KR102402836B1 - Air conditioner and operrating method thereof - Google Patents

Abstract

The air conditioner according to an embodiment of the present invention includes a compressor for compressing a refrigerant, an oil separator for separating oil from the refrigerant discharged from the compressor, an oil return pipe connected between the oil separator and the compressor, and operation of the compressor By including a control unit for determining whether to operate the oil recovery operation based on the frequency and the Q-axis current of the compressor. Oil can be effectively recovered.

Description

Air conditioner and its operation method

The present invention relates to an air conditioner and an operating method thereof, and more particularly, to an air conditioner capable of preventing damage to a compressor due to insufficient oil, and an operating method thereof.

The air conditioner is installed to provide a more comfortable indoor environment for humans by discharging cold and hot air into the room to adjust the indoor temperature and purify the indoor air in order to create a comfortable indoor environment. In general, an air conditioner includes an indoor unit configured as a heat exchanger and installed indoors, and an outdoor unit configured as a compressor and a heat exchanger and supplying refrigerant to the indoor unit.

A compressor is a device for compressing a refrigerant. An air conditioner provides lubrication through oil to protect the compressor from mechanical friction, and the oil in the compressor circulates in a refrigeration cycle together with the refrigerant discharged from the compressor.

As the refrigerant is compressed in the compressor, the oil contained in the compressor is mixed and discharged. When the refrigerant flows in a state where the oil is mixed, it collects on one side of the flow path to obstruct the refrigerant flow, and the amount of oil in the compressor is reduced, thereby reducing the performance of the compressor. can be The air conditioner performs an oil recovery operation in which oil is returned to the compressor to prevent damage to the compressor.

Prior Document 1 (Korean Patent Application Laid-Open No. 10-2013-0043978, published on November 06, 2007) improves the performance of the compressor by allowing oil to remain inside the compressor. Prior Document 1, the invention of allowing oil to remain in the compressor, cannot determine whether the oil in the compressor is insufficient. Accordingly, there is a need for a method capable of effectively determining an oil shortage and performing an oil recovery operation.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an air conditioner capable of efficiently recovering oil mixed with a refrigerant, and an operating method thereof.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an air conditioner capable of preventing oil shortage and compressor burnout, and an operating method thereof.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an air conditioner capable of accurately and quickly determining an oil shortage and an operating method thereof.

According to an embodiment of the present invention for achieving the above object, an air conditioner and an operating method thereof can effectively recover oil by using an operating frequency and Q-axis current of a compressor.

An air conditioner according to an embodiment of the present invention for achieving the above object includes a compressor for compressing a refrigerant, an oil separator for separating oil from the refrigerant discharged from the compressor, and an oil recovery connected between the oil separator and the compressor By including a control unit for determining whether to operate the oil recovery operation based on the tube, the operating frequency of the compressor, and the Q-axis current of the compressor. Oil can be effectively recovered.

Meanwhile, the controller may control the oil recovery operation to be performed when the amplitude of the Q-axis current is equal to or greater than an error reference value when the compressor is operating at a low frequency lower than the operating frequency of the oil recovery operation.

Also, the controller may control the oil recovery operation to be performed when the amplitude of the Q-axis current is equal to or greater than an error reference value while the compressor is operating at the low frequency for a predetermined time without changing the frequency.

In addition, the error reference value may be less than half of the Q-axis current during normal operation.

On the other hand, when the operating frequency of the compressor is smaller than a first frequency set lower than the operating frequency of the oil recovery operation and is larger than a second frequency set lower than the first frequency, the Q without changing the frequency If the amplitude of the shaft current is equal to or greater than the error reference value, the oil recovery operation may be performed.

In addition, the controller may control the oil recovery operation to be performed when a state in which the amplitude of the Q-axis current is equal to or greater than an error reference value is maintained for a predetermined time without changing the frequency.

Also, the controller may control the oil recovery operation to be performed when the operating frequency of the compressor is equal to or less than the second frequency.

In addition, the error reference value may be less than half of the Q-axis current during normal operation.

The air conditioner according to an embodiment of the present invention for achieving the above object may further include an oil return valve that opens and closes the oil return pipe under the control of the controller.

Meanwhile, the air conditioner according to an embodiment of the present invention for achieving the above object includes a dc stage capacitor and a plurality of switching elements, and by a switching operation of the plurality of switching elements, a DC power supply of the dc stage capacitor A compressor driving unit for driving the compressor comprising an inverter that converts the AC power to AC power and outputs the converted AC power to a compressor motor, and an output current detection unit disposed between the dc stage capacitor and the inverter to detect a current It further includes, wherein the Q-axis current may be based on the sensed data of the output current detector.

The method of operating an air conditioner according to an embodiment of the present invention for achieving the above object includes the steps of performing a compressor operation, whether the operating frequency of the compressor is in a low frequency operation that is less than or equal to a first frequency lower than the operation frequency of the oil recovery operation Determining whether the operating frequency of the compressor is equal to or less than the first frequency, determining whether the second frequency is set to be lower than the first frequency, the operating frequency of the compressor is not greater than the first frequency, The method may include performing the oil recovery operation when the amplitude of the Q-axis current of the compressor is greater than or equal to an error reference value when it is greater than the second frequency.

On the other hand, in the performing the oil recovery operation, the operation frequency of the compressor is not greater than the first frequency and greater than the second frequency, and the amplitude of the Q-axis current is greater than or equal to an error reference value without changing the frequency for a predetermined time. In this case, the oil recovery operation may be performed.

Meanwhile, the method of operating an air conditioner according to an embodiment of the present invention for achieving the above object further includes performing the oil recovery operation when the operating frequency of the compressor is equal to or less than the second frequency. can do.

Meanwhile, the error reference value may be less than half of the Q-axis current during normal operation.

Meanwhile, the method of operating an air conditioner according to an embodiment of the present invention for achieving the above object further includes performing the oil recovery operation when the operating frequency of the compressor is equal to or less than the second frequency. can do.

The method of operating an air conditioner according to an embodiment of the present invention for achieving the above object includes the steps of performing a compressor operation, determining the Q-axis current of the compressor, and the amplitude of the Q-axis current is an error If it is equal to or greater than the reference value, the method may include performing an oil recovery operation.

Meanwhile, the performing of the oil recovery operation may include performing the oil recovery operation when the operating frequency of the compressor maintains a state in which the amplitude of the Q-axis current of the compressor is equal to or greater than an error reference value for the predetermined time.

Meanwhile, the error reference value may be less than half of the Q-axis current during normal operation.

