US3742170A - Loud tap changer by-pass switch contact assembly and material composition thereof - Google Patents

Loud tap changer by-pass switch contact assembly and material composition thereof Download PDF

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Publication number
US3742170A
US3742170A US00185161A US3742170DA US3742170A US 3742170 A US3742170 A US 3742170A US 00185161 A US00185161 A US 00185161A US 3742170D A US3742170D A US 3742170DA US 3742170 A US3742170 A US 3742170A
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United States
Prior art keywords
face
switch
current interrupting
pass switch
sliding portion
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Expired - Lifetime
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US00185161A
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English (en)
Inventor
T Topper
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ABB Inc USA
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Westinghouse Electric Corp
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Publication of US3742170A publication Critical patent/US3742170A/en
Assigned to ABB POWER T&D COMPANY, INC., A DE CORP. reassignment ABB POWER T&D COMPANY, INC., A DE CORP. ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: WESTINGHOUSE ELECTRIC CORPORATION, A CORP. OF PA.
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H9/00—Details of switching devices, not covered by groups H01H1/00 - H01H7/00
    • H01H9/0005—Tap change devices
    • H01H9/0016—Contact arrangements for tap changers

Definitions

  • ABSTRACT Contact structures with composite materials arranged to increase the operating life of the contact when used in load tap changer by-pass switches.
  • An arc resistance 2 F' zoo/166 hai refractory material is dimensioned and positioned to 'F' B 4 interrupt the current when the switch is opened.
  • a 1 1e 0 care l 1 6 66 highly conductive metallic material forms a sliding portion of the contact structure and is dimensioned and 56 R f d positioned to conduct all of the switch current while 1 e erences the rotary blade of the switch is rotating.
  • the material UNITED STATES PATENTS of the sliding portion prevents galling of the rotary 2,931,876 4/1960 Weinfurt ZOO/166 C UX blade and considerably extends the operating life of the 1,978,516 10/1934 Weiger et a1 200/166 C UX by-pass switch. 2,464,591 3/1949 Larsen et al.
  • the tap changer disclosed in US. Pat. No. 3,553,395 uses a by-pass switch to divert the load current around the vacuum switch when the tap changer is not changing taps. This permits more efficient use of the vacuum switch and thus the maintenance free life of the tap changer is enhanced.
  • the contacts of the bypass switch must be capable of interrupting large currents for a relatively large number of times.
  • Vacuum switches of the type used to interrupt the load current have a contact life in excess of 1.5 million operations at a current of 2,000 amperes.
  • By-pass switch contacts are not presently available which give this excellent performance. In fact, the number of maintenance free operations which can be expected from the overall tap changer is substantially limited by the life expectancy of the by-pass switch contacts.
  • each stationary contact be capable of carrying large currents while sliding on a rotary blade which is normally constructed of high conductivity copper alloy. It is also a requirement that the contacts be constructed of a suitable material which will withstand the destructive effects of an electrical are which develops when the current is interrupted. Unfortunately, good are resisting materials do not provide suitable contact surfaces for the sliding portion of the contact. As a result of the poor performance of the contact material used in prior art by-pass switch contacts, galling or commutation arcing occurs between the contacts and the rotary blade. This pits the surface of the rotary blade which slides along the contacts and, when the pitting is severe enough, the switch becomes inoperative. Even in the liquid coolant of the tap changer the bypass contact life at 2,000 amperes may be as low as 50,000 operations.
  • the stationary contact structure comprises a body portion, a current interrupting portion attached thereto and constructed of an are resistant refractory material, and a sliding portion constructed of a highly conductive metallic material which is attached to a face of the current interrupting portion.
  • the sliding portion is the only part of the contact structure which touches the rotary blade of the by-pass switch when it is being rotated.
  • the current interrupting portion touches the rotary blade momentarily when the switch is opened and the are which develops occurs between the rotary blade and the current interrupting portion of the contact structure.
  • the sliding portion is attached directly to the body portion of the contact structure.
  • the current interrupting portion which is attached to the body portion adjacent to the sliding portion, has the face, which is adjacent to the rotary blade, beveled so that the current interrupting portion does not touch the rotary blade except when the switch is being opened. While sliding, only the sliding portion touches the rotary blade.
  • FIG. 1 is an electrical schematic of a load-type tap changer constructed according to the teachings of this invention
  • FIG. 2 is a view of a by-pass switch constructed according to the teachings of this invention.
