JP6160899B2 - Passive filter and air conditioner - Google Patents

Description

  The present invention relates to a passive filter that suppresses harmonic current and an air conditioner including the passive filter.

  Conventionally, various methods for suppressing harmonic currents generated from an inverter circuit that drives an electric motor of an air conditioner have been proposed (see, for example, Patent Document 1). The configuration of Patent Document 1 suppresses harmonic currents generated from a load circuit by a passive filter using a resonance circuit.

JP 2011-50111 A

The frequency of harmonics suppressed by the passive filter using the resonance circuit is determined by the inductance of the coil and the capacitance of the capacitor constituting the resonance circuit. For this reason, the inductance of the coil and the capacitance of the capacitor are usually selected in accordance with the frequency of the power supply system. For example, there are two types of commercial power supply frequencies in Japan, 50 Hz and 60 Hz, and the inductance of the coil and the capacitance of the capacitor are selected so as to correspond to either of them. Therefore, when installing the air conditioner, it is necessary to select a filter suitable for the commercial power frequency at the installation location.
The present invention has been made in view of the above-described circumstances, is not subject to power supply frequency restrictions, and is capable of suppressing harmonics generated from a load circuit driven by an AC power supply, and air. It aims at providing a harmony device.

  In order to achieve the above object, the present invention is a passive filter that suppresses harmonics of a load circuit that is driven by receiving supply of a three-phase alternating current, and is connected to the power supply system side of each phase. A first resonance circuit configured by connecting a first coil and a first capacitor in series, and connected in parallel to the first resonance circuit, and configured by connecting a second coil and a second capacitor in series A first resonance circuit, wherein an inductance of the first coil is 3.0 mH or more and 6.0 mH or less, a capacitance of the first capacitor is 65 μF or more and 130 μF or less, The inductance of the coil is 3.0 mH or more and 6.0 mH or less, and the capacitance of the second capacitor is 45 μF or more and 95 μF or less.

In order to achieve the above object, the present invention provides an electric motor driven by receiving a three-phase alternating current, a compressor driven by the electric motor, an inverter for supplying driving electric power to the electric motor, A passive filter connected to the power system side from the inverter, and a control unit that detects the frequency of the alternating current supplied from the power system, wherein the passive filter is connected to the power system side of each phase. A first resonance circuit configured by connecting a first coil and a first capacitor in series; a parallel connection to the first resonance circuit; and a second coil and a second capacitor connected in series. A second resonance circuit configured, wherein the inductance of the first coil is 3.0 mH or more and 6.0 mH or less, and the capacitance of the first capacitor is 65 μF or more and 130 μF or less. , And the inductance of the second coil is less 6.0mH least 3.0MH, the capacity of the second capacitor and said 95μF less der Rukoto, more 45MyuF.

  According to the present invention, harmonics can be suppressed corresponding to a plurality of AC power supplies having different frequencies.

It is a perspective view of the outdoor unit which constitutes the air harmony device concerning an embodiment. It is a circuit diagram of the passive filter in 1st Embodiment. It is a graph which shows the state of the harmonic current at the time of using a passive filter. It is a circuit diagram of the passive filter in 2nd Embodiment. It is a circuit diagram of the passive filter in 3rd Embodiment.

[First Embodiment]
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view of an outdoor unit 1 of an air conditioner according to a first embodiment to which the present invention is applied.
As shown in FIG. 1, the outdoor unit 1 has a substantially box-shaped outdoor unit body 10. A fan 12 is accommodated in the upper part of the outdoor unit main body 10, and an outdoor heat exchanger 14 is disposed below the fan 12. The outdoor heat exchanger 14 is exposed on the left and right side surfaces and the back surface of the outdoor unit main body 10, and the fan 12 sucks air through the outdoor heat exchanger 14 and exhausts from the upper opening of the outdoor unit main body 10.
The lower part of the outdoor unit main body 10 is a machine room 16 that houses each part of the refrigerant circuit, such as a compressor, an accumulator, a receiver tank, and a refrigerant pipe that connects them. The upper part of the outdoor unit main body 10 houses an electrical box 18 that houses a power circuit board including an inverter that supplies power to the motor of the compressor, a control board that controls the operation of the air conditioner, and the like. ing. The electrical box 18 is exposed on the front surface of the outdoor unit main body 10, so that maintenance of the circuit board inside the electrical box 18 can be easily performed.

