Adjustable inductor and method of using same

Abstract

An adjustable inductor includes an annular magnetic core defining a plurality of gaps, a compressible gap material positioned in the gaps, at least one winding wound on the magnetic core, a force applying structure, and a film substantially covering the adjustable inductor. The force applying structure is operable to apply a force to the magnetic core to adjust the gaps, and thereby adjust an inductance of the adjustable inductor. The film is configured to prevent movement of the force applying structure when above a predetermined temperature threshold, and to allow movement of the force applying structure when below the predetermined threshold.

Description

[0001] Related applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 62 / 862985, filed June 18, 2019, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The embodiments involve adjustable inductors. Summary of the Invention

[0004] Inductors, such as, but not limited to, toroidal inductors, may have a predetermined set inductance that can be adjusted off-site. For example, such a toroidal inductor can only be adjusted by adding or removing turns or by repositioning the wires on the core after winding.

[0005] Adding or removing turns only results in integer changes to the value – inductance is proportional to the square of the number of turns. The effects of repositioning the winding are negligible and not easily repeatable. Typically, for example, inductors with ±3% tolerances require careful clearance and / or material selection, consistent winding turns and / or location, and / or may require adding or removing turns. Often, parts fail to achieve the desired value and must be scrapped or disassembled and rewound.

[0006] Adjustable inductors, such as those described in U.S. Patent No. 10,102,952 (incorporated herein by reference), can be adjusted in the field. Because of this field-adjustable capability, adjustable inductors can have a wide range of applications.

[0007] For example, one embodiment provides an adjustable inductor including a toroidal core defining a plurality of gaps, a compressible gap material located in the gaps, at least one winding wound on the core, a force-applying structure, and a thin film substantially covering the adjustable inductor. The force-applying structure is operable to apply a force to the core to adjust the gaps, and thereby adjust the inductance of the adjustable inductor. The thin film is configured to prevent movement of the force-applying structure when above a predetermined temperature threshold and to allow movement of the force-applying structure when below a predetermined temperature threshold.

[0008] Another embodiment provides a tunable notch filter inductor including a tunable inductor and a capacitor. The tunable inductor includes a toroidal core defining a plurality of gaps, a compressible gap material located within the gaps, at least one winding wound on the core, and a force-applying structure operable to apply a force to the core to adjust the gaps, and thereby adjust the inductance of the tunable inductor. The capacitor is electrically connected in series with the tunable inductor.

[0009] Yet another embodiment provides a three-phase matched filter inductor including a first adjustable toroidal inductor having a first variable inductance, a second adjustable toroidal inductor having a second variable inductance, and a third adjustable toroidal inductor having a third variable inductance. Wherein the first variable inductance, the second variable inductance, and the third variable inductance are matched after production of the first adjustable toroidal inductor, the second adjustable toroidal inductor, and the third adjustable toroidal inductor.

[0010] Other aspects of the application will become apparent by consideration of the detailed description and accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 is a perspective view of an adjustable inductor according to some embodiments.

[0012] Figure 2 is a perspective view of a magnetic core according to some embodiments. Figure 1 is a top view of an inductor shown in

[0013] Figure 3 is a top view of a magnetic core assembled with gap material portions according to some embodiments.

[0014] Figure 4 is a top view of a magnetic core assembled with gap material and clamps according to some embodiments.

[0015] Figure 5 is a top view of a wound magnetic core according to some embodiments.

[0016] Figure 6 is a top view of a wound magnetic core with a partially removed detachable core portion according to some embodiments.

[0017] Figure 7 is a perspective view of an inductor including a thin film according to some embodiments. Figure 1 is a top view of an inductor shown in

[0018] Figure 8 is a circuit diagram of a tunable notch filter including one or more inductors as shown in Figure 1

[0019] Figure 9 is a perspective view of a three-phase matched filter inductor including one or more inductors as shown in Figure 1 DETAILED DESCRIPTION

[0020] Before any embodiments of this application are explained in detail, it is to be understood that the application is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. This application is capable of other embodiments and of being practiced or being carried out in various ways.​​

[0021] The phrase "series-type configuration" as used herein refers to an arrangement of circuit elements in which the described elements are typically arranged in a sequential manner such that the output of one element is coupled to the input of another element, although the same current can not pass through each element. For example, in a "series-type configuration," additional circuit elements can be connected in parallel with one or more elements in the "series-type configuration." Further, additional circuit elements can be connected at nodes in the series-type configuration such that branches exist in the circuit. Thus, the elements in a series-type configuration do not necessarily form a true "series circuit."

