JPH05207746A - Inverter - Google Patents

Abstract

PURPOSE:To obtain an inverter having a long life by reducing a capacity and a profile of a smoothing capacitor unit. CONSTITUTION:Capacitor units 13 of smoothing capacitor groups are contained vertically in multiple stages in a housing 12. Positive bus bars 8A, 8C and a negative bus bar 9A are stood on a backs of the units 13, a positive terminal of the unit 13 is connected to the bar 8C, and a negative terminal of the unit 13 is connected to the bar 9A.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter in which the unbalance of current and the inductance of wiring connecting a plurality of smoothing capacitors connected in series, parallel and series-parallel is reduced.

[0002]

2. Description of the Related Art FIG. 6 (a) shows a main circuit connection diagram of a three-phase voltage type transistor inverter which has been most widely used in the past, in which DC power obtained from an AC power source 1 through a rectifier bridge 2 is used. The pulsation is smoothed by an electrolytic capacitor 4 (hereinafter, referred to as a capacitor) connected in series to the reactor 3 and the fuse 5 on the load side thereof, and the transistor 6
The AC output is obtained by the inverter 7 configured as a bridge and the power is supplied to the load 20.

In the thus constructed inverter, the energy stored in the stray inductance of the circuit including the capacitor 4 is applied to the transistor 6 as a spike voltage when the transistor 6 is switched off. In order to suppress this spike voltage, it is necessary to reduce the stray inductance of the wiring from the capacitor 4 to the load side as much as possible. Further, as the capacity becomes larger, the current imbalance of the plurality of capacitors 4 connected in parallel greatly affects the life of the capacitor 4, so that reduction of this imbalance becomes important in this inverter. In order to reduce the stray inductance of the wiring and the current imbalance, various measures have been taken conventionally. This will be described below.

When the U-phase and Z-phase transistors 6 of the inverter circuit shown in FIG. 6 are on and the other transistors 6 are off, AC is converted by the rectifier bridge 2 and smoothed by the reactor 3 and the capacitor 4. The generated direct current is applied to the positive electrode bus 8, the U-phase transistor 6, the U-phase to V-phase, Z-phase transistor 6, and the negative bus 9 which are not shown in the load.
Through the rectifier bridge 2, which serves as a DC power supply.
The positive electrode busbar 8 and the negative electrode busbar 9 are close to each other or twisted together so that the magnetic flux generated by the current is canceled by each other.
The stray inductance of the wiring is reduced.

On the other hand, regarding the arrangement of a plurality of capacitors 4 in the case of parallel connection, as shown in FIG. 7, the unit capacitors 4a are arranged with the terminal portions upward, and are drawn out on the negative electrode side. The electric wire 10a of the above is connected between the positive electrode bus bar 8a and the negative electrode bus bar 9a.
The current flowing through 10a is arranged so that the directions of the currents are opposite to each other as shown by arrows A, B, and C, and the capacitor 4 formed by this combination is arranged close to the inverter 7 and is connected to the positive bus 8 and the negative bus 9. ..

In the inverter configured as described above, in the inverter having a relatively small capacity of 50 kVA class or less,
The unit capacitor has a small capacity and a small number, and can be easily arranged near the inverter by the series-parallel combination in the configuration of FIG. 7, and the wiring inductance between the capacitor 4 and the inverter 7 and the imbalance of the current flowing through each capacitor can be eliminated. Can be reduced.

[0007]

However, as the capacity of the inverter increases, the capacity and quantity of the capacitor increase.
Inevitably, the distance from the inverter 7 becomes far, and the wiring becomes long. Further, in the case of the common power supply method for supplying power to a plurality of inverters, both the capacity and the number of capacitors are increased, and only the capacitors have to be housed in a plurality of housings, and the positive bus 8 and the negative bus 9 are connected. The connection bus bar becomes longer.

For example, the total capacity of a plurality of inverters is 10
In the case of 00kVA class, approximately 100,000 μF capacitors connected in series and parallel are required, and as shown in FIG. 7, a plurality of unit 11 in which a plurality of unit capacitors 4a are connected in series and parallel are placed in a housing 12. It is housed in a multi-tiered manner and connected to the positive electrode busbar 8 and the negative electrode busbar 9 with an electric wire 10. Then, as the unit capacitor 4a in the upper stage becomes longer, the electric wire 10 becomes longer and the number of units also increases, so that the wiring length of each unit 11 is different and the inductance thereof is also different.

