Retention mechanism for electromagnetic cores

Abstract

To provide a holding mechanism for an electromagnetic core having a predetermined number of limbs.SOLUTION: A holding mechanism 200 includes a hub 202 having an axis 208. The hub includes a plurality of apertures 204 corresponding to the number of arc-shaped limbs of an electromagnetic core. Each of the apertures receives an end portion 106 of a respective arc-shaped limb radially around the axis. The axis of the hub is coincident with the central axis of the electromagnetic core when the arc-shaped limbs are received in the apertures. The holding mechanism also includes a plurality of jaws 206 corresponding to the number of arc-shaped limbs, and each of the jaws retains the end portion of a respective arc-shaped limb in a respective aperture when the arc-shaped limbs are received in the apertures. The holding mechanism further includes an adjustment mechanism (a toothed key 210, a scroll plate 212, and bevel gears) to adjustably move the plurality of jaws in a radial direction with respect to the axis of the hub. Accordingly, when the arc-shaped limbs are received in the apertures, adjustment causes each arc-shaped limb to move in the radial direction of the electromagnetic core.SELECTED DRAWING: Figure 2B

Description

[Technical field]

[0001] The following disclosure relates to retention mechanisms for electromagnetic cores, and more particularly, to electromagnetic cores having multiple limbs disposed about a central axis. [Background technology]

[0002] Magnetic cores are utilized across a variety of electromagnetic devices, such as transformers, electric motors, generators, and inductors. Three-phase power is often used in electrical distribution systems. An exemplary three-phase magnetic core of GB Patent Application No. 2115649.2 will be briefly described with reference to Figures 1A to 1C. An electromagnetic core 100 includes three arc-shaped limbs 102 equally spaced about a central axis 104. Each limb 102 is substantially identical. The arc-shaped limbs 102 are 180 degree arcs. Each limb 102 has a first end and a second end. Each first end has a first edge that lies along the central axis 104. Each second end has a second edge that lies along the central axis. Each limb 102 may be wound with one or more of a primary winding, a secondary winding, and a modulation winding on one or more bobbins 105 (not shown in FIGS. 1A-1C). Each limb 102 may comprise multiple magnetic steel strips curved and laminated together. The use of thin steel laminations reduces power losses caused by eddy currents induced when a sinusoidal voltage is applied to the windings. The width of the laminated magnetic steel strips may vary in an arrangement that results in the limb 102 having a cross-section that approximates a circle. Alternatively, the width of the laminated magnetic steel strips in a limb 102 may be constant such that the limb has a rectangular cross-section.

[0003]

[0003] The first end 106 of each limb 102 should be securely held or clamped together and the second end 108 of each limb 102 should be securely held or clamped together so that the limb ends are in direct or intimate contact with one another for optimal electromagnetic performance of the core. The present disclosure is directed to a retention mechanism to address such a need. Summary of the Invention

[0004]

[0004] A retention mechanism for an electromagnetic core having a predetermined number of limbs, e.g., three limbs, disposed about a central axis is provided. The retention mechanism includes a hub having an axis. The hub includes a plurality of apertures corresponding to the predetermined number of limbs of the electromagnetic core, i.e., an aperture in the hub for each limb of the electromagnetic core. Each of the apertures is configured to receive an end portion of a respective limb in a radial direction about the axis. The axis of the hub is coincident with a central axis of the electromagnetic core when the predetermined number of limbs are received in the plurality of apertures. The retention mechanism includes a plurality of jaws corresponding to the predetermined number of limbs, i.e., a jaw for each limb of the electromagnetic core. Each of the jaws is configured to maintain an end portion of a respective limb within a respective aperture when the predetermined number of limbs are received in the plurality of apertures. The retention mechanism includes an adjustment mechanism configured to adjustably move the plurality of jaws radially relative to the axis of the hub. Thus, when a predetermined number of limbs are received within the plurality of apertures, adjustment of the adjustment mechanism causes each limb to move radially toward or away from the axis of the hub and thus the central axis of the electromagnetic core. The adjustment mechanism may include a ring that may have an axis coaxial with the axis of the hub.