[0022] Further, the phrase "parallel-type configuration" as used herein refers to an arrangement of circuit elements in which the described elements are typically arranged in such a manner that one element is connected to another element such that the circuit forms a parallel branch of the circuit arrangement. In such a configuration, there can not be the same potential difference between the various elements of the circuit. For example, in a parallel-type configuration of a circuit, two circuit elements that are parallel to each other can be connected in series with one or more additional elements of the circuit. Thus, a circuit in a "parallel-type configuration" can include elements that do not necessarily individually form a true "parallel circuit."

[0023] Figures 1-6 An electrical assembly, such as a toroidal inductor 10, and a method of assembling the inductor 10 are shown in FIGS. 1-4. The illustrated inductor 10 is adjustable to adjust its inductance. The inductor 10 generally includes (see FIG. 2) Figures 1-2 ) a magnetic core 14 defining a plurality of gaps 18, a gap material 22 positioned in the gaps 18, a force application structure 26 (e.g., a hose clamp) for adjusting the gaps 18, and a winding coil 30.

[0024] In the illustrated construction, the magnetic core 14 has a toroidal shape and defines at least two gaps 18 Figures 3-4 four gaps 18 as shown in FIG. 4), to provide core pieces 34 (four core pieces 34, two about 120° each, and two about 60° each). In other constructions (not shown), the magnetic core 14 can be formed of different angular pieces (e.g., four 90° core pieces 34) and / or have fewer or more gaps 18 (e.g., six 60° core pieces 34).

[0025] The illustrated magnetic core 14 is formed of a band steel (e.g., M3, M6, M50, or other grade) that is wound and spot welded and annealed. The layers of the magnetic core 14 are held together (e.g., by varnish). The magnetic core 14 is then cut to provide the desired number of gaps 18.

[0026] In other configurations (not shown), the magnetic core 14 may be formed from different materials (e.g., amorphous sheets, iron powder, iron-silicon-aluminum powder, etc.) and / or through different processes (e.g., molding, casting, etc.). In such configurations, the magnetic core 14 may form (e.g., molding, compression, and firing) the required gap 18.

[0027] like Figures 3-4 As shown, gap material 22 is positioned in each gap 18. Gap material 22 may be substantially non-magnetic and non-conductive. Gap material 22 may also withstand magnetic temperatures (maximum temperatures in the range of about 130°C to about 220°C) and may operate at low temperatures (as low as about -55°C).

[0028] Essentially incompressible "rigid" gap materials 22a (e.g., high-temperature gap materials used in magnetic materials (glass epoxy resin, etc.) (Available from RochlingGlastic Composites, Cleveland, Ohio), GPO glass fiber epoxy resin Paper (available from DuPont in Wilmington, Delaware), circuit board materials, glass, treated paper, and combinations thereof, can be placed in a fixed gap 18a (e.g., a non-adjustable gap 18) (see Figures 3-4 In the illustrated configuration, the thickness of the gap material 22a in the fixed gap 18a is selected to establish the inductance adjustable range and basic inductance of the inductor 10.

[0029] For retention purposes during assembly, rigid gap material 22a is positioned within the adjustable gap 18b. A compressible "flexible" gap material 22b (e.g., silicone sheet, silicone foam, high-temperature soft rubber, etc., and combinations thereof) can then be placed within the adjustable gap 18b (see [link to relevant documentation]). Figure 2 and Figure 6 ).

[0030] The rigid core 38 is formed by securing (e.g., using high-temperature adhesive) a rigid gap material 22a in place among a plurality of separators 34 (e.g., three separators 34) of the magnetic core 14. The rigid gap material 22a can also be detachably positioned in the gap 18b during assembly (e.g., by debonding; see [link to product]). Figures 3-4 It can be used alone or in combination with the flexible gap material 22b in the final adjustable gap 18b.

[0031] The magnetic core 14 is assembled from one or more rigid cores 38 and at least one detachable core 42. (See the illustrated construction.) Figures 3-4In the illustrated configuration, the magnetic core 14 includes a rigid core portion 38 extending about 300° (e.g., three core pieces 34 of about 120°, 60°, and 120°) and a removable core portion 42 extending about 60°. In other configurations (not shown), the core portions 38 and 42 can subtend different angles (e.g., about 270° and about 90°, respectively).

[0032] In some illustrated configurations (e.g., see Figures 1-2 and Figure 6 ), the force application structure 26 includes a clamp 46 (e.g., a hose clamp) positioned at least partially around (e.g., about) the magnetic core 14. The clamp 46 can be non-magnetic (e.g., stainless steel, aluminum, etc.) and generally holds the portions 38, 42 of the magnetic core 14 together. When the clamp 46 is tightened (see Figures 1-2 ), it is operable to apply a force (e.g., a radial force) to the removable portion 42 of the magnetic core 14 to adjust the gap 18b.

