JPS61223446A - Air-conditioning machine - Google Patents

Abstract

PURPOSE:To permit stabilized and highly efficient operation by a method wherein the load condition and the electric source voltage fluctuation of the air- conditioning machine are detected and the optimum V/f pattern is selected in accordance with these conditions to control the motor of a compressor. CONSTITUTION:An inverter main circuit unit 1 sends D.C. current, obtained by a filter unit 5, into an inverter unit 7 while the compressor motor 8 is driven by the output of the inverter unit. An outdoor side inverter control unit 9 introduces current IDC into a current selecting unit 10 to select a zone in accordance with the detected current. A memory unit 11, receiving a selection signal, memorizes three different V/f patterns A, B, C, corresponding to three zones A, B, C and selects the V/f pattern in accordance with the selection signal while the memory unit 11 reads a voltage V corresponding to a frequency (f) specified by a frequency commanding unit 13 by receiving the command of an indoor side frequency commanding unit 12 and sends it to a driving unit 14 together with the specified frequency (f). The signals V, (f) from the driving unit 14 become the output of the inverter control unit 9 and control the inverter unit 7 of the inverter main circuit unit 1.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an air conditioner having a compressor that is driven at variable speed by an inverter device, and in particular, the present invention relates to an air conditioner that has a compressor that is driven at variable speed by an inverter device. This invention relates to a device that can always operate with high efficiency.

[Technical Background of the Invention] Conventionally, the voltage versus frequency (V/l) pattern of an inverter device that drives the compressor of an air conditioner at variable speed is one as shown in Fig. 14, and the load of the air conditioner is Despite fluctuations in the state and power supply voltage, the motor of the compressor was driven at a constant V/f ratio based on the single V/f pattern set according to the normal load.

] According to the above-mentioned conventional V/f constant control, there is only one V/f pattern, so there are the following problems.

■ It is difficult to drive a highly efficient compressor.

That is, as shown in FIG. 13, the inverter direct current Iryc and the inverter direct current 8! correspond to load conditions or power supply voltage fluctuations. When the voltage Voc changes, the motor efficiency of the compressor, which is driven based on a predetermined V/f ratio, changes greatly, but since the load condition of the air W4 generator constantly changes, it is possible to drive the compressor with high efficiency. Even if you try to get one V
/l pattern alone cannot handle this problem.

■ Compressor operation becomes unstable due to load fluctuations.

In other words, if the load suddenly becomes heavy, the motor may break down or excessive current flows, and if the load suddenly becomes light, excessive excitation current flows to the motor, causing the compressor to overheat. .

[Objective of the Invention] The present invention has been made in consideration of the above circumstances, and provides an air conditioner that can operate stably and with high efficiency despite fluctuations in the air conditioner's load condition and power supply voltage. It is intended for this purpose.

[Summary of the Invention] In order to achieve the above object, the present invention includes a detection means for detecting the quantity of electricity within an inverter device, and a plurality of pieces of electricity stored in a storage means according to the quantity of electricity detected by the detection means. It is equipped with a selection means for selecting one V/f pattern from among different V/f patterns, detects the load condition of the air conditioner and power supply voltage fluctuation, and selects the optimum V/f according to this condition.
The compressor motor is controlled by selecting a pattern.

E Practical IIM Examples of the Invention] Examples of the present invention will be described below with reference to FIGS. 1 to 12.

FIG. 1 shows a first embodiment of an inverter device included in an air conditioner according to the present invention. As shown in the figure, the inverter main circuit section 1 rectifies a single-phase or three-phase power supply 2 in a rectifier section 3, and then
A filter section 5 mainly including a smoothing capacitor 4 smoothes the DC current to obtain a DC current, and the obtained DC current is sent to a current sensor 6.
The signal is sent to the inverter section 7 via the inverter section, and the compression am motor 8 is driven by the output of this inverter section.

In addition, the inverter control section 9 on the outdoor side is configured to control I'l! as shown in FIG. 4, for example. ! 5! IDc in three zones A.