According to at least one of the embodiments of the present invention, the oil mixed with the refrigerant can be separated and efficiently recovered.

In addition, according to at least one of the embodiments of the present invention, it is possible to prevent oil shortage and damage to the compressor.

In addition, according to at least one of the embodiments of the present invention, it is possible to accurately and quickly determine the oil shortage.

On the other hand, various other effects will be disclosed directly or implicitly in the detailed description according to the embodiment of the present invention to be described later.

1 is a diagram illustrating the configuration of an air conditioner according to an embodiment of the present invention.
FIG. 2 is a schematic diagram of an outdoor unit and an indoor unit of FIG. 1 .
3 is a simplified internal block diagram of an air conditioner according to an embodiment of the present invention.
4 is an example of an internal block diagram of a motor driving apparatus according to an embodiment of the present invention.
FIG. 5 is an internal block diagram of the inverter control unit of FIG. 4 .
6 is a diagram referenced in the description of the oil shortage determination according to an embodiment of the present invention.
7 is a flowchart illustrating a method of operating an air conditioner according to an embodiment of the present invention.
8 is a flowchart illustrating a method of operating an air conditioner according to an embodiment of the present invention.
9 is a flowchart illustrating a method of operating an air conditioner according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, it goes without saying that the present invention is not limited to these embodiments and may be modified in various forms.

In the drawings, in order to clearly and briefly describe the present invention, the illustration of parts irrelevant to the description is omitted, and the same reference numerals are used for the same or extremely similar parts throughout the specification.

On the other hand, the suffixes "module" and "part" for the components used in the following description are given simply in consideration of the ease of writing the present specification, and do not give a particularly important meaning or role by themselves. Accordingly, the terms “module” and “unit” may be used interchangeably.

Also, in this specification, terms such as first and second may be used to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another.

1 is a diagram illustrating the configuration of an air conditioner according to an embodiment of the present invention.

Referring to FIG. 1 , the air conditioner 100 according to the present invention may include an indoor unit 21 and an outdoor unit 31 connected to the indoor unit 21 .

The indoor unit 21 of the air conditioner may be any of a stand-type air conditioner, a wall-mounted air conditioner, and a ceiling-type air conditioner, but in the drawings, the stand-type indoor unit 21 is exemplified.

Meanwhile, the air conditioner 100 may further include at least one of a ventilator, an air purifier, a humidifier, and a heater, and may operate in conjunction with the operation of the indoor unit and the outdoor unit.

The outdoor unit 31 includes a compressor (not shown) that receives and compresses a refrigerant, an outdoor heat exchanger (not shown) that exchanges heat between the refrigerant and outdoor air, and an accumulator (not shown) that extracts gaseous refrigerant from the supplied refrigerant and supplies it to the compressor. time) and a four-way valve (not shown) for selecting a flow path of the refrigerant according to the heating operation. In addition, a plurality of sensors, valves, and an oil recovery device are further included, but a description of the configuration will be omitted below.

The outdoor unit 31 supplies the refrigerant to the indoor unit 21 by operating a compressor and an outdoor heat exchanger provided to compress or heat exchange the refrigerant according to a setting. The outdoor unit 31 may be driven by a remote controller (not shown) or a demand of the indoor unit 21 . In this case, as the cooling/heating capacity is changed in response to the driven indoor unit, the number of outdoor units and the number of compressors installed in the outdoor unit may vary. Also, although one indoor unit 21 and one outdoor unit 31 are illustrated in FIG. 1 , the present invention is not limited thereto. For example, several indoor units 21 may be connected to one outdoor unit 31 through a refrigerant pipe.

At this time, the outdoor unit 31 supplies the compressed refrigerant to the connected indoor unit 21 .

The indoor unit 21 receives refrigerant from the outdoor unit 31 and discharges cold and hot air into the room. The indoor unit 21 includes an indoor heat exchanger (not shown), an indoor unit fan (not shown), an expansion valve (not shown) through which the supplied refrigerant is expanded, and a plurality of sensors (not shown).

At this time, the outdoor unit 31 and the indoor unit 21 are connected to each other by wire or wirelessly to transmit and receive data, and the outdoor unit 31 and the indoor unit 21 are connected to a remote controller (not shown) by wire or wirelessly to the remote controller ( (not shown) may operate under the control of the

A remote controller (not shown) may be connected to the indoor unit 21 , input a user's control command to the indoor unit 21 , and receive and display status information of the indoor unit 21 . In this case, the remote control may communicate with the indoor unit 21 by wire or wirelessly depending on the connection type.

FIG. 2 is a schematic diagram of an outdoor unit and an indoor unit of FIG. 1 .

Referring to FIG. 2 , the air conditioner 100 is largely divided into an indoor unit 21 and an outdoor unit 31 .

The outdoor unit 31 includes a compressor 102 serving to compress a refrigerant, a compressor electric motor 102b for driving the compressor, an outdoor heat exchanger 104 serving to radiate heat from the compressed refrigerant, and outdoor heat exchange. An outdoor blower 105 comprising an outdoor fan 105a disposed on one side of the unit 104 to promote heat dissipation of the refrigerant and a motor 105b rotating the outdoor fan 105a, and an expansion mechanism for expanding the condensed refrigerant Alternatively, the expansion valve 106, the cooling/heating switching valve or four-way valve 110 for changing the flow path of the compressed refrigerant, and the vaporized refrigerant are temporarily stored to remove moisture and foreign substances, and then the refrigerant at a constant pressure is supplied to the compressor. It may include an accumulator 103 and the like.

The indoor unit 21 includes an indoor heat exchanger 108 disposed indoors to perform a cooling/heating function, an indoor fan 109a disposed at one side of the indoor heat exchanger 108 to promote heat dissipation of the refrigerant, and an indoor fan ( and an indoor blower 109 including an electric motor 109b for rotating 109a).

At least one indoor heat exchanger 108 may be installed. At least one of an inverter compressor and a constant speed compressor may be used as the compressor 102 .

In addition, the air conditioner 100 may be configured as an air conditioner for cooling the room, or may be configured as a heat pump for cooling or heating the room.

The indoor heat exchanger 108 operates as an evaporator during a cooling operation and as a condenser during a heating operation, and the outdoor heat exchanger 104 operates as a condenser during a cooling operation and an evaporator during a heating operation.

In the air conditioner for heating and cooling, the refrigerant discharged from the compressor 102 changes the circulation direction of the cycle by switching the four-way valve 110, and the indoor heat exchanger 108 functions as an evaporator or condenser, to be cooled or heated.

