JP2582904B2 - Air conditioner control device - Google Patents

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) Recently, air conditioners of a type that drives a compressor motor by an output of an inverter are often used due to a demand for energy saving.

The output of the compressor motor is controlled by variably controlling the output voltage and output frequency of the inverter.

(Problems to be Solved by the Invention) By the way, the output frequency of the inverter was initially usually controlled in a frequency range of about 30 Hz or more,
As a result of recent technical improvements to inverters and compressors,
Those that can withstand practical use even in the low frequency range of 30 Hz or less have been developed.

However, in the conventional inverter for controlling the air conditioner, even in such a low frequency region, the output frequency change rate is kept constant, and the output voltage is changed in accordance with the change in the output frequency. .

For this reason, in the conventional motor, when the amount of frequency decrease displacement in the low frequency region is large, the output voltage also decreases greatly, and the compressor motor driven by this inverter may 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 which does not cause a breakdown of a compressor motor when changing the frequency of an inverter in a low frequency range.

[Configuration of the invention]

(Means for Solving the Problems) As means for solving the above problems, a first invention is an air conditioner control device for controlling the driving of a compressor motor by an output of an inverter controlled by a variable voltage and a variable frequency. An output frequency detecting means for detecting an output frequency of the inverter based on the variable frequency control, and comparing a value detected by the output frequency detecting means with a predetermined low frequency reference value, wherein the detected value is equal to or less than the low frequency reference value. And a change speed decrease signal output means for outputting a signal for decreasing the change speed of the output frequency of the inverter from the change speed when the detected value is equal to or higher than the low frequency reference value; and the change speed decrease signal. And inverter control means for controlling the output of the inverter based on a signal from the output means.

A second invention provides an air conditioner that drives and controls a compressor motor by frequency determining means for determining an output frequency of an inverter, and an output of an inverter controlled by a variable voltage and a variable frequency according to the frequency determined by the frequency determining means. In the control device, output frequency detection means for detecting the output frequency of the inverter based on the variable frequency control,
The value of the frequency determined by the frequency determining means is compared with the value detected by the output frequency detecting means to determine whether the subsequent frequency control is going to be up control or down control, and a determination signal is output. Rise and fall determination means, and a detection value by the output frequency detection means and a predetermined low-frequency reference value are compared, and the detection value is equal to or less than the low-frequency reference value, and A change speed reduction signal output unit that outputs a signal for reducing the change speed of the output frequency of the inverter from the change speed at which the detected value is equal to or higher than the low frequency reference value, if the change speed is determined to be the lowering control by the determination signal of And inverter control means for controlling the output of the inverter based on a signal from the change speed reduction signal output means.

(Operation) In the configuration of the first invention, the output frequency detection means detects the output frequency of the inverter and outputs a detection signal to the change speed reduction signal output means. When the change speed reduction signal output means determines that the detected value is equal to or lower than the low frequency reference value, it outputs a signal for reducing the change speed of the inverter to the inverter control means. With this signal, when the output frequency of the inverter changes in the low frequency region, the inverter control means controls the inverter so that the change speed is lower than the change speed at or above the low frequency reference value. Therefore, the output voltage of the inverter does not drastically change in the low frequency region, and breakdown of the compressor motor does not occur.

In the configuration of the second invention, the rise / fall determination means compares the frequency value from the output frequency detection means with the frequency value from the frequency determination means, and determines whether the subsequent frequency control is rise control or fall control. Is determined. The change speed decrease signal output means receives the frequency value from the output frequency detection means and the discrimination signal from the rise / fall discrimination means, and changes the change speed only when the frequency value is equal to or lower than the low frequency reference value and the descent control is performed. A decrease signal is output to the inverter control means. As a result, the inverter control means controls the frequency of the inverter at a slower change rate than the change rate at or above the low-band reference value. Therefore, the breakdown of the compressor motor can be effectively prevented even in the descending control at or below the low-frequency reference value where breakdown is most likely to occur.

Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

In FIG. 1, AC power from an AC power supply 1 is converted into DC power by a rectifier circuit 2 and then input to an inverter 3. The inverter 3 converts the DC power into AC power again and drives the compressor motor 4. Thereby, the compressor 5 is driven, and the refrigerant in the refrigerant circuit is circulated.

