Patent Publication Number: US-2017365401-A1

Title: Transformer having noise reduction structure

Description:
TECHNICAL FIELD 
     The present invention relates generally to a transformer having a noise reduction structure. More particularly, the present invention relates to a transformer having a noise reduction structure, the transformer being capable of minimizing transmission of vibration and noise through an insulating sheet provided on a surface of a coil. 
     BACKGROUND ART 
     As well known in the art, a transformer is a device that transforms alternating current voltage and alternating current by using electromagnetic induction. The transformer is widely used from a small electronic apparatus to a large-sized power transmission facility or transmission facility. In particular, a high-pressure large capacity transformer is used for the large-sized power transmission facility or transmission facility. 
     A schematic configuration of such a transformer is shown in  FIG. 1 . As shown in the drawing, a tank  3  forms an exterior of a transformer  1 . An iron core  5  is supported by frames  7  and  7 ′ in the tank  3 , and coils  9  are wound on the iron core  5 . The coils  9  are wound in a cylindrical shape, and an insulating sheet  9 ′ is attached to a surface of each coil  9 . The insulating sheet  9 ′ surrounds the coil  9  to perform insulation. 
     Further, the tank  3  is filled with an insulating oil that releases heat generated in the coils  9  and the iron core  5  and performs insulation. The insulating oil is transferred to a heat dissipating device (not shown), such that heat is discharged to outside through heat exchange with external air. 
     However, the conventional transformer having the above-described configuration is problematic in that when a current flows through the coils  9 , vibrations are generated due to electromagnetic force. Such vibrations are transmitted to the insulating oil through insulating sheets  9 ′. Vibrations generated in the coil  9  are transmitted to the insulating sheet  9 ′ and then directly transmitted to the insulating oil in a direction perpendicular to a surface of the insulating sheet  9 ′ as indicated by an arrow in  FIG. 2 . Thus, the vibrations transmitted to the insulating oil continue to be transmitted straight to the tank  3 , thereby generating vibration and noise in the tank  3 . 
     DISCLOSURE 
     Technical Problem 
     Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a transformer having a noise reduction structure, the transformer being capable of minimizing transmission of vibrations generated due to electromagnetic force in a coil to an insulating sheet. 
     Another object of the present invention is to provide transformer having a noise reduction structure, the transformer being capable of cancelling out vibrations generated due to electromagnetic force in a coil and transmitted through an insulating sheet to an insulating oil. 
     Technical Solution 
     In order to accomplish the above object, the present invention provides a transformer having a noise reduction structure, the transformer including: a tank provided therein with an inner space filled with an insulating oil; an iron core provided in the tank and serving as a passage for lines of magnetic force; coils wound on the iron core, and performing voltage and current transformation through electromagnetic interaction when electric power is applied to the coils; and an insulating sheet surrounding a surface of each of the coils and performing insulation, with ridge portions and groove portions alternately provided on a surface of the insulating sheet. 
     The insulating sheet may be provided such that ridge portions provided on a surface facing the surface of each of the coils are attached to the surface of the coil. 
     The opposite side surfaces of each of the groove portions may face each other in parallel. 
     The ridge portions and the groove portions may be provided on opposite surfaces of the insulating sheet to correspond to each other, such that groove portions of a second surface of the insulating sheet are formed by forming ridge portions of a first surface of the insulating sheet. 
     The ridge portions and the groove portions may extend in a height direction of each of the coils. 
     Advantageous Effects 
     The transformer having the noise reduction structure according to the present invention has the following effects. 
     First, the ridge portions and the groove portions are alternately provided on the surface of the insulating sheet, and the ridge portions of the first surface of the insulating sheet are attached to the surface of the coil. Thus, the contact area between the coil and the insulating sheet is minimized and thus the transmission of vibrations generated in the coil to the insulating sheet is minimized, thereby minimizing the transmission of vibrations through the insulating oil to the tank of the transformer. 
     Second, since the ridge portions and the groove portions are alternately provided on the insulating sheet, vibrations transmitted through surfaces of the ridge portions and the groove portions to the insulating oil destructively interfere with each other. Thus, the transmission of vibrations transmitted through the insulating oil to the tank of the transformer is minimized, thereby reducing vibration and noise of the transformer. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a view showing an internal configuration of a general transformer. 
         FIG. 2  is a cross-sectional view showing an insulating sheet attached to a surface of a coil of a transformer according to the prior art. 
