JPH03293997A - Air-conditioning machine - Google Patents

Abstract

PURPOSE:To smooth the operation of an air-conditioning machine at a low frequency by a method wherein a load in accordance with a power supply frequency applied on a compressor is detected and an impressing voltage is controlled in accordance with the detected value of the load, in the air- conditioning machine having the compressor variable in the rotating speed thereof. CONSTITUTION:An air-conditioning machine is constituted of an indoor unit, an outdoor unit and the like. The outdoor unit is provided with a compressor controlled by a frequency changer. In the control of the compressor, a reference current value Im=f1(Hz) is operated from a power supply frequency Hz at first and, then, the operating current value I of the compressor is detected. When Im>I, the operation is continued without any change. When Im< I, control is shifted into blocks 15, 16 simultaneously and the lowest value of the power supply frequency Hz and the impressing voltage V are changed. In this case, a new lowest power supply frequency HzminN is determined from the power supply frequency Hz and the operating current value I. Further, the increasing amount Vo of the impressing voltage V is obtained to correct the impressing voltage V.

Description

[Detailed description of the invention] (b) Industrial application fields The present invention relates to a variable capacity air conditioner.

(b) Conventional technology In general, air conditioners equipped with a compressor whose rotational speed can be changed are shown in Japanese Utility Model Application Laid-open No. 187599/1983, in which the compressor (the motor for driving the compressor) is The voltage/r is kept constant depending on the power supply frequency.

(c) Problems to be solved by the invention When the power frequency applied to the drive motor of the compressor becomes relatively small (during low frequency operation), the voltage (applied voltage) to this drive motor also becomes small. . This may cause the frequency waveform to be disturbed during low frequency operation, making it difficult for the compressor to operate smoothly.

An object of the present invention is to enable smooth operation of a compressor at low frequencies.

(d) Means for Solving the Problems In order to achieve this object, the present invention includes a detection means for detecting the load applied to the compressor according to the power frequency, and a detection means for detecting the load applied to the compressor according to the power frequency. A voltage control means for controlling the applied voltage is provided.

(*) The load applied to the compressor according to the power supply frequency is detected, and the voltage applied to the compressor is controlled according to the detected value.

(F) Embodiment In FIG. 2, numeral 1 denotes a separate air conditioner, which is composed of an indoor unit A, an outdoor unit B, and an inter-unit pipe 2 that connects both units. The indoor unit A has a built-in indoor heat exchanger 3 that acts as an evaporator during cooling operation and as a condenser during heating operation.

On the other hand, the outdoor unit B includes a compressor 4, a four-way valve 5, an outdoor heat exchanger 6 that acts as a condenser during cooling operation and an evaporator during heating operation, and a pressure reducing device 7. For example, when operating the air conditioner, the power frequency is set to 30Hz.
The rotation speed of the compressor 4 is changed using the input from the frequency converter 8, which can be varied from ~80Hz, and the cooling capacity is increased to 1.2/h.
It can be varied to ~2.7 per hour. here 3
0Hz is the lowest frequency at which the compressor 4 can operate. or,
During heating operation, the heating capacity is similarly varied by input from the frequency converter 8.

During the cooling operation, the four-way valve 5 is set to the solid line to allow the refrigerant to flow as shown by the solid line arrow, while during the heating operation, the four-way valve 5 is set to the broken line to allow the refrigerant to flow as shown by the broken line.

This compressor 4 is equipped with a current detector that detects the current flowing through the compressor 4, and the first
The operation of the compressor 4 is controlled based on the flowchart shown in the figure.

In other words, compression I! during cooling operation! 4 is operated, and the power frequency (
Hz). Then, a reference current value Im=r, (1(z)) corresponding to this power supply frequency is calculated. Here, the reference current value Im is a function f, (Hz) of the power supply frequency Hz.
(See Figure 3).

On the other hand, a current detector provided in the compressor 4 detects the operating current value I of the compressor 4 (blocks 10 to 13).

Then, in block 14, the reference current value Is and the operating current value ■ are compared, and if the reference current value 1m is larger than the operating current value I (for example, the state of point A in FIG. 3), the process goes to block 11. return. Here, the reference current value Km is the operating current value■
The fact that the load is greater than the reference value means that the load on the compressor 4 is smaller than the reference value. Specifically, the outside temperature is about 26°C and the air conditioner temperature setting is 25°C.
°C, the indoor temperature is approaching 25 °C, the outside temperature is relatively low, and the load on the compressor 4 is small.
This means that the compressor 4 continues to operate at the current power frequency.

On the other hand, the standard 'W! , when the flow value 1 m is smaller than the flow value I during operation (for example, the state at point B in Fig. 3), block 15,
16 at the same time, the power supply frequency H given to the compressor 4
Change the minimum value of 2 and the applied voltage. Here, the fact that the reference current value In is smaller than the operating current value I means that
This means that the load on the compressor 4 is greater than the reference value.