The 1IIi style IDC detected by the inverter main circuit section 1 is led to the current selection section 10, which is configured to distribute the current to B and C, and selects one of the zones according to this detected current. A storage unit 11 receiving the selection signal from the selection unit 10 stores the three zones A and B as shown in FIG.
, three different V/f patterns A, B, C corresponding to C.
is stored, and the storage unit 11 selects one of the V/f patterns according to the selection signal, and
In response to the command from the indoor frequency command unit 12, the frequency command unit 1
3 reads the voltage V corresponding to the specified frequency from the selected V/f pattern and sends it to the drive section 14 along with the specified frequency.
, f signals are output from the inverter control section 9, and the inverter section 7 of the inverter main circuit section 1 is controlled thereby.

Incidentally, when determining the A, B, and C zones by the selection section 10 forming the inverter control section 9, the time opening is also taken into account, and the selection is given a delay and hysteresis for stable operation.

Now, in the above-mentioned IIRgc, under normal load, the compressor motor 8 is driven at a <V/f ratio based on the same V/l pattern B as in the past, in which the compressor motor 8 is operated at maximum efficiency under this load. However, if the load condition changes, the device will be driven by a V/f pattern different from pattern B.

That is, as the load condition becomes heavier, the input current of the inverter section 7 increases accordingly, and when this input current detected by the current sensor 6 exceeds ID2 shown in FIG. 4, the selection section 10 switches the A zone. Then, the V/f pattern A with the higher voltage level is selected from the three patterns in the storage section 11. Therefore, as shown in the compressor motor efficiency characteristic diagram of FIG. 2, the compressor motor 8 is driven at a v/f ratio based on this V/l pattern A, which peaks at high loads.

Furthermore, when the load condition becomes lighter, the selection unit 10 determines the C zone and the compressor motor 8 is driven at a <V/f ratio based on the ■/f pattern C that obtains the efficiency peak at low load. .

In this way, according to the above embodiment, the high efficiency portions of each V/f pattern are combined to drive the compressor motor, so that a decrease in motor efficiency due to changes in the load condition of the air conditioner can be avoided. 1. Highly efficient compressor drive can be maintained at all times.

In addition, since a feedback system is configured even when the load changes suddenly, it is possible to effectively prevent motor breakdown, overcurrent generation, or overheating of the motor A winding due to generation of excessive excitation current. This allows stable compressor operation at all times.

Additionally, the current sensor can be used in conjunction with existing overcurrent sensors.

Note that if the V/f pattern is increased, the input current of the inverter section 7 will decrease accordingly.

However, since the zone selection section 10 has hysteresis etc., there is no need to worry about this.

Next, a second embodiment of the inverter device included in the air conditioner of the present invention shown in FIG. 5 will be described.

The difference from the inverter device shown in FIG.
The voltage sensor 15 detects the voltage, and the selection section selects the voltage VDC into three zones A as shown in FIG.
, 8.0, and select one zone from those zones according to the voltage VOC detected in the inverter main circuit section.

This is the point that the voltage selection section 16 is used.

Note that since the voltage across the smoothing capacitor 4 has instantaneous fluctuations, the selection section 16 is provided with a delay or hysteresis.

Therefore, when the detected voltage is high, V/f pattern C is selected and the voltage level of the V/f pattern is shifted down, and conversely, when the detected voltage is low, V/f pattern 8 is selected and the V/I pattern is shifted down. The voltage level of is shifted up,
The electric motor 8 is thereby driven.

By the way, in V/f pattern control that does not detect the power supply voltage of the air conditioner, even at the same frequency, when the voltage is high, the inverter section 7 outputs a high voltage, and when the voltage is low, the inverter unit 7 outputs a low voltage. tended to be greatly influenced by fluctuations in Also, when the load on the air conditioner becomes heavy, the voltage drop across the smoothing capacitor 4 cannot be ignored (
The effect of this voltage drop on the output voltage was also large.

