Classifications

• • 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
  • H01F27/26—Fastening parts of the core together; Fastening or mounting the core on casing or support
• • 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
  • H01F27/26—Fastening parts of the core together; Fastening or mounting the core on casing or support
  • H01F27/263—Fastening parts of the core together
• • 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
  • H01F27/28—Coils; Windings; Conductive connections
  • H01F27/30—Fastening or clamping coils, windings, or parts thereof together; Fastening or mounting coils or windings on core, casing, or other support
  • H01F27/303—Clamping coils, windings or parts thereof together

Definitions

• This invention relates to clamping means for the core and coil assembly of an electric transformer and, more particularly, to clamping means of this type in which the core is of amorphous metal.
• typical clamping means for this purpose comprises horizontal clamping plates at the top and bottom of the core and coil assembly and a flexible band, or strap, which extends between the two clamping plates at opposite sides of the assembly.
• the band is placed under tension to develop clamping forces which urge the two clamping plates toward each other, and suitable force- transmitting means is provided between the plates and the coil structure to transmit these clamping forces to opposite ends of the coil structure.
• a problem encountered in a transformer with an amor ⁇ phous metal core is that the forces developed by clamping means of the type described hereinabove can seriously impair the magnetic performance of the core. This is because amorphous metal is very sensitive to mechanical stresses, and the core tends to be stressed by the above-described clamping forces in a way that impairs its magnetic performance, i.e., increases core losses and exciting current.
• An object of my invention is to provide, for an amorphous-metal cored transformer, clamping means which is capable of effectively holding the parts of the core and coil assembly in their proper positions and yet does not -seriously impair the magnetic performance of the amorphous metal core.
• the core is of generally rectangular configuration and comprises two spaced-apart yokes and two spaced-apart legs at opposite.ends of yokes, with a single one of said yokes containing joints.
• Another object of my invention is to provide clamping means capable of performing as in the immediately-preceding object and also capable of exerting forces on such a core that act almost entirely longitudinally of said single yoke and virtually not at all longitudinally of said legs.
• I provide in combination with said core of rectangular configuration, coil structures respectively surrounding said legs and having passageways through which said legs extend.
• Clamping plates are provided at the yoke ends of said core and are spaced outwardly from the core.
• Means is provided for applying clamping forces to the plates to urge the plates together.
• Force-transmitting members transmit the clamping forces to the coil structures by paths bypassing the core.
• the clamping-force-applying means comprises flexible banding that extends through the coil passageways, alongside said legs, is held under tension, and engages said core at opposite ends of the single yoke containing the joints, thereby exerting forces on said single yoke acting longitudinally thereof.
• the banding is oriented so as to be lspaced from said core at opposite ends of the other of said yokes.
• Fig. 1 is a front elevational view, partly in section and partly schematic, showing a core and coil assembly embodying one form of my invention.
• Fig. 1A is an enlarged view of a portion of Fig. 1.
• Fig. 2 is a sectional view along the line 2-2 of Fig. 1
• Fig. 3 is a sectional view along the line 3-3 of Fig. 1 Detailed Description of Preferred Embodiment
• the transformer shown therein is a distribution transformer comprising a metal tank, a portion of which is shown at 12, containing an insulating liquid 14. Within the insulating liquid is the core and coil assembly J_5_ of the transformer.
• This assembly 15 comprises two coils 17 and 18 and a wound laminated core ⁇ 0_ of amorphous ferromagnetic alloy linked to the coils.
• the coils 17 and 18 are made in a conventional manner, preferably, being pre-wound before being incorporated into the assembly
• Each coil comprises a hollow winding form
• the winding form 19 is a thin-walled tubular structure having a rectangular cross-section, and each of the coils has a rectangular configuration when viewed in horizontal cross-section.
• the interior of form 19 defines a central passageway through the associated coil.
• the core 20 is made from amorphous alloy in strip form, such as that commercially available from Allied Corporation as its Metgla ⁇ 2506-S2 material.
• the core may be rrade in any number of different ways, but the illustrated core is preferably made by winding the amorphous strip into an annular form (not shown), cutting the annular form along a single radial line thereby creating separate laminations. and then reassembling the laminations to form a second annulus (not shown) with distributed gap lap joints in a localized region of the second annulus. Then the second annulus is formed into the generally rectangular shape shown in Fig.
• each of the yokes 21 and 22 has rounded surfaces 28 at its outer ends that merge smoothly into the outer planar surfaces of the adjacent legs 23 and 24.