A filter case 24 is attached to the lower front portion of the outdoor unit body 10 via a pair of upper and lower brackets 20 and 22. The filter case 24 accommodates a filter substrate on which a passive filter 30 described later is mounted.
By disposing the filter case 24 on the front surface of the outdoor unit body 10, the filter substrate in the filter case 24 is close to the power circuit board and control board inside the electrical box 18, the motor and the like disposed in the machine room 16. Can be installed at a position. For this reason, the operation | work which connects the filter board | substrate in the filter case 24 with the circuit board in the electrical equipment box 18, the compressor in the machine room 16, etc. can be performed easily. For example, the passive filter 30 can be easily retrofitted to the installed outdoor unit 1. Further, the filter case 24 is exposed on the front surface of the outdoor unit body 10. Maintenance of the filter substrate in the filter case 24 is easy.

FIG. 2 is a circuit diagram including the passive filter 30 included in the outdoor unit 1 and its peripheral circuits.
In FIG. 2, 2 is a three-phase AC power supply system (phase voltage 220V to 240V), and 32 is a load circuit connected to the power receiving points of the R, S, and T phases of the power supply system 2. The load circuit 32 of an Example is a circuit containing the electric motor 40 which drives the compressor 38 which comprises the refrigerant circuit of an air conditioner. In addition to the electric motor 4, the load circuit 32 includes a rectifier 34, an inverter 36, a smoothing capacitor 52, and a coil 50.

The three-phase AC power supplied from the power supply system 2 is rectified by the rectifier 34 and smoothed by the smoothing capacitor 52.
The inverter 36 includes three arms (not shown) in which two switching elements such as IGBTs are connected in series. The arms are connected in parallel to each other to form a three-phase inverter, and the gates of the switching elements are ON / OFF controlled by a control device (not shown) to generate three-phase AC power of a predetermined frequency from the smoothed DC power. Then, the electric motor 40 is driven.

  At this time, since the inverter 36 converts DC power into rectangular-wave AC power, a harmonic current is generated and flows into the power supply system 2. Therefore, the passive filter 30 of the present invention is connected between the power supply system 2 and the power receiving point P of the load circuit 32. The passive filter 30 includes a coil 54 (first coil) connected in series, and a resonance circuit 31 configured by connecting a coil 56 (second coil) and a capacitor 58 (first capacitor) in series. Consists of. The coil 54 and the resonance circuit 31 are connected to each phase of the RST. More specifically, one end of the coil 56 of the resonance circuit 31 is connected between the coil 54 and the power receiving point P, and the other ends of the capacitors 58 of the respective phases are connected to each other. The passive filter 30 is accommodated in the filter case 24 provided in the outdoor unit 1 as described above.

FIG. 3 is a chart showing the state of the harmonic current when the passive filter 30 is used. FIGS. 3A and 3B show current waveforms of RST phases when the passive filter 30 is not connected, and FIGS. 3C and 3D show current waveforms when the passive filter 30 is connected. 3A and 3C show the case where the power supply system 2 is a 50 Hz AC power supply, and FIGS. 3B and 3D show the case where the power supply system 2 is a 60 Hz AC power supply.
Since the frequency of the harmonic current generated by the load circuit 32 depends on the frequency of the power supply system 2, for example, as shown in FIGS. 3A and 3B, the AC frequency of the power supply system 2 is 50 Hz and 60 Hz. The frequency of the harmonic current is different from the case of.

In order to effectively suppress harmonics by the passive filter 30, it is necessary to adjust the resonance frequency of the resonance circuit 31 to match the harmonic frequency. In other words, the 50 Hz passive filter 30 and the 60 Hz passive filter 30 generally optimize the inductance of the coil 56 and the capacitance of the capacitor 58 to different values.
In contrast, the inventors configured the passive filter 30 so that the resonance frequency of the resonance circuit 31 is between 250 Hz and 300 Hz, the inductance of the coil 56 is small, and the capacitance of the capacitor 58 is large. Specifically, the inductance of the coil 56 is set to 1.0 mH to 1.8 mH, and the capacity of the capacitor 58 is set to 200 μF to 350 μF. As a more specific example, the inductance of the coil 56 can be 1.4 mH, and the capacity of the capacitor 58 can be 255 μF.
According to this configuration, since the width of the resonance peak frequency of the resonance circuit 31 is large, harmonics can be suppressed by applying the passive filter 30 corresponding to an alternating current having a wide range of frequencies. Therefore, for example, as shown in FIGS. 3C and 3D, harmonics generated by the load circuit 32 can be effectively suppressed regardless of whether the frequency of the power supply system 2 is 50 Hz or 60 Hz. Thereby, a harmonic can be suppressed corresponding to both frequency of 50 Hz and 60 Hz, without changing the structure of the passive filter 30 according to the frequency of the power supply system 2. FIG.
This configuration is particularly effective when the input current input from the power supply system 2 to the load circuit 32 is 60 A or less per phase.

  The inductance of the coil 54 is preferably 1.0 mH or more and 5.0 mH or less. By suppressing the high frequency component by this coil 54, the harmonics generated by the load circuit 32 can be more effectively suppressed together with the effect by the resonance circuit 31. As a more specific example, the inductance of the coil 54 can be set to 1.7 mH.

