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(11) | EP 0 600 612 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Air core reactor with conductor winding rigidly anchored to structural sleeve |
| (57) A tappable air core reactor in which the tappable portion has a conductor wound in
the form of an open helical winding on the outer surface of a sleeve of electrically
insulated material. The helical winding is partially embedded leaving exposed an outer
surface to which a tap can be attached at any peripheral location around the reactor.
The adjacent helices of the winding are separated by spacers and the conductor is
a solid rod of selected cross-sectional profile in which the base portion is wedge-like.
The cylinder, the valleys between the helically wound conductor and endrings at opposite
ends of the winding is a solid rigid unit of glass roving impregnated and embedded
in a set epoxy resin. |
Field of invention
[0001] This invention relates to air core reactors for electric power transmission systems. The invention is particularly directed to an improved tapped reactor for use in filter circuits where it is frequently necessary to adjust, in the field, the value of the inductance of the reactor. The invention also relates to a method of making an air core reactor and to a rigid cylindrical air core reactor with a partially embedded open helical winding securely anchored to a structurally rigid sleeve.
Background of Invention
[0002] Power system reactors are often used in combination with capacitors and resistors to perform filtering functions on power systems. They are used, for example, to control the in-rush and out-rush of currents from capacitor banks, to prevent unwanted frequencies generated by rectifying and inverting stations from finding their way onto the power grid, etc. In many of these applications it is impossible to know exactly the amount of inductance required in the reactor to ensure that the resulting filter is tuned to the correct frequency or frequency band. This is because there are many unknowns before the actual installation takes place. The normal strategy used to ensure that the filters are tuned to the correct frequency or frequency band is to order a reactor with a series of specified taps disposed in fixed locations.
[0003] Tapped air core reactors are known and by way of example reference may be had to Canadian Patent 1,065,028 issued October 23, 1979 to Trench Electric Limited, a predecessor in title of the owner of the present invention. The patented tapped reactor has a main air core reactor portion constructed basically from the teachings of the present owner's earlier U.S. Patent 3,264,590 which issued August 2, 1966, the construction being that as illustrated in Figure 11 wherein the concentric coil windings are embedded in a reinforced resinous material. There is a spider at each of opposite ends of the coil permitting partial turns and serving to connect the windings in parallel. Each spider is a rigid unit having a central hub with a plurality of arms radiating outwardly therefrom. The arms and hub are made entirely of an electrically conductive material or an electrically conductive material mounted on a rigid structural member. The axis of the hub is disposed on the axis of the coil unit. The tapped portion of the reactor is a pancake spiral open winding which is supported by the bottom spider and located on the underside thereof. The open spiral winding and can be tapped at different positions connecting it in series with the main coil.
[0004] Another form of tapped reactor is illustrated in a brochure of Trench Electric designated Bulletin 100-05 E dated September 1983 and entitled "Dry-Type Air Core Reactors". In Figure 5 there is illustrated a cylindrical reactor with taps in fixed locations passing through the insulative material that has the conductor embedded therein. Reference in the same publication is also made to having the tapping range of the reactor covered by a series connected single package cylinder of rod or cable conductor.
[0005] Air core reactors of high current capacity have many different uses in power transmission systems. One basic requirement for many is that they must have the ability to withstand very high mechanical and thermal stresses which are imposed upon them as the result of the passage of very high current flows which occur under short circuit conditions. To accomplish this a reactor must have high structural rigidity with the coil conductor securely anchored in position. Also the coil winding must have uniformity and this in part results from the manufacturing techniques involved.
Summary of Invention
[0006] An object of the present invention is to provide an air core reactor with a tapped rigid section for use in incrementally adjusting the inductance to exact values.
[0007] Another object is to provide an adjustable tapped reactor which may be adjusted in the field to achieve the exact value of inductance required.
[0008] A further object of the present invention is to provide a reactor with a rod type conductor in an open helical winding at least partially embedded and securely locked in position, with the design being such as to simplify the manufacturing techniques for making the same. Also an object is to provide a reactor of this type with part of the conductor exposed so as to be readily tappable at any circumferential location on the reactor.
