US3295084A - Transformer having a magnetic core comprising a main flux path having one definite grain orientation and a shunt flux path having a different definite grain orientation - Google Patents

Transformer having a magnetic core comprising a main flux path having one definite grain orientation and a shunt flux path having a different definite grain orientation Download PDF

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Publication number
US3295084A
US3295084A US417325A US41732564A US3295084A US 3295084 A US3295084 A US 3295084A US 417325 A US417325 A US 417325A US 41732564 A US41732564 A US 41732564A US 3295084 A US3295084 A US 3295084A
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shunt
core
magnetic circuit
flux
flux path
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Expired - Lifetime
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US417325A
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English (en)
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Clifford C Horstman
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CBS Corp
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Westinghouse Electric Corp
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Priority to US417325A priority Critical patent/US3295084A/en
Priority to DE19651538250 priority patent/DE1538250A1/de
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F38/00—Adaptations of transformers or inductances for specific applications or functions
    • H01F38/08—High-leakage transformers or inductances
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/24—Magnetic cores
    • H01F27/245—Magnetic cores made from sheets, e.g. grain-oriented

Definitions

  • TRANSFORMER HAVING A MAGNETIC CORE COMPRISING A MAIN FLUX PATH HAVING ONE DEFINITE GRAIN ORIENTATION AND A SHUNT FLUX PATH HAVING A DIFFERENT DEFINITE GRAIN ORIENTATION Filed Dec. 10, 1964 2 Sheets-Sheet 2 l6 F
  • It is another object of this invention to provide an improved magnetic core made from grain oriented sheet steel comprising a main magnetic circuit or flux path having a shunt magnetic circuit or flux path attached thereto wherein the flux always travels in the direction in which the grains of the magnetic sheet steel are oriented, which is the low reluctance direction of travel for the flux.
  • FIGURE 1 is a perspective view of a core provided according to this invention, with primary and secondary windings shown thereon;
  • FIG 2 is a second embodiment of the core shown in FIG. 1; with primary and secondary windings shown thereon;
  • FIG. 3 is a perspective view of the shunt magnetic circuit of the general type used in FIGS. 2 and 5,
  • FIG. 4 is a third embodiment of the core provided according to this invention with primary and secondary windings shown thereon;
  • FIG. 5 is a fourth embodiment of the core provided according to this invention showing primary and secondary windings thereon.
  • FIG. 1 illustrates one embodiment of the improved magnetic core having a shunt circuit as provided by this invention.
  • FIG. 1 shows a magnetic core 10.
  • the magnetic core 10 is comprised of a pair of core sections 12 and 14.
  • the core sections 12 and 14 are provided from magnetic sheet steel by winding the required number of layers of laminations to form a core loop. After the core loop has been wound to the required thickness, the core is cut as indicated at 16.
  • the purpose of cutting the core is to enable placing of preformed windings thereon as will be explained hereinafter.
  • the faces of the cut at 16 are worked by grinding and chemically etching to make the faces very smooth so that the sections 12 and 14 of the core may be fitted back together so that joint at 16 will be a low reluctance joint.
  • the cold rolled magnetic sheet steel from which the core sections 12 and 14 are formed is preferably oriented in at least two dimensions, that is in the direction of cold rolling and in a direction transverse to the direction of rolling.
  • the magnetic sheet steel from which the core sections 12 and 14 is formed is oriented in three directions, that is, in the direction of rolling as indicated by the arrow A, transverse to the direction of rolling as indicated by the arrow B and perpendicular to the sheet as indicated by the arrow C.
  • This type of multiple oriented magnetic electrical sheet steel is now commercially available.
  • the core 10 also comprises a shunt or auxiliary flux path provided by the member 18.
  • the shunt or auxiliary member 18 is also made up of a plurality of laminations of cold rolled electrical sheet steel.
  • the laminations from which the shunt element 18 is constructed are oriented in the direction of cold rolling only as indicated by the arrow D.
  • the faces of the laminations of the shunt element D are also ground and chemically etched to make the ends of the laminations very smooth.
  • the points 20 and 21 where the shunt element 18 connects to the sides of the laminations of the elements 12 and 14 are also ground very smooth and chemically etched so that the ends of the laminations of the shunt element 18 will make very good magnetic contact with the edges of the laminations of the core elements 12 and 14.
