JPH04312362A - Controller for air conditioner - Google Patents

Abstract

PURPOSE:To detect the voltage accurately and precisely with a voltage detection means regardless of charge or discharge of a capacitor, to secure the protection of an inverter against undervoltage surely, and to confirm that the protection against undervoltage is not applied to the inverter within the range of operating voltage of it, in a controller for an air conditioner equipped with an inverter. CONSTITUTION:This controller comprises a voltage detection means 12', which detects the voltage of a capacitor 7, and a voltage changeover means 20, which changes over the voltage of the capacitor, interlocking with the signal S3 outputted from a relay driving circuit 13 to a current limiting relay 5.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an air conditioner equipped with an inverter device for controlling the rotational speed of a compressor.

0002

BACKGROUND OF THE INVENTION In recent years, many air conditioner control devices have been used that control capacity by increasing or decreasing the rotation speed of a compressor using an inverter circuit that varies the frequency of a power source. As a conventional technique, for example, Utility Model Application No. 61-165
It is disclosed in Publication No. 093.

[0003] The above-mentioned air conditioner control device will be explained below with reference to the drawings. FIG. 5 is a block diagram of a conventional air conditioner control device, and FIG. 6 is a circuit diagram of a conventional voltage detection means. In Figure 5, 1 is a three-phase commercial AC power supply, 2 is an electromagnetic contactor having three contacts, 3 is a converter circuit that converts AC power to DC power, and one end of the electromagnetic contactor 2 is connected to a commercial AC power supply. 1 and the other end are connected to the AC input section of the converter circuit 3, respectively.

4 is an inrush current limiting resistor, and 5 is two contacts 5.
a, 5b, one end of the inrush current limiting resistor 4 is connected to the R phase of the commercial AC power supply 1, the other end is connected to the common terminal of the contact 5a of the inrush current limiting relay 5, and the inrush current A normally open terminal of the contact 5a of the limit relay 5 is connected to the R phase of the converter circuit 3.

The common terminal of the contact 5b of the rush current limiting relay 5 is connected to the S phase of the commercial AC power supply 1, and the normally open terminal is connected to the S phase of the converter circuit 3. These current limiting resistor 4 and current limiting relay 5 are collectively referred to as an inrush current limiting circuit 6.

Reference numeral 7 denotes a capacitor for smoothing the DC power output from the converter circuit 3. The positive electrode side of the capacitor 7 is connected to the positive electrode side of the converter circuit 3, and the negative electrode side is connected to the negative electrode side of the capacitor 7. 8 is an inverter circuit which inputs the DC power smoothed by the capacitor 7, converts it into three-phase AC power, and outputs it to the compressor 9.

Reference numeral 10 indicates an operation command input unit that determines whether to start or stop the compressor 9, 11 indicates an inverter control means, and 12 indicates a voltage for detecting a voltage shortage of the commercial AC power source using the voltage of the capacitor 7 converted to DC by the converter 3. The detection means 13 is a relay driving means, which inputs a signal from the inverter control means 11 and sends a signal S to the electromagnetic contactor 2 and the inrush current limiting relay 5.
5 and S3. 14 is an inverter base drive circuit which inputs a signal S6 from the inverter control means 11 and outputs a signal S7 to the inverter circuit 8;

Next, in FIG. 5, 12 is a voltage detection means, a voltage comparator 15, and a signal S8 of the capacitor 7 is connected to a resistor 16.
The positive electrode side of the voltage comparator 15 is connected to the signal S9 of the capacitor 7 via a resistor 17. The signal S9 of the capacitor 7 is connected to the negative side of the voltage comparator 15 via a resistor 18, and the negative side of the voltage comparator 15 is connected via a resistor 19 to the same 5V power supply as the inverter control means. .

The output of the voltage comparator 15 is also connected to S4. Note that the voltage generated by the voltage division ratio of the resistor 19 and the resistor 18 is called a comparison voltage.

The operation of the air conditioner control device configured as described above is shown in FIGS. 7, 8, 9, and 1.
This will be explained using 0. 7 is a flowchart explaining the operation when charging the capacitor 7, FIG. 8 is a time chart explaining the operation when charging the capacitor 7, FIG. 9 is a time chart showing the operation when discharging the capacitor 7, and FIG. 10 is a conventional example. 2 is a characteristic diagram showing the relationship between the voltages of the commercial AC power supply 1 and the capacitor 7. FIG.

In FIG. 7, in step 1, the commercial AC power supply 1
is injected. Next, in step 2, the signal S1 is output from the operation command input unit 10 to the inverter control means 11, and "operation" is started.
If so, go to step 3; otherwise, repeat step 2.