Therefore, the current flowing in the unit capacitor 4a of each unit 11 is different, and a large amount flows in the lower unit capacitor 4a near the power source bus side, and the capacitor is overheated and its life is shortened. Therefore, it is necessary to increase the number of series-parallel capacitors and the capacity of the unit capacitors in consideration of the unbalanced amount in advance, and the outer shape of the housing becomes large. Further, as the capacity of the inverter increases, the capacity of the capacitor inevitably increases, the number of series-parallel connections increases, and the wiring becomes complicated, so that it becomes more difficult to reduce the current imbalance and reduce the inductance.

Therefore, an object of the first, second and third inventions is to reduce the inductance of the wiring of the smoothing capacitor unit, reduce the imbalance of the currents flowing in the unit capacitors, and prevent the life from being shortened in a small size. To obtain an inverter that can

[0011]

According to a first aspect of the invention, in an inverter in which a smoothing capacitor composed of a plurality of capacitors is connected to a main circuit to which a switching element is connected, the capacitor groups are housed in upper and lower stages, It is characterized in that the capacitor group is connected to the main circuit on one side and a plurality of vertical buses arranged in parallel are provided.

A second aspect of the present invention is an inverter in which a smoothing capacitor composed of a plurality of capacitors is connected to a main circuit to which switching elements are connected, the capacitor groups are housed in upper and lower stages, and one side of the capacitor groups is provided. The capacitor group is connected to the main circuit and a plurality of vertical bus bars arranged in parallel are provided, and the plurality of vertical bus bars are connected to the first vertical bus bar connected to one side of the capacitor group and the other side of the capacitor group. And a third vertical busbar connected to one end of the second vertical busbar and provided between the first and second vertical busbars.

Further, according to a third aspect of the present invention, in an inverter in which a smoothing capacitor composed of a plurality of capacitors is connected to a main circuit to which switching elements are connected, the capacitor groups are housed in upper and lower stages, and one side of the capacitor groups is provided. It is characterized in that the capacitor group is connected to the main circuit and a plurality of vertical bus bars arranged in parallel are provided, and at the rear of the capacitor group, a connecting / disconnecting portion that comes in contact with and separates from the plurality of vertical bus bars is provided.

[0014]

In the first and second aspects of the invention, the directions of the currents flowing through the plurality of vertical buses are opposite, and the magnetic fluxes generated by the currents also have opposite directions and are cancelled. Further, in the third invention, as in the first and second inventions, the directions of the currents flowing through the plurality of vertical buses are opposite to each other, and the magnetic fluxes generated by the currents also have opposite directions to cancel each other. At the same time, the capacitor group is brought into contact with and separated from the connection / disconnection portion by the operation from the front surface of the box body.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the inverter of the present invention will be described in detail below with an example of a transistor inverter. FIG. 1 is a connection diagram of one unit 13 of a capacitor 4 used in the inverter of the present invention, in which four unit capacitors 4a are provided through a fuse 5 that disconnects the circuit when a short-circuit accident occurs and prevents the capacitor from exploding. This is a configuration in which four sets connected in series are connected in parallel. FIG. 2 shows the connection structure of the unit 13, and FIG. 3 is a front view showing the state in which the unit 13 is housed in the housing 12.

In FIG. 2, inside the unit 13, a group of capacitors 4a, in which four left and right capacitors are connected in series, are arranged in the front-rear direction.
They are arranged in rows. The positive and negative electrodes of the capacitors 4a are aligned in the same direction, and the floor plates 13A having the ventilation holes 13a between the capacitors 4a are arranged in four rows each in the vertical and horizontal directions.
The positive electrode and the negative electrode are connected by a strip-shaped bus bar 8a, and the electric wire 10 drawn from the negative electrode side of the capacitor at the left end
Wiring is made close to a and fixed by an electric wire support (not shown). A single row of capacitors 4a group configured in this way
The wires for connecting in parallel are the fuse 5 and the relay terminal.
In order to reduce the imbalance between the inductance and the current through the unit 14 to the terminal portion 15 of the unit 13, the positive and negative electric wires 10 are twisted on the right side, and the wiring length of each column is the same and the wiring is performed at the shortest.