First, during the cooling operation, the refrigerant is transferred to the compressor 102 - the four-way valve 110 - the outdoor heat exchanger 104 - the expansion valve 106 - the indoor heat exchanger 108 - the four way valve by the operation of the compressor 102 (110) - It circulates through the compressor (102). In this circulation process, the outdoor heat exchanger 104 functions as a condenser and the indoor heat exchanger 108 functions as an evaporator to maintain a cooling state while circulating cool air in the room.

And during the heating operation, by the operation of the compressor 102, the refrigerant is transferred to the compressor 102 - the four-way valve 110 - the indoor heat exchanger 108 - the expansion valve 106 - the outdoor heat exchanger 104 - the four-way valve ( 110) - It circulates through the compressor 102. In this circulation process, the indoor heat exchanger 108 serves as a condenser, and the outdoor heat exchanger 104 serves as an evaporator to maintain a heating state while circulating hot air in the room.

Meanwhile, the air conditioner 100 includes an oil separator 41 that separates oil from the refrigerant discharged from the compressor 102 , and an oil return pipe connected between the oil separator 41 and the compressor 102 . (43) may be further included.

The oil separator 41 may be connected to the compressor 102 to separate the refrigerant and oil. At this time, the separated oil is supplied back to the compressor 102 through the oil return pipe 42 .

The oil return pipe 43 is connected between the oil separator 41 and the compressor 102 , and the oil separated by the oil separator 41 is returned to the compressor 102 according to the oil recovery operation. can form.

According to an embodiment, the oil return pipe 43 is connected between the oil separator 41 and the accumulator 103 so that the oil separated in the oil separator 41 passes through the accumulator 103 and the compressor It is possible to form a flow path returned to (102).

The air conditioner 100 may further include a controller (refer to 260 of FIG. 3 ) for controlling the oil recovery operation. The oil recovery (oil supply) operation is to bring oil to the compressor 102 by operating the compressor 102 at a high frequency for a predetermined time, and may be performed under the control of the controller 260 .

According to an embodiment of the present invention, the control unit 260 may determine whether to operate the oil recovery operation based on the operating frequency of the compressor 102 and the Q-axis current of the compressor 102 .

According to an embodiment, the air conditioner 100 is provided in a predetermined area of the oil return pipe 42 to open and close the flow of oil flowing into the oil return pipe 42 through the oil separator 41 for oil recovery. A valve 43 may be further included.

The control unit 260 turns on the oil return valve 43 of the oil return pipe 42 during the oil recovery operation, so that the oil discharged from the oil separator 41 passes through the oil return pipe 42 to the compressor. As it is supplied back to 102 , it is possible to control so that an appropriate amount of oil is maintained in the compressor 102 .

On the other hand, if oil recovery is not performed properly, the oil discharged from the compressor may not return to the compressor and the compressor may be damaged. In particular, if it is not determined that the oil in the compressor is insufficient during the operation of the air conditioner 100 due to the low temperature leaving the air conditioner and insufficient oil supply, the possibility of damage to the compressor increases due to an increase in friction due to the lack of oil.

Conventionally, it was determined that the oil may be insufficient when the compressor 102 operates at a low frequency for a predetermined time or longer without a specific detection method. However, according to an embodiment of the present invention, by using the determination condition for confirming the current characteristics of the compressor 102 , the oil shortage in the compressor is detected more quickly and stably, and the oil is sent to the compressor 102 to send the compressor 102 ) to prevent burnout.

3 is a simplified internal block diagram of an air conditioner according to an embodiment of the present invention.

Referring to FIG. 3 , the air conditioner 100 includes a compressor 102 , an outdoor fan 105a , a sensor unit 210 , a fan driving unit 230 for driving the outdoor fan 105a , and a compressor 102 . It may include a compressor driving unit 240 , a control unit 260 , and a memory 250 to drive it.

The compressor 102 and the outdoor fan 105a may operate as described above with reference to FIGS. 1 and 2 .

The sensor unit 210 may include a plurality of sensors, and may transmit data on detection values detected through the plurality of sensors to the controller 260 .

The sensor unit 210 may include a plurality of sensors to acquire data related to the operation and state of the air conditioner 100 . The sensor unit 210 may include various sensors to acquire cycle driving data.

The sensor unit 210 may include a compressor temperature sensor. The compressor temperature sensor, for example, may be disposed at the inlet of the compressor 102 to detect the temperature of the gas refrigerant flowing into the compressor 102 .

The controller 260 controls the air conditioner 100 to operate based on at least one of the refrigerant discharge temperature, the detected outdoor temperature, and the sensed indoor temperature, and the input target temperature detected by the sensor unit 210 . can do.

The sensor unit 210 may include a pressure sensor. For example, the pressure sensor may detect the pressure of the gaseous refrigerant. For example, when the outdoor unit 21 includes one pressure sensor, the pressure sensor detects the pressure of the gas refrigerant flowing into the compressor 102 in the cooling mode among the refrigerant passages connected to the four-way valve (not shown). It can be detected and can be arranged in a flow path capable of detecting the pressure of the gas refrigerant discharged from the compressor 102 in the heating mode.

According to an embodiment, the sensor unit 210 may include a speed sensor sensing a rotation speed of a motor rotating the compressor 102, the indoor fan 109a, and the outdoor fan 105a, the compressor 102, the indoor fan ( 109a), and a current sensor for sensing the current applied to the outdoor fan 105a. In this case, the controller 260 may control a motor that rotates the compressor and/or the fan based on sensed data such as speed and current.

The fan driving unit 230 may drive the outdoor fan 105a. For example, the fan driving unit 230, a rectifier (not shown) for rectifying AC power into DC power and outputting it, a dc stage capacitor for storing the pulsating voltage from the rectifier, and a plurality of switching elements, a smoothed DC power supply may include an inverter (not shown) for converting and outputting 3-phase AC power of a predetermined frequency and/or an outdoor fan motor 105b for driving the outdoor fan 105a according to the 3-phase AC power output from the inverter have.

The fan driver 230 may change the operating frequency of the outdoor fan 105a under the control of the controller 260 . For example, the operating frequency of the outdoor fan 105a may be changed by changing the frequency of the three-phase AC power output to the outdoor fan motor 105b under the control of the controller 260 .

According to an embodiment, the fan driving unit 230 may drive the indoor fan 109a. According to an embodiment, the fan driving unit 230 may include an outdoor fan driving unit driving the outdoor fan 105a and an indoor fan driving unit driving the indoor fan 109a.

