高頻變壓器屏蔽的設計

1、精選優(yōu)質文檔-傾情為你奉上高頻變壓器屏蔽的設計高頻變壓器的一種屏蔽設計 供電電源系統(tǒng)采用的高頻變壓器和電感器如陰極射線管,CRT,顯示器用的回掃變壓器通常其幅射磁場很強但因為這種變壓器的工作頻率與CRT的行偏轉頻率一致故其輻射磁場對視覺效果不會造成明顯的影響。然而在一些超高分辨率的CRT顯示器中由于行偏轉頻率隨著高速掃描而提高電源變壓器的工作頻率不能與其保持一致供電電源只能在比CRT掃描頻率低的某一頻率工作。這種情況下即使電源的工作頻率完全與工作在CRT掃描頻率的某一諧波頻率相一致電源變壓器的電磁輻射依然會對CRT顯示器的圖象造成明顯的干擾使視覺效果變差工作頻率越高干擾越顯著。 對高頻電源變壓

2、器進行電磁屏蔽多數(shù)設計成將變壓器整體地封閉在一個密封的金屬盒內有時把驅動電路的部件也包括在內。采用這種屏蔽結構時為防止在高壓繞組和金屬盒內之間可能產(chǎn)生的飛弧兩者中間要留有足夠大的空隙。所以這種屏蔽結構對電磁場的屏蔽效果是不理想的同時還在CRT顯示器中占據(jù)相當大的空間。再一種屏蔽結構是將變壓器整體地灌封在具有高介電常數(shù)的絕緣材料中形成一體化無間隙結構。這種灌注成整體結構的問題是:要使灌封達到無間隙工藝操作上有相當難度,由于以環(huán)氧樹脂為代表的灌封材料的位移電荷在封裝材料表面形成高電位將通過較低介電常數(shù)的空氣向有足夠電位差的表面形成飛弧。 2屏蔽方式與設計 insulating properties

3、 of air . GB/T9966.3-2001 test methods for natural facing stones part 4: wear resistance test method for GB/T996 6.4-2001 test methods for natural facing stones 5th part: test method for scleroscope hardness GB/T996 6.5-2001 test methods for natural facing stones 6th part: test method for acid resis

4、tance GB/T996 6.6-2001 test methods for natural facing stone test methods for natural facing stones 8th part: by uniform static pressure difference test stone mounted Structure strength test method of GB/T996 6.8-2001 13, sealant technical standards of architectural curtain wall construction with Si

5、licon sealant silicone building sealant GB/T14683-2003 GB16776-2005 JC887-2001 dry hanging stone curtain wall with epoxy adhesive sealant for glass curtain wall joints JC/T882-2001 JC/T883-2001 mold for building stone building sealant sealant JC/ T885-2001 elastomeric sealant for insulating glass JC

6、/T486-2001 14, building curtain wall fasteners for standard steel high strength bolts with large Hexagon head, large Hexagon nuts, washers technology GB/T1231-2006 high strength plain washers for steel structures GB/T1230-2006 high strength large Hexagon nuts for steel GB/T1229-2006 high-strength bi

7、g six head bolts for steel GB/T1228-2006 mechanical properties of fasteners Multigrip blind rivets GB/T3099.2-2004 GB/T3098.19-2004 fastener terminology test methods for mechanical properties of fasteners for blind rivets GB/T3098.18-2004 wing nut fasteners mechanical properties ensure torque GB/T30

8、98.20-2004 mechanical properties of fasteners of stainless 2.1屏蔽方式 本設計所采用的高頻電源變壓器的屏蔽結構由三部分組成:磁路、安裝在磁路上的繞組、外表面層的等場強結構的屏蔽罩其包括大部分在電氣特性上與磁路完全一致的連續(xù)磁環(huán)路及部分繞組組件。同時為了防止飛弧還要在繞組部件有較高電場強度表面一定的距離上用空氣隙和環(huán)氧樹脂來增加強電場區(qū)域的屏蔽層厚度。 這里介紹這種屏蔽的一個典型設計實例:在緊靠高頻變壓器繞組較低電場區(qū)域設臵一個電氣特性上連續(xù)的屏蔽環(huán)路,在較高電場區(qū)域靠近繞組的外圍設臵另一個電氣特性上連續(xù)的屏蔽環(huán)路它應與繞組保持足夠的

