outputs of the power factor detection circuit and the reference value output circuit, and the size of the output of the power factor detection circuit is determined. The system is constructed with an abnormality detection circuit that detects the locked state of the compressor. By substituting the indirect power factor (phase difference) for detecting the rotation of the compressor, it is possible to detect the abnormal state of the inverter (compression machine lock) can be detected. Furthermore, phase difference detection optimum voltage control can be performed based on the detected phase difference.

According to a second aspect of the present invention, there is also a frequency comparison means for comparing the frequency of the inverter with a predetermined frequency, and a frequency resolution for changing the frequency resolution of the inverter section according to the comparison result by the comparison means. variable means, current detection means for detecting the current of the converter section;
The present invention includes a current comparing means for comparing the current detected by the current detecting means with a predetermined value, and a frequency controlling means for controlling the frequency of the inverter section according to the comparison result of the comparing means, so that the operating frequency of the compressor can be adjusted. When the current value is high, that is, when there is a large amount of current flowing into the frequency variable device, by increasing the frequency resolution, the width of current change per frequency step can be reduced, so there is no overshoot of the current at a value that is close to the outlet rating. This has the effect of providing an air conditioner control device that can be controlled without any noise and does not cause the outlet breaker to operate.

[Brief explanation of drawings]

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

FIG. 2 is a characteristic diagram showing the electrical 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 a second embodiment of the present invention.

FIG. 4 is a control flowchart of Embodiment 2 of the present invention.

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

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

FIG. 7 is a control flowchart of FIG. 6;

[Explanation of symbols]

4 Induction motor 4a Compressor 17 Current comparison means 20 Frequency control means 21 Power factor detection circuit 22 Voltage phase detection circuit 23 Current phase detection circuit 24 Comparison circuit 25 Reference value output circuit 26 Abnormality detection circuit 27 Frequency comparison means 28 Frequency resolution variable means

Claims (2)

[Claims] [Claim 1] In an air conditioner equipped with an inverter that converts AC power into DC power and converts the DC power into AC power of arbitrary frequency and voltage to drive a compressor whose drive source is an induction motor. , a voltage phase detection circuit that detects the phase of the AC voltage applied to the compressor, a current phase detection circuit that detects the phase of the current flowing through the compressor, and a power factor that detects the power factor from the phase difference between the voltage and current. It has a factor detection circuit, a reference value output circuit that outputs a power factor reference value, and a comparison circuit that compares the outputs of the power factor detection circuit and the reference value output circuit. An air conditioner control device characterized by having an abnormality detection circuit that detects a locked state of a compressor. 2. An air conditioner in which a compressor is driven by a variable frequency device comprising a converter section and an inverter section, comprising: a frequency comparing means for comparing the frequency of the inverter with a predetermined frequency; frequency resolution variable means for changing the frequency resolution of the inverter section; current detection means for detecting the current of the converter section; current comparison means for comparing the current detected by the current detection means with a predetermined value; and a current comparison means for comparing the current detected by the current detection means with a predetermined value. A control device for an air conditioner, comprising frequency control means for controlling the frequency of the inverter section according to a comparison result of the means.