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

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

At this time, the signal output from the frequency determination means 7 is also output to the rise / fall determination means 9. Here, the output frequency of the inverter 3 is determined by an output frequency detecting means.
The detection signal is also input to the ascent / descent determining means 9.

Then, the ascending / descending determining means 9 compares the value of the frequency determined by the frequency determining means 7 with the value of the frequency detected by the output frequency detecting means 10, and determines whether the subsequent frequency control becomes the ascending control. It is determined whether the control is going down, and the determination signal is output to the change speed reduction signal output means 11. Further, the detection signal from the output frequency detecting means 10 is also inputted to the change speed decreasing signal output means 11.

The change speed decrease signal output means 11 is an output frequency detection means.
The detection signal from 10 is below fHz (eg 25Hz),
And when the ascent / descent determination means 9 determines that the descent control is performed,
A change speed reduction signal is output to the inverter control means 8.

When the change speed reduction signal is input, the inverter control means 8 lowers the frequency change speed when performing frequency control on the inverter 3 than before. Therefore, the rate of change of the voltage that changes in response to the frequency change is also slower than the previous rate, so that there is no possibility that the compressor motor 4 will break down.

FIG. 2 is a characteristic diagram showing a change in the output frequency of the inverter 3 controlled as described above. As shown in this figure, when the output frequency gradually decreases and becomes equal to or lower than the frequency f _L Hz (25 Hz) which is the low-band reference value, the rate of change of the frequency decreases. At a position where the output frequency is lowered to some extent, a speed hold section, that is, a constant speed section is provided, and sufficient consideration is given to breakdown. Thereafter, when there is a request to further lower the output frequency, the output frequency is similarly reduced at the reduced change speed.

In the above-described embodiment, the frequency change speed is reduced only when the output frequency decreases. However, in the low frequency region, the frequency change speed is always reduced regardless of whether the output frequency increases or decreases. You may make it do. That is, it is also possible to adopt a configuration in which the up / down determining means 9 in FIG. 1 is omitted.

〔The invention's effect〕

As described above, according to the present invention, when the frequency of the inverter is changed in the low frequency region, the change speed is reduced, so that the compressor motor breaks down in the low frequency region. This can be effectively prevented.

[Brief description of the 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 FIG. 3 ... Inverter, 4 ... Compressor motor, 5 ...
Compressor 8, inverter control means 10, output frequency detection means 11, change rate decrease signal output means.

Claims (2)

(57) [Claims] 1. An air conditioner control device for driving and controlling a compressor motor by an output of an inverter controlled by a variable voltage and a variable frequency, comprising: an output frequency detecting means for detecting an output frequency of the inverter based on the variable frequency control; A value detected by the frequency detecting means is compared with a predetermined low-frequency reference value, and when the detected value is determined to be equal to or less than the low-frequency reference value, a change speed of the output frequency of the inverter is determined. A change speed decrease signal output unit that outputs a signal for decreasing the change speed from a change speed greater than or equal to the range reference value, and an inverter control unit that controls an output of the inverter based on a signal from the change speed decrease signal output unit. An air conditioner control device comprising: 2. An air conditioner control for driving and controlling a compressor motor by frequency determining means for determining an output frequency of an inverter, and an output of an inverter controlled by a variable voltage and a variable frequency according to the frequency determined by the frequency determining means. In the device, an output frequency detecting means for detecting an output frequency of the inverter based on the variable frequency control, and a value of the frequency determined by the frequency determining means, and a value detected by the output frequency detecting means, Discriminating whether the frequency control is going to be rise control or fall control, and comparing rise / fall discriminating means for outputting a discrimination signal with a predetermined low frequency reference value and a value detected by the output frequency detecting means. , The detection value is equal to or less than the low-frequency reference value, and it is determined that the control is the down control by the determination signal from the up / down determination means A change speed decrease signal output unit that outputs a signal for reducing a change speed of the output frequency of the inverter from a change speed at which the detected value is equal to or higher than the low frequency reference value; and the change speed decrease signal output unit. And an inverter control means for controlling the output of the inverter based on the signal of (1).