9、空間距離以防止屏蔽環(huán)內部電介質,這里指空氣與環(huán)氧樹脂,電擊穿。這樣便可從選定等場強的外形并結合適當選擇電氣特性上連續(xù)的環(huán)路數(shù)、屏蔽環(huán)的形狀和其間距以使高頻電源變壓器得到比較完善的屏蔽效果。在此結構形式的基礎上我們可以從適當變化屏蔽環(huán)的尺寸和布局為變壓器提供一個分布式散熱器增強變壓器的冷卻效果。 2.2屏蔽設計及說明 圖1所示為高頻電源變壓器及其屏蔽的基本結構和電場分布圖。圖中剖面(50)上可以看到磁路(52)通過圓柱形繞組(56)和一個或幾個低壓線圈(64)以及次級高壓線圈(66)。高壓線圈(66)是與其它線圈(62)、(64)分開的沿著繞組(56)的長度方向以線性分布繞制結insulatin

10、g properties of air . GB/T9966.3-2001 test methods for natural facing stones part 4: wear resistance test method for GB/T996 6.4-2001 test methods for natural facing stones 5th part: test method for scleroscope hardness GB/T996 6.5-2001 test methods for natural facing stones 6th part: test method fo

11、r acid resistance GB/T996 6.6-2001 test methods for natural facing stone test methods for natural facing stones 8th part: by uniform static pressure difference test stone mounted Structure strength test method of GB/T996 6.8-2001 13, sealant technical standards of architectural curtain wall construc

12、tion with Silicon sealant silicone building sealant GB/T14683-2003 GB16776-2005 JC887-2001 dry hanging stone curtain wall with epoxy adhesive sealant for glass curtain wall joints JC/T882-2001 JC/T883-2001 mold for building stone building sealant sealant JC/ T885-2001 elastomeric sealant for insulat

13、ing glass JC/T486-2001 14, building curtain wall fasteners for standard steel high strength bolts with large Hexagon head, large Hexagon nuts, washers technology GB/T1231-2006 high strength plain washers for steel structures GB/T1230-2006 high strength large Hexagon nuts for steel GB/T1229-2006 high

14、-strength big six head bolts for steel GB/T1228-2006 mechanical properties of fasteners Multigrip blind rivets GB/T3099.2-2004 GB/T3098.19-2004 fastener terminology test methods for mechanical properties of fasteners for blind rivets GB/T3098.18-2004 wing nut fasteners mechanical properties ensure t

15、orque GB/T3098.20-2004 mechanical properties of fasteners of stainless 合線圈(62)、(64)的布局及磁路(52)的結構形成了圖1(b)所示的電場強度分布狀況,沿圓柱形繞組(56)長度方向的電場強度分布曲線如圖1(b)之(80)所示。 線圈(62)和(66)制成以后用環(huán)氧樹脂進行灌封(74)以形成變壓器的機械支撐電氣絕緣和有關防護。初級繞組(62)和低壓線圈(64)在環(huán)氧樹脂(74)內的一端設計連續(xù)引腳(76)與印制電路(PCB)(78)相連接。高壓線圈(66)的“低”壓端(68)通過引線與PCB連接,高壓線圈的“高”壓端

16、(70)通過封固在環(huán)氧樹脂中的高壓二極管(72)與外電路或CRT相連接。 由圖1(b)電場分布曲線(80)可見變壓器的最大電場強度在靠近繞組(56)(見圖1(a)所示)末端處而不是在其邊緣。 圖2所示為這種屏蔽結構的分解示意圖(100)。圖1所示的變壓器(50)的剖面圖中包含的磁路(52A)是(110)和(112)兩部分緊密對接的鐵氧體在其結合部位(120)和(122)處留有適宜的氣隙絕緣導線(108)把CRT,圖中未畫出,和圖1中所示出的二極管(72)連續(xù)起來。普通的U型屏蔽罩(130)圍繞磁心(52A)延伸把繞組(56)的外側部分的磁路覆蓋住并包括了氣隙(120)在內也覆蓋了。 insul

17、ating properties of air . GB/T9966.3-2001 test methods for natural facing stones part 4: wear resistance test method for GB/T996 6.4-2001 test methods for natural facing stones 5th part: test method for scleroscope hardness GB/T996 6.5-2001 test methods for natural facing stones 6th part: test metho