  • FIG. 3 is a cross-sectional elevational view of the bypass switch contact structure taken along the line III- -lll,shown in FIG. 2;
  • FIG. 4 is a cross-sectional view of the contact structure taken along the line IV-IV of FIG. 3 illustrating one embodiment of the invention.
  • FIG. 5 is a cross-sectional view of a contact structure constructed according to the teachings of another embodiment of the invention.
  • FIG. I in particu lar, there is shown a schematic diagram of a load tap changer which utilizes the teachings of this invention.
  • the tap changer is connected to the windings 12, 14 and 16 of an electrical transformer.
  • the transformer may be single phase or polyphase, and of the autotransformer or isolated winding type, with only a portion of a single phase being illustrated in FIG. 1 since other phases would be similarly arranged.
  • the tap changer is of the type which includes a no load-type tap selector switch 20, having a plurality of stationary contacts C1, C2, C3, C4, C5, C6, C7 and C8 connected to the taps T1, T2, T3, T4, T5, T6, T7 and T8, respectively, on the winding 14, and a stationary contact C9 connected to the winding 16.
  • the tap selector switch has a pair of movable contact arms 22 and 24 for selectively and sequentially moving between the spaced stationary contacts Cl through C9.
  • the ends of the tapped winding 14 are connected to the stationary contacts 26 and 28 of a reversing switch 30, which has a movable contact 32 connected to the winding 16, and thus to the stationary contact C9of the tap selector switch 20.
  • the reversing switch 30 may be actuated to change its movable contact 32 from one stationary contact to the other when one of the movable contact arms 22 and 24 of the tap selector switch 20 is in engagement with the stationary contact C9 and the other arm is in transition to or from the contact C9. This allows the tapped winding voltage to be added to or subtracted from the voltage of the windings 12 and 16, depending upon the position of the reversing switch 30.
  • the contact arms are connected to the winding 12 through a split or divided preventive autotransformer or reactor 40 having windings 42 and 44 disposed on a common magnetic core 46.
  • the windings are wound to present a high impedance to circulating currents, while providing very little impedance to power current flow in the same direction through the two windings.
  • the movable contact 58 is connected to the winding 12, and the stationary contacts 54 and 56 are connected to the winding sections 42 and 44 of the reactor 40.
  • the movable contact 58 is arranged to engage both stationary contacts 54 and 56, or to select either of the stationary contacts individually.
  • the vacuum switch 50 has contacts 62 and 64 disposed within an evacuated envelope, with one of the contacts being movable relative to the other by way of a bellows which maintains the vacuum seal.
  • the vacuum switch 50 is connected across the contacts 54 and 56 of the by-pass switch 52.
  • the power circuit of the transformer When the tap-changer is in a steady state position, the power circuit of the transformer includes the winding 16, and the portion of the winding 14 which is between the closed positions of the reversing switch 30 and the tap selected by the contact arms 22 and 24 through the two branch circuits of the contact arms.
  • One of the branch circuits includes the contact arm 24, the winding section 42, and the portion of the by-pass switch 52 which includes the stationary contact 54.
  • the other branch circuit includes the contact arm 22, the winding section 44, and the portion of the by-pass switch 52 which includes the stationary contact 56.
  • the branch circuits combine in the movable contact 58 of the bypass switch 52, and the power circuit continues to the winding 12.
  • the tapped winding 14 may also be disposed at either end of a main transformer winding,
  • the vacuum switch 50 has its contact closed, but since it is normally shorted by the by-pass switch 50,
  • the tap changer drive means sequentially operates the by-pass switch 52, the vacuum switch S0, and the tapped selector switch 20, by suitable mechanical means, generally indicated by the dashed lines 72, 74 and 76, respectively.
  • suitable mechanical means generally indicated by the dashed lines 72, 74 and 76, respectively.
  • the by-pass switch 52 is illustrated showing the mechanical details of its construction in FIG. 2'.
  • the movable contact structure 58 which is shown schematically in FIG. 1, comprises the stationary contact structures and 82 and the rotary blade 84.
  • the rotary blade is alternately rotated clockwise and counterclockwise by the mechanical drive means 72 to engage and disengage the rotary blade 84 with the stationary contact structures 86 and 88.
  • the current flowing between the stationary contacts 80, 82, 86 and 88 crosses the sliding junction between the stationary contacts 86 and 88 and the rotary blade. If the rotary blade 84 is rotating in a counterclockwise direction, an arc will occur when the edge 90 of the rotary blade 84 disengages with the stationary contact structure 86.
  • the rotary blade 84 may be constructed of a highly conductive material, such as copper-cadmium, with the edges 90 and 92 thereof constructed of an are resistant refractory material, such as copper-tungsten.
  • FIG. 3 is a cross-sectional view of the stationary contact structure 86 taken along the line Ill-1II shown in FIG. 2.
