JP2546018Y2 - Inverter device smoothing circuit - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION The present invention relates to current control at the time of starting in an inverter device, in which operation of an induction motor using an inverter is used in various fields, and complicated speed control can be performed according to the application. However, this is because the inverter device has many features, but on the other hand, with the increase in the capacity of the inverter, the shape of the entire device is large and there are many inconveniences in installation. It is intended to provide a smoothing circuit of an inverter device which is downsized by improving the above.

[0002]

2. Description of the Related Art FIG. 3 shows a conventional inverter device which converts an AC power supply into a DC power by a converter and supplies a DC power supply through a filter circuit to the inverter. FIG. 3 is a simplified diagram of an inverter device, wherein 1 is a three-phase AC power supply, 2 is a power switch, 3 is a three-phase converter unit (hereinafter simply referred to as a converter unit) composed of six diodes, and 4 is a current limiter. Reference numeral 5 denotes a short-circuit switch, 6 denotes a brake resistor, 7 denotes a switching element for a brake circuit, 8 denotes a smoothing capacitor, 9 denotes a three-phase inverter (hereinafter simply referred to as an inverter), and 10 denotes an induction motor. In the inverter device configured as described above, when the induction motor 10 is operated, when the power switch 2 is turned on, the DC power smoothed by the smoothing capacitor 8 from the three-phase AC power source 1 through the converter unit 3 is supplied to the inverter 9. Is done. The brake circuit switching element 7 includes a brake resistor 6 for operating the regenerative energy of the induction motor 10 as a brake. As is well known, the inverter 9 internally generates a voltage and a frequency suitable for the operation of the induction motor 10. The description of the internal control device is omitted because it is not directly related to the present invention. When the power switch 2 is turned on, a large peak current flows through the smoothing capacitor 8.
A current limiting resistor 4 is provided for controlling this current. The capacity of the smoothing capacitor 8 is very large, usually tens of thousands of μF. Therefore, when the current control resistor 4 is not used, the peak current becomes large, which not only heats the smoothing capacitor 8 itself, but also significantly shortens the life,
In addition, the allowable value of the diode of the converter section 3 needs to be increased, which is often inconvenient. As a countermeasure, a means is generally used in which the power switch 2 is turned on and the short-circuit switch 5 is turned on when the charging of the smoothing capacitor 8 is completed or the charging current becomes sufficiently small.

[0003]

However, the current limiting resistor 4 and the short-circuit switch 5 are used only at the time of starting the inverter 9, and are usually unnecessary during the operation of the inverter. In addition, since the current limiting resistor 4 needs to suppress a large charging current, it is necessary to use a resistor having a large current capacity. Further, the short-circuit switch 5 needs to have a current capacity to allow the main circuit current to always flow when the induction motor 10 is energized. For this reason, the mounting area of the current limiting resistor 4 and the short-circuit switch 5 becomes large as a percentage of the entire inverter device. Of course, these unit prices cannot be ignored in terms of the overall ratio. The present invention has been made in view of the above points, and an object of the present invention is to improve the smoothing circuit including a smoothing capacitor, a brake resistor, and a brake circuit element by switching a short-circuit switch of a current limiting resistor. Accordingly, the inverter device can be made as small as possible.

[0004]

Means for achieving the object is to connect a converter section for replacing an AC power supply, a current limiting resistor for inputting the output of the converter section, and a short-circuit switch in parallel. And a braking circuit for inputting the output, and a smoothing capacitor including a smoothing capacitor connected in parallel with the brake circuit. Instead of the current limiting resistor and the short-circuiting switch connected in parallel, the braking circuit includes a diode. A diode connected in parallel with the brake resistor connected in parallel
A switching element connected in series with the brake circuit, a second switching element connected in parallel with a diode, and a smoothing capacitor and a resistor connected in series; The smoothing capacitor and the resistor are connected in parallel between the emitter of the first switching element and the collector of the second switching element.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the smoothing circuit of the inverter device according to the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram of a main part of an embodiment according to the present invention. In FIG. 1, the same reference numerals as those in FIG. 3 denote portions having the same configuration and function. In FIG. 1, reference numeral 15 designates a first switching element 13 and a second switching element 14 connected in series therein, and an emitter of the first switching element 13 and a second switching element 14 are connected.
Are connected in parallel, a resistor 11 and a smoothing capacitor 12 connected in series are connected in parallel, and a smoothing capacitor 8 connected between the resistor 11 and the smoothing capacitor 12 and between the respective switching elements is A charging current flows through the resistor 11. In such a circuit, when the power switch 2 is turned on, the switching element 14 is turned off, so that the initial charging current of the smoothing capacitor 12 flows through the current limiting resistor 11. After the completion of the initial charge, the charging / discharging current of the smoothing capacitor 12 can flow through the switching element 14 by turning on the switching element 14. That is, the same effect as when the current limiting resistor 4 in FIG. 3 is short-circuited is obtained. Further, since a series circuit 15 in which two switching elements are integrated is used, a considerable reduction in size can be achieved. FIG. 2 is a diagram showing a main part of another embodiment of the present invention. The difference from FIG. 1 is that one end of the inverter 9 of FIG. 1 is connected from the emitter side of the second switching element 14 to the collector side. The function is the same as that of FIG.

[0006]

As described above, according to the present invention, a switching element is used in place of the relatively large short-circuiting switch 5, and the switching element and the switching element of the brake circuit are connected in series. By using a commercially available device integrating two elements, the entire device can be miniaturized, and at least performance equivalent to that of a conventional device can be obtained, which is extremely useful in practical use.

[0007]

[Brief description of the drawings]

FIG. 1 is a main part configuration diagram showing one embodiment of a smoothing circuit of the inverter device of the present invention.

FIG. 2 is a main part configuration diagram showing another embodiment of the present invention.

FIG. 3 is a simplified diagram showing an example of a conventional device.

[0008]

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Three-phase AC power supply 2 Power switch 3 Converter part 4 Current limiting resistor 5 Short-circuit switch 6 Brake resistor 7 Switching element 8 Smoothing capacitor 9 Three-phase inverter 10 Induction motor 11 Resistance 12 Smoothing capacitor 13 First switching element 14 Second Switching element 15 Series circuit

Claims (1)

(57) [Scope of request for utility model registration] An inverter comprising a converter for converting an AC power supply to a DC voltage, a circuit for smoothing the DC voltage, a brake circuit for suppressing an increase in the DC voltage, and an inverter circuit for changing the DC voltage to the AC power supply. In the device,
A brake circuit is formed by connecting the brake resistor (6) and the first switching element (13) in series, and a charging circuit is formed by connecting the charging resistor (11) and the second switching element (14) in parallel. The two ends of the brake circuit and the charging circuit connected in series are connected to the converter (3), and the smoothing capacitor (12) is connected in parallel to both ends of the brake circuit, and the first switching element (13) and the second
The switching element (14) is a smoothing circuit of an inverter device, characterized in that the switching element (14) is formed by an integrated module in which the two switching elements are connected in series.