18、d for acid resistance GB/T996 6.6-2001 test methods for natural facing stone test methods for natural facing stones 8th part: by uniform static pressure difference test stone mounted Structure strength test method of GB/T996 6.8-2001 13, sealant technical standards of architectural curtain wall cons

19、truction with Silicon sealant silicone building sealant GB/T14683-2003 GB16776-2005 JC887-2001 dry hanging stone curtain wall with epoxy adhesive sealant for glass curtain wall joints JC/T882-2001 JC/T883-2001 mold for building stone building sealant sealant JC/ T885-2001 elastomeric sealant for ins

20、ulating glass JC/T486-2001 14, building curtain wall fasteners for standard steel high strength bolts with large Hexagon head, large Hexagon nuts, washers technology GB/T1231-2006 high strength plain washers for steel structures GB/T1230-2006 high strength large Hexagon nuts for steel GB/T1229-2006

21、high-strength big six head bolts for steel GB/T1228-2006 mechanical properties of fasteners Multigrip blind rivets GB/T3099.2-2004 GB/T3098.19-2004 fastener terminology test methods for mechanical properties of fasteners for blind rivets GB/T3098.18-2004 wing nut fasteners mechanical properties ensu

22、re torque GB/T3098.20-2004 mechanical properties of fasteners of stainless 第二磁路的屏蔽罩(140)由第一電氣特性連接環(huán)(150)和第二電氣特性連接環(huán)(160)組成它們以銅箔或其它金屬制作。二個環(huán)由屏蔽片(154)相連并選用一個合適的距離間隔(170)。在具體設計時環(huán)路(150)和(160)的寬度和相隔距離(170)各占繞組(56)長度的三分之一。屏蔽罩(140)延伸到整個變壓器(150A)和另一個屏蔽罩(130)其中第一個環(huán)(150)緊貼繞組部件外表面在低端(68A)接觸處有足夠厚度的環(huán)氧樹脂層。第二環(huán)(160)圍繞

23、繞組的高端與繞組間保持有足夠大的空間(其間或者充有其它介質)以防止環(huán)氧樹脂表面(74)與屏蔽環(huán)(160)之間產(chǎn)生飛弧。對不同的電場強度分布相應的電氣連接insulating properties of air . GB/T9966.3-2001 test methods for natural facing stones part 4: wear resistance test method for GB/T996 6.4-2001 test methods for natural facing stones 5th part: test method for scleroscope hard

24、ness GB/T996 6.5-2001 test methods for natural facing stones 6th part: test method for acid resistance GB/T996 6.6-2001 test methods for natural facing stone test methods for natural facing stones 8th part: by uniform static pressure difference test stone mounted Structure strength test method of GB

25、/T996 6.8-2001 13, sealant technical standards of architectural curtain wall construction with Silicon sealant silicone building sealant GB/T14683-2003 GB16776-2005 JC887-2001 dry hanging stone curtain wall with epoxy adhesive sealant for glass curtain wall joints JC/T882-2001 JC/T883-2001 mold for

26、building stone building sealant sealant JC/ T885-2001 elastomeric sealant for insulating glass JC/T486-2001 14, building curtain wall fasteners for standard steel high strength bolts with large Hexagon head, large Hexagon nuts, washers technology GB/T1231-2006 high strength plain washers for steel s

27、tructures GB/T1230-2006 high strength large Hexagon nuts for steel GB/T1229-2006 high-strength big six head bolts for steel GB/T1228-2006 mechanical properties of fasteners Multigrip blind rivets GB/T3099.2-2004 GB/T3098.19-2004 fastener terminology test methods for mechanical properties of fastener

28、s for blind rivets GB/T3098.18-2004 wing nut fasteners mechanical properties ensure torque GB/T3098.20-2004 mechanical properties of fasteners of stainless 環(huán)的數(shù)目和排布也不相同電場強度越高環(huán)的直徑越大。第一個環(huán)(150)和第二個環(huán)(160)包圍整個磁路環(huán)內磁通量的總和為零故屏蔽效果比較理想。 3屏蔽材料選擇與屏蔽罩設計 眾所周知電磁場產(chǎn)生的干擾影響可以通過磁屏蔽、磁隔離和轉移元件等產(chǎn)生的作用使其減至最小或消除。磁場通過導磁材料比其通過空氣