[0009] In keeping with the foregoing there is provided in accordance with one aspect of the present invention an air core reactor comprising a structurally rigid sleeve made of an electrically insulative material; a coil winding comprising a conductor in the form of an open helical winding disposed on the outer surface of said sleeve, said conductor being of selected cross-sectional outline configuration with a wedge-like base portion adjacent said sleeve; an insulative spacer of predetermined width between adjacent turns of the winding retaining the same in fixed predetermined spaced relation throughout the length of the winding; and a rigidly set settable material providing a packing at least partially filling the valley between adjacent turns, said packing together with said wedge-like base portion of the conductor locking the conductor in position and thereby providing a rigid assembly. In the preferred form an outer portion of the conductor is exposed. Also in the preferred form the spacer is a strip wound at the same time as the conductor and provides uniform spacing of the conductor turns during manufacturing. The spacer strip projects partially under the conductor and means is provided to positively position the conductor adjacent turns relative to one another. In one embodiment this positive positioning means comprises undercuts (also herein referred to as bottom edge grooves) one being in each of the two bottom longitudinal marginal edges of the conductor to receive opposed marginal edges of the strip in adjacent turns of the conductor. In another embodiment the spacer strip is effectively "T" shape in cross-section whereby part of the strip projects in a direction outwardly between two adjacent turns.
[0010] Tapped reactors provided by the present invention may comprise a single layer helically wound reactor with taps installed near one end or they may comprise two concentric helically wound reactors connected in series, the outer one of which is tapped. In each case the tapped coil portion is made from aluminum conductor having a special contour which gives it strength, ease of encapsulation and leaves the outer surface exposed so that taps may be easily installed where required. The taps may be fixedly secured or movably mounted.
[0011] Reactors of the present invention are relatively inexpensive to build and have a construction which makes it possible to achieve exactly the inductance required in any particular application by installing the required tap exactly where it is needed rather than by choosing from a number of fixed taps which will give only an approximately correct result.
[0012] The advantages of the present invention are that it allows the taps to be installed anywhere and even to be moved or adjusted in the field. In addition the construction is such that reactors of the present invention are very strong and at the same time are relatively economical to build with consistency in quality.
List of Drawings
[0013] The invention is illustrated by way of example with reference to the accompanying drawings wherein:
Figure 1 is an oblique diagrammatic view of one embodiment of a tapped reactor provided in accordance with the present invention;
Figure 2 is an oblique diagrammatic view of another embodiment of a tapped reactor provided in accordance with the present invention;
Figures 3 to 7 inclusive are cross-sectional views taken along essentially liles 2-2 of Figures 1 and 2 illustrating in detail two adjacent turns of the helical winding with various different cross-sectional conductor profiles;
Figure 8 illustrates in a sectional view a selectively movable tap terminal on a conductor which has a profile similar to that of Figures 3 and 4;
Figure 9 illustrates in sectional view a terminal tap fixedly secured to a conductor whose profile is similar to that of Figures 5 to 7;
Figure 10 is a cross-sectional view of a metal conductor illustrating a further profile;
Figure 11 is a schematic diagram of the main and tap coil in one as illustrated in Figure 1; and
Figure 12 is a schematic diagram of an outside tap coil as diagrammatically illustrated in Figure 2.
Description of Preferred Embodiment
[0014] The tapped reactor of the present invention may be in the form illustrated in Figure 1 or in the form illustrated in Figure 2. The reactor of Figure 1 comprises an upper main coil section of one or more coaxial windings connected in parallel and a lower tapped section in series therewith comprising a single extruded conductor, the individual turns of which are partially embedded and spaced from one another. The adjacent turns of the winding in the lower tapped section are preferably separated by an extruded strip of insulating material to be described in detail hereinafter with reference to Figures 3 to 9. An outer portion of the single extruded conductor is bare so that taps 10A (or a tap 10) may be secured in place at any position as may be required. It is possible to make the taps and exposed conductor so that the taps can be moved circumferentially permitting ease of adjustment in the field to provide an exact inductance as dictated by in the field operation. An electrical schematic diagram for the coil of Figure 1 is shown in Figure 11.
