JP2013024150A - Air conditioning device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such a problem that a compressor is susceptible to breakage since the compressor is operated in a region in which the compressor cannot be protected by a conventional current limit value, when the compressor of conventional voltage specifications is used in an area adopting high-voltage specifications, in the air conditioning device including an inverter device.SOLUTION: A control device 4 determines whether the air conditioning device is used in a conventional power-supply voltage area, or is used in a high power-supply voltage area, based on a voltage value detected by a direct-current bus bar voltage detection device 10. In the use in the high power-supply voltage area, a current limit value responding to a value of the direct-current bus bar voltage detection device 10 is delivered, and the compressor is protected by the delivered current limit value.

Description

  The present invention relates to an air conditioner that performs variable speed control of a compressor motor by an inverter.

The rotation control of the compressor motor in the air conditioner provided with the conventional inverter device will be described with reference to FIG. In FIG. 6, E [V] on the vertical axis represents the output voltage of the inverter device, and F [rps] on the horizontal axis represents the rotation speed of the compressor motor.
As shown in FIG. 6, the output voltage of the inverter rises according to the rotational speed of the motor. The upper limit value of this output voltage depends on the power supply voltage. This upper limit value is expressed as Em.

  A1 in FIG. 6A represents the transition of the voltage, and the operation is performed in proportion to the power supply voltage until the rotational speed of the motor reaches 0 → f1. When this f1 is reached, the voltage of the inverter becomes the maximum output voltage Em. In a general air conditioner, until the voltage reaches f1, the output voltage of the inverter is positively controlled to become Em in order to increase the voltage utilization rate.

  On the other hand, A2 in FIG. 6 (a) indicates that the inverter output voltage is in a saturated state, and if the rotational speed is f1 or more, the inverter output voltage cannot be increased. I was doing. The current value is limited so that it does not rotate any more when the rotational speed of the motor reaches f2. This is to protect the compressor so that the engine speed does not become excessive.

The above control is expressed by an equation. When the output power of the inverter device is P, the output voltage is V, the motor current is I, and the power factor is COSθ, the power P is obtained by the following equation (1).
P = √3VI · COSθ (1)
From the equation (1), the conventional control is operated by increasing the motor current I in order to increase the rotational speed even when the output voltage V of the inverter device reaches the maximum output voltage Em. (For example, see Patent Document 1)

  On the other hand, the operating range of the compressor can be represented by the relationship between the suction pressure Ps and the discharge pressure Pd (FIG. 6 (a1)). Although the operation range actually draws a complicated trajectory, it is schematically represented by a rectangle in FIG. This rectangle represents the allowable pressure, and the compressor must be operated within this allowable pressure range. If the internal pressure of the compressor exceeds the allowable pressure, the compressor will be damaged. Further, B1 in FIG. 6A1 represents the current limit value for protecting the compressor described above.

  In the conventional operation control, the compressor is protected by setting the current limit value B1 so that the rotational speed of the compressor does not exceed f2.

Japanese Unexamined Patent Publication No. 7-318205

  Since the power supply voltage varies depending on the area where the air conditioner is installed, an air conditioner corresponding to the power supply voltage in each area is required.

In particular, when a conventional compressor is used as it is in an area where the power supply voltage is high, the maximum output voltage Em of the inverter increases, so that the maximum rotation speed f2 of the compressor is reduced as shown in FIG. It will exceed.
When trying to take out the same output power as in the past according to the equation (1), the inverter output voltage increases due to the high power supply voltage, thereby reducing the motor current value. At this time, as shown in FIG. 6 (b1), the current limit value B2 deviates from the operating range, and the current limit is not applied.

  As described above, since the conventional control is controlled by the current value regardless of the power supply voltage (DC bus voltage), if the power supply voltage rises (DC bus voltage rises) like this time, it will be within the operating range of the compressor. It will have an effect.

  The present invention protects the compressor by changing the current limit value of the compressor motor according to the value of the DC bus voltage input to the inverter device while using the compressor in various power supply voltage regions. It is.