The compressor driving unit 240 may drive the compressor 102 . For example, the compressor driving unit 240 includes a rectifying unit (not shown) for rectifying AC power into DC power and outputting it, a dc stage capacitor for storing the pulsating voltage from the rectifying unit, and a plurality of switching elements, and a smoothed DC It may include an inverter (not shown) that converts power to three-phase AC power of a predetermined frequency and outputs, and/or a compressor motor 102b that drives the compressor 102 according to the three-phase AC power output from the inverter have.

The compressor driving unit 240 may change the operating frequency of the compressor 102 under the control of the control unit 260 . For example, the operating frequency of the compressor 102 may be changed by changing the frequency of the three-phase AC power output to the compressor motor 102b under the control of the controller 260 .

The output unit 220 may display the operating state of the air conditioner 100 . For example, the output unit 220 may include a display means for outputting the operation state of the indoor unit 21 to display the operation state and an error.

The memory 250 may store various data for the overall operation of the air conditioner 100 , such as a program for processing or control of the controller 360 .

The memory 250 may store data on detection values detected from a plurality of sensors provided in the sensor unit 210 . For example, the memory 250 stores data related to various reference temperatures for the temperature of the gas refrigerant flowing into the compressor 102 , data related to a temperature section for the temperature of the gas refrigerant flowing into the compressor 102 , and the like. can be saved

Meanwhile, the controller 260 may be provided in at least one of the outdoor unit 21 and/or the indoor unit 31 and/or a remote controller (not shown).

For example, the controller 260 may be provided in the outdoor unit 21 to be connected to each component provided in the outdoor unit 21 . The controller 260 may transmit/receive data to and from each component included in the outdoor unit 21 , and may control the overall operation of each component.

The controller 260 may check the operation mode of the air conditioner 100 . For example, the controller 260 may check whether the operation mode of the air conditioner 100 is a heating mode.

According to an embodiment, the controller 260 may control the fan driving unit 230 and/or the compressor driving unit 240 according to a sensorless algorithm. For example, the control unit 260 may estimate the voltage, calculate the operating frequency and power consumption of the compressor 102, and control the compressor 102 based on the calculated operating frequency and power consumption. have.

According to an embodiment, the controller 260 may receive data from the sensor unit 210 , and may control the fan driving unit 230 and/or the compressor driving unit 240 based on the received data.

The controller 260 may control the compressor driving unit 240 based on data received from the compressor temperature sensor, for example. For example, the controller 260 may compare the temperature of the gas refrigerant detected through the compressor temperature sensor with a preset reference temperature, and may control the compressor driving unit 240 according to the comparison result.

According to an embodiment of the present invention, when the oil discharged from the compressor 102 does not return to the compressor 102 due to reasons such as leaving the temperature at a low temperature and insufficient oil supply, the current of the compressor 102 is checked and the compressor ( 102) can detect the lack of oil.

The control unit 260 may accurately determine whether the oil is insufficient without additional detection means by using the current characteristics of the compressor 102 and perform a control to perform an oil recovery operation if necessary. In particular, the control unit 260 may determine whether to operate the oil recovery operation based on the Q-axis current of the compressor 102 .

The compressor driving unit 240 includes a dc stage capacitor and a plurality of switching elements, and by a switching operation of the plurality of switching elements, converts the DC power of the dc stage capacitor into AC power, and converts the converted AC power to It may include an inverter outputting to the compressor motor, and an output current detection unit disposed between the dc stage capacitor and the inverter to detect a current. In this case, the D-axis current may be based on sensing data of the output current detector.

4 is an example of an internal block diagram of a motor driving apparatus according to an embodiment of the present invention, and FIG. 5 is an internal block diagram of the inverter control unit of FIG. 4 .

As illustrated in the drawings, the motor driving apparatus according to an embodiment of the present invention may be included in the compressor driving unit 240 to drive a motor rotating the compressor. In addition, the motor driving apparatus according to an embodiment of the present invention illustrated in the drawings is provided in the fan driving unit 230 to drive an indoor/outdoor fan.

Hereinafter, a case in which the motor driving device is a compressor driving device 240 driving the compressor motor 440 rotating the compressor 102 will be described as an example, but the same method may be applied to driving a fan.

As illustrated in the drawings, the motor driving apparatus according to an embodiment of the present invention is for driving a motor in a sensorless manner, and may include an inverter 420 and an inverter control unit 430 .

In addition, the compressor driving apparatus 240 according to an embodiment of the present invention may further include a converter 410 that converts input AC power into DC power and outputs the converted power.

In addition, the compressor driving device 240 according to an embodiment of the present invention includes an input current detection unit (A), a reactor (L), a dc stage capacitor (C), a dc stage voltage detection unit (B), and an output current detection unit (E) may further include.

Meanwhile, the inverter control unit 430 according to an embodiment of the present invention may control the switching elements in the inverter 420 by variable control of a pulse width modulation (PWM) based on a space vector.

Hereinafter, the operation of each constituent unit in the compressor driving apparatus 240 of FIGS. 4 and 5 will be described.

The reactor L is disposed between the input AC power source 405 and the converter 410 to perform a power factor correction or a step-up operation. In addition, the reactor L may perform a function of limiting the harmonic current caused by high-speed switching of the converter 410 and the like.

The input current detection unit A may detect the input current is input from the commercial AC power source 405 . To this end, as the input current detection unit A, a current transformer (CT), a shunt resistor, or the like may be used. The detected input current is may be input to the inverter controller 430 as a discrete signal in the form of a pulse.

The converter 410 converts the commercial AC power 405 through the reactor L into DC power and outputs it to the dc terminal. Although the drawing shows the commercial AC power source 405 as a single-phase AC power source, it may be a three-phase AC power source. The internal structure of the converter 410 may also vary depending on the type of the commercial AC power source 405 .

Meanwhile, the converter 410 may be made of a diode or the like without a switching element, and may perform a rectification operation without a separate switching operation.

For example, in the case of a single-phase AC power supply, four diodes may be used in the form of a bridge, and in the case of a three-phase AC power, six diodes may be used in the form of a bridge.

Meanwhile, as the converter 410, for example, a half-bridge converter in which two switching elements and four diodes are connected may be used, and in the case of a three-phase AC power supply, six switching elements and six diodes may be used. . In this case, the converter 410 may be referred to as a rectifier.

When the converter 410 includes a switching element, a step-up operation, a power factor improvement, and a DC power conversion may be performed by a switching operation of the corresponding switching element.