However, in this embodiment, the power supply voltage and load condition are read by detecting the voltage across the smoothing capacitor 4.
Since the compressor motor is driven according to the optimum V/f pattern, the influence of changes in the power supply voltage and load on the output voltage can be minimized, and stable and highly efficient operation can always be performed.

Fig. 7 shows a third embodiment of the inverter device included in the air conditioner of the present invention.The basic principle is the same as the embodiments shown in Figs. 1 and 5, but even a single V/f pattern The same control can be achieved by having a plurality of V/f patterns.

That is, the difference from the embodiments shown in FIGS. 1 and 5 is that the storage unit 1
7 only remembers one V/f pattern,
Moreover, the input section into which the finger joint wave number f from the frequency command section 13 is input has an adder section 18 that adds a correction frequency r', and a selection section that outputs this correction frequency t' is configured to select either the detected current or the detected voltage ( In the illustrated example, the detected current IDC) is divided into two zones l-1 and 1, as shown in FIG.
In zone 1 where the current is low, f' = O, but at the end of zone 1 where the current is high, the current zone selection section 19 is configured to set f' to 0.

Therefore, if the detection current is larger than IDI, the 8th
As shown in the figure, a correction frequency f' is added to f from the frequency command unit 13, and a voltage v2 corresponding to this f+r'
is obtained from the V/f pattern B, and this 2 is sent to the drive section 14. However, the frequency "from the frequency command from indoors and outdoors is sent as is to the drive section 14, so even if the frequency is the same, the voltage shift V!→V2 This is equivalent to having two different V/f patterns in the storage unit 17.If the number of detected currents is three or more, of course there will be as many V/f patterns as there are. In particular, it becomes.

According to this, there is an advantage that the storage capacity of the storage section 17 is small because it is sufficient to store one V/l pattern.

10 to 12 show the filter section 5 constituting the main circuit.
An example of a discharge circuit required for the smoothing capacitor 4 is shown.

That is, FIG. 10 shows a first embodiment of the discharge circuit, in which a three-phase magnetic contactor 20 interposed between a three-phase power supply 2 and a rectifier 3 constituting the main circuit section is connected to the power supply line. It has contacts 21 corresponding to 5g1I. A discharge resistor 22 is connected in parallel to the smoothing capacitor 4 via the contact 21. The discharge resistor 22 is set to a low resistance value in order to quickly discharge the charges accumulated in the smoothing capacitor 4.

Therefore, when the inverter is operating, the magnetic contactor 20 is ONL, but the B contact 21 is OFF.
In the FF state, the discharge resistor 22 acts as an oven for the smoothing capacitor 4.

Also, when the inverter is stopped, rRfj
1 Contactor 20 is OFF,! :However, the B contact 21 is ON.
The discharge resistor 22 is connected in parallel to the smoothing capacitor 4, and the smoothing capacitor 4 is connected to the smoothing capacitor 4 through the discharge resistor 22.
The accumulated charge is discharged.

By the way, the smoothing capacitor of a normal inverter device is naturally discharged by a switching power supply used as a control power supply, and no discharge resistance is provided, so if the switching power supply breaks down, the energy of the capacitor cannot be consumed. Since the charged state is maintained as it is, it becomes extremely dangerous during repairs.

Furthermore, in the case where a discharge resistor is simply connected in parallel to a smoothing capacitor, the discharge resistance value is increased in order to reduce the leakage current caused by the smoothing capacitor, which improves the discharge time and causes power loss due to the discharge resistor during operation.

However, in this embodiment, since the energy of the smoothing capacitor 4 is released only when the inverter is stopped, both the resistance value and the capacitance of the resistor used can be reduced. Since the small resistance allows for reliable discharge in a short period of time, it is extremely safe even in the case of repairs. Furthermore, since no discharge occurs during operation, there is no power consumption loss, and the existing circuit configuration can be used as is.