A first form of an air conditioner according to the present invention includes a variable capacity compressor motor, an inverter device that rotationally drives the compressor motor, a suction pressure detection device that detects a suction pressure of the compressor, and a compressor A suction temperature detection device for detecting the suction temperature, a discharge pressure detection device for detecting the discharge pressure of the compressor, a discharge temperature detection device for detecting the discharge temperature of the compressor, and a motor current for detecting a current flowing through the compressor motor Detection device, DC bus voltage detection device for detecting DC bus voltage, value obtained by suction pressure detection device, value obtained by suction temperature detection device, value obtained by discharge pressure detection device, discharge temperature detection A control device that generates a control signal for an inverter device using a value obtained by the device, a value obtained by the motor current detection device, and a value obtained by the DC bus voltage detection device.
The control device
While judging whether the power supply voltage is a certain threshold voltage or more based on the voltage value detected by the DC bus voltage detection device,
When the power supply voltage is a high voltage specification, the current limit value corresponding to the DC bus voltage obtained by the DC bus voltage detector is derived and reset based on the relationship between the preset DC bus voltage and the current limit value. The compressor is driven.

  The air conditioner according to the present invention prevents the compressor from being destroyed by setting a current limit value flowing in the compressor motor based on information obtained from various detection devices attached to the compressor. In addition, since the output voltage of the inverter device is high in the high voltage specification, the current value is small if the power is constant, so that heat loss is reduced and the efficiency of the inverter device can be increased.

It is a block diagram which shows the structure of the air conditioning apparatus in Embodiment 1 of this invention. 3 is a graph showing an operation range of the compressor motor according to the first embodiment. FIG. 3 is a diagram illustrating an output voltage (drive signal) of the inverter according to the first embodiment. 4 is a flowchart illustrating an operation of rotation control of the compressor motor in the first embodiment. It is a flowchart explaining the operation | movement of rotation control of the compressor motor in Embodiment 2 of this invention. It is a figure which shows the transition of the inverter output voltage by a power supply voltage, the rotation speed, the relationship between an operating range, and a current limiting value.

Embodiment 1 FIG.
1 is a block diagram showing a configuration of an air-conditioning apparatus according to Embodiment 1 of the present invention. The air conditioner includes a rectifying unit 1 that converts AC power supplied from a commercial power supply 11 into DC power, an inverter device 2 that generates a signal for driving a motor, a compressor motor 3 that rotationally drives a compressor 30, and a control device. 4 and detection devices 5 to 10 for detecting various physical quantities.

  The detection devices 5 to 10 include a suction pressure detection device 5 that detects the suction pressure of the compressor 30, a suction temperature detection device 6 that detects the suction temperature of the compressor 30, and a discharge pressure detection that detects the discharge pressure of the compressor 30. There are a device 7, a discharge temperature detection device 8 that detects the discharge temperature of the compressor 30, a motor current detection device 9 that detects a current flowing through the compressor motor 3, and a DC bus voltage detection device 10 that detects a DC bus voltage. The control device 4 stores the values detected by these detection devices 5 to 10 in a built-in memory, and sets a current limit value based on the detected values.

Next, the rotation control of the compressor motor 3 according to the present invention will be described with reference to FIG.
FIG. 2 shows the operating range of the compressor motor 3. In FIG. 2, the horizontal axis indicates the suction pressure Ps on the low pressure side, and the vertical axis indicates the discharge pressure Pd on the high pressure side. The compressor 30 has an allowable pressure. If the internal pressure of the compressor 30 exceeds the allowable pressure, the compressor 30 is damaged. In FIG. 2A, A is the allowable pressure of the discharge pressure Pd, and B is the allowable pressure of the suction pressure Ps. E is a lower limit value of the discharge pressure Pd, and F is a lower limit value of the suction pressure Ps. The slanted line C represents the operating current value necessary for operation at that pressure.

  The operation of the compressor 30 performs an operation of rotating the compressor motor 3 to compress the sucked refrigerant and discharging it when a certain pressure is reached. When the suction pressure Ps is low and the discharge pressure Pd is high as in the area D1 in FIG. 2A, the refrigerant pressure sucked is low, so the amount of work of the compressor motor for increasing the discharge pressure increases, and heat is generated. Since the generated heat may exceed the allowable temperature of the compressor 30, the operating range is severe.

  When both the suction pressure Ps and the discharge pressure Pd are high as in the area D2 of FIG. 2A, the pressure of the sucked refrigerant is high from the beginning, and reaches the allowable pressure of the compressor 30 at the beginning of the compression process. The driving range is severe. That is, it is in an overload region. Therefore, the operating conditions become severe in the direction of high pressure on both the high pressure side and the low pressure side.

Here, FIG. 2 shows a detailed view of the pressure condition. C in FIG. 2A represents a motor current value, and the same current value is represented on the same line. As both Ps and Pd rise (as they go to the upper right), the operation is performed at a higher load, and the motor torque is required. Accordingly, the current value increases accordingly. A state where Ps and Pd are high at this time is called an overload state.
In the figure, C1 represents a current limit value, and the current value that reaches the rotational speed of f2 in FIG. 6A is C1. The operation is performed while protecting the compressor by controlling so as not to exceed the range drawn by the current value C1, Ps, and Pd.