The dc terminal capacitor (C) is connected to both ends of the dc, smooths the input power and stores it. In the drawing, one element is exemplified as a dc terminal capacitor (C), but a plurality of elements may be provided to ensure element stability.

Meanwhile, in the drawings, it is exemplified as being connected to the output terminal of the converter 410 , but the present invention is not limited thereto, and DC power may be directly inputted. For example, direct current power from the solar cell may be directly input to the dc terminal capacitor C or may be input after being converted to direct current/direct current. Hereinafter, the parts illustrated in the drawings will be mainly described.

On the other hand, since DC power is stored at both ends of the dc terminal capacitor C, this may be referred to as a dc terminal or a dc link terminal.

The dc terminal voltage detection unit B may detect the dc terminal voltage Vdc, which is both ends of the dc terminal capacitor C. To this end, the dc terminal voltage detection unit B may include a resistance element, an amplifier, and the like. The detected dc terminal voltage Vdc may be input to the inverter controller 430 as a discrete signal in the form of a pulse.

The inverter 420 includes a plurality of inverter switching elements, and converts the smoothed DC power (Vdc) by the on/off operation of the switching elements into three-phase AC power (va, vb, vc) of a predetermined frequency, three-phase It may output to the synchronous motor 440 .

Inverter 420 is a pair of upper-arm switching elements (Sa, Sb, Sc) and lower-arm switching elements (S'a, S'b, S'c) connected in series with each other, and a total of three pairs of upper and lower arms The switching elements are connected to each other in parallel (Sa&S'a, Sb&S'b, Sc&S'c). A diode is connected in anti-parallel to each of the switching elements Sa, S'a, Sb, S'b, Sc, and S'c.

The switching elements in the inverter 420 turn on/off the respective switching elements based on the inverter switching control signal Sic from the inverter controller 430 . Accordingly, the three-phase AC power having a predetermined frequency is output to the three-phase synchronous motor 440 .

The inverter controller 430 may control the switching operation of the inverter 420 based on the sensorless method. To this end, the inverter control unit 430 may receive the output current io detected by the output current detection unit E as an input.

The inverter controller 430 outputs the inverter switching control signal Sic to the inverter 420 in order to control the switching operation of the inverter 420 . The inverter switching control signal Sic is a pulse width modulation (PWM) switching control signal, and is generated and output based on the output current io detected by the output current detection unit E .

The output current detection unit E detects an output current io flowing between the inverter 420 and the three-phase motor 440 . That is, the current flowing through the motor 440 is detected. The output current detection unit E may detect all of the output currents ia, ib, and ic of each phase, or may detect the output currents of two phases using three-phase balance.

The output current detection unit E may be positioned between the inverter 420 and the motor 440 , and a current transformer (CT), a shunt resistor, or the like may be used to detect the current.

When a shunt resistor is used, three shunt resistors are located between the inverter 420 and the synchronous motor 440, or the three lower arm switching element elements S'a, S'b, S'c of the inverter 420. ), it is possible to have one end connected to each.

Alternatively, two shunt resistors are used, and it is also possible to calculate the current of the other phase using three-phase balance.

More preferably, one shunt resistor may be disposed between the dc stage capacitor C and the inverter 420 . This method may be referred to as a 1-shunt method.

According to the 1 shunt method, the output current detection unit E uses one shunt resistor element, and when the lower arm switching element of the inverter 420 is turned on, in time division, the output current io flowing through the motor 440 is A phase current can be detected.

The detected output current io may be applied to the inverter controller 430 as a discrete signal in the form of a pulse, and an inverter switching control signal Sic is generated based on the detected output current io do. Hereinafter, the detected output current io may be described in parallel as the three-phase output current ia, ib, ic.

On the other hand, the three-phase motor 440 includes a stator and a rotor, and each phase AC power of a predetermined frequency is applied to the coils of the stators of each phase (a, b, c phase), and the rotor rotates. will do

Such a motor 440 may include, for example, a Surface-Mounted Permanent-Magnet Synchronous Motor (SMPMSM), an Interidcr Permanent Magnet Synchronous Motor (IPMSM), and a synchronous relay. It may include a Synchronous Reluctance Motor (Synrm) and the like. Among them, SMPMSM and IPMSM are Permanent Magnet Synchronous Motors (PMSM) with permanent magnets, and Synrm is characterized by not having permanent magnets.

Referring to FIG. 5 , the inverter control unit 430 includes an axis conversion unit 310 , a speed calculating unit 320 , a current command generation unit 330 , a voltage command generation unit 340 , an axis conversion unit 350 , and A switching control signal output unit 360 may be included.

The axis conversion unit 310 may convert the output current (ia, ib, ic) detected by the output current detection unit (E) into the two-phase current (iα, iβ) of the stationary coordinate system.

Meanwhile, the axis conversion unit 310 may convert the two-phase currents (iα, iβ) of the stationary coordinate system into the two-phase currents (id, iq) of the rotational coordinate system. That is, the axis conversion unit 310 may output the two-phase current D-axis current (id) and the Q-axis current (iq) of the rotational coordinate system.

)를 추정하고, 추정된 위치를 미분하여, 속도(

)를 연산할 수 있다. The speed calculating unit 320, based on the output current (ia, ib, ic) detected by the output current detecting unit (E), the position value (

), and by differentiating the estimated position, the velocity (

) can be calculated.

)와 속도 지령치(ω^* _r)에 기초하여, 전류 지령치(i^* _q)를 생성한다. 예를 들어, 전류 지령 생성부(330)는, 연산 속도(

)와 속도 지령치(ω^* _r)의 차이에 기초하여, PI 제어기(335)에서 PI 제어를 수행하며, 전류 지령치(i^* _q)를 생성할 수 있다. 도면에서는, 전류 지령치로, q축 전류 지령치(i^* _q)를 예시하나, 도면과 달리, d축 전류 지령치(i^* _d)를 함께 생성하는 것도 가능하다. 한편, d축 전류 지령치(i^* _d)의 값은 0으로 설정될 수도 있다. On the other hand, the current command generation unit 330, the calculation speed (

) and the speed command value (ω ^* _r ), a current command value (i ^* _q ) is generated. For example, the current command generation unit 330 may set the calculation speed (

) and the speed command value (ω ^* _r ) based on the difference, the PI controller 335 performs PI control, it is possible to generate a current command value (i ^* _q ). In the drawing, the q-axis current command value (i ^* _q ) is exemplified as the current command value, but unlike the drawing, it is also possible to generate the d-axis current command value (i ^* _d ) together. On the other hand, the value of the d-axis current command value (i ^* _d ) may be set to 0.

