JPH1126261A - Electric appliance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the cooling performance of the metallic enclosure of an electric appliance and to reduce the using amount of a magnetic shield, by arranging ducts made of an insulator between the magnetic shield and the metallic enclosure and securing flow passages for a coolant. SOLUTION: A magnetic shield 2 is attached to a metallic enclosure 1 with fixtures 3. At the time of attaching the shield 2 to the enclosure 1, insulating paper 4 is wound around the shield 2 so as to prevent the shield 2 from coming into contact with the enclosure 1, and cooling ducts 5 made of an insulator are provided so as to secure flow passages 6 for a coolant. When a coolant such as the insulating oil, perfluoro-carbon, etc., having a high cooling performance is used in the enclosure 1, the cooling performance of the enclosure 1 is remarkably improved, because one side face of the enclosure 1 is cooled with the coolant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a large-capacity or high-impedance transformer and an electrical device having a large leakage flux such as a reactor.

[0002]

2. Description of the Related Art In an electric device having a large leakage magnetic flux, a magnetic shield having a high magnetic permeability is arranged inside a metal outer box in order to prevent local overheating due to penetration of the leak magnetic flux into a metal outer box such as a tank. This magnetic shield absorbs the leakage flux and suppresses and prevents the penetration of the leakage flux into the metal outer box.

[0003] The magnetic shield is fixed by a fixing member arranged around the magnetic shield, and insulating paper or the like is interposed between the fixing member and the magnetic shield so as to be in non-contact. This is because, when the metals are brought into contact with each other, the metals come into contact with or separate from each other due to vibration, thereby generating an arc current at the incompletely contacted portion, thereby generating decomposition gas of the insulating / cooling medium.

[0004]

In recent years, there has been a strong demand for miniaturization of electrical equipment, and restrictions on the arrangement range of magnetic shields have become strict. As a result, for example, there are few portions that absorb leakage magnetic flux at the end of the magnetic shield. As a result, it is assumed that a part of the magnetic flux leaks from the magnetic shield to the outer case side of the metal. In addition, the leakage flux itself tends to increase due to the increase in the capacity of electrical equipment accompanying the increase in power demand and the increase in the impedance of the transformer due to the demand for a system stabilization device. Local overheating may occur due to an increase in magnetic flux leakage into the box.

When a magnetic shield is installed, a cooling effect cannot be expected because one side of the metal outer box is in contact with insulating paper surrounding the magnetic shield, and the other side is often air-cooled. However, the cooling effect is small, and there are also cases where the outer case is further enclosed as a noise reduction measure.In this case, it is assumed that the air flow itself is greatly restricted and there is almost no cooling effect. Local overheating and deterioration of the insulator surrounding the magnetic shield may be a concern.

[0006]

SUMMARY OF THE INVENTION The present invention is characterized in that an insulating duct is arranged between a magnetic shield and a metal outer box to secure a flow path for a cooling medium.

[0007]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1A and 1B are an overall view and a partial view of a conventional magnetic shield. 2A and 2B show an embodiment of a magnetic shield structure to which the present invention is applied.

The configuration will be described with reference to FIGS. 1 and 2. A magnetic shield 2 is attached to a metal outer box 1 by a fixing bracket 3. At this time, the insulating paper 4 is wrapped around the magnetic shield to keep the magnetic shield and the metal outer box out of contact. Here, in FIG. 2, an insulating cooling duct 5 is provided to secure a flow path 6 through which a cooling medium flows.

In particular, the inside of the metal outer box is made of insulating oil or
In the case of a cooling medium such as perfluorocarbon which has better cooling performance than air, the cooling performance is greatly improved by cooling one side of the metal outer box with these cooling media. With respect to the magnetic shield as well, the insulator covered on one side can be eliminated by installing a cooling duct, whereby the entire magnetic shield can be cooled and the cooling effect of the magnetic shield is improved.

[0011]

As a result, in contrast to the conventional design in which the leakage flux to the metal outer box is eliminated and the generated loss is almost zero,
By improving the cooling performance of the metal outer case, an appropriate amount of leakage magnetic flux can be allowed to enter the metal outer case, the amount of magnetic shield used can be reduced, and a more economical design becomes possible.

Further, by inserting a cooling duct between the magnetic shield and the metal outer box, the magnetic reluctance between them is increased, and the magnetic flux leaking to the metal outer box in the conventional structure is increased. As a result, the magnetic flux leaking to the metal outer box can be reduced. Also, by increasing the thickness of the cooling duct, it is possible to further increase the magnetic resistance between the magnetic shield and the metal outer box, thereby making it possible to adjust the leakage magnetic flux to the metal outer box.

[Brief description of the drawings]

1A and 1B are an overall view and a partial view of a conventional magnetic shield structure.

2A and 2B are an overall view and a partial view of a magnetic shield structure to which the present invention is applied.

[Explanation of symbols]

1: Metal outer box, 2: Magnetic shield, 3: Fixing bracket, 4
... Insulator, 5 ... Cooling duct, 6 ... Flow path.

Claims (1)

[Claims] 1. A magnetic shield installed between a metal and a magnetic shield to prevent a leakage magnetic flux generated from a coil of an electric device such as a transformer or a reactor from invading a metal surrounding the coil and causing a loss. Electrical equipment characterized by securing a space through which a cooling medium passes.