In FIG. 2B, C1 represents a current limit value in an overload state in a certain state, C1 = G [A], C2 is a current value required in this overload state, and C2 = H [ A]. If the current state is just before the current limit is applied, C1 and C2 have the same current value (G = H). In an operation in a region where the power supply voltage is high, H [A] is small, but the current limit value C1 remains G [A] and therefore G> H. Therefore, when the power supply voltage is high, the current limit value is shifted to C3 in FIG. As a result, the current limit value deviates from the operating range of the compressor, and thus it cannot be protected by the current value. In this case, the engine continues to rotate in the overload region before the operation is restricted, and the compressor is destroyed.

During the operation of the air conditioner, a current limit value corresponding to the DC bus voltage detected by the DC bus voltage detection device 10 is derived from a preset “DC bus voltage and current limit value” table and reset.
This table is set using a relationship in which the DC bus voltage and the current value are inversely proportional as in Expression (1).

  Thus, the compressor 30 which is generated when the current control value is appropriately changed according to the value of the DC bus voltage detection device 10 and is operated by rotation control of the conventional compressor motor in an area where the power supply voltage is high. Can be prevented.

  Next, the control operation of the compressor 30 will be described using the flowchart of FIG. The control device 4 first detects the DC bus voltage using the DC bus voltage detection device 10 (step S1). The DC bus voltage is obtained by rectifying the AC voltage of the commercial power supply 11, and when the commercial bus 11 has a bus voltage A [V] at a certain value as a threshold and the DC bus voltage exceeds the threshold, the control device 4 Then, it is determined that the air conditioner is used in an area where the power supply voltage is high (step S2).

  When the value of the DC bus voltage is A [V] or more (Yes in step S2), the process proceeds to step S3, and the control device 4 uses a table of current limit values corresponding to the preset bus voltage, A current limit value is derived from the detected value of the DC bus voltage (step S3). Then, the current limit value is newly set and operation is performed (step S5). On the other hand, when the value of the DC bus voltage is less than A [V] and it is determined to be used in the conventional power supply voltage region (No in step S2), the control device 4 uses the conventional variable speed described with reference to FIG. Control is performed (step S4).

  Thus, the compressor 30 can always be operated in an appropriate pressure range by newly setting the current limit value according to the value detected by the DC bus voltage detection device 10.

Embodiment 2. FIG.
In the present embodiment, a method of changing the current value by changing the pulse width of the inverter device 2 and increasing the efficiency of the inverter will be described.
This will be described with reference to FIG. 6 and FIG. FIG. 3 shows the waveform of the compressor motor drive signal generated by the inverter device 2.

A solid line in the compressor motor drive signal shown in FIG. 3A indicates a drive signal in the case of the conventional voltage specification. In FIG. 6, in the case of the conventional voltage specification, the output voltage of the compressor motor 3 cannot output a voltage higher than Em because the power supply voltage is limited. When the operating environment changes to the high voltage specification, the voltage of the drive signal increases as shown by the broken line as the power supply voltage increases. As a result, the inverter device 2 outputs a voltage exceeding the voltage Em in FIG.

  Since the current value output from the inverter device 2 is proportional to the area of the pulse waveform, in the high voltage specification, the restriction on the output voltage is released, the current value flowing through the compressor motor 3 increases, and the torque of the compressor motor 3 increases. Increases, and in the worst case, the compressor 30 is destroyed.

  In order to avoid the above situation, the current value may be lowered. Therefore, as shown in FIG. 3B, the pulse output area is reduced by reducing the pulse width by the amount corresponding to the increase in the output voltage of the inverter. To decrease the current value.

  Further, in the conventional control, since the operation is performed with a constant current value regardless of the DC bus voltage (power supply voltage) (for example, even if there is an error (200V ± 10%) in the power supply voltage), the current is limited. In this embodiment, the inverter efficiency can be increased by adjusting the pulse width and performing control so as to operate at an optimum current value.

In order to calculate the optimum current value, the value of the compressor power Pm corresponding to the acquired command frequency of the inverter device 2 is obtained using a table indicating the relationship between the preset frequency and the compressor power Pm. To derive. The current at that time is obtained from the equation (1) by the following equation, and the obtained value becomes the optimum current value.
I = Pm / (√3 (Vdc / α) COSθ) (2)
Vdc represents a DC bus voltage, α represents a coefficient (≈√2) derived from an actual test, and Vdc / α represents an output voltage of the inverter.