  • the stationary contact structure 86 includes the upper and lower body portions 94 and 96, respectively, which are constructed of a suitable material, such as copper.
  • a suitable material such as coin silver, is attached to the end of the body portions 94 and 96 to provide the structures 98 and 100 which engage with the mounting plate 102.
  • the upper body portion is attached to a current interrupting portion 104 which has a sliding portion 106 attached thereto.
  • the current interrupting portion 108 and the sliding portion 110 are similarly disposed on the lower body portion 96.
  • the bolt 112 extends through holes in the body portions 94 and 96 and, with the nut 114 and the spring 116, pull the body portions together to make satisfactory electrical contact with the rotary blade 84 and'the mounting plate 102.
  • FIG. 4 A partial cross-sectional view of the lower contact structure, taken along the line IV-IV of FIG. 3, is illustrated in FIG. 4.
  • the current interrupting portion 108 is attached to the body portion 96 by a suitable process, such as silver soldering.
  • the current interrupting portion 108 is constructed of an are resistant refractory material, such as copper-tungsten.
  • the sliding portion 110 comprises a layer of highly conductive metallic material, such as coin silver, and is attached to the current interrupting portion 108 by a suitable process, such as silver soldering.
  • the current flowing between the body portion 96 and the rotary blade 84 must pass across the junction 113 where the sliding portion 110 and the rotary blade 84 meet.-
  • the material of the sliding portion 110 allows the current to flow, while the rotary blade 84 is being rotated, without substantial galling or commutation-arcing occurring between the surfaces comprising the junction 113.
  • the are resistant refractory material of the current interrupting portion 108 carries the main force of the are which occurs on opening the electrical circuit. Because of the high melting temperatures of the current interrupting portion 108, the surface erosion thereof is relatively small.
  • the side 117 of the current interrupting portion 108 is beveled to allow the rotary blade 84 to engage with the contact structure.
  • FIG. 5 represents another embodiment of this invention.
  • the body portion 96 is attached directly to the current interrupting portion 120 and to the sliding portion 122 by a suitable process, such as silver soldering.
  • a suitable process such as silver soldering.
  • This embodiment of the invention reduces galling or commutation-arcing" because of the characteristics of the materials which slide with respect to one another.
  • an arc occurs between the rotary blade 84 and the current interrupting portion 120.
  • the face portion 126 of the current interrupting portion 120 is beveled to prevent contact with the rotary blade 84 when the rotary blade is sliding across the sliding portion 122.
  • the face 128 of the sliding portion 122 is also beveled slightly beyond the junction of the current interrupting portion 120 and the sliding portion 122 to assure that the current interrupting portion 120 does not contact the rotary blade 84 while sliding over the sliding portion 122.
  • a bevel angle 130 of 5 is satisfactory.
  • the side 132 of the current interrupting portion 120 is beveled to permit the rotary blade 84 to engage with the contact structure.
  • the contact structures disclosed herein permit a substantial increase in the operating life of load-type tap changers using by-pass switches.
  • a by-pass switch comprising a rotary blade and stationary contact structures, said rotary blade being.
  • each of said contact structures having a body portion, a current interrupting portion constructed of an arc resistant refractory material, and a sliding portion constructed of a highly conductive metallic material, said sliding por tion being positioned adjacent to said current interrupting portion to provide the only current path between said rotary blade and said current interrupting portion when the switch is in a closed position, with any arcing, when the switch is being opened, occurring substan' tially between said rotary blade and said current interrupting portion.
  • the current interrupting portion comprises first and second faces, first and second sides, said first face being attached to the body portion of the contact structure, the second face being attached to the sliding portion of the contact structure, with the sliding portion covering substantially the entire surface of said second face.
  • the current interrupting portion comprises first and second faces and first and second sides
  • the sliding portion comprises first and second faces and first and second sides, said first face of the current interrupting portion being attached to the body portion of the contact structure, said first face of the sliding portion being attached to the body portion of the contact structure, said second side of the current interrupting portion being adjacent to the first side of the sliding portion, said second face of the sliding portion being a greater distance from the body member than said second face of the current interrupting portion, said second face of the current interrupting portion being sloped, with respect to the second face of the sliding portion, to prevent contact of the current interrupting portion with the rotary blade when the switch is in a closed position.