11 and 12 show second and third embodiments of the discharge circuit, in which 8 contacts 21 of a protection switch for suppressing rush current are interposed between the rectifier 3 and the smoothing capacitor 4. What is shown in Figure 11? !
The contactor 23 is different from the one shown in FIG. 12 in that it is a relay 24. Both have the same effect as the embodiment shown in Fig. @10.

[Effects of the Invention] In summary, the present invention exhibits the following excellent effects.

(1) By detecting the load or electric voltage of the air conditioner, selecting the optimum V/f pattern according to this detection layer, and controlling the inverter device using this optimum V/f pattern, The compressor can always be driven with high efficiency despite load fluctuations and power supply voltage fluctuations.

(2) The control system that controls the inverter device according to the detected amount constitutes a stable feedback system despite fluctuations in the power supply voltage, so instability does not occur and the compressor always operates in a stable manner. be able to.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a first embodiment of an inverter device for an air conditioner according to the present invention, FIG. 2 is a motor efficiency characteristic diagram of a compressor obtained by the inverter device shown in FIG. 1, and FIG. FIG. 4 is a diagram showing a plurality of different V/f patterns not shown in FIG. 1 and stored in the storage unit of the inverter device;
5 is a block diagram showing a second embodiment of the inverter device for an air conditioner according to the present invention, and FIG.
A diagram explaining the function of the selection section of the inverter device shown in the diagram,
FIG. 7 is a block diagram showing a third embodiment of the inverter device for an air conditioner according to the present invention, and FIG. 8 is a block diagram showing one V/f stored in the storage section of the inverter device shown in FIG.
A diagram explaining the pattern and the function of the storage unit based on the pattern,
FIG. 9 is a diagram explaining the function of the selection section of the inverter device shown in FIG. 7, and FIGS. 10 to 12 are discharge circuits of the smoothing capacitor of the inverter device shown in FIGS. 1, 5, and 7. FIG. 13 is a circuit configuration diagram showing the first to third embodiments of the invention, FIG. 13 is a compressor motor efficiency characteristic obtained by a conventional inverter device, and FIG. 14 is a diagram showing one V It is a figure which shows the /f pattern. In the figure, 1 and 9 are the inverter main circuit section and inverter control section that constitute the inverter device, 2 is the power supply for the air peace machine, 3 is the rectifier section, 4 is the smoothing capacitor, 5 is the filter section, and 6 is the detection means. 8 is a Ti motor of the compressor, 10.16° 19 is a selection section, 11.17 is a storage section, 14 is a drive section, 15 is a voltage sensor as a detection means, 20 is 'R11 as a power switch. contactor,
21 is a B contact, 22 is a discharge resistor, and 23 is ffi! as a protection switch for inrush current control. 1 contactor and 24 are also relays. Patent applicant Toshiba Corporation Patent attorney
Nobuo Kinutani No. 39 Figure 14 Figure 5 Figure 6 Figure 7E 81 Figure 9 Figure 10 Figure 11 Figure 12

Claims (4)

[Claims] (1) In an air conditioner having a compressor that is variably driven by an inverter device, a plurality of different Vs are prepared to change the motor efficiency characteristics of the compressor according to the load or power supply voltage of the air conditioner. a storage means for storing the /f pattern; a detection means for detecting the load or power supply voltage of the air conditioner; an air conditioner comprising: a selection means for selecting a V/f pattern; and a drive means for causing the inverter device to output a V/f ratio output of the V/f pattern selected by the selection means. . (2) The air conditioner according to claim 1, wherein the detection means for detecting the load of the air conditioner is a current sensor that detects the input current of an inverter section constituting the inverter device. . (3) Claim 1, characterized in that the detection means for detecting the load and power supply voltage of the air conditioner is a voltage sensor that detects the voltage across a smoothing capacitor that constitutes the filter section of the inverter device. Air conditioner as described in section. (4) The storage means stores one V/f pattern, and the voltage with respect to the frequency of this V/f pattern is shifted and corrected in stages according to the detected amount to equivalently store a plurality of V/f patterns. The air conditioner according to any one of claims 1 to 3, characterized in that the air conditioner has a /f pattern.