JP3132797B2 - Power converter having DC filter capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power converter having a DC main circuit, and more particularly, to the characteristics of a DC filter capacitor used in the DC main circuit to improve the size, weight and safety. The present invention relates to a power conversion device having a DC filter capacitor.

[0002]

2. Description of the Related Art There are various types of power converters having a DC main circuit, such as an AC-DC converter, an inverter, and a reactive power suppressor (SVG, active filter). The DC main circuit section of the apparatus is provided with a DC filter capacitor for the purpose of smoothing a DC voltage and temporarily absorbing and discharging DC power.

The most common type of AC-DC conversion power converter of this type will be described with reference to FIG. In FIG.
11 is a rectifier, 12 is a DC filter capacitor, 13 is a protective fuse, AC is an AC input terminal, and P and N are DC output terminals. The operating principle of this AC-DC converter is known, and AC power input to an AC input terminal AC is converted to DC power by a rectifier 11 composed of a semiconductor device such as a thyristor, and this DC power is converted to a DC filter. Smoothing is performed by the capacitor 12, and DC power is output from the DC output terminals P and N. Since the DC filter capacitor 12 has a large capacity, the protection fuse 13 is divided into several blocks to protect each of them.

In the AC-DC converter shown in FIG. 6, the type of the DC filter capacitor 12 differs depending on the level of the DC voltage (output voltage of the rectifier 11). DC voltage is D
At present, large-capacity aluminum electrolytic capacitors (specifically, capacitors specified in JIS C5141 fixed aluminum non-solid electrolytic capacitors for electronic equipment) are used up to about C1500V. Since this large-capacity aluminum electrolytic capacitor can realize a large capacitance in a relatively small volume, it is very effective to reduce the size of the DC filter capacitor 12 in a region where the DC voltage is low.
It has characteristics such as low as 50V, and its life is extended at 85 ° C-5000 hours.

As described above, the large-capacity aluminum electrolytic capacitor is used at a low DC voltage, and the working voltage and the ripple current are delayed from the rated values to extend the replacement life by 6 to 8 hours.
It has been used for a long time, with regular replacement. Therefore, a large DC filter capacitor of DC 1500 V class
, It is necessary to connect 5 to 6 large-capacity aluminum electrolytic capacitors in series and connect a large number of this series circuit in parallel. In addition, if a large-capacity aluminum electrolytic capacitor is destroyed by an overvoltage, the case may be broken and fire may occur in some cases, and there is a risk that the capacitor element will continue to burn. From these points, several series circuits of large-capacity aluminum electrolytic capacitors are combined in one block in parallel, and a protection fuse 13 is inserted in each block for protection. The DC filter capacitor 12 using a large-capacity aluminum electrolytic capacitor can be made relatively small and lightweight, but when the DC voltage is high, many capacitors must be connected in series, and when the capacitor voltage is destroyed. There is a problem in application from the viewpoint of safety.

When the DC voltage exceeds 1000 V DC, large-capacity oil-filled film capacitors (capacitors specified in JEM 1419 capacitors for power semiconductor converters, etc.) are often used as DC filter capacitors 12. There are various types of oil-filled film capacitors, but since the rated voltage of one capacitor can be designed in accordance with the DC voltage, individual capacitors can be designed as in the series connection circuit of large-capacity aluminum electrolytic capacitors as described above. There is no need to connect a balance resistor for voltage balancing, and the circuit configuration is simplified.

However, a large-capacity oil-filled film capacitor has a smaller capacitance per unit volume than a large-capacity aluminum electrolytic capacitor, and has a large outer shape. Since oil or vegetable oil is contained, it is necessary to provide protection with a protective fuse 13 or the like from a safety point of view. One of the factors that increase the size and weight of an oil-filled film capacitor is how to provide a design margin for withstand voltage. In other words, in the case of a vapor-deposited film in which zinc or aluminum metal is vapor-deposited on one side of a film (for example, a polypropylene film), the film pressure resistance is 400 to
Although it is about 460 V / μm, the potential gradient at the actual circuit voltage is about 80 to 110 V / μm (for film withstand voltage of 1 to improve reliability over the long term and secure the life of the capacitor for 20 years or more).
/ 4).

