JPH11289770A - Inverter device, and air conditioning unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize cost reduction by lowering the level of noise arising from the switching operation of a semiconductor element. SOLUTION: In an inverter device 27 which is equipped with a smoothing circuit for converting an AC power into a DC power and a plurality of semiconductor elements and has a converting circuit 29 for converting the DC power into an AC power of desired frequency through the switching operation of these semiconductor elements, and an inverter control circuit 30 for deciding the timing of the switching action of the semiconductor element, by the use of carriers, the carriers are formed by combining the plural carrier components of different frequencies with one another by each cycle or by each plural cycles.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter capable of changing the rotation speed of an electric motor and an air conditioner to which the inverter is applied.

[0002]

2. Description of the Related Art In general, there is an air conditioner in which the rotation speed of an electric motor of a compressor, an outdoor fan or an indoor fan can be changed by an inverter device.

In this inverter device, for example, a pulse width modulation (PWM) inverter device, an AC voltage having a rated frequency is converted into an AC voltage having a desired frequency and is output. The switching operation of the plurality of semiconductor elements produces a pulsed voltage, and the frequency of the output voltage is adjusted by modulating the width of the pulsed voltage.

The timing of the switching operation of the semiconductor element is determined by comparing a triangular wave carrier with a sine wave control voltage.

[0005]

At the time of the switching operation of the semiconductor element described above, noise is generated, and this noise has an adverse effect such as causing a malfunction in a device incorporating an electronic device such as an air conditioner. The noise is the fundamental frequency of the carrier and the third order of this fundamental frequency,
.., And the higher the frequency, the higher the frequency, the greater the number of switching operations, and the higher the noise level.

In order to attenuate this noise, the inverter device is provided with a noise filter. However, if the noise level is high, a noise filter having a high attenuation rate must be employed, which inevitably increases the cost. .

An object of the present invention has been made in view of the above circumstances, and an inverter device capable of reducing the level of noise generated by the switching operation of a semiconductor element and reducing the cost of a noise filter. And an air conditioner.

[0008]

According to the first aspect of the present invention,
A smoothing circuit for converting an AC power supply into a DC power supply, a plurality of semiconductor elements, and a switching circuit for converting the DC power supply into an AC power supply having a desired frequency by a switching operation of the semiconductor elements; An inverter control circuit that determines the switching timing of the element;
, Wherein the carrier is formed by combining a plurality of carrier components having different frequencies in one or a plurality of cycles.

According to a second aspect of the present invention, there is provided an outdoor unit having a compressor, an outdoor heat exchanger and an outdoor fan, and an indoor unit having an indoor heat exchanger and an indoor fan.
In an air conditioner in which at least one of the outdoor fan or the indoor fan is controlled in rotation speed by an individual inverter device, the inverter device includes a smoothing circuit that converts an AC power supply into a DC power supply, and a plurality of semiconductor elements. A conversion circuit that generates an AC power supply having a desired frequency from the DC power supply by a switching operation of these semiconductor elements; and an inverter control circuit that determines switching timing of the semiconductor element using a carrier. Are formed by combining a plurality of carrier components of different frequencies in one or a plurality of cycles.

The invention described in claim 1 or 2 has the following effects.

In the inverter device, the carrier frequency is not fixed, but a carrier is formed by combining a plurality of carrier components having different frequencies in every one cycle or a plurality of cycles. Noise can be dispersed and the noise level can be reduced. For this reason, a noise filter with a low attenuation rate can be adopted, and the cost of the noise filter can be reduced.

[0012]

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

FIG. 1 is a refrigerant circuit diagram showing an embodiment of an air conditioner according to the present invention.

As shown in FIG. 1, the air conditioner 10 includes:
It has an outdoor unit 11, an indoor unit 12, and an air-conditioning control device 13, and an outdoor refrigerant pipe 14 of the outdoor unit 11 and an indoor refrigerant pipe 15 of the indoor unit 12 are connected via connection pipes 24, 25. .

