JPH0398492A - Air-conditioner controller - Google Patents

Abstract

PURPOSE:To cause no breakdown of a compressor motor by reducing the change rate of an inverter output frequency, when the output frequency of an inverter is lower than a low pass reference value. CONSTITUTION:A change rate decreasing signal output means 11 outputs a change rate decreasing signal to an inverter control means 8, when a detected signal from an output frequency detection means 10 has a frequency lower than f Hz (e.g. 25Hz) and a rise and drop judging means 9 judges the signal to be a drop control. When this change rate decreasing signal is inputted to the inverter control means 8, the control means makes a frequency change rate at the time of performing the frequency control of an inverter 3 slower than that used therefore. Accordingly, the change rate of voltage changing in the manner corresponding to the frequency change becomes slower than the rate used therefore so that there is no possibility of occurrence of the breakdown of a compressor motor 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an air conditioner control device that drives a compressor motor via an inverter.

(Prior Art) Due to the demand for energy conservation, many modern air conditioners employ a system in which a compressor motor is driven by the output of an inverter.

The output of the compressor motor has been controlled by variable control of the output voltage and output frequency of the inverter.

(Problem to be solved by the invention) By the way, the output frequency of the inverter was initially 30}1
Normally, control was carried out in the frequency range above about 3z, but as a result of recent technological improvements to inverters and compressors, devices that can be put into practical use even in the low frequency range below 3011z have been developed. It has been reached.

However, with conventional inverters for controlling air conditioners,
Even in such a low frequency region, the rate of change of the output frequency is kept constant, and the output voltage is changed in response to the change in the output frequency.

Therefore, in the conventional type, if the amount of frequency decrease in the low frequency region is large, the output voltage will also decrease significantly, and there is a risk that the compressor motor driven by this inverter will break down. there were.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an air conditioner control device that is free from the risk of compressor motor breakdown when changing the frequency of an inverter in a low frequency region.

[Structure of the invention]

(Means for Solving the Problems) As a means for solving the above problems, the present invention provides an air conditioner control device that drives and controls a compressor motor using the output of an inverter that is subjected to variable voltage and variable frequency control. Output frequency detection means for detecting the output frequency of the inverter for control, and a change rate of the output frequency of the inverter when the detected value by the output frequency detection means falls below a predetermined low frequency standard value. The present invention is configured to include: a change speed reduction signal output means for outputting a signal for reducing the change speed; and an inverter control means for controlling the output of the inverter based on the signal from the change speed reduction signal output means.

(Function) In the above configuration, the output frequency detection means detects the output frequency of the inverter, and outputs the detection signal to the change rate reduction signal output means. The change speed reduction signal output means outputs a signal for reducing the change speed of the inverter to the inverter control means when the detected value becomes lower than the low frequency reference value. Based on this signal, the inverter control circuit controls the inverter so that when the output frequency of the inverter changes in a low frequency region, the rate of change is slow. Therefore, the output voltage of the inverter does not change drastically in the low frequency range, and breakdown of the compressor motor does not occur.

(Example) Hereinafter, an example of the present invention will be described based on FIGS. 1 and 2.

In FIG. 1, AC power from an AC power source 1 is converted into DC power by a rectifier circuit 2, and then input to an inverter 3. The inverter 3 converts this DC power back into AC power to drive the compressor motor 4. This results in
The compressor 5 is driven, and the refrigerant in the refrigerant circuit is circulated.

The temperature difference detection means 6 detects the temperature difference between the temperature detection value from the room temperature sensor and the set value given from the temperature setting device, and outputs the detection signal to the frequency determination stage 7.

The frequency determination stage 7 determines the output frequency of the inverter 3 to be controlled based on this detection signal, and outputs the signal to the inverter control means 8. The inverter control means 8 is
The inverter 3 is controlled so that the output frequency of the inverter 3 becomes the value determined by the frequency determining means 7.

At this time, the signal output from the frequency determining means 7 is also output to the rise/fall determination means 9. Here, the output frequency of the inverter 3 is determined by the output frequency detection means 1
0, but this detection signal is also input to the rise/fall determination means 9.

Then, the rise/fall determination means 9 compares the frequency value determined by the frequency determination means 7 and the frequency value detected by the output frequency detection means 10, and determines whether the subsequent frequency control will be a rise control. It is determined whether the downward control is to be performed, and the determination signal is output to the change speed reduction signal output means 11. Further, the detection signal from the output frequency detection means 10 is also manually inputted to this change rate reduction signal output means 11.

The change rate reduction signal output means 11 detects that the detection signal from the output frequency detection means 10 is f llz (for example, 2511z
) or less, and when the ascending/descending determining means 9 determines that it is descending control, a change speed reduction signal is output to the inverter controlling means 8.

When the inverter control means 8 receives this change rate reduction signal manually, the inverter control means 8 makes the frequency change rate slower than before when performing frequency control on the inverter 3. Therefore, the rate of change of voltage that changes in response to frequency changes is also
Since the speed becomes slower than before, there is no risk of breakdown of the compressor motor 4.

FIG. 2 is a characteristic diagram showing changes in the output frequency of the inverter 3 controlled in this manner. As shown in this figure, when the output frequency gradually decreases to below the frequency f LIlz (2 511z), which is the low-frequency reference value, the rate of change in frequency decreases. A speed hold section, that is, a constant speed section is provided at a position where the output frequency has become low to a certain extent, and sufficient consideration is given to breakdown. Thereafter, when a request to further reduce the output frequency arises, the output frequency is similarly reduced at a reduced rate of change.

Note that in the above embodiment, the rate of change in frequency is reduced only when the output frequency is decreasing;
In the low frequency region, the frequency change rate may be always reduced regardless of whether it is rising or falling.

That is, it is also possible to have a configuration in which the ascending/descending determining means 9 in FIG. 1 is omitted.

〔Effect of the invention〕

As explained above, according to the present invention, when changing the frequency of the inverter within the low frequency range, the rate of change is reduced, so that the compressor motor does not break down within the low frequency range. can be effectively prevented.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a characteristic diagram for explaining the operation of diagram 'W41. 3... Inverter, 4... Compressor motor, 5
...Compressor, 8...Inverter control means, 1
0: Output frequency detection means, 11: Change speed reduction signal output means.

Claims (1)

[Scope of Claims] An air conditioner control device that drives and controls a compressor motor using the output of an inverter that is subjected to variable voltage and variable frequency control, comprising: output frequency detection means that detects the output frequency of the inverter based on the variable frequency control; Change speed reduction signal output means for outputting a signal for reducing the change speed of the output frequency of the inverter when the detected value by the output frequency detection means falls below a predetermined low-frequency reference value; An air conditioner control device comprising: inverter control means for controlling the output of the inverter based on a signal from a speed reduction signal output means.