JPS61106072A - Inverter device - Google Patents

Abstract

PURPOSE:To improve the power factor of an input by inserting a series circuit of a reactor and a diode into a DC intermediate circuit of a rectifier and an inverter, and providing a capacitor in parallel therewith. CONSTITUTION:An AC power source 1 is converted through a rectifier 2 of diodes and a smoothing condenser 3 into a DC voltage, which is converted by an inverter 4 into an AC, and supplied to a load 5. A reactor 9 for improving the power factor of the input is inserted between the power source 1 and the rectifier 2, a diode 7 is provided, and a capacitor 8 is connected in parallel therewith. Thus, a current flowed to the reactor 9 for improving the power factor is charged reversely in the capacitor 8 in a path of the reactor 9, the diode 7, the condenser 8 and the reactor 9. The reverse redischarge of the condenser 8 is blocked by the diode 7 to remain charged to increase the period that the current of the same direction as the voltage is flowed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inverter device, and more particularly to an inverter device for improving the power factor of an inverter input.

[Prior art and its problems]

As this type of inverter device, conventional
The one shown in the figure is known. In the figure, 1 is an AC power supply, 2 is a bridge rectifier circuit using diodes, and 3 is a smoothing capacitor inserted in a DC intermediate circuit connecting the bridge rectifier circuit 2 and the inverter 4. The above-mentioned inverter 4 is composed of transistors or SIRIS and converts DC power into AC power. The most basic main circuit of the inverter device is composed of the bridge rectifier circuit 2 described above, a DC intermediate circuit, and the inverter 4. A load 5 is connected to the inverter 4.

In FIG. 4, a glue handle 6 for improving the power factor of the inverter input is inserted between the AC power source 1 and the bridge rectifier circuit 2, and in FIG. 5, it is inserted in the DC intermediate circuit.

However, in such conventional circuits, the degree to which the power factor can be improved is very small, and a good improvement effect is hardly obtained.

[Purpose of the invention]

It is an object of the present invention to provide an inverter device that eliminates the above-mentioned drawbacks and improves the power factor of the inverter input.

[Key points of the invention]

This invention inserts a series circuit of a reactor and a diode into the DC intermediate circuit between the rectifier circuit and the inverter, and connects a capacitor in parallel to the series circuit, thereby reducing the voltage while the voltage is being applied. The period during which current flows in the same direction is made wider.

[Embodiments of the invention]

First, regarding improving the power factor mentioned above, see Figure 3 (a
) will be further explained with reference to FIG. 3(b). Whether the power factor is good or bad is considered from the voltage and current waveforms, and it can be said that the power factor is good if the period during which the current flows in the same direction as the voltage is as wide as possible while the voltage is applied. That is, when the current has a narrow pulse-like intermittent waveform as shown in FIG. 3(a), the distortion becomes large and the power factor becomes the worst. It can be said that the power factor is best when the current is continuous as shown in FIG. 3(b).

FIG. 1 shows an embodiment of the present invention, in which the period during which current flows in the same direction as voltage is widened. In the figures, the same reference numerals as in FIG. 4 indicate the same members. In the DC intermediate circuit connecting the bridge rectifier circuit 2 and the inverter 4, there is a diode handle 9 in a direction that allows current to flow to the inverter 4.
A series circuit is inserted in the series circuit, and a capacitor 8 is connected in parallel to the series circuit.

The operation of such a configuration will be explained based on FIG. 2.

When voltage and current are supplied from the AC power supply 1 to the reactor 9 and the capacitor 8 through the rectifier circuit 2 at a time point P1, the capacitor 8 is charged to the opposite polarity during a period T1 as shown in the figure. Therefore, the voltage obtained by adding the voltage of capacitor 8 and the voltage of capacitor 3 is lower than the voltage of capacitor 3 alone. In order for current to flow from the AC power source 1 through the diode 7, the voltage of the AC power source 1 must be higher than the sum of the voltages of the capacitor 8 and the capacitor 3. Therefore, at the initial point of period T2, the AC power supply becomes higher than the sum of the voltage of capacitor 8 and the voltage of capacitor 3, and the AC power supply 1
Input current starts flowing from . If capacitor 8 were not present, the voltage would be only the voltage of capacitor 3, and since the power supply voltage is still lower than the voltage of capacitor 3 at the beginning of period T2, the current from power supply 1 cannot start flowing. That is, by providing the capacitor 8, the power factor was improved.

Next, period T3 is a period during which current flows from AC power supply 1 through rectifier circuit 2, reactor 9, diode 7, capacitor 3, inverter 4, and load 5. Then, in period T4, the voltage of capacitor 3 is higher than the voltage of power supply 1.

At this time, if the accelerator 9 were not present, the current of the power source 1 would not be able to flow, but since the reactor 9 is connected, the current of the power source 1 would continue to flow due to its follow-on effect. Therefore, the power factor is improved in the accelerator 9 during this period.

Then, in period T5, the current of the power supply 1 becomes zero, and the current flowing through the reactor 9 is reduced to the accelerator 9, diode 7,
It flows through the path returning to the capacitor 8 and reactor 9, charging the capacitor 8 in the opposite direction. Even if the charged capacitor 8 tries to discharge again in the reverse direction, it is blocked by the diode 7 and cannot be discharged, so it remains charged for a period of time T.
6. After period T6, the same operation as from period T1 to period T5 will be repeated.

In this way, the period during which current flows in the same direction as voltage becomes wider, and the power factor of the inverter input can be improved.

〔Effect of the invention〕

According to this invention, a series circuit of a reactor and a diode is inserted into the DC intermediate circuit between the rectifier circuit and the inverter, and a capacitor is connected in parallel to the series circuit.
In the input current of the inverter, while the voltage is applied, the period in which the current flows in the same direction as the voltage becomes wider, and the input power factor is significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of an inverter device according to the present invention, FIG. 2 is a voltage and current waveform diagram of each part for explaining the present invention in detail, and FIGS. 3(a) and 3(b) 1 is a diagram showing an example of a waveform for explaining the quality of the input power factor, and FIGS. 4 and 5 are circuit diagrams of a conventional inverter device. 2... Rectifier circuit, 3.8... Capacitor, 4...
Inverter, 6, 9...reactor, 7...diode. Fig. 3ffl (G) Fig. 3 (b) Pl Fig. 2 Fig. 4 Fig. 5

Claims (1)

[Claims] 1) A rectifier circuit that converts AC power into DC power, a power conversion inverter connected to the rectifier circuit, and a DC intermediate circuit connected between the rectifier circuit and the inverter and having a smoothing capacitor. An inverter device characterized in that a circuit formed by connecting a capacitor in parallel to a series circuit of a reactor and a diode is inserted into the DC intermediate circuit.