Next, in step 3, as shown in FIG. 9, the inverter control means 11 outputs the signal S2 to the relay drive means 13, and the relay drive means 13 further outputs the signal S3 to the current limiting relay 5, which connects the contacts 5a and 5b. Turn on. When contacts 5a and 5b are turned on, capacitor 7 is charged via inrush current limiting resistor 4 and inrush current limiting relay 5.

Next, in step 4, the voltage detection means 12 detects the charged voltage of the capacitor 7, outputs a signal S4 to the inverter control means 11, and if the charged voltage is equal to or higher than the comparison voltage Va, the process proceeds to step 5. Otherwise, return to step 3. In addition, the voltage charged in the capacitor generated between signal S8 and signal S9 is connected to resistor 16 and resistor 1.
When the voltage divided by 7 becomes larger than the comparison voltage, that is, when the voltage of the capacitor becomes Va, the output signal S4 of the voltage comparator 15 changes from "H to L".

Furthermore, when the voltage comparator 15 operates, the inrush current limiting circuit 6 becomes a single-phase full-wave circuit. When the voltage is Va, the commercial AC power supply is V
It becomes b.

Next, in step 5, the inverter control means 11 outputs the signal S2 to the relay drive means 13,
Further, the relay driving means 13 outputs a signal S3 to the inrush current limiting relay 5, turning off the contacts 5a and 5b.

Next, in step 6, the relay driving means 1
3 outputs a signal S5 to the electromagnetic contactor 2 to turn on the electromagnetic contactor 2. Next, in step 7, a signal S7 (actually an inverter waveform signal) is sent from the inverter control means 11.
is output to the inverter base drive circuit 13 to drive the inverter circuit 8 and supply an alternating current voltage of a predetermined frequency to the compressor 9. (Step 8).

Next, referring to FIG. 9, a case will be described in which the commercial AC power supply 1 is no longer supplied to the converter circuit 3 due to a momentary power outage or the like. When the commercial AC power supply 1 is stopped during operation of the compressor, the voltage of the capacitor 7 drops, and the voltage detection means 12 detects the point in time when the voltage of the capacitor 7 reaches Va.

At this time, due to the relationship between the voltage of the capacitor 7 and the commercial AC power supply 1 shown in FIG. 10, when the compressor 9 is in operation, the electromagnetic contactor 2 is in the on state, so it is supplied with a three-phase full wave. The commercial AC power supply 1 when detecting the capacitor voltage Va is Vc, which is different from when the capacitor 7 is being charged. After that, the compressor 9 is stopped.

[0019]

[Problems to be Solved by the Invention] However, in the above-mentioned conventional configuration, the voltage of the capacitor detected by the voltage detecting means when the compressor starts operating, when charging the capacitor, and when the capacitor is discharging due to a momentary power outage, etc. The voltage of the capacitor detected by the voltage detection means is supplied to the load (inverter control means, etc.) based on the difference in ripple voltage due to the difference in commercial AC power supply method between single-phase full-wave and three-phase full-wave, and the current limiting resistor. Because the current is limited, the voltage drop across the capacitor for single-phase full-wave and three-phase full-wave tends to be larger for single-phase full-wave, so the voltage of the commercial AC power supply is more sensitive to the detection of the capacitor voltage. Different for voltage.

[0020] Therefore, the problem is that it is not possible to accurately set the voltage detected by the capacitor so as to protect the inverter circuit, which functions as a voltage detection means, from undervoltage of the commercial AC power supply and to guarantee the operating voltage range of the inverter. had.

In view of the above problems, the present invention detects the voltage detected by the voltage detection means accurately and accurately regardless of whether the capacitor is charged or discharged, ensures the undervoltage protection for the inverter works, and widens the operating voltage range of the inverter. The purpose is to provide an air conditioner control device that guarantees

[0022]

[Means for Solving the Problems] In order to achieve this object, the air conditioner control device of the present invention operates in conjunction with a signal output from the relay drive means to the current limiting relay, and controls the capacitor inside the voltage detection means. A voltage switching means for switching the voltage to be compared is provided for detecting the voltage.

[0023]

[Operation] With this configuration, when charging or discharging the capacitor, the voltage detected by the capacitor of the voltage detection means is changed by the voltage switching means inside the voltage detection means, thereby adjusting the value of the undervoltage of the commercial AC power supply. It is possible to set accurately and accurately, ensure that undervoltage protection for the inverter works, and prevent undervoltage protection from occurring within the operating voltage range of the inverter.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A control device for an air conditioner according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a control device for an air conditioner according to an embodiment of the present invention. FIG. 2 is a circuit diagram of the voltage detection means of the present invention. In FIG. 1, 1 is a three-phase commercial AC power supply, 2 is an electromagnetic contactor having three contacts, and 3 is a converter that converts AC power into DC power. In the circuit, one end of the electromagnetic contactor 2 is connected to the commercial AC power supply 1, and the other end is connected to the AC input section of the converter circuit 3, respectively.