The fuse 5 is arranged at a position visible when the door on the front surface of the unit 13 is opened, so that it is easy to confirm a trigger indicating the fusing of the fuse 5 in the event of an accident. unit
Although the wiring is slightly distant to the terminal portion 15 of 13, the wiring inductance in this unit can be reduced because the units 13 are connected in parallel, and the wiring inductance is not greatly affected.

At the rear of the unit 13, a disconnecting connecting portion 15 having a contact for keeping contact pressure by a tulip-shaped leaf spring made of copper alloy is attached. As shown in FIG. 3, which is a front view of FIG. 2, the unit configured as described above is housed in a plurality of multiple stages (five stages in FIG. 3) inside the housing 12, and during maintenance and inspection. Housing 12 for easy attachment and detachment
Drawout mechanisms 16 are provided on the inner surfaces on the left and right sides of the.

As shown in FIG. 4 which is a sectional view taken along the line XX of FIG. 3 and FIG. 2, the positive and negative electrodes connected to the forward conversion rectifier bridge 2 and the inverter 7 are adjacent to each other at the rear part of the lower part of the housing 12. ,
The insulated busbars 8 and 9 are arranged laterally, the positive electrode busbar 8A and the negative electrode busbar 9A are raised upward from the rear center of the housing 12, and the positive electrode side is connected to the upper end of the positive electrode busbar 8C via the uppermost spacer 8B. They are connected to form an inverted U-shaped electric path.

Positive busbars 8A, 8C and negative busbar 9
An insulating plate 17 is inserted between A to minimize the distance between the buses. As shown in FIG. 5, the flow of the current of the capacitor unit configured as described above is such that the direct current obtained by the rectifier bridge 2 for forward conversion is shown by arrows D, E, and F in the housing 12. It flows from the lower positive electrode bus bar 8 through the positive electrode bus bar 8A, the spacer 8B, the positive electrode bus bar 8C, the unit 13 and the negative electrode bus bar 9A connected to the central portion of the housing 12 to the negative electrode bus bar 9 below the housing. From the positive electrode bus bar 8C and the negative electrode bus bar 9A, the terminal portion 8Ca and the terminal portion 9Aa are attached by brazing at a position facing the unit 13, and the terminal portion 8Ca and the terminal portion 9Aa are fitted and connected to the disconnecting connection portion 15 provided at the rear of the capacitor unit. There is. Therefore, this condenser board is a front maintenance type in which the unit 13 can be pulled out forward and maintenance / inspection can be performed from the front.

As shown in FIG. 3, the cooling method of this condenser panel is such that the cooling fan 18 provided on the ceiling of the housing 12 raises the ventilation hole 13a of the floor plate 13A of the unit 13 from the ventilation hole (not shown) under the door. The cooled cooling air is discharged upward from the ceiling.

In the above embodiment, the fuse 5
Although the example in which the fuse 5 is provided on the right side of the unit 13 has been described, the fuse 5 is arranged at the rear of the unit 13 in order to reduce the inductance, and the blowout of the fuse 5 can be confirmed by checking the blowout detection microswitch of the fuse 5. An LED or the like may be provided on the front side of the unit 13 for display.

As a result, in the inverter configured as described above, (1) the capacitors are connected in series and in parallel so that the magnetic flux generated in each bus bar cancels each other out as indicated by arrows D, E, and F in FIG. It can be arranged, and the wiring inductance can be reduced. (2) Since the length of the current path of each capacitor unit can be made equal, the imbalance of the current flowing through each capacitor can be reduced. (3) Since the imbalance of the current flowing through each capacitor has been reduced, it is not necessary to increase the capacity of the capacitor in advance to prepare for imbalance or to increase the number of parallel connections, reducing the mounting space and obtaining a miniaturized capacitor unit. be able to. (4) The capacitor and bus bar are connected at the disconnection connection part at the rear of the capacitor unit, and the front maintenance type is used, which facilitates maintenance.