[0033] In the illustrated configuration, the force application structure 26 includes only one clamp 46. In other configurations, more than one clamp 46 can be provided (e.g., two Figure 1 in dashed lines), three or more). As Figure 1 shown, the drive portions of the force application structures 26, 26' (clamps 46, 46') are shown spaced apart circumferentially, but in other configurations (not shown) can be aligned circumferentially.

[0034] In other configurations (not shown), the force application structure 26 can include another mechanical device, such as a radially oriented screw (e.g., thumb screw) supported on a circumferential band, applying a radial force to the removable portion 42. In other configurations (not shown), the force application structure 26 can include cable ties, zip ties, a binding material applied by a binding machine, etc.

[0035] The wound coil 30 includes (see Figures 1-2 and Figures 5-6 ) one or more windings 50 that are wound on the rigid core portion 38 but not on the removable core portion 42. The windings 50 can include film-coated wire, (available from DuPont), other magnetically temperature resistant materials, glass winding, etc. Each winding 50 has a desired number of turns, a number of strands of wire (e.g., single strand, multiple strands), etc. In the illustrated configuration, the coil 30 includes dual windings 50. The number of core pieces 34 and the relative sizes of the core portions 38, 42 can be determined based on the desired size of the coil 30 on the rigid core portion 38.

[0036] Prior to winding, the rigid core 38 can be wrapped (with tape 54), impregnated, glued with epoxy, otherwise coated, etc. for electrical insulation. In the illustrated construction, the removable core 42 is wrapped separately from the rigid core 38 with one or more strips of tape 54.

[0037] While the cores 38, 42 are firmly secured by the clamp 46 (to withstand winding forces), in the illustrated construction (see Figure 5 ), the winding 50 is wound onto the rigid core 38 only for the desired number of turns. In other constructions (not shown), the winding 50 can be wound onto a portion of the removable core 42.

[0038] After winding, the clamp 46 is loosened (see Figure 6 ), and the rigid gap material 22a in at least one gap 18b (two adjustable gaps 18b in the illustrated construction) is replaced with a flexible gap material 22b (see Figure 2 ) or a combination of the flexible gap material 22b and the rigid gap material 22a. The clamp 46 is tightened to set the lower limit of adjustment for the gap 18b and the inductance.

[0039] The clamp 46 is adjusted (e.g., tightened to increase the inductance, loosened to decrease the inductance) to move the removable core 42 radially to adjust the gap 18b (both gaps 18b can be adjusted in the illustrated construction) and, thereby, adjust the inductance of the inductor 10 to the desired value. In the illustrated construction, the inductance of the inductor 10 can be adjusted within a range of 10% of the inductance value. This range of adjustment can vary with different sizes of the adjustable gap 18b, the amount or compressibility of the compressible gap material 22b, etc.

[0040] In alternative constructions, the adjustable gap 18b can be adjusted only with the rigid gap material 22a. After winding, the thickness of the rigid gap material 22a in the adjustable gap 18b is changed to change the inductance. The thickness is changed (the number of pieces of the rigid gap material 22a and / or the thickness of each piece) until the desired inductance is reached.

[0041] As shown in Figure 7 , the inductor 10 can be at least partially wrapped by a finish or film (shown by dashed lines 60). In some embodiments, the film can be a varnish. In operation, the film is configured to inhibit movement of the force application structure 26, and thereby inhibit adjustment of the inductance of the inductor 10, when below a predetermined temperature threshold. When heated to a temperature above the predetermined temperature threshold, the film can soften enough to allow movement of the force application structure 26, and thus allow adjustment of the inductance of the inductor 10. It should be appreciated that in other embodiments, the inductor 10 can not be finished, and such an inductor 10 will remain adjustable during use.

[0042] Figure 8 is a circuit diagram illustrating a tunable notch filter 100 incorporating one or more inductors 10 according to some embodiments. As shown, the tunable notch filter 100 can include one or more capacitors CI -C4, each electrically connected in series with an inductor LI -L4, respectively. The capacitor and inductor pairs can then be electrically connected to one another in a shunt-type connection. In the illustrated embodiment, each inductor LI -L4 has a similar construction to inductor 10 described in detail above.

[0043] Incorporating inductors 10 into the tunable notch filter 100 can allow each inductor LI -L4 to be tuned according to an intended harmonic. For example, the 5th, 7th, 11th, and 13th intended harmonics, among others, are dependent on the phase connection.

[0044] Because inductors LI -L4 are capable of being adjusted in the field, inductors LI -L4 can be paired with capacitors CI -C4 and adjusted not only for inductance values, but also for capacitance variations, allowing individual tuning sections to be tuned to the correct resonant frequency.