• the core is annealed to relieve the stresses resulting from the earlier fabrication steps.
• a thin layer of adhesive bonding agent shown at 26 in Fig. 1, is applied to the lateral edges of the laminations in the upper yoke 21 and in the two legs 23 and 24.
• the lower yoke 22 and the corner regions of the core at opposite ends of the lower yoke are kept free of this bonding agent in order to permit ready displacement of these core portions during subse ⁇ uent lacing of the core into the coils.
• the joints 25 are opened, and the portions of the yoke 22 at opposite sides of the joints 25 are displaced into positions of alignment with the legs 23 and 24 to convert the core into a U-shaped structure that can be easily laced into the two pre-wound coils 17 and 18.
• Lacing is accomplished by simultaneously inserting one leg of the above-described U-shaped core structure into the central passageway of pre-wound tubular winding 17 and the other leg into the central pasageway of pre-wound tubular winding 18. Thereafter the displaced yoke portions of the core are returned to their closed-joint positions of Fig. 1 to remake the joints 25.
• two channel-shaped insulating members 34 and 36 are respectively applied to the coils in the locations shown in Fig. 1.
• the horizontal flanges of these channel-shaped members act as spacers which prevent the inner surfaces of the yokes 21 and 22 from directly contacting the edges of coils 17 and 18 and thus reducing the dielectric strength of the coil structure.
• the insulating members 34 and 36 also space and provide insulation between the juxtaposed outer peripheries o the coils 17 and 18.
• the core 2_0_ also comprises, in addition to the above- described amorphous metal parts, an outer wrapper 27 of silicon steel that closely surrounds the amorphous metal laminations and is bonded thereto by the adhesive coating 26. Only a portion of the outer * wrapper is shown on Fig. 1, but it should be understood that it extends completely around the outer periphery of the core.
• the core also comprises an inner liner 29 of silicon iron that snugly fits within the amorphous metal laminations and is bonded thereto by adhesive coating 26. -
• the outer wrapper 27 and the inner liner 29, among other functions, help to protect the amorphous metal laminations of the core against mechanical damage during manufacture, installation, and operation of the core.
• the wrapper 27 and the liner 29 are preferably made of the same type of silicon iron strip that is typically used for the cores of conventional distribu ⁇ tion transformers, having a thickness of about 10 mils as compared to a typical thickness of about 1 mil for the amorphous metal strip.
• clamping means for holding these parts together.
• This clamping means comprises a bottom clamping plate 50, a top clamping plate 52, and a flexible band 58, preferably of steel, that extends between these clamping plates at opposite sides of the assembly.
• the flexible band 58 extends through spaced openings 60 in the bottom clamping plate 50, upwardly through the central passageways of the coils 17 and 18, then through spaced openings 66 in the upper clamping plate 52.
• the band is looped around the portion of the bottom plate between openings 60 and has its upper ends connected together by means of a suitable clip 68.
• the band 58 is suitably tightened to place it in tension, thereby developing clamping forces which urge plates 50 and 52 toward each other.
• the clamping forces are transmitted from the clamping plates 50 and 52 to the coil structure 17, 18 by means of rigid force-transmitting plates 54 of insulating material that are located between the clamping plates 50, 52 and the coil structure 17, 18.
• These plates 54 are disposed perpendicular to the clamping plates 50, 52 and are located adjacent opposite faces of the core, as best seen in Fig. 3.
• the upper plates 54 bear on the top surface of coil structure 17, 18, and the lower plates 54 bear on the bottom surface of coil structure 17, 18.
• the coil structure is clamped between these plates 54 when the band 58 is tightened.
• Plates 54 have sufficient height to leave clearances at 80 and 82 between the core _2_0_ and the end plates 50 and 52, respectively, and thus to avoid applying clamping forces from the plates 50 and 52 to the core 20.
• the core _20_ is prevented from, moving in a vertical direction by the coil structure 17, 18, including the channel-shaped core shields 34 and 36.
• This stationary structure is located within the window of the core and has virtually no vertical clearance with respect to the core and, hence, is capable of restraining any vertical motion -9-
• the coil structure is rendered stationary by reason of the top clamping plate 52 being fixed to the stationary tank 12.
• mounting bolts 85 are provided for connecting together abutting portions of the top clamping plate and the tank.
• the core j20_ is prevented from moving in a horizontal direction by the steel band 58 itself.
• the holes 60 in the lower clamping plate 50 are so located that the band 58, which is positioned by holes 60, contacts the core on the rounded surfaces 28 at opposite ends of the lower yoke 22.
• the band 58 makes an angle D of about 3 degrees at each end of the yoke with a reference plane 61 containing the vertical outer surface of the associated leg 23 or 24 of the core. In effect, the band 58 is wrapped around the core at the rounded ends of the lower yoke, contacting the core at locations 62. If the band is disposed inside the reference plane 61, the angle between the band and the reference plane is considered to be a positive angle, and if disposed outside this plane, this reference angle is considered to be negative.