4 is an inrush current limiting resistor, 5 is two contacts 5
In the inrush current limiting relay, one end of the inrush current limiting resistor 4 is connected to the R phase of the commercial AC power supply 1, and the other end is connected to the common terminal of the contact 5a of the inrush current limiting relay 5. A normally open terminal of the contact 5a of the inrush current limiting relay 5 is connected to the R phase of the converter circuit 3. Further, the cathode terminal of the current limiting resistor 4 is connected to the normal terminal of the contact 5b. The common terminal of the contact 5b of the inrush current limiting relay 5 is connected to the S phase of the commercial AC power supply 1. These current limiting resistor 4 and current limiting relay 5 are collectively referred to as an inrush current limiting circuit 6.

Reference numeral 7 denotes a capacitor for smoothing the DC power output from the converter circuit 3. The positive electrode side of the capacitor 7 is connected to the positive electrode side of the converter circuit 3, and the negative electrode side is connected to the negative electrode side of the capacitor 7. 8 is an inverter circuit which inputs the DC power smoothed by the capacitor 7, converts it into three-phase AC power, and outputs it to the compressor 9.

Reference numeral 10 indicates an operation command input unit for determining whether to start or stop the compressor 9, 11 indicates an inverter control means, 12' indicates a voltage detection means for detecting the voltage across the capacitor 7, and 13 indicates a relay drive means, which controls the inverter. A signal is input from means 11 and signals S3 and S5 to electromagnetic contactor 2 and inrush current limiting relay 5 are output. The signal S3 is also input to the voltage detection means. 14 is an inverter base drive circuit which inputs a signal S6 from the inverter control means 11 and outputs a signal S7 to the inverter circuit 8;

Next, in FIG. 2, reference numeral 12' denotes a voltage detection means, in which the voltage signal S8 of the voltage comparator 15 and the capacitor 7 is connected to the positive side of the voltage comparator 15 via a resistor 16. The positive terminal side of the capacitor 7 is connected to the voltage signal S9 of the capacitor 7 via a resistor 17. The voltage signal S9 of the capacitor 7 is connected to the negative electrode side of the voltage comparator 15 via a resistor 18, and the negative electrode side of the voltage comparator 15 is connected to a 5V power source via a resistor 19. Further, the output of the voltage comparator 15 is connected to S4.

Reference numeral 20 denotes voltage switching means, which is connected from the negative terminal side of the voltage comparator 15 through a resistor 21, through the collector of the transistor 22, and from the emitter of the transistor 22 to the signal S19. Also transistor 2
The base of 2 is connected to the signal S13 from the relay driving means 13. Therefore, it is possible to switch between two comparison voltages: the comparison voltage V1 which is the voltage divided by the resistor 19 and the resistor 18, and the comparison voltage V2 which is the voltage divided by the resistor 18, the resistor 19, and the resistor 21 by the operation of the transistor 22.

The operation of the air conditioner control device configured as described above will be explained with reference to FIGS. 3, 4, 7, and 8. FIG. 3 is a characteristic diagram showing the relationship between the commercial AC power supply and the voltage of the capacitor according to the present invention, and FIG. 4 is a time chart showing the operation of the capacitor 7 during discharging according to the present invention.

In FIG. 7, in step 1, the commercial AC power supply 1
is injected. Next, in step 2, the signal S1 is output from the operation command input unit 10 to the inverter control means 11, and "operation" is started.
If so, go to step 3; otherwise, repeat step 2.

Next, in step 3, the inverter control means 11 outputs the signal S2 to the relay drive means 13,
Further, the relay driving means 13 outputs a signal S3 to the current limiting relay 5 to turn on the contacts 5a and 5b. Contacts 5a, 5
When b is turned on, capacitor 7 is charged via inrush current limiting resistor 4 and inrush current limiting relay 5.

Next, in step 4, the voltage detection means 12' detects the charging voltage of the capacitor 7, outputs a signal S4 to the inverter control means 11, and if the charging voltage is equal to or higher than the comparison voltage, the process goes to step 5; If so, return to step 3. At this time, the output of the signal S3 of the relay driving means 13 becomes "H" level, so the transistor 20 in FIG. The voltage becomes V1.

From this, according to the relationship between the voltage of the commercial AC power supply 1 and the capacitor shown in FIG. The detected value of the power supply is Vb. Thereafter, the output of the voltage comparator 15 outputs a signal S4 from "H to L" to the inverter control means.

