JPS58163271A - Power factor improvement circuit for air conditioners - 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 The present invention relates to improving the power factor of a capacity-controlled room air conditioner, and is particularly suitable for improving the power factor of a room air conditioner having a capacitor smoothing rectifier circuit. Regarding circuits.

Conventional capacity-controlled room air conditioners, particularly rotational speed-controlled room air conditioners, generally have a rectifier circuit consisting of a diode bridge and a smoothing capacitor in the power input section, so that a capacitor charging current flows through the rectifier circuit.

For this reason, the power supply current includes large third and fifth harmonics, causing a decrease in the power factor of the entire air conditioner. As a way to solve this problem, methods have been considered such as inserting a large capacity inductor into the power supply line, or using switching elements such as power transistors to create a step-up chopper to shape the waveform. In the latter case, it is not possible to improve the power factor significantly, and in the latter case, since semiconductor switching elements such as power transistors are used, a control circuit is required, and there is no possibility of improving reliability. there were. Therefore, there is a strong demand for a method of reducing the third and fifth harmonics of the input current and greatly improving the power factor using only passive elements such as inductors and capacitors.

The present invention was made to eliminate the above-mentioned defects, and
In equipment with a capacitor smoothing rectifier circuit, such as rotation speed controlled room air conditioners, by inserting a filter consisting of a combination of only an inductor and a capacitor, the 3rd and 5th harmonics caused by the capacitor charging current can be reduced. The object of the present invention is to provide a method for greatly improving the power factor.

The cause of the power factor drop in the capacitor smoothing rectifier circuit is not due to the phase shift of the voltage and current, but is due to the inclusion of the 3rd and 5th harmonics in the capacitor charging current. In this case, the above object is achieved by inserting a filter on the power supply side that exhibits a large impedance value and has zero or very small impedance value for the fundamental wave component.

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3. FIG. 1 is an electrical circuit diagram of the present invention, where 1 is a commercial power supply;
2 is an inductor, 3 is a capacitor, 4 is a rectifier diode, 5 is a smoothing capacitor, and 6 is a load. or,
Figure 2 shows the voltage waveform Vs of the commercial power supply 1 and the inductor 2.
and the output voltage waveform of the filter 7 consisting of the capacitor 3 ■.

shows. Figure 3 shows the commercial power supply voltage waveform VS, filter 7
The phase relationship between the input current Is when the filter 7 is not inserted and the input current Is' when the filter 7 is inserted is shown. Next, the operation of this circuit will be briefly explained. When the filter 7 is not inserted, as shown in FIG. 3, the input current Is takes a steep peak value at the electrical angle position of 90 degrees and contains many third and fifth harmonics. This is for charging the smoothing capacitor. When the filter 7 is inserted, the input current Is' has a trapezoidal waveform. This is filter 7
However, since the circuit constants are such that the third harmonic frequency is the resonant frequency, it becomes difficult for the third harmonic component to flow. From another perspective, the output voltage of filter 7 is
As shown in Figure 2, it becomes a trapezoidal waveform (Vo), and the input voltage Vg
This means that an oscillating voltage with a frequency three times the fundamental frequency is generated in one filter 7. That is, this triple frequency oscillating voltage functions to prevent the third harmonic current from flowing.

Another embodiment will be explained with reference to FIGS. 4 and 5.

Figure 4 shows the configuration of another filter, and the circuit constants are:
When the fundamental frequency is f, select so that the following relationship holds true. At this time, the filter impedance is 0Ω for the fundamental wave, making it difficult to pass the third wave.

In the case of FIG. 5, the circuit constants are selected so that the following relationship holds. At this time, the third harmonic is bypassed within the filter 7 and the input current waveform is improved.

According to the present invention, the third and fifth harmonics of the input current can be reduced using only passive elements such as an inductor and a capacitor, and the power factor is 64 when the filter of the present invention is not inserted.
%, we confirmed that it could be significantly improved to 90%.

It goes without saying that the present invention can be applied not only to full-wave rectifier circuits but also to voltage doubler rectifier circuits, and can greatly improve the power factor.

[Brief explanation of drawings]

Fig. 1 is an electric circuit diagram of the present invention, Fig. 2 is a commercial power supply voltage waveform and a filter voltage waveform of the present invention, and Fig. 3 is a commercial power supply voltage and input with and without a filter inserted. The phase relationships of the terminals, FIGS. 4 and 5, are part of a filter according to another embodiment of the present invention. 1... Commercial power supply, 2... Inductor, 3... Capacitor, 4... Rectifier diode, 5... Smoothing capacitor, 6... Load, 7... Power factor improvement filter, 8... Rectifier, ■"S... Input terminal waveform,
vo... Output voltage waveform of filter 7, ■s... Input current waveform when filter 7 is not inserted, ■s'.
...Input current waveform when filter 7 is inserted. '#1 G '#2 t) pg 3'#4 Lower 45 Fig.

Claims (1)

[Claims] 1. In an air conditioner equipped with a variable speed motor for driving a compressor and an inverter device for driving the variable speed motor, one or more A power factor correction circuit for an air conditioner, characterized in that a filter circuit including an inductor and one or more cannulators is inserted. 2. The air conditioner according to claim 1, characterized in that a filter circuit consisting of one inductor and one capacitor connected in parallel is connected in series with an inverter device. Power factor correction circuit. 3. So that the resonant frequency is an odd multiple of the commercial power supply frequency,
A power factor improvement circuit for an air conditioner according to claim 2, wherein the inductor and capacitor have a set capacity. A power factor improvement circuit for an air conditioner according to claim 1, wherein a filter circuit consisting of two 11r-type capacitors and one capacitor is connected in series with an inverter device. 5. A power factor improvement circuit for an air conditioner according to claim 1, wherein a filter circuit consisting of one inductor and one capacitor connected in parallel is connected in parallel with an inverter device. 6. In series. The power factor improvement circuit for an air conditioner according to claim 1, wherein a filter circuit including one inductor and one capacitor connected in parallel with an inverter device.