[0024]

As described above, according to the first aspect of the invention, in the inverter in which the smoothing capacitors made up of a plurality of capacitors are connected to the main circuit to which the switching elements are connected, the capacitor groups are housed in upper and lower stages, and By providing a plurality of vertical buses arranged in parallel by connecting this capacitor group to the main circuit on one side, the direction of the current flowing through the plurality of vertical buses and the direction of the magnetic flux generated by this current are reversed, Since the reactance is reduced and the imbalance of the current flowing through each capacitor is reduced, it is possible to obtain an inverter that can reduce the capacitance of the capacitor and the outer shape of the unit and can prolong the life.

According to the second aspect of the invention, in the inverter in which the smoothing capacitors made up of a plurality of capacitors are connected to the main circuit to which the switching elements are connected, the capacitor groups are housed in upper and lower stages, and one side of the capacitor groups is accommodated. Is provided with a plurality of vertical busbars connected in parallel to the main circuit, and the plurality of vertical busbars are connected to one side of the capacitor group with a first vertical busbar and another vertical busbar. The second vertical busbar connected to the side and the third vertical busbar connected to one end of the second vertical busbar and provided between the first and second vertical busbars And the current flowing through the second vertical busbar and the current flowing through the third vertical busbar have the same values in opposite directions, and the magnetic fluxes generated by these currents cancel each other out, thereby making the reactance larger. Reduce each con Since reducing the imbalance of current flowing through the capacitors, the volume reduced and the outer shape of the capacitor, it is possible to obtain the inverter which can prolong the life.

Further, according to the third aspect of the invention, in the inverter in which the smoothing capacitors made up of a plurality of capacitors are connected to the main circuit to which the switching elements are connected, the capacitor groups are housed in the upper and lower stages and one side of the capacitor groups. In addition to providing a plurality of vertical busbars that are connected in parallel to the main circuit to the main circuit, and at the rear of the capacitor group, by providing a connection disconnecting portion that connects and disconnects with the plurality of vertical busbars, a plurality of vertical busbars is provided. The direction of the current flowing through and the direction of the magnetic flux generated by this current are reversed to reduce the reactance and reduce the unbalance flowing in each capacitor, and the capacitor group is connected at the connection disconnection part by the operation from the front of the box. Since they are brought into contact with and separated from each other, it is possible to obtain an inverter in which the outer shape of the unit is reduced, maintenance and inspection are easy, and the life is extended.

[Brief description of drawings]

FIG. 1 is a connection diagram of a smoothing capacitor showing an embodiment of an inverter of the present invention.

FIG. 2 is a plan view of a capacitor box showing an embodiment of the inverter of the present invention.

FIG. 3 is a front view of FIG.

4 is a sectional view taken along line XX of FIG.

FIG. 5 is a connection diagram showing the operation of the inverter of the present invention.

FIG. 6 (a) is a main circuit connection diagram of this kind of inverter,
(B) is a connection diagram of a capacitor group that constitutes a smoothing capacitor of a conventional inverter.

FIG. 7 is an explanatory view showing the connection of a capacitor box of a conventional inverter.

[Explanation of symbols]

1 ... Three-phase AC power supply, 2 ... Rectifier bridge, 3 ... Reactor, 4 ... Electrolytic capacitor, 5 ... Fuse, 6 ... Transistor as switching element, 7 ... Inverter, 8 ...
Positive electrode busbar, 9 ... Negative electrode busbar, 10 ... Electric wire, 11, 13 ... Unit, 12 ... Housing.

Claims (3)

[Claims] 1. In an inverter in which a smoothing capacitor composed of a plurality of capacitors is connected to a main circuit to which a switching element is connected, the capacitor groups are housed in upper and lower stages, and the capacitor groups are provided on one side of the capacitor group. An inverter characterized in that it is provided with a plurality of vertical busbars connected in parallel to the main circuit. 2. A plurality of vertical busbars, a first vertical busbar connected to one side of a capacitor group, a second vertical busbar connected to the other side of the capacitor group, and a second vertical busbar of the second vertical busbar. 2. The inverter according to claim 1, wherein the inverter is formed of a third vertical bus bar connected to one end and provided between the first and second vertical bus lines. 3. The connecting / disconnecting portion that comes in contact with and separates from a plurality of vertical bus bars is provided at the rear of the capacitor group.
Inverter described.