  • a primary winding 22 having terminals 23 is fitted onto one section of the el ment 12 and a secondary winding 24 having terminal 25 is fitted onto one section of the core section 14.
  • the core sections 12 and 14 are fitted together and the shunt circuit 18 is placed in position and a metallic band 26 is placed around the ,core sections 12 and 14 and tensioned to provide a good joint between the elements 12 and 14 at 16.
  • this band 26 is clamped so as to maintain a constant tension on the joint between the elements 12 and 14.
  • another metallic band 28 is placed around the shunt element 18 and tensioned to provide good contact between the ends of the laminations of the shunt element 18 and .the sides of the iaminations of the elements 12 and 14.
  • the band When proper tension has been provided to the band 18, the band is clamped so as to maintain constant tension in the joints between the laminations in the elements 12 and 14 and the ends of the laminations in the shunt element 18.
  • the core elements 12 and 14 provide the main flux path for flux set up due to current flowing in the primary winding 22. It is seen that the magnetic circuit provided by the core elements 12 and 14 for flux caused by current flowing in the primary winding 22 is shorter than the flux path provided by the element 12 and the shunt 18. This means that the flux path provided by the core elements 12 and 14 has less reluctance than the flux path provided by the core element 12 and the shunt element 18. This means that most of the flux due to the current flowing in the primary winding 22 will flow through the magnetic circuit provided by the core elements 12 and 14. On the other hand it is seen that the flux path provided by the core element 14 and the shunt 18 is shorter than the flux path provided by the core elements 12 and 14.
  • the flux path provided by the core elements 14 and shunt 18 has less reluctance than the flux path provided by the core elements 12 and 14. This means that most of the flux due to abnormal current flowing in the secondary winding 24 will travel the flux path provided by the core elements 14 and the shunt 18, rather than through the main core provided by the core elements 14 and 12.
  • the physical length of the shunt element 18 may be kept reasonable by providing an air gap 19 in the shunt element 18.
  • This air gap 19 may be filled with an insulating material such as micarta, glass or paper.
  • the air gap 19 provides lumped reluctance in the shunt element 18. Under normal operating conditions most of the flux due to current flowing in the primary winding 22 and the secondary winding 24 will flow through the magnetic path provided by the core sections 12 and 14, because of the high reluctance of the shunt element 18.
  • FIG. 1 provides a magnetic core having a main flux path provided by the core elements 12 and 14 of very low reluctance and also a shunt flux path provided by the shunt 18 which also has very low reluctance.
  • the low reluctance of these flux paths is accomplished because as described hereinbefore the magnetic sheet steel laminations used in the core sections 12 and 14 are oriented in such direction that all flux flowing in the main magnetic circuit provided by the core sections Hand 14 is always flowing the direction of orientation of theg'r'ains of the steel and the flux flowing in the shunt ci'rcuit is also always flowing in the direction of orientation of the grains of magnetic sheet steel in the shunt section. From an examination of FIG.
  • a transformer as described in FIG. 1 will in effect be a current regulating transformer.
  • the transformer provided according to FIG. 1 is especially desirable and has special utility in installations wherein short circuits frequently occur on the secondary winding.
  • a particular application for this type transformer is found in the electrostatic air cleaning equipment where the plates or dust collectors of the air cleaner constitute the load on the secondary winding and frequent short circuits occur on these plates or dust collectors due to foreign matter passing through the air cleaners.
  • FIG. 2 the main magnetic circuit or flux path is shaped identical to that illustrated in'FIG. 1, however, the shunt circuit in FIG. 2 instead of being a C-shaped section as shown in FIG. 1 is merely a bundle of straight laminations fitted in between the C-legs of the core sections 12 ,and 14.
  • the secondary winding 24 is fitted onto the shunt section 18.
  • the secondary winding 24 is placed on the shunt element 18 so that most of the flux set up due to the current flowing in the primary winding 22 will link the secondary winding 24.
  • the core section 12 and the shunt 18 is shorter and has less reluctance than the magnetic circuit comprising the core section 12 and 14. This will force most of the flux due to the current flowing in the primary winding 22 to traverse the shunt 18 in the secondary coil 24.
