JPH0817571B2 - Compression cooling device - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a compression type cooling device equipped with an inverter device, and more particularly to reduction of leakage current thereof.

[Conventional technology]

FIG. 5 is an electric circuit diagram of a compression type cooling device equipped with a conventional inverter device disclosed in, for example, Japanese Patent Laid-Open No. 60-59978, in which (1) is an AC power supply and (2) is this AC power supply. A noise filter connected in parallel to the power supply (1), (3) a capacitor that constitutes this noise filter (2), (4) a grounding capacitor, (5) an inductor, and (6) a power factor. Reactor for improvement, (7)
Is a voltage doubler rectifier circuit connected in parallel to the noise filter (2) through the power factor improving reactor (6),
(8) is a smoothing capacitor connected in parallel to the voltage doubler rectifier circuit (7), (9) is an inverter device similarly connected in parallel to the voltage doubler rectifier circuit (7), and (10) is this inverter device ( Compressor motor connected to 9), (1
1) is the floating capacitance between this compressor motor (10) and the ground, (12) is the fan motor connected to the AC power supply (1), and (13) is other electrical parts. (M) is an output line of the inverter device (9), and (E) is a ground line connecting the ground part of the compression cooling device and the ground.

The conventional compression cooling device is configured as described above, and converts the alternating current of the alternating current power source (1) into direct current by the voltage doubler rectifier circuit (7), and this direct current is smoothed by the smoothing capacitor (8), and the inverter device By the operation of the switching element in (9), DC is converted to three-phase AC. The compressor motor (10) is driven by this three-phase alternating current.

The noise generated during the operation of the switching element of the inverter device (9) and the noise caused by the commutation action of the voltage doubler rectifier circuit (7) are converted by the noise filter (2) into the AC power supply (1)
Leakage to

The voltage generated in the output line (M) of the inverter device (9) has a waveform as shown in FIG. 6 (a), and the leakage current as shown in FIG. 6 (b) occurs at the rising and falling moments. It flows to the ground wire (E). The relationship between the leakage current when the compressor motor (10) is driven and the capacity of the grounding capacitor (4) provided in the noise filter (2) is examined, and the result is as shown in FIG. 7 (a). That is, the leakage current becomes minimum at a certain capacity, and when the capacity becomes larger than that, the leakage current increases, and even when the capacity becomes smaller, the leakage current increases. This is because the leakage current of the switching carrier frequency component, which is the main frequency component generated in the inverter device (9), and the leakage current of the frequency component of the AC power supply (1) have the characteristics shown in FIG. 7 (b). Since both frequency components have a canceling effect to some extent, the combined value is considered to be as shown in FIG. 7 (a).

[Problems to be Solved by the Invention]

Since the conventional compression cooling device is configured as described above, the grounding capacitor (4) of the noise filter (2) is reduced so that the leakage current of the ground wire (E) during driving of the compressor motor (10) becomes small. When the capacity of) is determined, as can be seen from FIG. 7 (b), the leakage current becomes only the frequency component of the AC power supply during the air blow operation in which only the fan motor (12) is driven with the compressor motor (10) stopped. Therefore, there is a problem that the canceling effect of both components may be lost, and there is a problem that the leakage current increases, and in order to reduce this AC power supply frequency component, the capacitance of the grounding capacitor (4) of the noise filter (2) is increased. If the amount is reduced, the frequency component of the switching carrier increases when the compressor motor is driven, and the leakage current increases.

The above problems tend to become more prominent when the switching carrier frequency is increased in order to reduce noise when driving the compressor motor (10), and some solution has been desired. .

The present invention has been made in order to solve the above-mentioned problems, and it is possible to reduce the leakage current both when the compressor motor is driven and when it is stopped, and at the same time, it is a compression type cooling device which can cope with a high switching carrier frequency. Aim to get.

[Means for solving the problem]

The compression cooling device according to the present invention is connected to an AC power supply, is connected to an noise filter including an inductance, a capacitor, and a first grounding capacitor, and is connected in parallel with the noise filter to convert an AC voltage into a DC voltage. A voltage rectifier circuit for converting, an inverter device connected in parallel with the voltage rectifier circuit for converting a DC voltage into a variable frequency AC, a compressor motor connected to the inverter device, and various types connected to the AC power supply. In a compression cooling device including an electric load device, a second grounding capacitor connected in parallel with a circuit of the first grounding capacitor in the noise filter, and a series of the second grounding capacitor. When the compressor motor is stopped, the switch is turned off and grounded based on the switch connected to and the operation result of the compressor motor. And control means for controlling the volume of Condesa, those having a.

[Work]

The compression-type cooling device according to the present invention compresses a second grounding capacitor connected in parallel with the first grounding capacitor circuit in the noise filter and a switch connected in series with the second grounding capacitor. When the machine motor is stopped, it is turned off to control the capacity of the grounding capacitor, so the compressor motor and various electric load devices such as the fan motor are driven individually during cooling / heating operation and during thermo operation. The leakage current to the ground is optimally maintained even when the compressor motor is stopped and only various electric loads are operated.

