JP5306262B2 - Drive controller for compressor for air conditioner - Google Patents

Description

  The present invention relates to an air conditioner compressor, and more particularly to an air conditioner compressor drive control device for preventing refrigerant stagnation in which refrigerant is dissolved in refrigerating machine oil in the compressor during operation stop. .

In an air conditioner, a refrigerant stagnation phenomenon may occur in which refrigerant accumulates in the compressor due to a temperature difference or pressure difference of the refrigerant while the compressor is stopped. When the refrigerant stagnation occurs, the start-up load of the compressor increases, or at the time of start-up, a large amount of the mixture of refrigeration oil and refrigerant in the compressor is blown out of the compressor in a short time, and the refrigeration oil in the compressor is depleted. As a result, problems such as shaft breakage may occur.
In general, as a measure to prevent stagnation in the compressor, when the compressor is stopped, the inside of the compressor is heated by a heater, or the compressor motor winding is energized (voltage that does not drive the compressor motor) by an inverter. The inside of the compressor is heated. However, there is a problem that power is always consumed for heating in the compressor during operation stop, and standby power is increased.
Therefore, the conventional compressor heating control detects the outside air temperature with an outside air temperature detector, and when the detected outside air temperature exceeds a predetermined value, stops energization or heating by the heater to reduce power consumption. (For example, refer to Patent Document 1).

  In the heating control of other compressors, a heating means for heating the compressor during operation stop and an outside air temperature detector for detecting the outside air temperature are provided, and the heat capacity is the largest while the outside air temperature tends to decrease. It is determined that refrigerant stagnation does not occur because the compressor is at the highest temperature, and there is one that reduces power consumption during stoppage by holding the compressor in a stopped state (for example, see Patent Document 2). .

  In addition, the above two methods predict the refrigerant state in the compressor by detecting the outside air temperature and the temperature of other parts, but directly by installing a sensor for detecting the refrigerant state in the compressor. There is a method for detecting the refrigerant state. This system includes a heater that heats the compressor and an insulation resistance sensor that detects the electrical resistance of the refrigerant and the refrigeration oil. When the insulation resistance value detected by the sensor falls below a predetermined value, the heater is energized. Then, two-phase separation of the refrigerant is prevented by heating the refrigerator oil. In addition, when the insulation resistance value is equal to or greater than a predetermined value, the power supply to the heater is reduced by stopping energization of the heater (see, for example, Patent Document 3).

JP 2000-292014 A (page 4, FIG. 2) JP 2007-64447 A (page 12, FIG. 1) JP 2000-145640 A (page 3, FIG. 1)

  The heating control of the compressor described in Patent Document 1 shortens the heating time of the compressor by the outside air temperature and reduces the power consumption during operation stop, but predicts the refrigerant state inside the compressor from the outside air temperature. However, the refrigerant state is not reliably detected. When the operation is stopped, the refrigerant in the refrigerant circuit has a characteristic of gathering at the lowest temperature portion, and the refrigerant often accumulates in the compressor when the outside air temperature at which the temperature difference between the indoor unit and the outdoor unit becomes large is low. However, even when the outside air temperature is high due to a temperature difference in the refrigerant circuit of the outdoor unit, there is a state where the temperature of the compressor is the lowest in the refrigerant circuit of the outdoor unit. Even when the outside air temperature is low, the outdoor heat exchanger may be cooler than the compressor in the refrigerant circuit of the outdoor unit, and the refrigerant may not accumulate in the compressor. Therefore, wasteful power is consumed because the inside of the compressor is heated even when refrigerant stagnation that does not require heating of the compressor has actually occurred. In addition, when the refrigerant stagnation, which actually requires heating of the compressor, is stopped, the heating of the compressor may be stopped, which may cause problems such as breakage of the compressor shaft.

  In the heating control of the compressor in Patent Document 2, the outside air temperature is detected, the heating in the compressor by the heater or restraint energization is stopped while the outside air temperature is decreasing, and the inside of the compressor is heated by the heater or restraint energization during the rise. Is. Refrigerant condenses at the coldest part in the refrigerant circuit and uses the property of accumulating in that part to detect whether the outside air temperature is rising or falling and determining whether the compressor needs to be heated However, heating the compressor only when necessary reduces power consumption, but it predicts when the refrigerant will accumulate from the outside air temperature, ensuring that the compressor needs to be heated. It is not something that can be detected. However, the heat capacity of the heat exchanger and the compressor in the refrigerant circuit varies depending on the model, and an error occurs in the timing when the compressor becomes the lowest temperature due to the rise or fall of the outside air temperature. The moment when the refrigerant accumulates cannot be detected. Therefore, in order to prevent the refrigerant from stagnating in the compressor, it is necessary to provide a certain margin, and even when the compressor does not need to be heated, the compressor is heated and wasteful power may be consumed.