  • the magnetic circuit comprising the core section 14 and the shunt 18 is much shorter than the magnetic circuit comprising the core sections 12 and the shunt 18. Therefore, if the current in the secondary winding 24 should rise abnormally high, most of the flux due to the current flowing in the secondary winding 24 will flow through the magnetic circuit comprising the core section 14 and the shunt 18 and will not link with the primary winding 22 to cause the current in the primary winding 22 to rise abnormally high to counteract the flux due to the current flowing in the secondary winding.
  • FIG. 4 illustrates still another embodiment of the core and transformer as provided by this invention.
  • the core sections 12 and 14 are constructed from cold rolled magnetic sheet steel which is oriented in a single direction, that is, the direction of rolling as indicated by the arrow H.
  • the shunt element 18 is constructed from laminations of magnetic electrical sheet steel which is oriented in a plurality of directions.
  • the magnetic sheet steel of the element 18 is oriented in the direction of rolling as indicated by the arrow E, in the direction transverse to the direction of rolling as indicated by the arrow F, and in the direction perpendicular to the sheets as indicated by the arrow G.
  • all of the joints between the main elements 12 and 14 of the main magnetic circuit or core loop and between the shunt element 18 are ground and chemically etched to provide good electrical joints, the same as for the embodiments shown in FIGS. 1 and 2.
  • a metal band 28 is placed around the core sections 12 and 14 and properly tensioned and clamped to maintain proper tension on all of the joints of the core to provide low reluctance joints.
  • the main flux path provided for flux due to current flowing in the primary coil 22 is through the core section 12, through the section 30 of the shunt element 18, through the core section 14 and back through the winding 22.
  • the magnetic circuit path through the core element 12, through the section 30 of the shunt 18, and through the core section 14 is the shorter flux path and has less reluctance than the flux path through the core section 12 and through the shunt element 18. From this it is seen that most of the flux set up due to current flowing in the primary winding 22 links with the secondary winding 24. However, the main path for flux due to current flowing in the secondary winding 24 will be through the core section 14, through section 30 of the shunt 18, and back through the coil 24.
  • this path is much shorter and has much less reluctance than the flux path through the core element 14 through the section 30 of the shunt and through the core element 12.
  • this flux would traverse 6 the core section 24 and the shunt 18 and would not link with the primary winding 22 to cause the current in the primary to rise to abnormal value which often burns out and destroys the primary winding of the transformer.
  • FIG. 5 illustrates a second embodiment of the core described above for FIG. 4.
  • This embodiment is identical to the embodiment of FIG. 4 except that the shunt element 18 is made from a stack of laminations of cold rolled electrical sheet steel oriented in the direction of rolling as indicated by the arrow E, in the direction transverse to rolling, as indicated by the arrow F and in the direction perpendicular to the sheets as indicated by the arrow G.
  • the secondary winding 24 is placed on the shunt element 18.
  • the flux due to current flowing in the primary winding 22 flows through the core section 12 and through the shunt element 18 thereby linking the seconddary winding 24.
  • the main flux path for the flux due to current flowing in the secondary winding is through the core element 14 and through the shunt element 18.
  • the core element 14 and the shunt 18 provides a much shorter flux path than the core element 12 and the shunt 18; therefore, the flux path provided by the core element 14 and the shunt element 18 has much less reluctance than the flux path provided by the core element 12 and the shunt element 18 and therefore most of the flux due to current flowing in the secondary winding will flow through the core element 14 and the shunt element 18 rather than through the shunt element 18 and the core element 12. Consequently, in case of short circuits or other conditions where the current would rise abnormally in the secondary winding 24 flux due to this current will not link with the primary winding 22 to cause the current in the primary winding 22 to rise to an abnormal value which would destroy the transformer.
  • An air gap 19 is also illustrated in the shunt element 18, shown in the transformer of FIG. 4, and in the core section 14 for the transformers shown in FIGS. 2 and 5.
  • the air gap 19 shown in these figures function the same as the air gap 19 explained hereinbefore for FIG. 1.