Therefore, if a large-capacity oil-filled film capacitor is used as the DC filter capacitor 12, it is necessary to connect a large number of capacitors in parallel, and since the case of the capacitor contains flammable oil, protection is required. It is necessary to protect each block by the fuse 13.

The protection fuse 13 is a DC filter capacitor
Although the DC voltage is required when the DC voltage is relatively high from the point of safety protection of 12, it is necessary to select a small rated current so that each block of the protected DC filter capacitor 12 can be protected in the event of an accident. In some cases, load current or short-circuit current is blown to cause erroneous protection, and it is very difficult to select the rating of the protective fuse 12.

[0010]

When the DC voltage exceeds 1000 V DC, the DC filter capacitor 12 of the power converter is required to have a small size, light weight, safety against fire, and the like. The power converter could not meet the demand.

That is, in the conventional power converter, when a large-capacity aluminum electrolytic capacitor is used for the DC filter capacitor 12, it is necessary to connect a large number of capacitors connected in series and connect them in parallel. In this case, the service life has expired, replacement is required, and a series-connected balance resistor and protective fuse 13 are required.

On the other hand, when a large-capacity oil-filled film capacitor is used as the DC filter capacitor 12, the capacitor portion becomes larger, and the DC filter capacitor 12 becomes about 1.5 to 2 times as large as the rectifier 11 in terms of device volume. There was a problem that the whole was enlarged. A protective fuse 13 is required regardless of whether a large-capacity aluminum electrolytic capacitor or an oil-filled film capacitor is used.However, it is very difficult to select the rated current of the protective fuse 13 as described above. However, it was difficult to cooperate with the current tolerance required by the power converter and the capacitor protection current, and was not satisfied from the viewpoint of capacitor safety.

When a large-capacity oil-filled film capacitor is employed, a capacitor having a life expectancy of 15 years or 20 years can be designed, and a conversion in 6 to 8 years is required like a large-capacity aluminum electrolytic capacitor. However, for this purpose, it is necessary to reduce the potential gradient of the capacitor when used in the DC circuit of the power conversion device to about 1/4 or less of the film withstand voltage. It is necessary to increase the size of the film capacitor, and there are problems such as an increase in the size of the capacitor and an increase in flammable oil.

As described above, in the power converter having the DC filter capacitor 12, the DC filter capacitor 12 occupies most of the outer shape and weight of the device. 12
The downsizing and weight reduction of the helmet were important issues. In addition, it is necessary to improve the safety of the DC filter capacitor 12 in order to improve the safety of the power converter against fire.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its object to use a new capacitor with a segment fuse mechanism as a DC filter capacitor, thereby reducing the size, weight, and safety of a power converter. Is to provide.

[0016]

[0017]

[0018]

[0019]

According to a first aspect of the present invention, there is provided a power converter having a DC filter capacitor in a DC main circuit section, wherein the DC filter capacitor is formed by using a metal-deposited film having a segment fuse mechanism. Are connected in parallel and housed in a case, and the terminals of the capacitors connected in parallel are led out through a conductive protector cut by mechanical force.

[0020]

[0021]

[0022]

[0023]

[0024]

According to the first aspect of the present invention, since a short-circuit accident such as a connection line of a capacitor can be assumed, a conductive protector which is cut by a mechanical force caused by deformation of a capacitor case or the like is provided. By separating the DC filter capacitor, the safety of the DC filter capacitor itself can be further improved, and a power converter with further improved safety can be provided.

[0025]

1 and 2 show an embodiment showing a main part of the present invention.
Shown in FIG. 1 and FIG. 2 are main part configuration diagrams of a DC filter capacitor used in the power converter of the present invention.