Example of Invention

FIG. 1 is an electric circuit diagram showing one embodiment of the compression type cooling device according to the present invention, which is (1) to (3), (5) to (1
3) is exactly the same as the above conventional device. (14) is a first grounding capacitor provided in the noise filter (2), (15) is a second grounding capacitor connected in parallel with the first grounding capacitor (14), and (16) is this second grounding capacitor. 2 A switch for opening and closing the grounding capacitor (15), and (17) is a control circuit composed of a micro computer for controlling the switch (16). The switch (16) and the control circuit (17)
It constitutes the control means.

The operation of the compression type cooling device configured as described above will be described with reference to the flow chart of FIG. In the figure, the step (21) determines whether the compressor motor (10) is driven or stopped, and the step (22) in the case of driving turns on the switch (16) by the control circuit (17). The capacitor (15) conducts, the capacity of the grounding capacitor increases, and the charge / discharge current from the floating capacitance (11) is returned to the power supply side and the leakage current flowing through the ground wire (E) decreases.
The relationship between the capacitance of the grounding capacitor and the leakage current at this time is as shown in FIG. 7 (a) as in the conventional device. Therefore, the capacity of the second grounding capacitor (15) is selected so that the sum with the first grounding capacitor (14) is equal to the capacity that minimizes the leakage current in FIG. 7 (a). Leakage current can be reduced. In FIG. 2, when the compressor is stopped at step (21), the switch (16) is turned off by the control circuit (17) at step (23).
The grounding capacitor (15) becomes non-conductive, the capacity of the grounding capacitor decreases, and becomes the capacity of the first grounding capacitor (14). Since the relationship between the capacity of the grounding capacitor and the leakage current at this time is the curve of the frequency component of the AC power supply in FIG. 7 (b), the leakage current has a small value corresponding to the capacity of the first grounding capacitor (14). . The capacity of the first grounding capacitor (14) is determined for another purpose of reducing noise generated in the inverter device (9) and the voltage doubler rectifier circuit (7).

In the above embodiment, the first grounding capacitor (14) and the second grounding capacitor (15) are provided on the secondary side of the noise filter (2). The same effect can be obtained with the configuration provided on the next side.

FIG. 3 shows an electric circuit of a compression type cooling device showing another embodiment of the inverter device in which the first grounding capacitor (14) and the second grounding capacitor (15) are provided on the primary side of the noise filter (2). It is a figure. The reference numerals are exactly the same as those of the embodiment shown in FIG.

In the above two embodiments, the AC voltage of the AC power source (1) is converted into the DC voltage by the voltage doubler rectifier circuit (7). However, it is also possible to use full-wave rectification as the rectification method. Applicable.

FIG. 4 is an electric circuit diagram showing another embodiment of the compression-type cooling device using the full-wave rectification method.

In the figure, (18) is a full-wave rectifier circuit that converts the AC voltage of the AC power supply (1) into a DC voltage and supplies it to the inverter device (9). The function and effect are the same as those of the embodiment shown in FIG.

〔The invention's effect〕

As described above, the present invention compresses the second grounding capacitor connected in parallel with the first grounding capacitor circuit in the noise filter and the switch connected in series with the second grounding capacitor. When the machine motor is stopped, it is turned off to control the capacity of the grounding capacitor, so the compressor motor and various electric load devices such as the fan motor are driven individually during cooling / heating operation and during thermo operation. Even when the compressor motor is stopped and only various electric load devices are operated, the leakage current to the ground is optimally maintained, so an electric shock accident caused by this leakage current is prevented and the reliability is high. A compression cooling device is obtained.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram of an embodiment of the compression type cooling device of the present invention, FIG. 2 is a flow chart for explaining the operation of the present invention, and FIGS. 3 and 4 are other embodiments of the present invention. Fig. 5 shows the electric circuit diagram of the conventional compression cooling device, and Fig. 6 shows the relationship between the generated voltage waveform of the inverter device of the conventional compression cooling device and the leakage current waveform to the ground. FIG. 7 is a characteristic diagram showing the relationship between the leakage current and the capacitance of the grounding capacitor. In the figure, (1) is an AC power supply, (2) is a noise filter, (3) is a capacitor, (5) is an inductance,
(7) is a rectifier circuit, (9) is an inverter device, (10) is a compressor motor, (12) is a fan motor, (13) is an electrical component, (14) is a first grounding capacitor, and (15) is The second grounding capacitor, (16) is a switch, and (17) is a control circuit. The same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A noise filter comprising an inductance, a capacitor and a first grounding capacitor, which is connected to an AC power supply, and a voltage rectifying circuit which is connected in parallel with the noise filter and converts an AC voltage into a DC voltage. An inverter device that is connected in parallel with the voltage rectifier circuit and that converts a DC voltage into a variable frequency AC, a compressor motor connected to the inverter device, and various electric load devices connected to the AC power supply, In a compression cooling device including a second grounding capacitor connected in parallel with the circuit of the first grounding capacitor in the noise filter, and a switch connected in series with the second grounding capacitor. When,
A compression cooling device comprising: a control unit that controls the capacity of the grounding capacitor by turning off the switch when the compressor motor is stopped based on the operation result of the compressor motor.