  • the air gap 19 forces most of the flux under normal operating conditions to flow through the magnetic circuit linking the primary winding 22 and the secondary winding 24.
  • the current flowing in the sec ondary winding 24 should become abnormal, most of the flux due to this abnormal current in the secondary winding 24 would be forced through the shunt magnetic circuit and would not link with the primary winding 22.
  • the shunt element 18 used in the embodiments shown in FIGS. 2 and 5 is illustrated in FIG. 3.
  • the shunt element 18 of FIG. 3 is built by stacking a bundle of straight laminations. However, it is understood that in the embodi- 7 ment of FIG. 3 the laminations of the shunt element 18 are grain orientated in only one dimension of the sheet, the direction of rolling; whereas, in the embodiment of FIG. 5 the laminations of the shunt element 18 are orientated in a plurality of directions, as explained hereinbefore.
  • all abutting surfaces in all of the butt-joints are ground and etched so that the part of the core may be assembled with a minimum of reluctance in the joints due to the air gaps between the abutting parts.
  • this invention has provided an improved magnetic circuit or core for use with induction electrical apparatus comprising a main magnetic circuit or flux path and a shunt magnetic circuit or flux path wherein the core has high permeability and low watts loss: It is also seen that a transformer built with the core provided by this invention is essentially a current regulating transformer which has built in protection which will prevent the transformer from burning out or becoming damaged in case of abnormal rise of secondary current, such as happens when a short circuit occurs on the secondary.
  • this invention provides a magnetic circuit or core for use with induction electrical apparatus wherein the core has a main magnetic circuit or flux path with an auxiliary or shunt magnetic circuit or flux path attached thereto and all of the joints between the main flux path and auxiliary flux path are arranged so that the fiux is always traveling in a direction of orientation of the grains of the magnetic sheet steel from which the main flux path and auxiliary flux path are constructed, thereby providing a core with low rcluctance joints and a core which has high permeability and low watts loss.
  • a transformer comprising a four sided main magnetic circuit for carrying flux, said main magnetic circuit being formed from laminations of magnetic sheet steel having a definite grain orientation, a primary winding for carrying current on one side of said main magnetic circuit, a secondary winding for carrying current on the opposite side of said main magnetic circuit from said primary winding, a shunt magnetic circuit connected to said main magnetic circuit intermediate said two winding sides, said shunt magnetic circuit comprising laminations of magnetic sheet steel having a definite grain orientation, the laminations of at least one of said magnetic circuits being grain oriented in at least two directions,
  • the'magnetic circuit from said primary winding through said secondary winding and back through said primary winding having less reluctance than the magnetic circuit from said primary winding through said shunt magnetic circuit and back through said primary winding, and the reluctance of the magnetic circuit from said secondary winding through said shunt magnetic circuit and back through said secondary winding being of such magnitude relative to the reluctance of the main magnetic circuit from said secondary winding through said primary wind-- ing that upon abnormal current flow in said secondary winding that most of the flux due to abnormal current flow in said secondary winding flows through said shunt magnetic circuit and back through said secondary winding.
  • a transformer comprising a four sided main magnetic circuit for carrying flux, said main magnetic circuit being formed from laminations of magnetic sheet steel having a definite grain orientation, a primary winding for carrying current on one side of said main magnetic circuit, a secondary winding for carrying current on the opposite side of said main magnetic circuit from said primary winding, the laminations of said primary winding leg having a different grain orientation from the grain orientation of the laminations of said secondary winding leg, the laminations of one of said winding legs being oriented in at least two directions, a shunt magnetic circuit connected to said secondary winding leg, said shunt magnetic circuit comprising laminations of magnetic sheet steel having a definite grain orientation, the magnetic circuit from said primary winding through said secondary winding and back through said primary winding having less reluctance than the magnetic circuit from said primary winding through said shunt magnetic circuit and back through said primary winding, and the reluctance of the magnetic circuit from said secondary winding through said shunt magnetic circuit and back through said secondary winding being of such magnitude relative