Specifically, this is a case where the outside air temperature is 30°C, the air conditioner set temperature is 25°C, and the indoor temperature is approaching this 25°C. The load on block 4 is large, thus block 11
- Block 14 detects the load applied to the compressor 4 according to the power frequency, and blocks 11 to 1
4 serves as means for detecting the load applied to the compressor 4.

When the load is large, block 15 is used as described above.
, 17.18 to increase the source frequency. That is, the frequency increase amount f'4 (Hz, I) is determined by the magnitude of the power supply frequency Hz given to the compressor 4 and the operating current value I of this compressor 4 (here,
This amount of increase is usually about 5 Hz), and the current minimum power frequency Hzmirx of the compressor 4 and the amount of increase f'
4 (Hz, I) as the new minimum power supply frequency H
Let zminN. Next, in block 17, this minimum power supply frequency Hzmin N is compared with the frequency (Hz) currently given to the compressor 4, and when the frequency (Hz) is smaller than the minimum frequency (Hzin N ), In the opposite case, that is, when the frequency (Hz) currently applied to the compressor 4 is greater than the lowest frequency (HzminN), the frequency currently applied to the compressor 4 The current frequency is maintained as it is and the process returns to block 11. In this way, when the reference current value I■ is smaller than the operating 'It flow value I (the load on the compressor is greater than the reference value), this compression tj1
The frequency given to 4 is increased from the lowest frequency (
HzminN), the compressor ja4 is operated to perform an operation commensurate with the load placed on the compressor 4.

Therefore, when the indoor temperature and the set temperature become small due to the cooling operation of the air conditioner while the outside temperature is high (when the load on the compressor 4 is large), the air conditioner is forced to operate in blocks 15, 17, and 18. The frequency increase control means increases the lowest frequency given to the compressor 4 to increase the rotational speed of the compressor 4. Thereby, the operating time of the compressor 4 at the lowest operable frequency, which has poor operating efficiency and large vibrations, can be minimized.

Block 16.1 at the same time as changing the lowest frequency such as
The voltage control means 9, 20, and 21 also change the voltage applied to the compression ja4. That is, when the reference current value Is is smaller than the operating current value I, as at point B in FIG. , First, in block 16, the amount of increase in the applied voltage V, -r is determined in accordance with the operating frequency and operating flow value given to the compressor.

(Hz,!> is determined. Also, in block 19, the maximum increase amount Vmax=f' n (Hz) of the applied voltage based on the operating frequency (Hz) given to this compressor 4 is determined. Then, block 20 Then, the amount of increase in this applied voltage V,
and the maximum increase amount Vmax of the applied voltage. Here, when the increase amount V of the applied voltage is smaller than the maximum increase amount of the applied voltage, the increase amount V. is added to the current applied voltage value V of the compressor 4, and that value is applied to the compressor 4. Also, the amount of increase in applied voltage V.

When V is larger than the maximum increase in the applied voltage, the process returns to block 11 without adding this increase V.

That is, the power supply frequency Hz applied to the compressor 4 changes, the current value l flowing through the compressor 4 changes accordingly, and the voltage applied to the compression fa4 can be changed in accordance with this change. be. Thereby, the current value I flowing through the compressor 4 and the voltage V applied to the compressor 4 can be set to optimal values according to the operation of the compressor 4.

Furthermore, when the air conditioner starts operating, as shown by curve 30 in Fig. 3, if the current value temporarily becomes higher than the power supply frequency 31, the current value f is applied based on this increased current value f. Voltage increases. Furthermore, in general, when the power supply frequency is low (range 32 shown with diagonal lines in Figure 3), the waveform of the power supply frequency may be disturbed and the compressor may not operate smoothly. By increasing the applied voltage as shown at 33, the tf! I.

You can remove the frequency.

(G) Effects of the Invention As described above, the present invention detects the load applied to the compressor according to the power frequency and controls the voltage applied to the compressor according to this detected value. In particular, the compressor can be operated smoothly at low frequencies.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention. Fig. 1 is a flowchart showing the operation of the air conditioner, Fig. 2 is a refrigerant circuit of this air conditioner, and Fig. 3 is a diagram showing the frequency and current of this air conditioner. FIG. 4... Compressor, 8... Frequency converter, 11,
12.13.14...Detection means (block), 16
．． 19,20.21... Voltage control means (block).

Claims (1)

[Claims] 1) In an air conditioner equipped with a frequency converter that supplies an AC output of an applied voltage/power supply frequency, and a compressor whose rotational speed can be changed in response to the AC output from the frequency converter, An air conditioner comprising: a detection means for detecting a load according to a power supply frequency; and a voltage control means for controlling a voltage applied to the compressor according to an output from the detection means.