JPH0567192U - Inverter smoothing circuit - Google Patents

Abstract

(57) [Abstract] [Purpose] To eliminate the short-circuit switch and current limiting resistor for suppressing the initial charge inrush current of the smoothing capacitor of the power inverter device, and to downsize the entire device. [Structure] A switching element is connected in series to a smoothing capacitor connected in parallel with a brake circuit, and the gate voltage of this switching element is controlled by an electronic circuit.
Further, the switching element included in the brake circuit and the switching element are integrally formed.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to the current control at the time of starting in the inverter device, and the operation of the induction motor using the inverter is used in various fields, and it is possible to perform complicated speed control according to the application. However, on the other hand, as the capacity of the inverter increases, the overall size of the device becomes larger and there are many installation inconveniences. It is intended to provide a smoothing circuit for an inverter device to be converted into a new one.

[0002]

[Prior Art]

 Conventionally, an inverter device for converting an alternating current power source into a direct current in a converter section and supplying the direct current power source through a filter circuit to an inverter is shown in FIG. FIG. 3 is a simplified diagram of an inverter device. 1 is a three-phase AC power source, 2 is a power switch, 3 is a three-phase converter unit composed of 6 diodes (hereinafter simply referred to as a converter unit), and 4 is a current limiter. A resistor, 5 is a short-circuit switch, 6 is a brake resistor, 7 is a switching element for a brake circuit, 8 is a smoothing capacitor, 9 is a three-phase inverter (hereinafter simply referred to as an inverter), and 10 is an induction motor. In the thus configured inverter device, 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 fed to the inverter 9. Supplied. The switching element 7 for the brake circuit 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 is internally provided with a voltage and 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. At the moment 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 the purpose of controlling this current. The capacity of the smoothing capacitor 8 is usually as large as tens of thousands of μF. Therefore, when the current control resistor 4 is not used, a large peak current is generated, which not only heats the smoothing capacitor 8 itself, but also shortens the life significantly, and it is necessary to increase the allowable value of the diode of the converter unit 3. There are often inconveniences. As a countermeasure against this, a means for turning on the power switch 2 and turning on the short-circuiting switch 5 when charging of the smoothing capacitor 8 is completed or when the charging current is sufficiently small is generally used.

[0003]

[Problems to be solved by the device]

 However, the current limiting resistor 4 and the short-circuiting switch 5 are used only when the inverter 9 is started, and are normally unnecessary during the operation of the inverter. In addition, the current limiting resistor 4 needs to be a resistor having a large current capacity in order to suppress a large charging current. Further, the short-circuit switch 5 needs to have a current capacity that allows the main circuit current to always flow when the induction motor 10 is energized. From this, the mounting area of the current limiting resistor 4 and the short-circuiting switch 5 becomes large as a proportion of the entire inverter device. Of course, these unit prices cannot be ignored in terms of the total ratio. The present invention was made in view of the above-mentioned points, and an object thereof is to eliminate the current limiting resistance and the short-circuiting switch 5 and to make the inverter device as small as possible.

[0004]

[Means for Solving the Problems]

 In other words, the means for achieving the purpose are the converter section for exchanging the AC power supply, the parallel connection of the current limiting resistor for inputting the output of this converter section and the short-circuiting switch, and the brake for inputting this output. In a smoothing circuit consisting of a circuit and a smoothing capacitor connected in parallel with this brake circuit, instead of connecting the current limiting resistor and the short-circuiting switch in parallel, the brake circuit is connected in series with a brake resistor in which a diode is connected in anti-parallel. , A first switching element with a diode connected in anti-parallel is connected, and a second switching element with a diode connected in anti-parallel is connected in series with this brake circuit, and a smoothing capacitor and a resistor are connected in series. Connected in parallel with each of the above-mentioned ones connected in series. Transmitters and those configured to connect the resistor and the smoothing capacitor between the collector of the second switching element.

[Action]

 The operation will be described together with the embodiment described below.

[0005]

【Example】

 An embodiment of the smoothing circuit of the inverter device of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic view of the essential part of an embodiment according to the present invention. In the figure, the same reference numerals as those in FIG. In FIG. 1, reference numeral 15 is an internal structure in which a first switching element 13 and a second switching element 14 are connected in series, and the emitter of the first switching element 13 and the collector of the second switching element 14 are connected. In addition, this and the smoothing capacitor 8 in which the resistor 11 and the smoothing capacitor 12 are connected in series are connected in parallel, and the resistor 11 and the smoothing capacitor 12 and the respective switching elements described above are connected to each other. A charging current flows through the switching element 14 of. In such a circuit, when the power switch 2 is turned on, the switching element 12 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 switching element 14 is turned on to allow the charging / discharging current of the smoothing capacitor 12 to flow through this switching element. That is, the same effect as short-circuiting the current limiting resistor 4 in FIG. 3 is obtained. Further, since the series circuit 15 in which two switching elements are integrated is used, the size can be considerably reduced. FIG. 2 is a block diagram showing the 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 moved from the emitter side of the second switching element 14 to the collector side. The functions are the same as in FIG.

[0006]

As described above, according to the present invention, the capacitor for smoothing the output voltage of the converter, the resistor for the DC voltage applied to this capacitor, and the effective current flowing through this resistor are controlled. By connecting in series with the switching element, the brake circuit that suppresses the rise in DC voltage and the current limiting resistor and short-circuiting switch that suppress the initial charge inrush current of the capacitor connected in series, By connecting a voltage-driven switching element in which a diode is connected in series with a smoothing capacitor and a brake circuit in antiparallel, the current limiting resistor and the short-circuiting switch are removed, and it is used to suppress the initial charge inrush current of the smoothing capacitor. The gate voltage of the voltage-driven switching element connected in series with this smoothing capacitor is used as the three-phase converter. The DC power source rectified by the power supply controls the charging circuit at the same time when this power source starts up. This eliminates the need for the relatively large current limiting resistor 4 and the short-circuiting switch 5, thus reducing the overall size of the device and achieving at least the same performance as the conventional one, which is extremely useful in practice. It is expensive.

[0007]

[Brief description of drawings]

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

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

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

[0008]

[Explanation of symbols]

 1 Three-phase AC power supply 2 Power switch 3 Converter section 4 Current limiting resistance 5 Short-circuit switch 6 Brake resistance 7 Switching element 8 Smoothing capacitor 9 Three-phase inverter 10 Induction motor 11 Resistor 12 Smoothing capacitor 13 First switching element 14 Second Switching element 15 series circuit

Claims (1)

[Scope of utility model registration request] 1. A converter section for exchanging an AC power supply, a parallel connection of a current limiting resistor for inputting the output of the converter section and a short-circuiting switch, a brake circuit for inputting the output, and this brake circuit. In a smoothing circuit including a smoothing capacitor connected in parallel, instead of connecting the current limiting resistor and a short-circuiting switch in parallel, the brake circuit connects a diode in antiparallel to the brake resistor in series, and connects the diode in antiparallel. Done first
A switching element is connected, a second switching element in which a diode is connected in anti-parallel is connected in series with the brake circuit, and a smoothing capacitor and a resistor are connected in series, and the above respective elements are connected in series. Is connected in parallel with the emitter of the first switching element and the second
A smoothing circuit for an inverter device, characterized in that the smoothing capacitor and the resistor are connected between the collectors of the switching elements.