         FIG. 3  is a schematic perspective view showing a configuration of a transformer according to a preferred embodiment of the present invention. 
         FIG. 4  is a cross-sectional view showing a configuration of a main part of the transformer in the embodiment of the present invention. 
         FIGS. 5 a  and 5 b    are views showing that vibrations transmitted to an insulating oil cancel each other out in the embodiment of the present invention. 
     
    
    
     MODE FOR INVENTION 
     Hereinafter, exemplary embodiments of the present invention will be described in further detail with reference to the accompanying drawings. Wherever possible, the same reference numerals will be used throughout the drawings and the description to refer to the same or like elements or parts. In the following description, it is to be noted that, when the functions of conventional elements and the detailed description of elements related with the present invention may make the gist of the present invention unclear, a detailed description of those elements will be omitted. 
     Further, when describing the components of the present invention, terms such as first, second, A, B, (a), or (b) may be used. Since these terms are provided merely for the purpose of distinguishing the components from each other, they do not limit the nature, sequence, or order of the components. It will be understood that when an element is referred to as being “coupled” or “connected” to another element, it can be directly coupled or connected to the other element or intervening elements may be present therebetween. In contrast, it should be understood that when an element is referred to as being “directly coupled” or “directly connected” to another element, there are no intervening elements present. 
     Referring to  FIGS. 3 to 5 , a transformer  10  according to the present invention is provided with a tank  12  forming an exterior of the transformer. In the drawings of the present specification, only the position and approximate shape of the tank  12  are shown. The tank  12  is provided therein with an inner space  14 . The inner space  14  is provided with a transformer body that will be described below. The tank  12  serves to isolate components installed in the transformer  10  from outside. 
     The configuration of the transformer body is described. A lower frame  16  and an upper frame  18  are installed in the inner space of the tank  12 , an iron core  20  is installed such that the iron core is erected by the lower and upper frames  16  and  18 . The configuration of the iron core  20  remains the same as that shown in  FIG. 1 . The iron core  20  serves as a passage for lines of magnetic force. In general, the iron core  20  is formed by laminating thin plates containing silicon so as to reduce iron loss. 
     The iron core  20  is provided with coils  22  wound on vertical portions of the iron core  20 . The coils  22  are formed by winding an insulated wire made of copper or a copper alloy having a high conductivity. When electric power is applied to the coils  22 , an induced electromotive force or an electromagnetic force can be generated. 
     An insulating sheet  24  is attached to a surface of each of the coils  22 . The insulating sheet  24  is configured to surround the surface of the cylindrical shaped coil  22  and performs insulation between the coil  22  and a periphery of the coil. As shown in  FIG. 4 , the insulating sheet  24  is provided with ridge portions  26  and groove portions  28  provided in an alternate manner, such that the insulating sheet has a corrugated structure. The ridge portions  26  and the groove portions  28  extend in a height direction of each of the coils  22 . The ridge portions  26  and the groove portions  28  are provided on opposite surfaces of the insulating sheet to correspond to each other. In other words, groove portions  28  of a second surface of the insulating sheet are formed by forming ridge portions  26  of a first surface of the insulating sheet. 
     The insulating sheet  24  is provided such that ridge portions  26  provided on a surface facing the surface of each of the coils  22 , serve as contact portions  30 . The contact portions  30  are portions where the insulating sheet  24  is attached to the surface of the coil  22 . Thus, the insulating sheet  24  is attached to the surface of the coil  22  only at the contact portions  30 . 
     Meanwhile, the groove portions  28  have a substantially ‘U’-shape in cross section. In other words, opposite side surfaces of each of the groove portions  28  face each other in parallel. By forming the opposite side surfaces of each of the groove portions  28  to substantially face each other, when vibrations transmitted to the insulating sheet  24  are transmitted to the insulating oil through the surface of the insulating sheet  24 , the vibrations are transmitted in a direction perpendicular to the surface of the insulating sheet  24 . Accordingly, as shown in  FIG. 5 b   , the vibrations transmitted to the insulating oil through the side surfaces of each of the groove portions  28  cancel each other out in one groove portion  28 . Of course, although vibrations are transmitted to the insulating oil through a peak of each of the ridge portions  26  as well as the side surfaces of each of the groove portions  28 , not all of the vibrations transmitted through the ridge portions are transmitted to the insulating oil. 
