JPH0731194A - Air-conditioner - Google Patents

Abstract

PURPOSE:To provide an air-conditioner in which the compressor is protected positively against fracture due to locking especially in low frequency band. CONSTITUTION:The level of current in an inverter power supply is detected by a current detector and compared with an abnormality decision reference value by a current comparing/deciding means. If a decision is made that the current is abnormal, the duration of abnormal current is compared with a time reference value by a time comparing/deciding means. When abnormal current sustains longer than the time reference value, operation of the inverter power supply is interrupted forcibly by a stop control means thus protecting the compressor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air conditioner such as a room air conditioner (hereinafter referred to as an air conditioner), and more particularly to an improvement of a frequency variable control type air conditioner using an inverter power supply.

[0002]

2. Description of the Related Art In a variable frequency control type air conditioner using an inverter power supply, for example, 15
The compression capacity of the compressor is adjusted by changing the frequency in the range of 75 Hz.

In such an inverter air conditioner, when the operation of the compressor is locked (stopped) for some reason, an excessive current flows in the motor winding of the compressor more than necessary, and if left unattended, the winding will be burnt or the built-in oil will be contaminated. May occur.

Conventionally, in order to prevent overcurrent, a current detector such as a CT (current transformer) is provided in the inverter power supply, and a current detector such as a shunt resistance flowing in the power transistor module of the inverter is provided, and each current is supplied. The detection value is monitored by the controller, and the operation of the inverter power supply is stopped in the case of an abnormality.

[0005]

The above-described overcurrent detection function works effectively because the detected current is sufficiently large when the operating frequency is relatively high.

However, when a lock abnormality occurs in the compressor in a band where the operating frequency is extremely low (for example, 15 to 20 Hz near the lower limit frequency), an excessive current flows even if it does not reach the above overcurrent determination standard. However, there were cases where anomalies were not detected.

Therefore, it is an object of the present invention to provide an air conditioner capable of reliably preventing the compressor from being damaged due to the lock of the compressor in a low frequency band.

[0008]

In order to solve the above problems, the present invention provides an air conditioner in which an inverter power supply variably controls an operating frequency of a compressor according to an air conditioning load. A current detector for detecting a flowing current, a current comparison / determination means for comparing and judging the detected current with a predetermined abnormality judgment reference value, and a result of the current comparison / judgment, when an abnormal current value is detected, Time comparison and determination means for comparing and judging the duration with a predetermined time reference value, and stop control means for stopping the operation of the inverter power supply when the abnormal current value continues for the time reference value or more as a result of the time comparison and determination. And are provided.

[0009]

According to the present invention, the detected value of the current flowing through the inverter power supply detected by the current detector is compared with the abnormality determination reference value by the current comparison and determination means. When it is determined that the current is abnormal as a result of the comparison, the time comparison / determination means further compares the duration of the abnormal current with the time reference value. As a result, when the abnormal current continues for a time equal to or longer than the time reference value, the stop control means forcibly stops the operation of the inverter power supply to protect the compressor.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, preferred embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an outline of an inverter air conditioner according to the present invention. In FIG. 1, a three-phase AC power supply (R.S.T.) is supplied to a converter 1 which constitutes an inverter power supply. The converter 1 rectifies the three-phase alternating current into direct current and supplies the direct current power to the inverter 2 which constitutes the inverter power supply. The inverter 2 drives the drive power P (three-phase) having a frequency according to the air conditioning load according to the control signal C from the controller 8.
Is supplied to the compressor 3, the circulation amount of the refrigerant in the air conditioning unit 4 is controlled by the change in the compression capacity of the compressor 3, and the air conditioning operation according to the load is performed.

A CT (current transformer) 5 is provided on any one-phase current wiring on the AC side (input side) of the converter 1. Since the detection signal of CT5 is AC, it is converted to a DC voltage via the rectifier circuit 6 and given to the input port of the controller 8 as the detection signal Id1.