• the band 58 is out of contact with the core.
• I locate the holes 66 in the upper clamping plate 52 so that at the upper ends of core legs 23 and 24, the angle D between the band and the associated vertical reference plane is between zero degrees and -2 degrees.
• Tightening of the band applies no substantial horizontal forces to the legs 23, 24 (except as transmitted through the lower yoke 22) since the band angle with respect to the outer surface of each associated leg remains between zero degrees and a negative value at all points hetween the locations 62 and the holes 66 in the upper clamping plate 52.
• While the preferred angle D at each end of the bottom yoke is 3° or less, a maximum value for this angle is about 6 ⁇ . If a greater value is used for this angle, the horizontal forces on the lower yoke are so high that the resulting stresses unduly increase the core losses and exciting current. While the preferred angle D at each end of the top yoke is between 0 and -2 * , this angle can be increased in a negative direction to a maximum of about -6 * .
• the core winding form 19 must be unduly large in order to accomodate banding 58 or else the banding bears with an unduly high force against the inside face of the radially-outer side of the winding form, thus creating a risk of cutting the winding form and damaging adjacent winding insulation.
• Sample #1 had a positive angle D of 5.4 * at both the bottom and top yokes.
• Sample #2 was the same as Sample #1 except that the band 58 was cut in Sample #2 so that no forces were applied to the core therethrough.
• Sample #3 was the same as Sample #1 except that the band 58 had a - 1 2-
• Sample #3 compared to Sample #1, had a reduction in exciting current of about 44% at 120V and of about 32% at 132V. This was even better than the results achieved with Sample #2, where the band was cut, producing drops in exciting current of 36.5% and 27.9% at 120V and 132V, respectively, as compared to Sample #1.
• Sample #3 compared to Sample #1, had a reduction in core loss of 9.4% and 7.9% at 120V and 132V, respectively. This was slightly better than the 7.9% and 7.1% reductions achieved with Sample #2.
• the core includes an outer wrapper 27 of silicon iron that is relatively thick compared to the amorphous metal lamina ⁇ tions.
• This outer wrapper 27 helps to distribute the forces directed longitudinally of the yoke 22 over relatively large areas at the ends of yoke 22, thus avoid ⁇ ing localized stress concentrations that could detract from the magnetic performance of the amorphous alloy and applying the forces more uniformly to the joints 25 so that more of the joints benefit in the above-described manner from such forces.
• each band would be of substantially the same configuration as shown in Fig. 1.
• the band 58 serves not only as a key element of the above-described clamping means but also as a very effective means for connecting the core 20 to ground.
• the band makes good elec- trical contact with the outer wrapper 27 of the core at locations 62 and also makes good electrical contact with the upper clamping plate 52 at the edge of holes 66.
• Clam ⁇ ping plate 52 is connected to ground through the bolted connection at 85 with the tank 12, which is at ground potential.
• any coating on the outer wrapper is of such a character that it does not block such good contact. A thin glass coating that will be penetrated by the band 58, when tensioned, is satisfactory.
• the core is of amorphous ferromagnetic alloy. While my, invention is especially effective with such a core, the invention in its broader aspects also has application to a core and coil assembly such as shown that includes a core of conventional silicon iron. Such iron, though not as sensitive to mechanical stresses as the usual amorphous alloy, still has some sensitivity; and the clamping means of my ivention when used with such a core will substantially reduce core loss and exciting current. In such an embodiment of the invention, all components of the assembly remain the same except for the core, which is of silicon iron, has laminations of about 10 mils in thickness, and has joints in the lower yoke to allow for opening of the core during lacing into the coil structures.
• each coil structure having a passageway through which one of said legs extends
• said means for applying clamping forces comprising flexible banding that extends through said coil passageways alongside said legs, is held under

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Transformers For Measuring Instruments (AREA)
• Coils Or Transformers For Communication (AREA)
• Manufacturing Cores, Coils, And Magnets (AREA)

Priority Applications (2)

Applications Claiming Priority (2)

Publications (1)

Family

ID=25211487

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Citations (3)

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• 1986
  • 1986-12-08 DE DE19863690640 patent/DE3690640T1/de not_active Withdrawn
  • 1986-12-08 JP JP62500305A patent/JPS63501997A/ja active Pending
  • 1986-12-08 WO PCT/US1986/002612 patent/WO1987004000A1/en active Application Filing
• 1987
  • 1987-08-17 SE SE8703187A patent/SE8703187D0/xx not_active Application Discontinuation
  • 1987-08-24 KR KR870700768A patent/KR880701012A/ko not_active Application Discontinuation

Patent Citations (3)

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