29、或其它介質材料時更容易被轉移。所以常常使用高磁導率的磁性材料來制成環(huán)狀或密封的屏蔽元件。 3.1屏蔽材料的類型 屏蔽效果是根據(jù)設備或元器件被屏蔽后磁場強度衰減的程度來度量的。屏蔽后磁場強度的衰減率或衰減量是材料的磁導率、厚度和屏蔽罩的尺寸的函數(shù)。高磁導率材料比低磁導率材料昂貴但如果用單層高磁導率材料的屏蔽效果與多層低磁導率材料的屏蔽效果相同則可能選用厚度薄的高磁導率材料更經(jīng)濟。 目前用于屏蔽的主要磁性材料見表1。 insulating properties of air . GB/T9966.3-2001 test methods for natural facing stones part

30、4: wear resistance test method for GB/T996 6.4-2001 test methods for natural facing stones 5th part: test method for scleroscope hardness GB/T996 6.5-2001 test methods for natural facing stones 6th part: test method for acid resistance GB/T996 6.6-2001 test methods for natural facing stone test meth

31、ods for natural facing stones 8th part: by uniform static pressure difference test stone mounted Structure strength test method of GB/T996 6.8-2001 13, sealant technical standards of architectural curtain wall construction with Silicon sealant silicone building sealant GB/T14683-2003 GB16776-2005 JC

32、887-2001 dry hanging stone curtain wall with epoxy adhesive sealant for glass curtain wall joints JC/T882-2001 JC/T883-2001 mold for building stone building sealant sealant JC/ T885-2001 elastomeric sealant for insulating glass JC/T486-2001 14, building curtain wall fasteners for standard steel high

33、 strength bolts with large Hexagon head, large Hexagon nuts, washers technology GB/T1231-2006 high strength plain washers for steel structures GB/T1230-2006 high strength large Hexagon nuts for steel GB/T1229-2006 high-strength big six head bolts for steel GB/T1228-2006 mechanical properties of fast

34、eners Multigrip blind rivets GB/T3099.2-2004 GB/T3098.19-2004 fastener terminology test methods for mechanical properties of fasteners for blind rivets GB/T3098.18-2004 wing nut fasteners mechanical properties ensure torque GB/T3098.20-2004 mechanical properties of fasteners of stainless 3.2屏蔽材料的選擇

35、如上所述屏蔽材料的磁導率、屏蔽罩的幾何形狀材料的厚度等都影響磁屏蔽的效果所以選用屏蔽材料的原則是: a.要使外部磁場得到最大衰減需要用高磁導率()的材料, b.磁屏蔽的效果也是屏蔽罩材料壁厚對屏蔽罩直徑,在采用矩形屏蔽罩時為其對角線,之比率,t/D,的函數(shù)。 c.如果外部的干擾磁場太高屏蔽罩的衰減作用將減小。這是因為外部磁場太高時磁性材料將接近于磁飽和狀態(tài)。 d.在通常情況下用厚的金屬材料制造屏蔽罩是不現(xiàn)實的。因為其成本高?？梢杂帽⌒徒饘俨芎唵蔚乩p繞在受磁場影響的元件上來替代屏蔽罩。 insulating properties of air . GB/T9966.3-2001 test me

36、thods for natural facing stones part 4: wear resistance test method for GB/T996 6.4-2001 test methods for natural facing stones 5th part: test method for scleroscope hardness GB/T996 6.5-2001 test methods for natural facing stones 6th part: test method for acid resistance GB/T996 6.6-2001 test metho

37、ds for natural facing stone test methods for natural facing stones 8th part: by uniform static pressure difference test stone mounted Structure strength test method of GB/T996 6.8-2001 13, sealant technical standards of architectural curtain wall construction with Silicon sealant silicone building s

38、ealant GB/T14683-2003 GB16776-2005 JC887-2001 dry hanging stone curtain wall with epoxy adhesive sealant for glass curtain wall joints JC/T882-2001 JC/T883-2001 mold for building stone building sealant sealant JC/ T885-2001 elastomeric sealant for insulating glass JC/T486-2001 14, building curtain w

39、all fasteners for standard steel high strength bolts with large Hexagon head, large Hexagon nuts, washers technology GB/T1231-2006 high strength plain washers for steel structures GB/T1230-2006 high strength large Hexagon nuts for steel GB/T1229-2006 high-strength big six head bolts for steel GB/T12