[0015] Alternatively, as shown in Figure 2, there may be an inner reactor 3, comprising one or more coaxial windings connected in parallel which is connected in series with an outer tapped reactor 4 built in the same manner as the lower end of the reactor shown in Figure 1. An electrical schematic of this alternative is shown in Figure 12. The reactors of Figures 1 and 2 are shown with a tap changer 7 which allows the taps 10, 10A to be easily changed in the field without disconnecting the reactor from the main bus.
[0016] Referring to Figure 1, which illustrates the simplest form of reactor, there is an upper main reactor portion A of a Conventional construction as for example disclosed in applicant's U.S. Patent 2,264,590 issued August 2, 1966 and a lower tapped portion 4 in series with the upper section. The lower tapped section 4 comprises an open helical winding wound from a bare extruded aluminum conductor 9 of special cross section illustrated in Figures 3 to 9. The conductor 9 is wound over a sleeve 8 (see Figures 3 to 9) consisting of glass fibre and resin. The successive turns of the winding are spaced from each other preferably by preformed spacer strip 13 which is wound on the sleeve 8 simultaneously with the aluminum conductor 9. The spacer 13 and insulative material of sleeve 8 insulate the turns of the winding from one another. At the time of winding the conductor on to the sleeve, the sleeve which is made of glass fibre and a settable resin is wet and uncured so that both the conductor and insulating strip are seated firmly therein.
[0017] At the top and bottom of the cylinder are respective multi-arm spiders 1 and 2. The spiders at opposite ends are tied together by suitable means (not shown). The general construction is known from the teachings of applicant's aforementioned brochure and United States Patent 3,264,590 issued August 2, 1966.
[0018] After the conductor 9 with its insulating spacer strip 13 is wound in place, a glass fibre and epoxy roving 14 is wound in the space, i.e, valleys between turns to secure them mechanically. The settable material partially fills the valleys leaving an outer part of the conductor exposed. The conductor in cross-section has a tapered or wedge-like base portion that decreases in area in a direction away from the sleeve. This wedge-like shape results in the filler material securely anchoring the conductor onto the sleeve. At the upper and lower ends the glass fibre and epoxy roving is wound a number of times around the inner cylinder to form an endring 12. when completed the entire unit is oven cured resulting in a very strong overall construction having high short circuit capability.
[0019] Figures 3 to 9 are partial sectional views through two adjacent turns of a conductor wound in an open helix around a sleeve and show details of the winding construction and several typical conductor cross sections. Figures 3, 4 and 8 show typical conductor 9 cross sections for the case where movable taps are used in the case where the reactor is a tapped or tappable reactor. In this embodiment the conductor has a channel 9A on its outer face such that a rotatable tap terminal, 10, (see Figure 8) may be attached to the conductor using a bolt 20, the head 21 of which is trapped in the conductor channel. The rotatable tap terminal is shown in Figure 8.
[0020] Figures 3 to 9 show the sleeve 8 which consists of glass fibre and epoxy resin and is a structurally rigid unit. They also show the extruded spacer strip 13 which is wound on simultaneously with the conductor 9 against the surface of the glass sleeve 8 which is in a wet state when the winding operation takes place. Shown also in Figures 3 to 9 is a glass fibre and epoxy roving 14 which is wound in place between successive turns of the winding in order to form a very rugged and compact unit once the epoxy is cured. The quantity of interturn roving is dependent on the glass fibre spacer 13 size and anticipated mechanical stresses in service. Shown also is the endring 12 which is also wound in place against the outer surface of sleeve 8 and which serves to clamp the end turn solidly resulting in a very strong construction once the unit is oven cured.