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US417325A 1964-12-10 1964-12-10 Transformer having a magnetic core comprising a main flux path having one definite grain orientation and a shunt flux path having a different definite grain orientation Expired - Lifetime US3295084A (en)

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DE19651538250 DE1538250A1 (de) 1964-12-10 1965-07-02 Transformatorkerne mit Streujoch

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3504318A (en) * 1969-05-07 1970-03-31 Westinghouse Electric Corp Three-phase transformer with four legged magnetic core
US4612527A (en) * 1984-08-10 1986-09-16 United Kingdom Atomic Energy Authority Electric power transfer system
US5073765A (en) * 1989-05-09 1991-12-17 Cooper Power Systems, Inc. Retaining band for a transformer core
US5092027A (en) * 1989-05-09 1992-03-03 Cooper Industries, Inc. Method for retaining and protecting a transformer core
US5155676A (en) * 1991-11-01 1992-10-13 International Business Machines Corporation Gapped/ungapped magnetic core
US20070086131A1 (en) * 2005-10-19 2007-04-19 Eaton Corporation Current transformer including a low permeability shunt and a trip device employing the same
CN106062915A (zh) * 2014-02-06 2016-10-26 Abb股份公司 用于监视相对于预定电流阈值的主导体的电流的设备以及相关的脱扣组件和切换设备

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP6667826B2 (ja) 2016-04-13 2020-03-18 ローム株式会社 交流電源装置

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2558110A (en) * 1948-05-15 1951-06-26 Westinghouse Electric Corp Three-phase transformer core
US2771587A (en) * 1953-11-12 1956-11-20 Gen Electric Inductive device
US3195090A (en) * 1961-06-07 1965-07-13 Westinghouse Electric Corp Magnetic core structures

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2558110A (en) * 1948-05-15 1951-06-26 Westinghouse Electric Corp Three-phase transformer core
US2771587A (en) * 1953-11-12 1956-11-20 Gen Electric Inductive device
US3195090A (en) * 1961-06-07 1965-07-13 Westinghouse Electric Corp Magnetic core structures

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3504318A (en) * 1969-05-07 1970-03-31 Westinghouse Electric Corp Three-phase transformer with four legged magnetic core
US4612527A (en) * 1984-08-10 1986-09-16 United Kingdom Atomic Energy Authority Electric power transfer system
US5073765A (en) * 1989-05-09 1991-12-17 Cooper Power Systems, Inc. Retaining band for a transformer core
US5092027A (en) * 1989-05-09 1992-03-03 Cooper Industries, Inc. Method for retaining and protecting a transformer core
US5155676A (en) * 1991-11-01 1992-10-13 International Business Machines Corporation Gapped/ungapped magnetic core
US20070086131A1 (en) * 2005-10-19 2007-04-19 Eaton Corporation Current transformer including a low permeability shunt and a trip device employing the same
WO2007045985A1 (en) * 2005-10-19 2007-04-26 Eaton Corporation A current transformer including a low permeability shunt and a trip device employing the same
US7561387B2 (en) * 2005-10-19 2009-07-14 Eaton Corporation Current transformer including a low permeability shunt and a trip device employing the same
CN101313375B (zh) * 2005-10-19 2011-04-20 伊顿公司 包含低磁导率分路器的电流互感器以及使用它的跳闸装置
CN106062915A (zh) * 2014-02-06 2016-10-26 Abb股份公司 用于监视相对于预定电流阈值的主导体的电流的设备以及相关的脱扣组件和切换设备
CN106062915B (zh) * 2014-02-06 2018-08-31 Abb股份公司 用于监视相对于预定电流阈值的主导体的电流的设备以及相关的脱扣组件和切换设备

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