JPS62210353A - Controller for air conditioner, etc. - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control device for an air conditioner or the like that includes an inverter for variable speed control of an induction motor.

[Conventional technology]

FIG. 4 is a circuit diagram of a conventional control device disclosed in, for example, Japanese Utility Model Application Publication No. 57-189299. In the figure,
Reference numeral 1 indicates a commercial AC power supply, 2 indicates an inverter, and includes a diode stack 2a, a smoothing capacitor 2b, and a power transistor module 2C. 3 indicates a compressor motor driven by the output of the inverter 2, and 4 indicates a control unit. A command input circuit; 5 a control circuit for controlling the power transistor module 2Ct; 6 a current transformer 6a;
A current detector detects the input current to the motor 30, and a detection signal is input to the control circuit 5.

Next, the operation will be described. AC input from the AC current g1 to the inverter 2 is converted into DC by the diode stack 2a, and further smoothed by the capacitor 2b.

This direct current is converted back into alternating current by the power transistor module 2C, and is given to the compressor motor 3 as a load as a variable frequency output. At that time, the power transistor module 2C'fr is appropriately controlled based on the command from the control circuit 5r1 input circuit 4 and the signal from the detection circuit 6. lJ and controls the drive of the electric motor 41A3. The pattern of the output voltage and frequency of the inverter 2 applied to the electric motor 3 is a predetermined pattern as shown in FIG. There are two patterns, ) and (b), which are selected depending on the magnitude of the input current to the motor 30 at that time.

[Problem that the invention seeks to solve]

Conventional control devices for air conditioners, etc., control the output of the inverter 2 based on the control command and the detected value of the load's current as described above, which requires a dedicated current detection means, which reduces costs. There is a problem that the voltage rises, and other protection such as protection from overcurrent is required. ! ! ! Since control is not performed in conjunction with the function, changing the output pattern in the low output range below the specific frequency f cannot be expected to have much effect, and the protection function will act in the event of an overload, causing the motor 3 to stall and stop. There was a problem with this.

The present invention has been made to solve these problems, and aims to provide a control device for an air conditioner or the like that is inexpensive and prevents the load from stalling or stopping.

[Failure to solve the problem]

In a control device for an air conditioner, etc. equipped with an inverter that provides a variable frequency output to a load such as an electric motor, a detection means for detecting an overload condition that activates a protection function, and a detection means for detecting an overload condition that activates a protection function, and a detection means for detecting an overload condition that activates a protection function, and a detection means for detecting an overload condition that activates a protection function, and a detection means for detecting an overload condition that activates a protection function, and a detection means that detects an overload condition when the overload condition is detected. A changing means is provided for changing the output voltage and frequency pattern.

[For production]

When the detection means detects an overload condition such as overcurrent in which a protection function is activated, the output voltage and frequency pattern of the inverter are switched by the change means. Therefore, it is possible to prevent the load from stalling or stopping, and an overcurrent detection circuit or the like can be used as the overload condition detection means.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

In the figure, 1 is a commercial AC power supply, 2 is an inverter consisting of a diode stack 2as smoothing capacitor 2b, and a power transistor module 2C, 3 is a compressor motor, and 4 is a control command input circuit, which are conventional ones (
This is the same part as in Figure 4). A current detector 7 detects the input current of the inverter 2 using a current transformer 7a, and is provided as a means for detecting an overload condition in which a protection function for protecting the internal circuit from an abnormal state such as an overcurrent is activated. 8 is the signal from the current detector 7 and the input circuit 4
This is a control circuit that controls the output of the inverter 2 based on commands from the inverter, and also serves as a means for changing the output pattern of the inverter.
change the output voltage and frequency pattern.

Next, the operation will be explained. The compressor electric motor 3 of the air conditioner is driven by the inverter 2 in a voltage-frequency pattern based on a control command, and normally the output voltage-frequency pattern given to the electric motor 3 is the same as in the conventional case, as shown in FIG. The pattern is shown in . In this state, for example, when a heating overload state occurs and the load on the air conditioner becomes heavy, the input current (primary side current) of the inverter 20 increases, and the overcurrent protection function comes into operation. Therefore, the control circuit 8 constantly monitors the input current of the inverter 2 through the current detector 7, and prevents the protection breaker (not shown) attached to the AC power supply 1 from tripping. The output frequency is lowered to continue operation, and so-called stall control (draft control) is performed.

However, if the load on the air conditioner is still heavy and the stall control continues and the output frequency of the inverter 2 exceeds the lower limit, the air conditioner will stop. At this time, the control circuit 8 records the data of the overload condition that led to the operation stop (in this case, the input current value of the inverter 2) (1-, , l, '-1) and stores it next time. When the data of the overload condition is detected, the output voltage and frequency pattern of the inverter 2 are changed.Specifically, the output voltage of the inverter 2 is increased and the operation is started, and as a result, the primary side current of the inverter 2 is increased. This decreases compared to the previous stop, making it possible to prevent a stall from coming to a stop.

The flowchart in FIG. 2 shows the above-mentioned operation, and in general, in an air conditioner, the compressor motor 3 is stopped while only blowing air for about 3 minutes after the start of operation. Then, the compressor motor 3 is normally driven in the pattern shown in FIG. 5(a), for example, heating operation is performed.

In this state, the control circuit 8 monitors the primary side current of the inverter, and when the current value exceeds the rated current value of the breaker, the output frequency of the inverter 2 is decreased to perform stall control. Then, when the output frequency of the inverter 2 becomes lower than the lower limit frequency, the operation of the air conditioner is stopped, and after stopping for about 3 minutes due to the above-mentioned reason, a high output voltage pattern as shown in (b) of Fig. 5 is started. The drive of the compressor electric motor 3 is started. Thereafter, when the data of the overload condition at the time of stopping the operation is detected next time, the output cover turn is further changed, the output voltage is further increased, and the operation is continued.

In this way, the data from the previous stop is stored, and the output turn is further changed the next time the data is detected, thereby making it possible to prevent the load from stalling or stopping. Here, for example, parts for overcurrent detection for protection can also be used for detecting the above data, so a dedicated part is not required and it can be made inexpensive.

@3 Figure is a circuit configuration diagram showing another embodiment of the present invention. In this embodiment, a current detector 9 is provided to detect the bus current using a shunt resistor (shunt resistor) 9a interposed in the DC bus of the inverter 2, thereby detecting an overload condition. . That is, as the load on the air conditioner increases, the direct current flowing through the bus increases, so it can be determined whether there is an overload or not based on the bus current. In this case, if the bus current detected by the shunt 9a is compared with a reference value, the same operation as in the flowchart shown in FIG. 2 will be performed.

〔Effect of the invention〕

As explained above, according to the present invention, the overload condition at the time of the previous stop is memorized, and the next time the overload condition is detected, the pattern of the inverter's output voltage and frequency is changed. This has the effect of more reliably preventing stalling and stopping of the motor, and since the parts of the circuit can also be used, special parts are not required and the cost is low.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a circuit diagram showing one embodiment of the present invention, FIG. 2 is a flowchart showing its operation, and FIG. 3 is a circuit diagram showing another embodiment of the invention. FIG. 4 is a circuit configuration diagram showing a conventional control device, and FIG. 5 is a diagram showing patterns of output voltage and frequency of an inverter. 2... Inverter 3... Compressor motor (load) 7...
...Current detector (detection means) 8...
. . . Control circuit (changing means) 9 . . . Current detector 9 a .

Claims (3)

[Claims] (1) In a control device for an air conditioner, etc. equipped with an inverter that provides a variable frequency output to a load such as an electric motor, a detection means for detecting an overload condition that activates a protection function, and the overload condition is detected. 1. A control device for an air conditioner, etc., characterized in that it is equipped with a changing means for changing the output voltage and frequency pattern of an inverter. (2) A control device for an air conditioner or the like according to claim 1, wherein the overload condition detection means is constituted by a current detector that detects an input current of an inverter. (3) A control device for an air conditioner or the like as set forth in claim 1, wherein the overload condition detection means is constituted by a shunt interposed in the middle of the electric wire through which the direct current of the inverter flows. .