[0021] Figures 5, 6, 7 and 9 illustrate typical cross sections of conductor 9 for the case where taps such as the one designated 10A are fixedly attached by welding (see Figure 9). Figures 1 and 2 each illustrate three taps designated 10A. Alternatively there may be a single tap 10 as shown in Figure 8 that can be moved to any position circumferentially around the unit and clamped at the position selected.
[0022] Figures 1 and 2 illustrate a tap changer conducting link 7, which is used to connect to a selected tap to an arm of the bottom spider in the field. The selected tap is simply connected by the conducting link 7 which is anchored thereto at one end as by bolting and attached at the other end to the lower spider arm nearest to the tap. The tapped reactors illustrated in Figures 1 and 2 each have an in terminal 5 and an out terminal 6.
[0023] Figure 2 shows a more complex embodiment of a tapped reactor where the reactor consists of an inner reactor 3 connected in series with an outer reactor 4. Both inner and outer reactors share a common spider 2 at the lower end of the structure and this spider is the series connection between the two units. The permanent output arm 6 in this configuration is now located at the top of the outer of the two reactors. The construction of the inner reactor 3 is described in detail in applicant's aforementioned brochure 100-05E. More particularly the dry type air core reactor consists of coaxial, concentric, closely coupled layers of small diameter aluminum conductor each conductor being individually insulated. There may be a single layer or two to ten layers wound consecutively on top of each other and encapsulated with epoxy resin impregnated filament glass fibre forming a winding group referred to as a package. Concentric packages are separated by axial cooling ducts. The duct spacing is maintained by means of rectangular glass fibre reinforced sticks. The number of packages, length of winding and cooling duct size depend on the application and electrical rating of the reactor. For further information and illustration of the construction reference may be had to pages 3 and s of the aforementioned Bulletin 100-05 E. The outer reactor 4 is constructed in the same manner as has already been described for the lower tapped portion of the reactor of Figure 1.
[0024] In the embodiment shown in Figures 3 to 6, 8, 9 and 10 conductor 9 has an undercut or groove in the edges of its bottom face. In Figures 3 and 10 these grooves are designated 9B and 9C and receive therein a marginal edge portion of the spacer strip 13. These undercuts, also referred to herein as grooves in the edges of the bottom face, provide conductor positive positioning means during manufacturing with the conductor 9 and strip 13 being wound simultaneously. An alternative to this is illustrated in Figure 7 wherein there is illustrated a spacer strip having base wing portions 13A and 13B underlying a bottom.portion of two adjacent turns of the conductor 9 and a conductor separator portion 13C projecting between the two adjacent turns. In each of these embodiments the spacer strip 13 serves to positively maintain a selected spacing between adjacent turns during the winding process in manufacturing the coil and remains in place in the finished product. The filler material 14 in the valley between adjacent turns and the wedge-like shape of the bottom portion of the conductor locks in conductor in its position as has been determined by the spacer 13.
[0025] A modified cross-sectional profile of conductor 9 is shown in Figure 10. As shown therein the conductor 9 has a base portion 9W which is wedge-like in cross-section and an enlarged outer portion 9D. The base portion 9W and outer portion 9D are joined by a narrower neck portion 9E resulting in respective V-shaped grooves 9F and 9G in opposite edge faces of the conductor. The bottom face 9H has the aforementioned grooves 9B and 9C therein as do also the embodiments illustrated in Figures 3 to 6, 8 and 9. The V-shaped grooves are useful during winding of the conductor onto the sleeve in preventing the conductor from twisting. The wedge shape, as in the other embodiments, positively locks the conductor in position by the filler 14 acting thereon. With reference to the conductor 9 in a reactor of the present invention the term bottom face is used herein to define the face of the conductor that faces the outer surface of the sleeve 8, i.e. face 9H in Figure 10 and the equivalent face in the other figures. The opposite side faces are the faces which have the grooves 9F and 9G in the Figure 10 embodiment and equivalent faces in Figures 3 to 9. The term wedge-like with reference to the base portion of the conductor is intended herein to refer to any cross-sectional profile where the cross-sectional area decreases for a portion of the conductor adjacent the sleeve in a direction away from such sleeve. Radially further outwardly however the area can increase as for example outer portion 9B in the Figure 10 embodiment. The conductor may by way of example have an "I" beam profile in cross-section.