[Second Embodiment]
FIG. 4 is a circuit diagram showing a configuration of a passive filter 60 as another example of the passive filter included in the outdoor unit 1. FIG. 4 shows the peripheral circuit along with the passive filter 60.
In the second embodiment, a passive filter 60 is provided in the outdoor unit 1 in place of the passive filter 30 described in the first embodiment. The same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

The passive filter 60 includes a coil 62 connected between the power supply system 2 and the power receiving point P, and a resonance circuit unit 65 connected in parallel to the load circuit 32 between the coil 62 and the power receiving point P. Yes. The coil 62 and the resonance circuit unit 65 are connected to each phase of the RST.
The resonance circuit unit 65 includes a first resonance circuit 63 configured by connecting a coil 66 (first coil) and a capacitor 67 (first capacitor) in series, a coil 68 (second coil), and a capacitor. 69 (second capacitor) and a second resonance circuit 64 configured by serial connection. In the first resonance circuit 63, the other ends of the capacitors 67 of the respective phases are commonly connected, and in the second resonance circuit 64, the other ends of the capacitors 69 of the respective phases are commonly connected.

  The first resonance circuit 63 and the second resonance circuit 64 correspond to the case where the frequency of the alternating current supplied by the power supply system 2 is 50 Hz and 60 Hz, respectively. In other words, the inductance of the coil 66 and the capacitance of the capacitor 67 constituting the first resonance circuit 63 are set to be suitable for suppressing harmonics generated when a 50 Hz alternating current is supplied. On the other hand, the inductance of the coil 68 and the capacitance of the capacitor 69 constituting the second resonance circuit 64 are set to be suitable for suppressing harmonics generated when an alternating current of 60 Hz is supplied.

More specifically, the inductance of the coil 66 is 3.0 mH or more and 6.0 mH or less, and the capacity of the capacitor 67 is 65 μF or more and 130 μF or less. Thereby, the first resonance circuit 63 suppresses harmonics when the power source is 50 Hz. Further, the inductance of the coil 68 is 3.0 mH or more and 6.0 mH or less, the capacitance of the capacitor 69 is 45 μF or more and 95 μF or less, and harmonics when the power source is 60 Hz is suppressed.
As a more specific example, the inductance of the coil 66 can be 4 mH, the capacity of the capacitor 67 can be 100 μF, the inductance of the coil 68 can be 4 mH, and the capacity of the capacitor 69 can be 70 μF.
According to the passive filter 60, even if a 50 Hz or 60 Hz alternating current is supplied and a harmonic is generated by the load circuit 32, the passive filter 60 is operated by either the first resonance circuit 63 or the second resonance circuit 64 connected in parallel. Harmonics are suppressed. Here, if the frequency of the alternating current supplied from the power supply system 2 is either 50 Hz or 60 Hz, harmonics can be suppressed without performing a special setting operation or switching.

  The inductance of the coil 62 is preferably 1.0 mH or more and 5.0 mH or less. By suppressing the high-frequency component by the coil 62, the harmonics generated by the load circuit 32 can be more effectively suppressed together with the effect of the resonance circuit unit 65. As a more specific example, the inductance of the coil 62 can be 2.5 mH.

[Third Embodiment]
FIG. 5 is a circuit diagram illustrating a configuration of a passive filter 70 as another example of the passive filter included in the outdoor unit 1. FIG. 5 shows the peripheral circuit along with the passive filter 70.
In the third embodiment, instead of the passive filter 30 described in the first embodiment, a passive filter 70 is provided in the outdoor unit 1. The same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

The passive filter 70 includes a coil 71 connected between the power supply system 2 and the power receiving point P, a resonance circuit 72 connected in parallel to the load circuit 32 between the coil 71 and the power receiving point P, and a switch 76. And a capacitor 79 connected to the resonance circuit 72 via The coil 71, the resonance circuit 72, and the capacitor 79 are connected to each phase of the RST.
The resonance circuit 72 is configured by connecting a coil 73 (first coil) and a capacitor 74 (first capacitor) in series. In the resonance circuit 72, the other ends of the capacitors 74 are commonly connected. The capacitor 79 (second capacitor) is connected in parallel to the capacitor 74 via the switch 76, and the other end of the capacitor 79 is commonly connected to each phase of RST.

  The switch 76 is a switch that simultaneously connects and disconnects three capacitors 79 connected to the R, S, and T phases. When the switch 76 is closed, the capacitance of the capacitor of the resonance circuit 72 is the combined capacitance of the capacitors 74 and 79 connected in parallel. When the switch 76 is open, the capacity of the capacitor of the resonance circuit 72 becomes the capacity of the capacitor 74. That is, by opening and closing the switch 76, the capacitance of the resonance circuit 72 can be changed, and the resonance frequency can be switched in two stages.