Next, in step 5, the inverter control means 11 outputs the signal S2 to the relay drive means 13,
Further, the relay driving means 13 outputs a signal S3 to the inrush current limiting relay 5, turning off the contacts 5a and 5b. Next, in step 6, the relay driving means 13 outputs a signal S5 to the electromagnetic contactor 2 to turn on the electromagnetic contactor 2.

Next, in step 7, the inverter control means 11 outputs a signal S7 (actually an inverter waveform signal).
is outputted to the inverter base drive circuit 13, which further drives the inverter circuit 8, and supplies AC power of a predetermined frequency to the compressor 9. (Step 8).

Next, referring to FIG. 4, a case will be described in which the commercial AC power supply 1 is no longer supplied to the converter circuit 3 due to a momentary power outage or the like. When the commercial AC power supply 1 is stopped while the compressor is operating, the voltage of the capacitor 7 drops, and the voltage of the capacitor is detected by the voltage detection means 12'. At this time, since the signal S3 is at "L" level, the transistor 22 is The voltage comparator 15 is turned off, and the comparison voltage on the negative side of the voltage comparator 15 becomes V2 from the voltage division of the resistors 19 and 18. Since the commercial AC power supply is a three-phase full wave from the on state of the magnetic contactor 2, the voltage shown in FIG. Due to the relationship between the voltages of the commercial AC power supply 1 and the capacitor 7, when the comparison voltage is V2, the voltage detected by the capacitor is Va', and the voltage detected by the capacitor is Vb, which is the same as when the commercial AC power supply 1 is charging the capacitor. After that, the compressor 9 is stopped.

As described above, according to this embodiment, the voltage detected by the capacitor of the voltage detection means is accurately and accurately detected regardless of whether the capacitor is charged or discharged, and the undervoltage protection for the inverter is reliably activated. Undervoltage protection will no longer apply within the operating voltage range of the inverter's commercial AC power supply.

[0040]

As explained above, the present invention provides a voltage that switches the voltage to be compared in order to detect the voltage of the capacitor inside the voltage detection means in conjunction with the signal output from the relay driving means to the current limiting relay. Since the switching means is provided, the voltage detected by the capacitor of the voltage detection means can be set accurately and precisely regardless of whether the capacitor is charging or discharging, ensuring that undervoltage protection for the inverter works and ensuring that the voltage is within the operating voltage range of the inverter. The objective is to realize an air conditioner control device that can operate accurately without undervoltage protection.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an air conditioner control device according to an embodiment of the present invention.

[Figure 2] Circuit diagram of voltage detection means in the same embodiment

[Figure 3
]Characteristic diagram showing the relationship between the commercial AC power supply and the voltage of the capacitor in the same example

[Figure 4] Timing chart for explaining the operation during capacitor discharge in the same embodiment

[Fig. 5] Schematic configuration diagram of a conventional air conditioner control device

[Fig. 6] Circuit diagram of voltage detection means in a conventional example

[Figure 7]
Flowchart when turning on the power to explain the operation when charging a capacitor in the conventional example

[Figure 8] Time chart when power is turned on to explain the operation when charging a capacitor in the conventional example

[Figure 9] Time chart when power is turned on to explain the operation during capacitor discharge in the conventional example

[Figure 10] Characteristic diagram showing the relationship between commercial AC power supply and capacitor voltage in a conventional example

[Explanation of symbols]

1 Three-phase commercial AC power supply 2 Electromagnetic contactor 3 Converter circuit 6 Inrush current limiting circuit 7 Capacitor 8 Inverter circuit 9 Compressor 10 Operation command input section 11 Inverter control means 12' Voltage detection means 13 Relay drive means 14 Inverter base drive circuit 19 Voltage switching means

Claims (1)

[Claims] 1. A converter circuit that converts three-phase AC power into DC power, an electromagnetic contactor that opens and closes the converter circuit and the three-phase commercial AC power supply, and a converter circuit that smoothes the DC power converted by the converter circuit. an inverter circuit that inputs the DC power smoothed by the capacitor and converts it into three-phase AC power to control the compressor; and an inrush current limiting circuit, which is connected to the input/output of the other one phase through the second contact of the current limiting relay and a current limiting resistor, and determines whether to operate or stop the compressor. an operation command input section, a voltage detection means for detecting a voltage shortage of the commercial AC power source using the voltage of the capacitor, an inverter control means for inputting signals from the operation command input section and the voltage detection means; relay driving means that receives a signal from the inverter control means and outputs a signal to the electromagnetic contactor and the inrush current limiting circuit; and a relay drive means that receives a signal from the inverter control means and outputs a signal to the inverter circuit. an inverter base drive circuit, and a voltage switching means for switching a voltage to be compared in conjunction with a signal output from the relay driving means to the current limiting relay to detect the voltage of the capacitor within the voltage detecting means. An air conditioner control device characterized by: