JPH01131840A - Control device for air conditioner - Google Patents

Abstract

PURPOSE:To avoid the shutdown of an air conditioner, inhibit the electric current from flowing to a compressor motor, and reduce operation cost even when the load of air conditioning is increased by performing operation control so that the input current of an air conditioner may not exceed a predetermined maximum allowable current value. CONSTITUTION:An electric current detection means 4 is provided to directly detect the electric current flowing to a compressor motor 2d. When this detected electric current turns into an excess current to said motor 2d, it is necessary to reduce the maximum allowable current value, to reset the maximum value, and to lower gradually the operation frequency required for inverter control, thereby reducing the electric current flowing to the motor 1. It is, therefore, possible to maintain the specified indoor environment without halting the operation of an air conditioner. Since the maximum electric current which flows the compressor motor 2d can be determined, the rating of a power transistor module can be decided with no margin, thereby reducing operation cost.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an inverter-type control device for a heat pump type air conditioner, and more specifically, it relates to an inverter-type control device for a heat pump type air conditioner, and more specifically, it relates to an inverter-type control device for a heat pump type air conditioner. The present invention relates to a control device for an air conditioner that prevents the electric motor from stopping.

[Conventional Example] Conventionally, this type of control device has a circuit configuration as shown in FIG. 2, for example. That is, in the figure, an indoor unit 1 is equipped with a fan motor 1a that circulates cold or warm air indoors, an indoor control device 1b, etc., and an outdoor unit 2 is equipped with a heat exchanger fan motor 2a, which is switched during heating and cooling. It is equipped with an outdoor control device including a four-way valve 2b1, a variable frequency device 20, etc., and a compressor motor 2d, which is controlled by an inverter by the outdoor control device.

The indoor control device 1b receives a transmission signal from an infrared remote control,
Alternatively, the operation request is determined based on the operation signal from the operation panel, the operating conditions are calculated that match the ambient environment such as the indoor temperature, and the calculated operating conditions are sent to the outdoor unit 2 side together with the AC power supply (commercial) 3. It is designed to output .

The outdoor control device decodes commands such as frequencies for cooling/heating operation and inverter control based on the signals, and controls driving of the fan motor 2a and switching of the four-way valve 2b, etc. while monitoring the operating status of the outdoor unit. At the same time, the optimum frequency is calculated and the compressor motor 2d is controlled by an inverter.

In this way, the operation command transmitted from the indoor unit to the outdoor unit,
Operating conditions and the like are transmitted from the outdoor unit to the indoor unit using AC power lines, for example, as bidirectional serial signals, thereby maintaining a better indoor environment.

Incidentally, fluctuations in the air conditioning load are influenced by the operating environment temperature and the like. Therefore, 1. For example, in the summer when the temperature difference between indoors and outdoors is extremely large, the air conditioning load becomes large, and if you try to maintain the indoor environment by following commands from the indoor unit, the frequency that controls the compressor motor 2d will be reduced. Something happens that raises the price. Then, as the current flowing through the compressor motor 2d increases, the input current of the air conditioner may exceed the rated current of the household AC power supply, or an overcurrent may flow through the compressor motor 2d. At times like this, the home breaker may trip, or in extreme cases, the compressor may trip. The power transistor module 2C1 that drives the tilJJ machine 2d may be destroyed or damaged.

Therefore, an input current detection device 2c that detects the input terminal with a current sensor is provided in the manual power stage on the outdoor unit 2 side. A current detection device 2c is provided for detecting the current of the power transistor module 2c using a current detection resistor. If the input current exceeds the set maximum allowable current value due to various conditions, the control section (in the frequency variable/control device 2c)
2c4 (including the CPU, etc.) was protected by lowering the operating frequency set by the command from the indoor unit 1. In addition, if the air conditioning load increases and overcurrent flows to the compressor motor 2d, the power transistor module 2
In order to protect c1, the control unit 2c4 controls the drive of the compressor motor 2d to stop, that is, it does not supply power to the compressor motor 2d.

[Problems to be Solved by the Invention] However, as shown in FIGS. 3 and 4, the current changes due to changes in the air conditioning load are larger in the current of the compressor motor 2d than the input current, so the power - Overcurrent protection such as the transistor module 201 was easier to operate first, and the compressor motor 2d was stopped, making it impossible to maintain the indoor environment.

Also, a power transistor module 2c.

When determining the rating of the power transistor module 2c, the power transistor module 2c must have a margin sufficient to satisfy the operating load conditions of the air conditioner, which is uneconomical in terms of cost.

This invention was made in view of the above problems, and its purpose is to prevent operation from stopping even when the air conditioning load increases.
An object of the present invention is to provide a control device for an air conditioner that can suppress the current flowing to a compressor motor and reduce costs.

[Means for Solving the Problems] In order to achieve the above object, the present invention includes an indoor unit and an outdoor unit, and the compressor provided on the outdoor unit side is a heat pump type that is controlled by an inverter. A control device for controlling the operation of an air conditioner so that the input current of the air conditioner does not exceed a set maximum allowable current value, the control device comprising a current detection means for directly detecting the current flowing to the motor of the compressor. In case this detected current becomes an overcurrent for the electric motor, the maximum allowable current value is changed to a smaller value, and the operating frequency for controlling the inverter is gradually lowered to reduce the current flowing to the electric motor. This is how it was done.

[Function] With the above configuration, the current flowing through the compressor motor of the air conditioner is directly detected by the current detection means, and when the detected current exceeds a predetermined value, the set value of the input terminal is lowered. Therefore, the input current is suppressed, the operating frequency of the inverter control is lowered, and the current flowing through the power transistor module that drives the compressor motor is kept within the ratings of the transistors making up the module.

[Example] Hereinafter, an embodiment of the present invention will be described based on FIG.

In the figure, the same parts as in FIG. 2 are denoted by the same reference numerals, and redundant explanation will be omitted.

In the figure, the current flowing through the compressor motor 2d is detected by a current detection resistor at the connection point between the power transistor module 2cm of the frequency variable/control device 2c that controls the compressor motor 2d using an inverter, and the compressor motor 2d. A motor current detection device (current detection means) 4 is provided. The current value detected by the current detection device 4 is input as data to the frequency variable/control device 2c. That is, in this embodiment, instead of detecting the current at the input stage of the power transistor module 2cm, the current at the output side of the power transistor module 2c1 is detected. Therefore, compressor motor 2d
The maximum value of the current flowing through the power transistor module 2c1 can be determined, and the rating of the power transistor module 2c1 can also be determined accordingly.

Then, based on the current detected by the current detection device 4, the frequency variable/control device 2c changes and sets the maximum allowable current value of the input current to a small value, and changes the frequency calculated based on the command from the indoor unit 1 to a predetermined value. , the compressor motor 2d is controlled at that frequency.

Next, the operation of the control device will be explained.

First, an operation command is issued from the indoor unit 1 of the air conditioner for which the maximum allowable current value of the input current has been set, and based on the operation command, the detected current of the input terminal detection device 2c is detected on the outdoor unit 2 side. For reference, it is assumed that the compressor motor 2d is being driven at a predetermined operating frequency.

Here, if the temperature difference between indoors and outdoors is extremely large, the air conditioning load will increase when the air conditioner is operated, and the frequency of inverter control will become high.
A large current will be passed through d. Then, a current corresponding to an overcurrent flows to the power transistor module 2c and the compressor motor 2d. At this time.

The current is detected by the motor current detection device 4, and the frequency variable/control device 2c to which the value data is input sets the maximum allowable current value to a small value, and also sets the maximum allowable current value to a small value.
The operating frequency is lowered stepwise from the previous frequency in order to make the current detected at step c less than or equal to the set maximum allowable current value.

That is, the frequency of the signal that drives the power transistor module that is the driver of the compressor motor is lowered, and the current flowing through the compressor motor 2d is suppressed.

In this way, the current flowing through the compressor motor 2d is detected,
Even in a situation where an overcurrent occurs in the compressor motor 2d, the frequency of the inverter control can be lowered and the current flowing through the compressor motor 2d can be suppressed without stopping the compressor.

[Effects of the Invention] As explained above, according to the present invention, a heat pump air conditioner includes an indoor unit and an outdoor unit, and the compressor provided on the outdoor unit side is controlled by an inverter. This is a control device that controls the operation of an air conditioner so that the input current does not exceed a set maximum allowable current value, and is equipped with a current detection means that directly detects the current flowing to the compressor motor. If an overcurrent occurs in the motor, the maximum allowable current value above is changed to a smaller value, and the operating frequency for inverter control is gradually lowered to reduce the current flowing to the motor, making it easier to operate the air conditioner. The indoor environment can be maintained without stopping, and the maximum current flowing to the compressor motor is determined.

The rating of the power transistor module can be determined without margin, and costs can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a schematic circuit block diagram of a control device for an air conditioner showing an embodiment of the present invention, FIG. 2 is a schematic circuit block diagram of a conventional control device for an air conditioner, and FIGS.
The figure is a graph diagram for explaining the drawbacks of the conventional control device. In the figure, 1 is an indoor unit, 1a is a fan motor, lb
is an indoor control device, and 2 is an indoor unit. 2a is a fan motor for a heat exchanger, 2b is a four-way valve, 2c is a frequency variable control device, 2c1 is a power transistor module, 2c is an input current detection device, 2c is a current detection device, 2c4 is a control unit, 2d is a A compressor motor, 3 an AC power source (commercial), and 4 a motor current detection device (current detection means). Patent applicant: Fujitsu General Co., Ltd. Representative, Patent attorney: Takuya Ohara Figure 3 Figure 4

Claims (1)

[Claims] A heat pump air conditioner including an indoor unit and an outdoor unit, in which a compressor provided on the outdoor unit is controlled by an inverter, wherein the input current of the air conditioner is a set maximum. A control device for controlling operation so as not to exceed an allowable current value, comprising current detection means for directly detecting a current flowing through the motor of the compressor, and when the detected current becomes an overcurrent for the motor, A control device for an air conditioner, characterized in that the maximum allowable current value is changed and set to a small value, and the operating frequency for controlling the inverter is lowered stepwise to lower the current flowing to the electric motor.