  Further, in the refrigeration apparatus described in Patent Document 3, an insulation resistance sensor is installed below the oil supply pipe of the compressor so that two-phase separation between the refrigerant and the refrigeration oil is detected by the insulation resistance. Only when the insulation resistance becomes a predetermined value or less, the heater is energized to heat the refrigerating machine oil, thereby consuming the consumed power. However, there is a problem that an expensive insulation resistance sensor is required to detect the insulation resistance with high accuracy.

  The present invention has been made to solve the above-described problems, and a first object is to use a detector capable of detecting the refrigerant state inside the compressor to heat the compressor. It is possible to obtain a drive control device for an air conditioner compressor capable of suppressing power consumption during operation stop of a compressor by restricting energization or heating a heater only when necessary.

  A second object is to provide a drive control device for a compressor for an air conditioner that can detect the state of the refrigerant inside the compressor with high accuracy even with a low-cost leakage current detector. .

  A compressor drive control device for an air conditioner according to the present invention includes a DC power supply circuit that converts an AC voltage of an AC power supply into a DC voltage, a DC voltage converted by the DC power supply circuit, into an AC voltage, An inverter for driving the compressor motor of the motor, a leakage current detector for detecting a leakage current flowing from the compressor to the ground, and controlling the inverter with a predetermined carrier frequency at predetermined intervals while the compressor is stopped. A carrier frequency control unit for increasing the refrigerant, and a refrigerant stagnation prevention control unit that reads the leakage current detected by the leakage current detector and determines whether the leakage current is less than a predetermined value and heats the inside of the compressor when the leakage current is larger than the predetermined value It is equipped with.

  In the present invention, while the compressor is stopped, the inverter is controlled by a predetermined carrier frequency at predetermined intervals to increase the leakage current between the compressor and the ground, and the leakage current is detected by the leakage current detector. Whether or not it is less than a predetermined value is determined, and the inside of the compressor is heated only when the leakage current is larger than the predetermined value. As a result, even a low-cost leakage current detector can accurately detect the leakage current, reduce the power consumption during the shutdown of the compressor 5, and reliably generate refrigerant accumulation. Can be prevented.

It is a block diagram which shows schematic structure of the drive control apparatus of the compressor for air conditioners which concerns on embodiment. It is a flowchart which shows the operation | movement at the time of the driving | operation stop of the compressor motor in the drive control apparatus of FIG.

FIG. 1 is a block diagram of a schematic configuration showing a drive control device for an air conditioner compressor according to an embodiment of the present invention.
In FIG. 1, the drive control apparatus of the present embodiment includes a rectifier 2 that performs full-wave rectification of an AC voltage of an AC power source 1, a smoothing capacitor 2a that smoothes the output voltage of the rectifier 2, and a DC that is smoothed by the smoothing capacitor 2a. The inverter 3 that converts the voltage into an AC voltage having an arbitrary frequency and drives the compressor motor 4 provided in the compressor 5, the inverter control device 6 that controls the inverter 3, the compressor motor 4, and the compressor 5 And a leakage current detector 9 for detecting a leakage current flowing from the compressor 5 to the ground via the stray capacitance 10 generated between the In the present embodiment, the rectifier 2 and the smoothing capacitor 2a constitute a DC power supply circuit.

  In the inverter control device 6 described above, a refrigerant stagnation prevention control unit 7 and a carrier frequency control unit 8 are provided. The carrier frequency control unit 8 controls the inverter 3 with a predetermined carrier frequency at predetermined intervals and for a predetermined time while the operation of the compressor 5 is stopped, and the stray capacitance 10 between the compressor motor 4 and the compressor 5 is controlled. To increase the leakage current between the compressor 5 and the ground. The predetermined carrier frequency is a frequency for allowing a large current to flow in the winding without driving the compressor motor 4. The refrigerant stagnation prevention control unit 7 reads the leakage current detected by the leakage current detector 9 and determines whether or not it is equal to or less than a predetermined value. When the leakage current is larger than the predetermined value, the liquid refrigerant stagnates in the compressor 5. When the leakage current is equal to or less than a predetermined value, it is determined that the liquid refrigerant has not stagnated in the compressor 5. When the refrigerant stagnation prevention control unit 7 determines that the liquid refrigerant is stagnation in the compressor 5, the refrigerant stagnation prevention control unit 7 controls the inverter 3 so that the winding of the compressor motor 4 is energized. Heat is generated to heat the inside of the compressor 5 and prevent the refrigerant from stagnating.