In FIG. 1, reference numeral 14 denotes a capacitor film, and reference numeral 15 denotes a metal of zinc or aluminum deposited on one surface of the film 14. In this manner, two metal-deposited films 14 on which the metal 15 is deposited are stacked to constitute an element of an oil-filled film capacitor. The metal 15 deposited on the film 14 constitutes a number of segments 16 surrounded by a number of slits 17 as shown in FIG. 2, and a fuse mechanism narrowed by the slits 17 between adjacent segments 16.
Make up 18. The slit 17 is formed of a portion where the metal 15 is not deposited.

A technique for producing such a metal-deposited film with a segment fuse mechanism is known, for example, in Japanese Patent Application Laid-Open No. 4-225508. Capacitors can be manufactured.

The slits 17 separate the peripheries of the segments 16 that perform the capacitor action, and each segment 16 is connected to the adjacent segment 16 by a fuse mechanism 18. If a specific segment 16 has a voltage defect, the fuse mechanism 18
Is blown and cut off, the defective segment is automatically removed, and the remaining healthy segment 16 continues to function as a capacitor. Therefore, even if the device is used with a higher potential gradient than before, the electrical reliability does not decrease.

If the potential gradient of the film at the rated voltage of the capacitor is set to 150 V / μm or more, which is about 1.4 times or more of the conventional 110 to 80 V / μm, the volume of the oil-filled film capacitor is roughly determined by the square of the potential gradient. Thus, a power conversion device that is about half of the conventional one and has a small and light DC filter capacitor can be provided.

In order to quickly separate a specific segment 16 having a voltage defect, it is desirable to make the width W of the fuse mechanism 18 as small as possible to facilitate fusing. However, when used as a DC filter capacitor 12 of a power converter, the overburden current and the short-circuit current peculiar to the power converter repeatedly cause the deposited metal 15 in the fuse mechanism 18 to be fatigued and worn to prevent unnecessary fusing. You need to avoid it. The present inventors have determined from the experimental results of the current flowing through the DC filter capacitor of the power converter that the width W of the fuse mechanism 18 is in the range of 0.5 mm to 1.4 mm to prevent fatigue and wear due to the current and prevent voltage defects. It has been confirmed that both quick separation of parts can be realized.

As described above, the width W of the fuse mechanism 18 is reduced.
If an oil-filled film capacitor using a metal-deposited film with a segment fuse mechanism with a specific width of 0.5 mm to 1.4 mm is used as a DC filter capacitor of a power conversion device, if an accident such as a short circuit of the capacitor element occurs, the The mechanism 18 operates, and the short-circuited capacitor element is automatically cut off, thereby greatly improving the safety of an oil-filled film capacitor using flammable oil. Since the potential gradient can be increased as described above, the capacitor itself can be reduced in size and weight, and the power converter can be reduced in size and weight and improved in safety.

FIG. 3 is a characteristic diagram showing the relationship between the capacitance C of the capacitor with the segment fuse mechanism and the operating time T of the capacitor using the potential gradient as a parameter. As is clear from this figure, the capacitance changes depending on the potential gradient. When the potential gradient is increased, the capacitance rapidly decreases, and when the potential gradient exceeds a predetermined value, the capacitance C rapidly decreases. .

Although these characteristics are obtained by experiments, FIG. 3 shows the potential gradient V in a range where the potential gradient is lower than a predetermined value.
FIG. 3 is a diagram showing ₁ as a parameter. As shown in FIG. 3, the time T in which the electrostatic capacity decreases to C ₁ to 10 ⁿ when the potential gradient V _1, when a 10% higher 1.1V ₁ becomes 10 ^n-1 or less, 10% less At 0.9 V _1, the time is 10 ^{n + 1} or more. Thus, the life of the capacitor is greatly affected by the potential gradient.

The inventors of the present invention have confirmed that the capacitor having the segment fuse mechanism can be used with a potential gradient of 195 to 150 V / μm from the results of an experiment using a DC filter capacitor of a power converter. This allows
By using a small and lightweight DC filter capacitor that guarantees a long service life of 20 years or more required by the power converter, it is possible to provide a power converter with improved component life and safety.