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  • Arc-Extinguishing Devices That Are Switches (AREA)
US00185161A 1971-09-30 1971-09-30 Loud tap changer by-pass switch contact assembly and material composition thereof Expired - Lifetime US3742170A (en)

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Application Number Priority Date Filing Date Title
US18516171A 1971-09-30 1971-09-30

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JP (2) JPS4848919A (ja)
BE (1) BE789421A (ja)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4959554A (en) * 1989-05-08 1990-09-25 Underwood Iv Joseph W T Dual input-dual output electric switch
US5051548A (en) * 1989-05-08 1991-09-24 Wood 'n Rock, A Florida Partnership Dual input-dual output electric switch

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2536771B2 (de) * 1975-08-19 1980-01-03 Transformatoren Union Ag, 7000 Stuttgart Kontaktanordnung für Wähler von Stufenschaltern
JPH0574303U (ja) * 1992-03-14 1993-10-12 月星化成株式会社 靴の舌片

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1978516A (en) * 1933-02-15 1934-10-30 Mallory & Co Inc P R X-ray target
US2464591A (en) * 1944-04-04 1949-03-15 Mallory & Co Inc P R Method of bonding a tungsten member to a backing member
US2717296A (en) * 1953-09-14 1955-09-06 Gen Electric Electrical switch contacts
US2931876A (en) * 1957-04-17 1960-04-05 Mc Graw Edison Co Electric contact
US3140373A (en) * 1962-01-24 1964-07-07 Gen Electric Arc ionizable beryllium electrodes for vacuum arc devices
US3166660A (en) * 1960-05-09 1965-01-19 Square D Co Contact construction with metallic contact members and auxiliary metallic arc suppressant conducting members
US3192328A (en) * 1963-02-01 1965-06-29 Mc Graw Edison Co Movable switch contact assembly with self-aligning bridging plate members
US3226517A (en) * 1961-09-26 1965-12-28 Siemens Ag Electrical contact device

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS4525783Y1 (ja) * 1968-01-18 1970-10-07

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1978516A (en) * 1933-02-15 1934-10-30 Mallory & Co Inc P R X-ray target
US2464591A (en) * 1944-04-04 1949-03-15 Mallory & Co Inc P R Method of bonding a tungsten member to a backing member
US2717296A (en) * 1953-09-14 1955-09-06 Gen Electric Electrical switch contacts
US2931876A (en) * 1957-04-17 1960-04-05 Mc Graw Edison Co Electric contact
US3166660A (en) * 1960-05-09 1965-01-19 Square D Co Contact construction with metallic contact members and auxiliary metallic arc suppressant conducting members
US3226517A (en) * 1961-09-26 1965-12-28 Siemens Ag Electrical contact device
US3140373A (en) * 1962-01-24 1964-07-07 Gen Electric Arc ionizable beryllium electrodes for vacuum arc devices
US3192328A (en) * 1963-02-01 1965-06-29 Mc Graw Edison Co Movable switch contact assembly with self-aligning bridging plate members

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4959554A (en) * 1989-05-08 1990-09-25 Underwood Iv Joseph W T Dual input-dual output electric switch
US5051548A (en) * 1989-05-08 1991-09-24 Wood 'n Rock, A Florida Partnership Dual input-dual output electric switch

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Publication number Publication date
JPS4848919A (ja) 1973-07-11
JPS539419U (ja) 1978-01-26
BE789421A (fr) 1973-03-28

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AS Assignment

Owner name: ABB POWER T&D COMPANY, INC., A DE CORP., PENNSYLV

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:WESTINGHOUSE ELECTRIC CORPORATION, A CORP. OF PA.;REEL/FRAME:005368/0692

Effective date: 19891229