The leakage current is proportional to the dielectric constant and the carrier frequency as shown in the following equation.
Ir∝ε · f
Ir: Leakage current [A]
ε: dielectric constant f: carrier frequency [Hz]

  The dielectric constant ε of the refrigerant in the air conditioner has a characteristic that the refrigerant is larger in the liquid state than in the gas state. In addition, the leakage current Ir is stipulated to be a reference value or less by the Electrical Appliance and Material Safety Law, and therefore has a very small current value. Therefore, in the present embodiment, the leakage current Ir is increased by increasing the carrier frequency f using the characteristic of the dielectric constant ε. By increasing the carrier frequency f, the change in the leakage current Ir can be read by the low-cost leakage current detector 9 without using an expensive leakage current detector. Instead of this, the value when the refrigerant is gas may be monitored, and a predetermined multiple thereof may be set as the predetermined value.

Next, the operation of the present embodiment will be described with reference to FIG.
FIG. 2 is a flowchart showing the operation of the compressor motor in FIG. 1 when the operation of the compressor motor is stopped.
When detecting that the operation of the compressor 5 is stopped by the inverter control device 6 (step 1), the carrier frequency control unit 8 controls the inverter 3 by increasing the carrier frequency so as to be a predetermined carrier frequency (step 1). 2) Increase the stray capacitance 10 between the compressor motor 4 and the compressor 5. At this time, the leakage current detector 9 detects the leakage current flowing from the compressor 5 to the ground through the stray capacitance 10 (step 3), and the refrigerant stagnation prevention control unit 7 is detected by the leakage current detector 9. Read the leak current. On the other hand, when the leakage current is read by the refrigerant stagnation prevention control unit 7, the carrier frequency control unit 8 decreases the carrier frequency to decrease the leakage current (step 4).

  On the other hand, the refrigerant stagnation prevention control unit 7 determines whether or not the leakage current read from the leakage current detector 9 is equal to or less than a predetermined value (step 5). The refrigerant stagnation prevention control unit 7 ends without performing energization of the compressor motor 4 when the leakage current is less than or equal to a predetermined value (step 7), and notifies the carrier frequency control unit 8 to that effect and lowered it. Stops carrier frequency output. Further, the refrigerant stagnation prevention control unit 7 determines that the liquid refrigerant has accumulated in the compressor 5 when the leakage current value is higher than a predetermined value, so that the energization of the compressor motor 4 is restrained. Inverter 3 is controlled (step 6). Due to this energization, the windings of the compressor motor 4 generate heat, and the compressor 5 is heated. The series of operations described above are repeated at predetermined intervals and for a fixed time, and the compressor 5 is heated only when the liquid refrigerant has accumulated in the compressor 5.

  As described above, in the present embodiment, the inverter 3 is controlled at a predetermined interval and at a predetermined time with a predetermined carrier frequency while the operation of the compressor 5 is stopped. The stray capacitance 10 is increased to increase the leakage current between the compressor 5 and the ground. For this reason, the leakage current detector 9 with low cost can detect the leakage current with high accuracy, and the cost can be reduced. Further, only when the leakage current detected by the leakage current detector 9 is larger than a predetermined value, the coil 5 of the compressor motor 4 is energized to heat the compressor 5. As a result, it is possible to reduce the power consumption during the operation stop of the compressor 5 and reliably prevent the refrigerant from being accumulated.

  In the embodiment, when the leakage current detected by the leakage current detector 9 is larger than the predetermined value, the winding of the compressor motor 4 is energized to heat the compressor 5. In the compressor provided with the heater for heating, the inside of the compressor 5 is heated by energizing the heater for heating without energizing the windings of the compressor motor 4.

  1 AC power source, 2 rectifier, 2a smoothing capacitor, 3 inverter, 4 compressor motor, 5 compressor, 6 inverter control device, 7 refrigerant stagnation prevention control unit, 8 carrier frequency control unit, 9 leakage current detector, 10 floating capacity .

Claims (3)

A DC power supply circuit that converts the AC voltage of the AC power supply into a DC voltage;
An inverter that converts the DC voltage converted by the DC power supply circuit into an AC voltage and drives a compressor motor in the compressor;
A leakage current detector for detecting leakage current flowing from the compressor to the ground;
A carrier frequency control unit that controls the inverter with a predetermined carrier frequency at predetermined intervals while the compressor is stopped, and increases the leakage current;
A refrigerant stagnation prevention control unit that reads the leakage current detected by the leakage current detector, determines whether the leakage current is less than or equal to a predetermined value, and heats the inside of the compressor when the leakage current is larger than the predetermined value. A drive control device for a compressor for an air conditioner.   The refrigerant stagnation prevention control unit controls the inverter to energize the compressor motor when the leakage current detected by the leakage current detector is larger than a predetermined value, thereby heating the inside of the compressor. The drive control apparatus of the compressor for air conditioners of Claim 1.   The refrigerant stagnation prevention control unit heats the inside of the compressor by energizing a heater for heating provided in the compressor when the leakage current detected by the leakage current detector is larger than a predetermined value. Item 2. A drive control device for an air conditioner compressor according to Item 1.

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