FIG. 4 is a structural view of another embodiment of the metal deposition film. As shown in FIG. 4, the slit 17 is formed in a cross shape to form a fuse mechanism 18 between adjacent slits, and the position of the fuse mechanism 18 is separated from the corner portion of the segment 16 to reduce the capacitance C of the capacitor. Rate can be reduced.

According to this embodiment, one segment 16
Is divided into four segments 16 via four fuse mechanisms 18.
Connected to When there is a voltage defect in a specific segment 16 and a short circuit current flows, and the fuse mechanism 18 performs the disconnection operation,
Depending on the magnitude of this short-circuit current, adjacent segments 16
May also damage. In such a case, the number of adjacent segments 16 is smaller in this embodiment as shown in FIG.
The rate of decrease in the capacitance C of the capacitor is smaller than that connected to the eight segments 16 via the two fuse mechanisms 18.

Accordingly, in the capacitor using the metal-deposited film with the segment fuse mechanism shown in FIG. 4, the rate of decrease in the capacitance C is reduced even if the potential gradient is the same, and this capacitor is used as a DC filter for a power converter. By adopting as the capacitor 12, a power converter with improved reliability can be provided.

FIG. 5 shows an embodiment of a DC filter capacitor used in the power converter of the present invention. This figure shows an assembled sectional view of a capacitor. In a capacitor case 19, a required number of capacitor elements 20 using a metal deposited film with a segment fuse mechanism described in FIG. , One capacitor terminal
23, the other end is connected to one end of the protector 24, and the other end of the protector 24 is connected to the other end of the capacitor terminal 23 via the wiring 22.

The protector 24 is made of a conductor and is mechanically fixed to the capacitor case 19 via an insulator.
When the insulating oil in the capacitor case 19 is gasified and the pressure increases and the capacitor case 19 is deformed, the conductive part of the protector 24 is cut by the mechanical force of this deformation, and the wiring is removed.
It is configured to open between 21 and 22.

Although the failure of the capacitor element 20 itself can be sufficiently protected by the fuse mechanism 18 as described above, the entire capacitor such as the failure of connection between the capacitor elements 20 cannot be protected by the fuse mechanism 18 alone. Such a protector 24 is provided.

According to the capacitor of the present embodiment, the safety of the capacitor can be further improved, and by using this capacitor as the DC filter capacitor of the power converter, a power converter with further improved safety is provided. be able to.

[0042]

[0043]

[0044]

[0045]

According to the first aspect of the present invention, since the protector which is cut off by a mechanical force is provided to protect against a defect other than the capacitor element, the safety of the DC filter capacitor is further improved. In addition, it is possible to realize a power converter having a DC filter capacitor with improved safety.

[Brief description of the drawings]

FIG. 1 is an embodiment showing a cross section of a main part of a capacitor used in a power converter having a DC filter capacitor of the present invention.

FIG. 2 is a specific configuration diagram of a metal-deposited film of the capacitor of FIG.

FIG. 3 is a characteristic diagram of a capacitor used in a power converter having a DC filter capacitor according to the present invention.

FIG. 4 is another specific configuration diagram of the metal-deposited film of the capacitor of FIG. 1;

FIG. 5 is an assembled sectional view of a capacitor used in a power converter having a DC filter capacitor of the present invention.

FIG. 6 is a main circuit configuration diagram of a power conversion device having a conventional DC filter capacitor.

[Explanation of symbols]

11 rectifier, 12 DC filter capacitor, 13 protective fuse, 14 film, 15 deposited metal, 16 segment, 17 slit, 18 fuse mechanism, 19 capacitor case, 20 capacitor element, 21 and 22 ... wiring, 23
... capacitor terminals, 24 ... protectors, AC ... AC input terminals, P, N ... DC output terminals.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01G 4/00-4/40 H01G 13/00-13/06

Claims (1)

(57) [Claims] 1. A DC filter capacitor in a DC main circuit section.
Comprising a power converter having:
A metal-deposited film with a segment fuse mechanism.
Multiple capacitors used are connected in parallel and stored in the case
And connect the terminals of the capacitors connected in parallel
Guided through a conductive protector that is cut by
DC filter capacitor characterized in that
A power conversion device having a sensor.