On the other hand, the current command generation unit 330, the current command value (i ^* _q ) may further include a limiter (not shown) for limiting the level so as not to exceed the allowable range.

Next, the voltage command generation unit 340 includes the d-axis and q-axis currents (i _d ,i _q ) that are axis-transformed into the two-phase rotational coordinate system by the axis transformation unit, and the current command values ( Based on i ^* _d ,i ^* _q ), d-axis and q-axis voltage command values (v ^* _d ,v ^* _q ) are generated. For example, the voltage command generation unit 340 performs PI control in the PI controller 344 based on the difference between the q-axis current (i _q ) and the q-axis current command value (i ^* _q ), q A shaft voltage setpoint (v ^* _q ) can be generated. In addition, the voltage command generator 340 performs PI control in the PI controller 348 based on the difference between the d-axis current (i _d ) and the d-axis current command value (i ^* _d ), and the d-axis voltage A setpoint (v ^* _d ) can be generated. On the other hand, the voltage command generation unit 340, the d-axis, q-axis voltage command value (v ^* _d , v ^* _q ) may further include a limiter (not shown) for limiting the level so as not to exceed the allowable range. .

On the other hand, the generated d-axis and q-axis voltage command values (v ^* _d , v ^* _q ) are input to the axis conversion unit 350 .

)와, d축, q축 전압 지령치(v^* _d,v^* _q)를 입력받아, 축변환을 수행한다.The axis conversion unit 350, the position calculated by the speed calculating unit 320 (

) and d-axis and q-axis voltage command values (v ^* _d ,v ^* _q ) are received and axis transformation is performed.

)가 사용될 수 있다.First, the axis transformation unit 350 performs transformation from a two-phase rotational coordinate system to a two-phase stationary coordinate system. At this time, the position calculated by the speed calculating unit 320 (

) can be used.

Then, the axis transformation unit 350 performs transformation from the two-phase stationary coordinate system to the three-phase stationary coordinate system. Through this conversion, the axis conversion unit 1050 outputs a three-phase output voltage command value (v ^* a, v ^* b, v ^* c).

The switching control signal output unit 360 generates a switching control signal (Sic) for an inverter according to a pulse width modulation (PWM) method based on the three-phase output voltage command value (v ^* a, v ^* b, v ^* c) to output

The output inverter switching control signal Sic may be converted into a gate driving signal by a gate driver (not shown) and input to a gate of each switching element in the inverter 420 . Accordingly, each of the switching elements Sa, S'a, Sb, S'b, Sc, and S'c in the inverter 420 performs a switching operation.

On the other hand, the compressor driving device 240, through the inverter 420 control, to perform a vector control for driving the motor 440 to detect the output current, in particular, the phase current flowing through the motor 440 can

The inverter control unit 430 uses the sensed phase current to control the motor 440 to a desired speed and torque through the current command generation unit 330 and the voltage command generation unit 340 . do.

If the compressor 102 continues to operate at a low frequency without detecting the oil shortage, the compressor 102 may be damaged due to continuous friction.

According to an embodiment of the present invention, it is possible to more quickly and stably identify the oil shortage state and perform the oil recovery operation by using the judgment condition for confirming the current characteristics of the accumulator 102 .

For example, the control unit 260 checks the Q-axis current of the compressor 102 when the compressor 102 is operating. Accordingly, even when the outdoor temperature is low, the air conditioner 100 can be protected by quickly determining the oil shortage state without damaging the compressor 102 .

Meanwhile, the controller 260 may rapidly rotate the compressor 102 at a predetermined frequency or higher during the oil recovery operation. Accordingly, the amount of refrigerant discharged from the compressor 102 is greater than in the case of normal operation, the flow rate of the refrigerant is increased, and the oil remaining on the flow path is recovered to the compressor 102 together with the refrigerant. According to an embodiment, the controller 260 may drive the compressor 102 at the maximum frequency.

Meanwhile, the controller 260 may control the oil recovery operation to be performed when the amplitude of the Q-axis current is greater than or equal to an error reference value when the compressor 102 is operating at a low frequency lower than the operating frequency of the oil recovery operation. have.

The oil recovery operation rotates the compressor 102 quickly so that the oil recovery operation is sufficiently performed, and the controller 260 may rotate the compressor 102 at a frequency greater than or equal to a certain level during the oil recovery operation.

If the compressor 102 is driven at a frequency lower than the operating frequency of the oil recovery operation, the oil recovery operation may not be smoothly performed.

Therefore, when the compressor 102 is operating at a low frequency lower than the operating frequency of the oil recovery operation, it is important to quickly determine whether the oil is insufficient, and the control unit 260 checks the amplitude of the Q-axis current during the low frequency operation, You can determine whether there is a shortage of oil. If the amplitude of the Q-axis current is equal to or greater than the error reference value, the controller 260 may control the oil recovery operation to be performed.

According to an embodiment, the controller 260 may control to perform the oil recovery operation if the amplitude of the Q-axis current is greater than or equal to an error reference value while the compressor 102 is operating at the low frequency for a predetermined time without changing the frequency. can When the operating frequency of the compressor 102 is changed, the control unit 260 waits for the operating frequency to be maintained at a certain level, and then when the compressor 102 operation is stabilized, check the amplitude of the Q-axis current to determine whether there is an oil shortage. can be discerned.

Meanwhile, the error reference value may be less than half of the Q-axis current during normal operation. Here, the Q-axis current in the normal operation may be a Q-axis current measured when the oil is at least the lowest oil level or more during a general cooling or heating operation, not an oil recovery operation. In this case, the error reference value may be set to a value of 50% or less of the measured Q-axis current when the minimum oil level is higher.

According to an embodiment, it may be determined whether the oil recovery operation is performed using a different logic according to the operation frequency of the compressor 102 .

For example, when the operating frequency of the compressor 102 is smaller than a first frequency set lower than the operating frequency of the oil recovery operation, the controller 260 is greater than a second frequency set lower than the first frequency For example, when the amplitude of the Q-axis current is equal to or greater than an error reference value, the oil recovery operation may be performed.

Here, the first frequency is greater than the second frequency and has a relatively small difference from the operating frequency of the oil recovery operation. Accordingly, if the operating frequency of the compressor 102 is greater than the first frequency, the normal operation may be performed without checking the current characteristics of the compressor 102 .