[0045] In addition, capacitors used in notch filters can age and lose capacitance values. This can cause the notch filter to detune, shifting its frequency up and away from its intended value. This detuning can significantly reduce the filter’s attenuation at the intended notch frequency, as well as shift the filter’s center frequency away from its intended frequency and into a frequency region that can have a resonant peak, creating a resonant circuit that can cause severe ringing and potential damage to the filter components. By incorporating tunable inductors LI -L4 into the tunable notch filter 100, the frequency can be corrected without the need to replace the capacitors, reducing downtime.

[0046] Figure 9 A three-phase matched filter inductor 150 according to some embodiments is shown. As shown, the three-phase matched filter inductor 150 can include inductors 155a-155c. In the illustrated embodiment, each inductor 155a-155c has a similar construction to inductor 10 described in detail above (e.g., inductors 155a-155c can be tunable inductors).

[0047] Incorporating inductors 155a-155c into the three-phase matched filter inductor 150 allows inductors 155a-155c to be matched in the field without the need for extensive rework. For example, inductors 155a-155c can be adjusted after the windings are positioned, eliminating the need to unspool and re-spool the windings.

[0048] During production of fixed inductors used in three-phase matched filter inductors, each inductor is grouped together based on matching magnetic cores. However, the magnetism generated during winding can vary depending on the winding position, the size of the gap between the start winding and the end winding if multiple strands of wire are used, and the relative position of each strand of wire per turn. This variation in inductance values stemming from winding characteristics can cause inductors with matching magnetic cores to become mismatched when installed in the field. Three-phase matched filter inductors 150 address these deficiencies by allowing for adjustment of inductors 155a-155c in the field.

[0049] Furthermore, embodiments provide an adjustable inductor. Various features and advantages of the present application are set forth in the following claims.

Claims

1. An adjustable inductor, comprising: A toroidal magnetic core with multiple gaps defined; Compressible gap material located in the plurality of gaps; At least one winding wound on the toroidal magnetic core; A force-applying structure operable to apply a force to the magnetic core to adjust the plurality of gaps, and thereby adjust the inductance of the adjustable inductor; as well as The thin film that substantially covers the adjustable inductor is configured as follows: When the temperature exceeds a predetermined threshold, it prevents the force-applying structure from moving, and When the temperature is below the predetermined temperature threshold, the force-applying structure is allowed to move.

2. The adjustable inductor according to claim 1, wherein, The predetermined temperature threshold is approximately 150°C.

3. The adjustable inductor according to claim 1, wherein, The film is a varnish.

4. A tunable notch filter inductor, comprising: An adjustable inductor, the adjustable inductor comprising: A toroidal magnetic core with multiple gaps defined; Compressible gap material located in the plurality of gaps; At least one winding wound on the toroidal magnetic core; A force-applying structure operable to apply a force to the toroidal core to adjust the plurality of gaps, and thereby adjust the inductance of the adjustable inductor; and The capacitor connected in series with the adjustable inductor The adjustable inductor also includes a thin film that substantially covers the adjustable inductor.

5. The tunable notch filter inductor according to claim 4, wherein, The inductance of the adjustable inductor is adjusted according to the change in the capacitance of the capacitor.

6. The tunable notch filter inductor according to claim 4, wherein, The thin film is configured as follows: When the temperature exceeds a predetermined threshold, it prevents the force-applying structure from moving, and When the temperature is below the predetermined temperature threshold, the force-applying structure is allowed to move.

7. The tunable notch filter inductor according to claim 6, wherein, The predetermined temperature threshold is approximately 150°C.

8. The tunable notch filter inductor according to claim 4, wherein, The film is a varnish.

9. A three-matched filter inductor, comprising: A first adjustable inductor having a first variable inductance; A second adjustable inductor having a second variable inductance; as well as A third adjustable inductor with a third variable inductance; The first, second, and third variable inductors are matched after the first, second, and third adjustable inductors are manufactured. The first adjustable inductor includes: A toroidal magnetic core with multiple gaps defined; Compressible gap material located in the plurality of gaps; At least one winding wound on the toroidal core; and A force-applying structure operable to apply a force to the magnetic core to adjust the plurality of gaps, and thereby adjust the first variable inductance; and The first adjustable inductor also includes a thin film that substantially covers the first adjustable inductor.

10. The three-matched filter inductor according to claim 9, wherein, The thin film is configured as follows: When the temperature exceeds a predetermined threshold, it prevents the force-applying structure from moving, and When the temperature is below the predetermined temperature threshold, the force-applying structure is allowed to move.

11. The three-matched filter inductor according to claim 10, wherein, The predetermined temperature threshold is approximately 150°C.

12. The three-matched filter inductor according to claim 9, wherein, The film is a varnish.

Images