The outdoor unit 11 is installed outdoors, and a compressor 16 is disposed on the outdoor refrigerant pipe 14. An accumulator 17 is provided on the suction side of the compressor 16 and a four-way valve 18 is provided on the discharge side of the compressor 16 via the outdoor refrigerant pipe 14. The four-way valve 1
8 is connected to an outdoor heat exchanger 19 via an outdoor refrigerant pipe 14. An outdoor fan 20 that blows air toward the outdoor heat exchanger 19 is disposed adjacent to the outdoor heat exchanger 19.

The outdoor fan 20 is driven to rotate by a fan motor (three-phase induction motor) 26, and the rotation speed of the fan motor 26 is changed and adjusted by an inverter device 27. Then, the inverter device 27 is controlled by the air conditioning control device 13.

On the other hand, the outdoor unit 12 is installed indoors, and the indoor heat exchanger 21 is disposed in the indoor refrigerant pipe 15.
An electric expansion valve 22 is provided near the indoor heat exchanger 21 in the indoor refrigerant pipe 15. An indoor fan 23 for blowing air to the indoor heat exchanger 21 is disposed adjacent to the indoor heat exchanger 21.

The air-conditioning control device 13 includes the outdoor unit 1
1 and the operation of the indoor unit 12. Specifically, the compressor 16, the four-way valve 18 and the outdoor fan 2 in the outdoor unit 11 are controlled.
0, and controls the electric expansion valve 22 and the indoor fan 23 in the indoor unit 12, respectively.

When the four-way valve 18 is switched by the air conditioning controller 13, the air conditioner 10 is set to the cooling operation or the heating operation. That is, when the air-conditioning control device 13 switches the four-way valve 18 to the cooling side, the refrigerant flows as indicated by the solid line arrow, the outdoor heat exchanger 19 becomes the condenser, and the indoor heat exchanger 21 becomes the evaporator, and the cooling operation state is established. Then, the indoor heat exchanger 21 of the indoor unit 12 cools the room. When the air-conditioning control device 13 switches the four-way valve 18 to the heating side, the refrigerant flows as indicated by the dashed arrow, and the indoor heat exchanger 21 functions as a condenser, and the outdoor heat exchanger 19 functions as an evaporator. Then, the indoor heat exchanger 21 of the indoor unit 12 heats the room.

The air-conditioning control device 13 controls the electric expansion valve 22 of the indoor unit 12 according to the air-conditioning load of the indoor unit 12.
And controls the indoor fan 23 of the indoor unit 12.

The inverter device 27 is a pulse width modulation type inverter (PWM inverter) and includes a smoothing circuit 28, a conversion circuit 29, an inverter control circuit 30, and a filter circuit 31, as shown in FIG. You.

The smoothing circuit 28 is a circuit for converting a single-phase or three-phase AC voltage into a constant DC voltage. The conversion circuit 29 includes six semiconductor elements, for example, transistors,
Thyristor or GTO (gate turn off)
a DC voltage converted by the smoothing circuit 28 by a switching operation of these semiconductor elements into a pulsed AC output voltage, and by modulating the width of the pulsed output voltage, the AC output voltage Is adjusted to a desired frequency. FIG. 3C shows the output voltage waveform.

The inverter control circuit 30 includes a conversion circuit 29
And outputs a signal for instructing a switching operation to the semiconductor element. That is, the inverter control circuit 30
Triangular wave carrier (A in FIG. 3 shows a carrier waveform)
And the sine wave control voltage (B in FIG. 3 indicates a control voltage waveform), determines the switching operation timing in the semiconductor element of the conversion circuit 29, and outputs a signal instructing the switching operation to the conversion circuit 29. I do.

Switching noise is generated by the switching operation of the semiconductor element. The above filter circuit 3
Numeral 1 includes a noise filter (not shown), which attenuates switching noise.