In addition, if the operating frequency of the compressor 102 is in the range between the first frequency and the second frequency, the control unit 260 checks the current characteristics of the compressor 102 to determine whether the oil is insufficient, At the time, it is possible to control to perform an oil recovery operation.

That is, when the operating frequency of the compressor 102 is smaller than the first frequency and larger than the second frequency, the control unit 260 is configured to recover the oil when the amplitude of the Q-axis current is equal to or greater than an error reference value. You can control it to drive.

Also, when the operating frequency of the compressor 102 is equal to or less than the second frequency, the control unit 260 may control the oil recovery operation to be performed. Since the second frequency is a low frequency operation that is smaller than the first frequency and has a large difference from the oil recovery operation frequency, the oil recovery operation may be directly performed without checking the current characteristics of the compressor 102 .

6 is a diagram referenced in the description of determining the oil shortage according to an embodiment of the present invention, and shows the current and frequency characteristics measured during heating operation after leaving at a low temperature (outside of -20 degrees Celsius).

6 illustrates an inverter input current, a Q-axis current, a D-axis current, and an operating frequency of the compressor 102 over time when a heating operation is performed after being left at a low temperature.

When the oil in the compressor 102 is insufficient due to the friction of the mechanism, the compressor 102 does not rotate smoothly and the torque is shaken. The lapse of torque fluctuation appears in the compressor 102 Q-axis current.

Therefore, if oil supply is insufficient below the minimum oil level during heating operation after leaving at a low temperature, the amplitude of the compressor Q-axis current may greatly increase.

Due to the lack of oil in the compressor, it is not possible to determine the lack of oil in the compressor during operation of the air conditioner due to unattended low temperature and insufficient oil supply.

According to an embodiment of the present invention, it is possible to quickly determine whether the oil is insufficient by checking the Q-axis current of the compressor 102 .

Referring to FIG. 6 , during low-frequency operation after leaving at a low temperature, in the insufficient oil supply section 610 , the compressor 102 Q-axis current is severely shaken due to insufficient oil in the compressor 102 . For example, in the insufficient oil supply section 610, the amplitude of the Q-axis current of the compressor 102 is about 3A, and when the amount of oil in the compressor is appropriate (630), the amplitude of the Q-axis current of the compressor is about 0.6A 5 times level increases significantly.

The controller 260 may control to perform an oil recovery (refueling) operation when the amplitude of the compressor Q-axis current is greater than the error reference value, for example, 1A.

For example, the air conditioner 100 may perform an oil recovery operation by driving the compressor 102 at 50 to 60 Hz for 2 to 3 minutes.

Referring to FIG. 6 , during normal refueling 630 according to oil level recovery after the oil recovery operation 620, the Q-axis current amplitude is at a level of 0.8A or less, and when oil supply is insufficient, the Q-axis reference current amplitude is lowered to 1/3 or less. .

Accordingly, proper oil supply can be maintained by determining the oil shortage based on the amplitude of the compressor Q-axis current and performing the oil recovery operation.

7 is a flowchart illustrating a method of operating an air conditioner according to an embodiment of the present invention.

Referring to FIG. 7 , the air conditioner 100 according to an embodiment of the present invention may perform the operation of the compressor 102 ( S710 ), and the controller 260 may control the operation frequency of the compressor 102 . It may be determined whether the low-frequency operation is in operation that is less than or equal to a first frequency lower than the operation frequency of the oil recovery operation ( S720 ).

If the operating frequency of the compressor 102 is greater than the first frequency (S720), the controller 260 may control the current compressor 102 to maintain the normal operation (S710).

When the operating frequency of the compressor 102 is equal to or less than the first frequency (S720), the controller 260 may determine whether it is greater than a second frequency set lower than the first frequency (S730).

When the operating frequency of the compressor 102 is not greater than the first frequency and greater than the second frequency (S730), the controller 260 may check the Q-axis current characteristic of the compressor (S740).

According to an embodiment, the control unit 260 checks whether the operating frequency of the compressor 102 is changed, and when there is no frequency change (S735), the control unit 260 checks the Q-axis current characteristic of the compressor It can be (S740). That is, when the amplitude of the Q-axis current of the compressor 102 maintains a state equal to or greater than the error reference value for the predetermined time (S730 and S735), the controller 260 may control the oil recovery operation to be performed (S760). . Also, if there is a change in frequency, the previous process may be repeated again (S710, S720, S730).

Meanwhile, the control unit 260 may determine whether the oil is insufficient by checking the amplitude of the Q-axis current of the compressor 102 during the low-frequency operation (S730) (S740). If the amplitude of the Q-axis current is equal to or greater than the error reference value (S740), the controller 260 may control the oil recovery operation to be performed (S760).

Meanwhile, the error reference value may be less than half of the Q-axis current during normal operation. Here, the Q-axis current in the normal operation may be a Q-axis current measured when the oil is at least the lowest oil level or more during a general cooling or heating operation, not an oil recovery operation. In this case, the error reference value may be set to a value of 50% or less of the measured Q-axis current when the minimum oil level is higher.

When the operating frequency of the compressor 102 is equal to or less than the second frequency (S730), the controller 260 may control to perform the oil recovery operation (S760). Since the second frequency is a low frequency operation that is smaller than the first frequency and has a large difference from the oil recovery operation frequency, the oil recovery operation may be directly performed without checking the current characteristics of the compressor 102 .

Even in this case (S730), it may be determined whether the operating frequency is maintained for a predetermined time (S750). The controller 260 may check whether the operating frequency of the compressor 102 lower than the second frequency is maintained for a predetermined time, and when there is no frequency change (S750), control to perform the oil recovery operation (S760) ).

8 is a flowchart illustrating a method of operating an air conditioner according to an embodiment of the present invention, and includes an example of setting an optional changeable frequency reference, amplitude error reference, and time reference.

Referring to FIG. 8 , the compressor 102 may perform normal operation (S810), and the control unit 260 may determine whether the compressor 102 is operating at a low frequency with a first frequency of 40 Hz or less ( S820).

If the low-frequency operation is under 40Hz (Option) (S820), at the same frequency (S830), the Q-axis current amplitude (difference between Min and Max) for 10 seconds (Option) is greater than the error threshold of 2.5A (Option) ( S840), the control unit 260 may determine that the oil is insufficient and control the oil supply (recovery) operation to be performed (S860).

If the low frequency operation is not under 40Hz (Option) (S820), there is a frequency change (S830), or the Q-axis current amplitude does not correspond to the error criterion (S840), the controller 260 controls to maintain the normal operation It can be done (S825).