40、28-2006 mechanical properties of fasteners Multigrip blind rivets GB/T3099.2-2004 GB/T3098.19-2004 fastener terminology test methods for mechanical properties of fasteners for blind rivets GB/T3098.18-2004 wing nut fasteners mechanical properties ensure torque GB/T3098.20-2004 mechanical properties

41、of fasteners of stainless 3.3屏蔽罩的設計 a.進行屏蔽罩設計時需要以下一些數(shù)據(jù): ?對屏蔽材料能夠衰減多少磁場強度必須進行測量或估算得出數(shù)據(jù)。 ?為了得到良好的磁屏蔽效果必須挑選最合適的屏蔽罩形狀。典型的或相對可被選用的幾何形狀包括長圓柱體、矩形殼體,另有球體、平板或圓錐體也會被采用。 b.設計屏蔽罩時必須首先確定磁通密度值,高斯,同時以此選擇屏蔽材料的厚度。因為屏蔽材料的值與值的分布圖是非線性關系作用于屏蔽罩的磁通密度必須使材料達到其峰值磁導率例如坡莫合金和mumetal的磁通密度應在3600高斯左右。 屏蔽材料的厚度可由以下公式計算確定: t,1.25DH/B

42、 ,英寸, 式中D是衰減率由屏蔽前的磁場強度除屏蔽后的磁場強度得到。鎳含量高的磁性材料的值最小可達到80000。 c.設計屏蔽罩時應注意以下事項: insulating properties of air . GB/T9966.3-2001 test methods for natural facing stones part 4: wear resistance test method for GB/T996 6.4-2001 test methods for natural facing stones 5th part: test method for scleroscope hardne

43、ss GB/T996 6.5-2001 test methods for natural facing stones 6th part: test method for acid resistance GB/T996 6.6-2001 test methods for natural facing stone test methods for natural facing stones 8th part: by uniform static pressure difference test stone mounted Structure strength test method of GB/T

44、996 6.8-2001 13, sealant technical standards of architectural curtain wall construction with Silicon sealant silicone building sealant GB/T14683-2003 GB16776-2005 JC887-2001 dry hanging stone curtain wall with epoxy adhesive sealant for glass curtain wall joints JC/T882-2001 JC/T883-2001 mold for bu

45、ilding stone building sealant sealant JC/ T885-2001 elastomeric sealant for insulating glass JC/T486-2001 14, building curtain wall fasteners for standard steel high strength bolts with large Hexagon head, large Hexagon nuts, washers technology GB/T1231-2006 high strength plain washers for steel str

46、uctures GB/T1230-2006 high strength large Hexagon nuts for steel GB/T1229-2006 high-strength big six head bolts for steel GB/T1228-2006 mechanical properties of fasteners Multigrip blind rivets GB/T3099.2-2004 GB/T3098.19-2004 fastener terminology test methods for mechanical properties of fasteners

47、for blind rivets GB/T3098.18-2004 wing nut fasteners mechanical properties ensure torque GB/T3098.20-2004 mechanical properties of fasteners of stainless ?對于強度很高的磁場可以使用多層材料制作屏蔽罩最靠近強磁場的那一層材料應是能夠削弱較大磁通量的合金材料如48合金、magnesill,而第二層應采用高磁導率的材料如坡莫合金,如果有條件應允許磁場發(fā)射源和最靠近它的那一層屏蔽材料之間的空隙最小,1/2左右,。在設計與制造習慣上于多層屏蔽材料的每

48、層之間是用聚酯薄膜相間隔的。 ?如果屏蔽罩對屏蔽的目標實現(xiàn)不了封閉磁場發(fā)射源雜散磁場的目的則常常采用平板插在它們兩者之間。如果平板的高度與寬度比磁場發(fā)射源和要求屏蔽物的尺寸大得多則可以封閉雜散磁場。 ?如果用厚度小于0.006的金屬板作屏蔽材料則一般是用于樣機上因為這種厚度便于手工成型。如果是批量生產(chǎn)用機械方法制作屏蔽罩應該采用較厚的材料。但應注意任何較強力的機械作業(yè)如折彎、沖壓、焊接等都會使材料產(chǎn)生應力從而使材料性能下降這就需要通過合適溫度的退火來改善。 ?通常在低頻,600Hz左右,狀態(tài)屏蔽罩的長度對直徑的比率大于3時把屏蔽材料的厚度從0.014增厚至0.050則屏蔽效果增強,如果比率低于3增加材料厚度至0.025時則