  The resonance frequency of the resonance circuit 72 corresponds to the case where the frequency of the alternating current supplied by the power supply system 2 is either 50 Hz or 60 Hz. That is, the inductance of the coil 73 and the capacitance of the capacitor 74 are set to be suitable for suppressing harmonics generated when an alternating current of 50 Hz or 60 Hz is supplied. On the other hand, the capacity of the resonance circuit 72 when the switch 76 is closed is set to be suitable for suppressing harmonics generated when a 60 Hz or 50 Hz alternating current is supplied.

More specifically, the inductance of the coil 73 is 3.0 mH or more and 6.0 mH or less, and the capacitance of the capacitor 74 is 45 μF or more and 95 μF or less. Thereby, the resonance circuit 72 suppresses harmonics when the power source is 50 Hz. Further, the capacitance of the capacitor 79 is 20 μF or more and 35 μF or less. When the switch 76 is closed, harmonics generated when the power source is 60 Hz are suppressed by the resonance circuit 72. That is, when the switch 76 is closed, the combined capacitance of the capacitor 74 and the capacitor 79 is 65 μF or more and 130 μF or less.
As a more specific example, the inductance of the coil 73 can be 4 mH, the capacitance of the capacitor 74 can be 70 μF, and the capacitance of the capacitor 79 can be 30 μF.

Further, the switch 76 is configured by a relay, for example, and is opened and closed by a control board accommodated in the electrical box 18 of the outdoor unit 1. This control board has a function of detecting the frequency of the AC power supplied from the power supply system 2. When the detected frequency of the power is 50 Hz, the switch 76 is opened, and the detected frequency of the power is 60 Hz. If there is, control to close the switch 76 is performed.
As a result, the switch 76 is automatically opened and closed appropriately in accordance with the frequency of the AC power supplied from the power supply system 2. For this reason, even if it does not perform special operation, a harmonic can be suppressed corresponding to the some alternating current from which a frequency differs.

  The inductance of the coil 71 is preferably 1.0 mH or more and 5.0 mH or less. By suppressing the high-frequency component by the coil 71, the harmonics generated by the load circuit 32 can be more effectively suppressed together with the effect by the resonance circuit 72. As a more specific example, the inductance of the coil 71 can be 2.5 mH.

  Each of the above embodiments shows one aspect to which the present invention is applied, and does not limit the present invention. For example, in each of the above embodiments, the configuration including the electric motor 40 that drives the compressor of the air conditioner has been described as an example. However, the present invention is not limited to this, and for example, hot water storage of a water heater The present invention is also applicable to a configuration in which an electric motor that drives a compressor that constitutes a refrigerant circuit that heats the tank is provided, and the electric motor is driven by an inverter. Of course, other details can be changed as appropriate without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 Outdoor unit 2 Power supply system 4 Electric motor 30, 60, 70 Passive filter 31, 72 Resonant circuit 32 Load circuit 34 Rectifier 36 Inverter 38 Compressor 40 Electric motor 50, 54, 56, 62, 66, 68, 71, 73 Coil 52 Smooth Capacitors 58, 67, 69, 74, 79 Capacitors 63 First resonant circuit 64 Second resonant circuit 65 Resonant circuit section 76 Switch P Power receiving point

Claims (2)

A passive filter that suppresses harmonics of a load circuit driven by receiving a three-phase alternating current,
A first resonance circuit connected to the power system side of each phase and configured by connecting a first coil and a first capacitor in series;
A second resonance circuit connected in parallel to the first resonance circuit and configured by connecting a second coil and a second capacitor in series,
The inductance of the first coil is not less than 3.0 mH and not more than 6.0 mH, and the capacitance of the first capacitor is not less than 65 μF and not more than 130 μF;
The inductance of the second coil is not less than 3.0 mH and not more than 6.0 mH, and the capacitance of the second capacitor is not less than 45 μF and not more than 95 μF;
Passive filter characterized by An electric motor driven by the supply of three-phase alternating current;
A compressor driven by the electric motor;
An inverter for supplying driving power to the electric motor;
A passive filter connected to the power system from the inverter;
A controller that detects the frequency of the alternating current supplied from the power supply system,
The passive filter is connected to the power supply system side of each phase, and is connected in parallel to a first resonance circuit configured by connecting a first coil and a first capacitor in series, and the first resonance circuit. A second resonance circuit configured by connecting a second coil and a second capacitor in series, wherein the inductance of the first coil is not less than 3.0 mH and not more than 6.0 mH, the capacitance of the capacitor is less 130μF least 65MyuF, the inductance of the second coil is less 6.0mH least 3.0MH, the capacitance 95μF less der Rukoto least 45μF of the second capacitor,
An air conditioner characterized by.

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