If the low frequency operation below 25Hz (Option) is in operation (S830) and the operation is maintained for 30 minutes (Option) (S850), there is a high possibility that the oil cannot return to the compressor 102. By performing the operation (S860), it is possible to prevent oil shortage in advance.

9 is a flowchart illustrating a method of operating an air conditioner according to an embodiment of the present invention.

Referring to FIG. 9 , the air conditioner 100 according to an embodiment of the present invention may perform an operation of the compressor 102 ( S910 ), and the control unit 260 may provide a current characteristic of the compressor 102 . can be checked to determine whether the oil is insufficient (S920).

In particular, the controller 260 may use the amplitude of the Q-axis current of the compressor 102 as a criterion for determining whether the oil is insufficient.

If the amplitude of the Q-axis current is equal to or greater than the error reference value (S740), the controller 260 may control the oil recovery operation to be performed (S930).

According to an embodiment, when the amplitude of the Q-axis current of the compressor 102 maintains a state equal to or greater than the error reference value for the predetermined time, the controller 260 may control the oil recovery operation to be performed. It can be (S930).

Also in this embodiment, the error reference value may be less than half of the Q-axis current during normal operation.

According to at least one of the embodiments of the present invention, it is possible to determine whether the oil is insufficient or whether to perform the oil recovery operation using the compressor current characteristic. Accordingly, oil can be efficiently recovered and oil shortage can be prevented.

The configuration and method of the embodiments described above are not limitedly applicable to the air conditioner and the method of operation thereof according to the embodiment of the present invention, but the embodiments are the examples of each embodiment so that various modifications can be made. All or a part may be selectively combined and configured.

In addition, although preferred embodiments of the present invention have been illustrated and described above, the present invention is not limited to the specific embodiments described above, and the technical field to which the present invention pertains without departing from the gist of the present invention as claimed in the claims Various modifications may be made by those of ordinary skill in the art, and these modifications should not be individually understood from the technical spirit or perspective of the present invention.

102: compressor
41: oil separator
42: oil return pipe
43: oil return valve

Claims (18)

a compressor that compresses the refrigerant;
an oil separator for separating oil from the refrigerant discharged from the compressor;
an oil return pipe connected between the oil separator and the compressor;
An inverter comprising a dc stage capacitor and a plurality of switching elements, converting the DC power of the dc stage capacitor into an AC power by a switching operation of the plurality of switching elements, and outputting the converted AC power to the compressor motor; an output current detection unit disposed between the dc stage capacitor and the inverter to detect a current; and a compressor driving unit including a shaft converting unit converting the output current detected by the output current detecting unit and outputting a Q-axis current;
The air conditioner comprising a; based on the operating frequency of the compressor and the amplitude of the Q-axis current of the compressor to determine whether to operate the oil recovery operation; According to claim 1,
The control unit is
When the compressor is operating at a low frequency lower than the operating frequency of the oil recovery operation, and the amplitude of the Q-axis current is equal to or greater than an error reference value, the air conditioner, characterized in that the oil recovery operation is controlled to be performed; 3. The method of claim 2,
The control unit is
Air conditioner, characterized in that when the amplitude of the Q-axis current is greater than or equal to an error reference value when the compressor is operating at the low frequency for a predetermined time without changing the frequency, controlling the oil recovery operation to be performed; 3. The method of claim 2,
The error threshold is
Air conditioner, characterized in that less than half of the Q-axis current during normal operation. According to claim 1,
The control unit is
The operating frequency of the compressor is smaller than the first frequency set lower than the operating frequency of the oil recovery operation and is larger than the second frequency set lower than the first frequency,
When the amplitude of the Q-axis current is greater than or equal to an error reference value, the air conditioner, characterized in that the control is performed to perform the oil recovery operation; 6. The method of claim 5,
The control unit is
An air conditioner, wherein the oil recovery operation is controlled to be performed when the amplitude of the Q-axis current maintains a state equal to or greater than an error reference value for a predetermined time without changing the operating frequency of the compressor; 6. The method of claim 5,
The control unit is
An air conditioner, characterized in that when the operating frequency of the compressor is equal to or less than the second frequency, controlling the oil recovery operation to be performed; 6. The method of claim 5,
The error threshold is
Air conditioner, characterized in that less than half of the Q-axis current during normal operation. According to claim 1,
and an oil return valve configured to open and close the oil return pipe under the control of the controller. delete delete performing compressor operation;
determining whether the operating frequency of the compressor is in a low frequency operation that is less than or equal to a first frequency lower than an operation frequency of the oil recovery operation;
determining whether the operating frequency of the compressor is greater than a second frequency set lower than the first frequency when the operating frequency is equal to or less than the first frequency;
determining the Q-axis current of the compressor;
When the operating frequency of the compressor is not greater than the first frequency and greater than the second frequency and the amplitude of the Q-axis current of the compressor is greater than or equal to an error reference value, performing the oil recovery operation;
The step of determining the Q-axis current of the compressor,
An operating method of an air conditioner, characterized in that it is disposed between the dc stage capacitor and the inverter and outputs the Q-axis current by converting the output current detected by the output current detecting unit for detecting the current. 13. The method of claim 12,
The step of performing the oil recovery operation is
While the operating frequency of the compressor is not greater than the first frequency and greater than the second frequency,
An operating method of an air conditioner, characterized in that the oil recovery operation is performed when the amplitude of the Q-axis current is maintained for a predetermined time or more without changing the operating frequency of the compressor; 13. The method of claim 12,
performing the oil recovery operation when the operating frequency of the compressor is equal to or less than the second frequency; 13. The method of claim 12,
The error threshold is
An operating method of an air conditioner, characterized in that less than half of the Q-axis current during normal operation. performing compressor operation;
determining the Q-axis current of the compressor; and,
When the amplitude of the Q-axis current is greater than or equal to the error reference value, performing an oil recovery operation;
The step of determining the Q-axis current of the compressor,
An operating method of an air conditioner, characterized in that it is disposed between the dc stage capacitor and the inverter and outputs the Q-axis current by converting the output current detected by the output current detecting unit for detecting the current. 17. The method of claim 16,
The step of performing the oil recovery operation is
When the operating frequency of the compressor maintains a state in which the amplitude of the Q-axis current of the compressor is equal to or greater than an error reference value for a predetermined time, the oil recovery operation is performed; 17. The method of claim 16,
The error threshold is
An operating method of an air conditioner, characterized in that less than half of the Q-axis current during normal operation.

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