     In addition,  FIG. 5 a    shows that the opposite side surfaces of each of the groove portions  28  are provided inclinedly without facing each other. Even in this case, vibrations transmitted through the side surfaces of each of the groove portion  28  to the insulating oil can cancel each other out to some extent. However, not all of the vibrations transmitted to the insulating oil cancel each other out, and a part of the vibrations is transmitted to the tank  12 . 
     Hereinafter, a use of the transformer having the noise reduction structure according to the present invention with the above configuration will be described in detail. 
     In the transformer  10  of the present invention, when an alternating current is applied to one coil  22 , a magnetic field that changes continuously in the coil  22  is generated. When the magnetic field passes through the other coil  22 , an alternating current voltage is generated in the other coil  22 , wherein a level of the alternating current voltage may be varied depending on a ratio of the number of turns of two coils  22 . 
     During this operation, vibrations are generated by the alternating current applied to the coil  22 . Vibrations generated in each of the coils  22  are transmitted to the insulating sheet  24  provided on the surface of the coil  22 . The vibrations transmitted to the insulating sheet  24  are transmitted through the insulating sheet  24  to the insulating oil filled in the inner space  14  of the tank  12 . 
     Here, the ridge portions  26  and the groove portions  28  are alternately provided on the insulating sheet  24 , and the ridge portions  26  provided on the first surface of the insulating sheet are employed as the contact portions  30  and are attached to the coil  22 . As a result, vibrations generated in the coil  22  are transmitted to the insulating sheets  24  only through the contact portions  30 . Thus, vibrations transmitted to the insulating sheets  24  can be relatively reduced. 
     Further, vibrations are transmitted to the insulating oil in the direction perpendicular to the surface of the insulating sheet  24 . Since the groove portions  28  of the insulating sheet  24  are formed in a ‘U’-shape, vibrations transmitted through the opposite side surfaces of each of the groove portions  28  to the insulating oil cancel each other out. Such vibrations cancelling each other out in this manner are the same as an arrow B shown in an enlarged view of  FIG. 4 . 
     Of course, vibrations transmitted through the peak and a periphery of each of the ridge portions  26  are also transmitted to the insulating oil in the direction perpendicular to the surface of the insulating sheet  24 . As indicated by A in the enlarged view of  FIG. 4 , a part of the vibrations transmitted through each of the ridge portions  26  and vibrations transmitted through an adjacent ridge portion  26  cancel each other out. Of course, not all of vibrations transmitted through ridge portions  26  cancel each other out. 
     However, as described above, since the insulating sheet  24  is attached to the surface of the coil  24  only at the contact portions  30 , vibrations generated in the coil  24  are partially transmitted to the insulating sheet  24 . In addition, vibrations transmitted to the insulating oil in opposite directions through the side surfaces of each of the groove portions  28  of the insulating sheet cancel each other out, and vibrations transmitted to the insulating oil through the ridge portions  26  partially cancel each other out. Thus, vibrations generated in the coil  24  and then transmitted to the tank  12  can be relatively reduced, whereby vibration and noise generated in the tank  12  can be relatively reduced. 
     Meanwhile, the insulating oil receives heat generated in the iron core  20  or the coils  22  and then flows into the heat dissipating device (not shown), thereby performing heat exchange with external air. In this way, the insulating oil having released heat to the external air renters the inner space  14  of the tank  12  to perform insulation and heat dissipation. 
     Although a preferred embodiment of the present invention has been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions, and substitutions are possible without departing from the scope and spirit of the invention as disclosed in the accompanying claims. Therefore, the embodiments of the present invention are disclosed only for illustrative purposes and should not be construed as limiting the present invention. The scope of the invention should be determined on the basis of the descriptions in the appended claims, not any specific embodiment, and all equivalents thereof should belong to the scope of the invention. 
     For reference, although in the illustrated embodiment, the opposite side surfaces of each of the groove portions  28  are parallel to each other, the present invention is not necessarily limited thereto. As shown in  FIG. 5 a   , the opposite side surfaces of each of the groove portions  28  may have a predetermined inclination angle such that virtual lines extending therefrom meet each other. Of course, when the opposite side surfaces of each of the groove portions  28  have the predetermined inclination angle such that the virtual lines meet each other, a certain degree of vibration canceling can be achieved, but the effect of canceling is relatively inferior to the case in which the side surfaces of each of the groove portions  28  are parallel to each other.