A shunt resistor 7 such as a non-inductive resistor is inserted in series in the current wiring on the AC side (output side) of the converter 1 and the DC side (input side) of the inverter 2, for example, on the load voltage side. The voltage corresponding to the voltage drop at the shunt resistor 7 is also applied to the input port of the controller 8 as the abnormality detection signal Id2.

The controller 8 detects these detection currents Id.
With 1 and Id2 as input data, a built-in microcomputer (not shown) determines an abnormality. This abnormality determination is performed by a ROM (Read Only M) in the microcomputer.
It is executed by the operation control program stored in emory).

FIG. 2 shows the correlation between the operating frequency fd of the inverter 2 and the detection signal (current value) Id by CT5. As can be seen from FIG. 2, the operating frequency is variably controlled in the range of the lower limit frequency f1 to the upper limit frequency fmax, and at that time, the current flowing through the inverter current changes within the width shown by the diagonal lines. As described above, it is difficult to detect an abnormality due to locking in the band of the lower limit frequencies f1 to f2. Therefore, in the present invention, this low frequency band f
1 to f2 are used as the monitoring band, and hereinafter referred to as such.

FIG. 3 shows an example of the operation control program as the control means of the air conditioner according to the present invention. In FIG. 3, step 101 corresponds to the current comparison determination means, step 102 corresponds to the time comparison determination means, and step 103 corresponds to the stop control means.

Next, the control operation at the time of abnormality of the air conditioner according to the present invention will be described. (See Figure 3).

In the main routine (not shown) of the operation control program in the controller 8 (see FIG. 1), it is constantly monitored whether the operation frequency fd falls within the monitoring band f1 to f2, and the operation frequency fd is monitored. Band f1 to f2
When it is entered, the program of FIG. 3 is started by a subroutine.

Now, it is assumed that the operating frequency fd of the air conditioner enters the monitoring band f1 to f2 (step 100). Then, in step 101, the detected current Id (corresponding to the current value flowing into the inverter current at present) and f1 to
The predetermined reference current value Iref1 in the range of f2 is compared.

If Id> Iref1 is not satisfied (NO), it is determined to be normal, the processing in FIG. 3 is terminated, and the process returns to the main routine.

If Id> Iref1 (YES), the process proceeds to step 102 to confirm the occurrence of an abnormality.

In step 102, it is judged whether or not the state of Id> Iref1 continues for a predetermined reference time tref or longer. As a result, if the above is transient (NO), the process ends and jumps to step 104.

If td ≥tref (YES), the current flowing through the inverter power supply is abnormal, and it is considered that the compressor 3 is locked, and the inverter current (converter 1, converter 1, Forcibly stop the operation of the inverter 2). As a result, the supply of overcurrent to the compressor 3 is blocked and the compressor 3 is protected.

[0024]

As described above, according to the present invention, the current comparison and judgment means monitors the current value and the time comparison and judgment means monitors the abnormal time. It is possible to surely prevent the compressor from being broken due to the lock of the compressor.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of an air conditioner according to the present invention.

FIG. 2 is an explanatory diagram showing a correlation between an operating frequency of an inverter current and a current.

FIG. 3 is a flowchart showing a control means of the present invention.

[Explanation of symbols]

 fd Operating frequency f1 Lower limit frequency fmax Upper limit frequency Id Operating current Iref1 First reference current Iref2 Second reference current

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Claims (1)

[Claims] 1. An air conditioner in which an operating frequency of a compressor is variably controlled by an inverter power supply according to an air conditioning load, and a current detector for detecting a current flowing through the inverter power supply and the detected current are predetermined. The current comparison and judgment means for comparing and judging with the specified abnormality judgment reference value, and the time comparison for comparing and judging the duration of the abnormal current with the predetermined time reference value when the abnormal current value is detected as a result of the current comparison judgment. An air conditioner comprising: a determination unit; and a stop control unit that stops the operation of the inverter power supply when an abnormal current value continues for a time reference value or more as a result of time comparison determination.