This embodiment will be described with reference to the flowchart of FIG. As in the first embodiment, first, the DC bus voltage detection device 10 is used to detect the DC bus voltage (step S1), and the obtained DC bus voltage value is used to determine whether the power supply voltage region is higher than the conventional one (step S2). If it is not in the high power supply voltage region, conventional variable speed control is performed (step 4).
When it is determined that the air conditioner is used in a high power supply voltage region (Yes in step S2), the command frequency value of the inverter device 2 is acquired (step S3). Based on the table showing the relationship between the frequency and the power Pm of the compressor, the value of Pm corresponding to the acquired command frequency value is derived. (Step S5)
Thereafter, the optimum current value I is obtained from the value obtained by Pm and the DC bus voltage detector 10 using the equation (2) (step S6).
The pulse width of the inverter output voltage is adjusted so that the optimum current value I is obtained (step S7).

  As described above, in the present embodiment, the power Pm corresponding to the value of the command frequency acquired by the inverter device 2 is derived from the relationship between the preset frequency and the power Pm of the compressor 30, and the DC bus voltage detection device By calculating with the value of 10, the optimum current value is calculated, and the pulse width of the output voltage of the inverter device 2 is adjusted so as to be the current value. As a result, the motor can be operated at an optimum current value, so that the efficiency of the inverter can be increased.

DESCRIPTION OF SYMBOLS 1 Rectification part 2 Inverter apparatus 3 Compressor motor 4 Control apparatus 5 Suction pressure detection apparatus 6 Suction temperature detection apparatus 7 Discharge pressure detection apparatus 8 Discharge temperature detection apparatus 9 Motor current detection apparatus 10 DC bus voltage detection apparatus 11 Commercial power supply 30 Compressor

Claims (2)

A variable capacity compressor motor;
An inverter device for rotationally driving the compressor motor;
A suction pressure detection device for detecting the suction pressure of the compressor;
An intake temperature detecting device for detecting an intake temperature of the compressor;
A discharge pressure detecting device for detecting a discharge pressure of the compressor;
A discharge temperature detecting device for detecting a discharge temperature of the compressor;
A frequency detection device for detecting the frequency of the compressor motor;
A motor current detection device for detecting a current flowing in the compressor motor;
A DC bus voltage detecting device for detecting a DC bus voltage;
The value obtained by the suction pressure detection device, the value obtained by the suction temperature detection device, the value obtained by the discharge pressure detection device, the value obtained by the discharge temperature detection device, and the motor current detection device A control device that generates a control signal of the inverter device using the obtained value, the value obtained by the DC bus voltage detection device, and the value obtained by the frequency detection device,
The controller is
Based on the voltage value detected by the DC bus voltage detector, it is determined whether to use in a region where the power supply voltage is high or in a conventional region,
When used in an area where the power supply voltage is high, a current limit value corresponding to the DC bus voltage obtained by the DC bus voltage detection device is derived based on a preset relationship between the DC bus voltage and the current limit value. An air conditioner for operating the compressor. A variable capacity compressor motor;
An inverter device for rotationally driving the compressor motor;
A suction pressure detection device for detecting the suction pressure of the compressor;
An intake temperature detecting device for detecting an intake temperature of the compressor;
A discharge pressure detecting device for detecting a discharge pressure of the compressor;
A discharge temperature detecting device for detecting a discharge temperature of the compressor;
A frequency detection device for detecting the frequency of the compressor motor;
A motor current detection device for detecting a current flowing in the compressor motor;
A DC bus voltage detecting device for detecting a DC bus voltage;
The value obtained by the suction pressure detection device, the value obtained by the suction temperature detection device, the value obtained by the discharge pressure detection device, the value obtained by the discharge temperature detection device, and the motor current detection device A control device that generates a control signal of the inverter device using the obtained value, the value obtained by the DC bus voltage detection device, and the value obtained by the frequency detection device,
The controller is
Based on the voltage value detected by the DC bus voltage detector, it is determined whether to use in a region where the power supply voltage is high or in a conventional region,
When used in a region where the power supply voltage is high, obtain the command frequency of the inverter device, and based on the relationship between the preset frequency and the compressor power, derive the value of the compressor power according to the command frequency, The pulse width of the output voltage of the inverter device is adjusted so that the optimum current value calculated by the value of the compressor power and the value detected by the DC bus voltage detection device is output, and the optimum current value An air conditioner that operates the compressor.

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