[0026] While reference herein has been made to the preferred form of a tapped filter reactor, other air core reactors for other purposes can usefully be constructed in keeping with the present invention.
[0027] Figure 4 illustrates a combined spacer and valley filler 13E that is preformed and wound onto the sleeve 8 along with the conductor 9.
1. An air core reactor for use in electric power transmission systems in which the reactor
has a sleeve (8) of an electrically insulative material with a coil winding of a conductor
(9) in the form of an open helical winding disposed on the outer surface of such sleeve
and an electrically insulative spacer (13) between adjacent turns of the winding providing
a fixed spacing therebetween characterized in that the conductor has a bottom portion
(9W) which is generally wedge-like in cross-section and that a rigidly set settable
material (14) is in the valley between adjacent turns along at least part of said
wedge-like base portion of the conductor thereby securely anchoring the conductor
to said sleeve.
2. A device as defined in claim 1 characterized in that a portion (9D) of said conductor
(9) is exposed permitting connecting a tap thereto.
3. A device as defined in claim 1 characterized in that the conductor (9) has opposite
side faces that taper inwardly toward one another in a direction away from its bottom
face (9H).
4. A device as defined in claim 1 characterized in that the spacer 13 is a preformed
strip disposed flatwise in helical form on the sleeve (8) separating adjacent turns
of said helically wound conductor (9) from one another.
5. A device as defined in claim 4 characterized in that the spacer (13) projects (13A,
13B) under a portion of the bottom face of adjacent turns of the conductor.
6. A device as defined in claim 5 characterized in that the bottom face (9H) of the conductor
(9) has a groove (9B, 9C) in each of the longitudinal marginal edges receiving therein
a marginal edge portion of the spacer strip (13).
7. A device as defined in claim 5 characterized in that the spacer strip (13) is essentially
T-shape (13A, 13B, 13C) in cross section.
8. A device as defined in claim 1 characterized in that there are endrings (12) at opposite
ends of the winding and in that the sleeve (8), valley filling material (14) and endrings
(12) are all filament glass fiber wound about the axis of the cylinder and impregnated
with and encapsulated in a set resinous material.
9. A device as defined in claim 1 characterized in that the helically wound conductor
(9) has a channel (9A) extending therealong in an outer exposed surface thereof and
in that such channel is open outwardly for use in adjustably anchoring a tap (10)
to such conductor.
10. A physically rigid air core reactor coil unit having as defined in claim 8 characterized
in that the metal conductor (9) is at least partially embedded in a cured epoxy glass
roving constituting an integrally formed inner sleeve (8), filler (14) between the
helices of the winding and the endrings (12).
11. A device as defined in claim 1 characterized in that the conductor (9), in cross-section,
has a bulbous base portion (9W) adjacent the sleeve (8); a bulbous outer portion (9D)
spaced radially outwardly of the base portion (9W) and a neck portion (9E) interconnecting
the inner and outer bulbous portions, and in that the neck portion (9E) has a thickness
in the axial lengthwise direction of the coil unit which is less than that of the
base and outer bulbous portions.
12. A method of making an air core reactor comprising:
(a) forming an inner cylinder of glass fibre impregnated with an epoxy in an uncured state;
(b) winding a rod conductor of selected cross-sectional shape in an open cylindrical helical form on said sleeve while at the same time during winding placing a preformed strip form spacer on the sleeve to locate the conductor with a predetermined fixed spacing between adjacent turns;
(c) at least partially filling the space between adjacent helices with glass-epoxy roving in an uncured state to anchor the winding turns in said fixed spaced relationship;
(d) winding endrings of uncured epoxy-glass roving at respective opposite ends of the conductor winding; and
(e) curing said epoxy-glass fibre to provide a physically rigid unit preferably with an outer surface of the winding exposed for attaching a tap thereto at any circumferential position around the reactor.