Here, the carrier used in the inverter control circuit 30 and displayed as the carrier waveform A in FIG. 3 is formed by combining carrier components a, b, c,... Every cycle. Here, the carrier components a, b, c,...
(Period T1), fc2 (period T2), fc3 (period T
3), and fc1>fc2>fc3>.
Here, the frequency fc1 of the carrier component a is, for example, about 10
KHz.

Therefore, as compared with the case where the frequency of the carrier is fixed at fc1, the conversion circuit 29 according to the present embodiment is used.
, The third harmonic frequencies 3fc1, 3fc2, 3fc3,... And the fifth harmonic frequencies 5fc1, 5fc2, 5fc3,. , And at higher harmonic frequencies. Moreover, fc1>fc2>fc3>
.., The number of switching operations of the semiconductor element of the conversion circuit 29 is reduced. For these reasons, the level of noise generated by the switching operation of the semiconductor element of the conversion circuit 29 can be reduced.

As described above, since the level of noise caused by the switching operation of the semiconductor element generated in the conversion circuit 29 is reduced, a filter having a low attenuation factor can be employed as the noise filter of the filter circuit 31. As a result, the noise filter Cost can be reduced.

Although the present invention has been described based on one embodiment, the present invention is not limited to this.

For example, the carrier shown by the carrier waveform A in FIG. 3 is a combination of carrier components a, b, c,... Having different frequencies for each cycle. .. may be combined for each of a plurality of cycles. In addition, the inverter device 27
Has been described for the outdoor fan 20, but the present invention can also be applied to the compressor 16 or the indoor fan 23.

[0030]

As described above, according to the inverter device and the air conditioner according to the present invention, the inverter device has:
Since a carrier formed by combining a plurality of carrier components of different frequencies in one or more cycles is used, noise generated by the switching operation of the semiconductor element can be dispersed, and the noise level can be reduced. For this reason, a noise filter with a low attenuation rate can be adopted, and the cost of the noise filter can be reduced.

[Brief description of the drawings]

FIG. 1 is a refrigerant circuit diagram showing an embodiment of an air conditioner according to the present invention.

FIG. 2 is a block diagram showing the inverter device shown in FIG. 1;

FIG. 3 is a graph showing a carrier waveform A, a control voltage waveform B, and an output voltage waveform C.

[Explanation of symbols]

 Reference Signs List 10 air conditioner 11 outdoor unit 12 indoor unit 16 compressor 19 outdoor heat exchanger 20 outdoor fan 21 indoor heat exchanger 23 indoor fan 27 inverter device 28 smoothing circuit 29 conversion circuit 30 inverter control circuit 31 filter circuit a, b, c Carrier component A Carrier waveform C Output voltage waveform

Claims (2)

[Claims] 1. A smoothing circuit for converting an AC power supply to a DC power supply, a plurality of semiconductor elements, and a conversion circuit for converting the DC power supply to an AC power supply having a desired frequency by a switching operation of the semiconductor elements; And an inverter control circuit that determines a switching operation timing of the semiconductor element by using a plurality of carrier components having different frequencies, each of which is formed by combining one or more cycles. An inverter device characterized in that: 2. An outdoor unit having a compressor, an outdoor heat exchanger and an outdoor fan, and an indoor unit having an indoor heat exchanger and an indoor fan, wherein the compressor, the outdoor fan or the indoor fan is provided. An air conditioner in which at least one of the rotation speeds is controlled by an individual inverter device.The inverter device includes a smoothing circuit that converts an AC power supply into a DC power supply, and a plurality of semiconductor elements. A switching circuit that generates an AC power supply having a desired frequency from the DC power supply by a switching operation; and an inverter control circuit that determines a switching timing of the semiconductor element using a carrier. Characterized in that the carrier component is formed by combining one or more carrier components in one or more cycles. Apparatus.