JPH0459547B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Technical Field> The present invention relates to an inverter-driven air conditioner.

<Prior art> In a conventional air conditioner, that is, an air conditioner that is not driven by an inverter but has a constant operating frequency, if the compressor malfunctions and locks up, a large current will flow, causing the breaker to trip or the compressor to generate heat due to the locked current. , the current will flow until the temperature protection device is activated. In addition, inverter-driven air conditioners have a current limiting function that lowers the fundamental wave voltage applied to the compressor and the load side frequency to suppress the current value when the current value exceeds a certain level. Due to the action of the limiting function, the frequency is at the lowest level of normal operation, and a large current flows. In this case, the compressor will not operate and the heat will be dissipated, and if this continues for a long time, there is a risk that the control circuit will be destroyed due to overcurrent.

<Purpose> In view of these conventional problems, the present invention can protect the control circuit and improve safety by quickly sensing when an abnormality occurs in the compressor and stopping the compressor. The present invention aims to provide an inverter-driven air conditioner that can be improved.

<Embodiment> Hereinafter, the present invention will be described in detail with reference to the illustrated embodiment. This invention is applied to an inverter-driven air conditioner having an inverter 2 that controls a three-phase AC voltage applied to an electric compressor 1 and a load-side frequency. , a current detection device 3 that detects the operating current applied to the compressor 1;
A control device 4 is provided which outputs a compressor control signal to the inverter 2 based on a detection signal from the current detection device 3.

FIG. 1 is a block diagram showing the outline of an inverter-driven air conditioner. The air conditioner of this example rectifies a single-phase or three-phase AC power source 5 with a converter 6, and
After converting the rectified output of the converter 6 into an AC voltage of variable frequency and variable voltage by the inverter 2, the converted AC voltage is applied to the electric compressor 1, and the compressor 1 has a chamber. An inner heat exchanger 7, a pressure reducer 8, and an outdoor heat exchanger 9 are connected by pipes in this order, and a refrigerant compression cycle 10 is configured by these. Then, as shown in Fig. 2, for example, a compressor 1 with a three-phase rated output of 750W is connected to an inverter 2, and the load side frequency is changed to the starting frequency.
F0 (Hz) to normal operating frequency F1 (Hz) ~ F2 (Hz)
If the ratio of the fundamental wave voltage applied to the compressor 1 and the frequency is kept constant, the current value during normal operation is within the shaded range in FIG. 2.

In a normal non-locked compressor 1, the current value is I0 (A) at the starting frequency F0 (Hz), and the maximum current value at the lowest frequency F1 (Hz) of the normal operating frequency is I1 (A).
On the other hand, the current change when the compressor is locked is:
The starting frequency is I0 (A) at F0 (Hz), but the maximum current value at F1 (Hz) is I3 (A). Therefore, when the current value for abnormal lock detection is I2, set it to a value in the range of I1 < I2 < I3, for example, I2 = (I1 + I3) / 2, start the compressor, and set it to the lowest frequency of normal operation. In the process of increasing the frequency so that the current exceeds I2(A), it is determined that the compressor is locked and the compressor is controlled to stop.
This prevents heat generation in the compressor 1, protects the control circuit, improves safety, and eliminates the need for unnecessary current to flow for a long time.

FIG. 3 shows a block diagram of a control device having a simple abnormality detection function according to the present invention. Here, the current detection device 3 includes a current detector (current transformer) 12 that detects the current of the AC power supply 5, and an A that converts an analog signal from the current detector 12 into a digital signal and outputs it to the control device 4. /D converter 13.

The control device 4 is a microcomputer, and includes a compressor starting means 20 that starts the compressor 1 at a starting frequency lower than the lowest frequency of normal operation based on the operation command signal, and after starting the compressor 1,
a frequency increasing means 21 for increasing the operating frequency of the compressor 1 from the starting frequency to the lowest frequency;
Abnormal current determining means 22 for determining whether or not the operating current of the compressor 1 has reached a set current value for abnormal lock detection based on the detection signal from the current detecting device 3; an operation stop means 23 for stopping the operation of the compressor 1 when the abnormal current determining means 22 determines that the operating current of the compressor 1 exceeds the abnormal lock detection current value in the process from the starting frequency to the lowest frequency; is allowed to exist. Further, numeral 14 in the figure is an inverter drive section.

Next, to explain how to control the compressor 1, first, the current of the AC power supply 5 is detected by the current detector (current transformer) 12, and the value is inputted to the control device 4 through the A/D converter 13. .

When the microcomputer 4a receives an operation command, it starts driving the compressor 1 at the starting frequency F0 (Hz). Therefore, the case when an operation command is received when the compressor 1 is locked will be explained with reference to the flowchart shown in FIG. First, upon receiving an operation command, the starting means 20 of the control device 4 activates the compressor 1.
An inverter drive waveform (PWM waveform) is output to the inverter drive unit 14 so that the inverter is started at a starting frequency F0 (Hz), and a certain time TI (0.2 to 1.0 seconds) is set.

Then, the abnormal current discriminating means 22 determines that the value detected by the current detector 12 is the current value I2 for abnormal lock detection.
(A) When it is determined that it is below, the frequency increasing means 21 increases the frequency from the starting frequency F0 (Hz) to the lowest frequency F1 (Hz) after time T1 based on this.

On the other hand, when the abnormal current determining means 22 determines that the detected current has reached the current value I2 (A) for abnormal lock detection before reaching the lowest frequency F1 (Hz) of the normal operating frequency, the compressor 1 abnormality (lock)
The operation stop means 23 stops the compressor 1.

<Effects> As is clear from the above explanation, according to the present invention, the compressor is started at a starting frequency lower than the lowest possible frequency of normal operation, and the current is reduced in the process of reaching the lowest frequency from the starting frequency. When the detection signal from the detection device exceeds a certain value, it is determined that the compressor is abnormal and the compressor is stopped and controlled, which prevents heat generation in the compressor, protects the control circuit, and improves safety. This has the excellent effect of eliminating unnecessary current consumption.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention; Fig. 1 is a block diagram showing an overview of an air conditioner, Fig. 2 is a characteristic diagram showing the relationship between frequency and current, and Fig. 3 is a control circuit for a compressor. FIG. 4 is a flowchart. DESCRIPTION OF SYMBOLS 1... Compressor, 2... Inverter, 3... Current detection device, 4... Control device, 12... Current detector, 13... A/D converter, 14... Inverter drive unit, 20... Starting means, 21... Frequency increasing means, 22... Abnormal current determining means, 23... Operation stopping means.

Claims (1)

[Claims] 1. In an inverter-driven air conditioner having an inverter that controls a three-phase AC voltage applied to an electric compressor and a load-side frequency, a current detection device is provided to detect an operating current applied to the compressor. A control device is provided that outputs a compressor control signal to the inverter based on a detection signal from the current detection device, and the control device operates the compressor at a starting frequency lower than the lowest frequency of normal operation based on the operation command signal. a frequency increasing means for increasing the operating frequency of the compressor from the starting frequency to the lowest frequency after starting the compressor; and operating the compressor based on the detection signal from the current detection device. abnormal current discriminating means for discriminating whether or not the current has reached a set current value for abnormal lock detection; An inverter-driven air conditioner characterized in that the inverter-driven air conditioner is provided with an operation stop means for stopping the operation of the compressor when it is determined that the operating current of the compressor exceeds the abnormal lock detection current value.