[0005]

[0005] The adjustment mechanism may include a plurality of toothed keys corresponding to a predetermined number of limbs, i.e., one toothed key for each limb of the electromagnetic core or one toothed key for each jaw of the retaining mechanism. The adjustment mechanism may include a scroll plate having a first side and a second side. Each toothed key may be coupled to a respective jaw. The first side of the scroll plate may include a helical projection for engaging the toothed key of each of the jaws. The second side of the scroll plate may include a first bevel gear. The retaining mechanism may include a second bevel gear having an axle and configured to engage the first bevel gear. The hub may include an opening for rotatably supporting the second bevel gear, and an end of the axle may have a drive socket and be engageable with a tool, for example, to rotate the second bevel gear. The retention mechanism may include a third bevel gear and / or a fourth bevel gear, each configured to engage the first bevel gear and each having a shaft with an end engageable with a tool. Preferably, this allows the scroll plate to be rotated by turning either the second, third, or fourth bevel gear using a tool. The hub may include a number of slots corresponding to the predetermined number of limbs, and a toothed key of each of the jaws may be received within a respective slot of the number of slots. Each toothed key of each of the jaws may include a number of teeth, the number of teeth including an arcuate projection for engaging a helical projection of the scroll plate.

[0006] Alternatively or additionally, the adjustment mechanism may engage the radially outer side of the jaws. The adjustment mechanism may include a band or strap for engaging the radially outer side of the jaws, the band or strap having a first end and a second end. The first end and the second end may be joined using a closure means. The closure means may include a threaded fastener arranged to engage a threaded nut. For example, the threaded nut may be a barrel nut and the threaded fastener may be a bolt. Alternatively, the closure means may include a biasing member, such as a spring, arranged to bias the first end and the second end together. Each of the jaws may include a flange for maintaining the band on the radially outer side of the jaws.

[0007] The hub may be integrally formed, i.e., formed of a single piece. Alternatively, the hub may be formed of two or more pieces joined together. The apertures and / or jaws may be shaped to conform to the shape of the limb.

[0008]

[0008] An assembly is provided that includes an electromagnetic core having a number of limbs disposed about a central axis and a retention mechanism as described above. The number of limbs are received within a plurality of apertures in the retention mechanism. The retention mechanism may be a first retention mechanism configured to receive first ends of the limbs of the electromagnetic core, and the assembly may include a second retention mechanism configured to receive second ends of the limbs of the electromagnetic core, as described above. The number of limbs may be three.

[0009] Further details, aspects and embodiments of the present invention will now be described, by way of example only, with reference to the drawings in which elements are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For ease of understanding, like reference numerals have been included within the respective figures. [Brief description of the drawings]

[0010] [Figure 1A] FIG. 2 is a schematic diagram of a magnetic core. [Figure 1B] FIG. 2 is a schematic diagram of a magnetic core. [Figure 1C] FIG. 2 is a schematic diagram of a magnetic core. [Figure 2A] FIG. [Figure 2B] FIG. [Figure 2C] FIG. 2 is a schematic diagram of a retention mechanism with features omitted for clarity of illustration. [Figure 2D] FIG. 2 is a schematic diagram of a retention mechanism with features omitted for clarity of illustration. [Diagram 3] FIG. 2E is a schematic diagram of components of an adjustment mechanism for the retention mechanism of FIGS. 2A to 2D. [Figure 4A] FIG. [Figure 4B] FIG. [Figure 4C] FIG. 2 is a schematic and exploded view of a retention mechanism. [Diagram 5] 1 is a flow chart of a process for assembling an electromagnetic core using a retention mechanism. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011]

[0010] The present disclosure relates to a retention mechanism for clamping or holding together the limbs of a multi-limb electromagnetic core, such as the electromagnetic core described with reference to Figures 1A-1C. The retention mechanism maintains the limbs in direct or intimate contact with one another to minimize any discontinuities that may be caused by gaps between the limbs that may otherwise be detrimental to the flow of magnetic flux within the electromagnetic core. Certain exemplary retention mechanisms are discussed with reference to Figures 2A-2D and 4A-4C.

[0012] 2A-2D, a retention mechanism 200 retains a three-limb electromagnetic core, such as electromagnetic core 100. The retention mechanism 200 includes a hub 202. The hub 202 includes a first portion 202a, a second portion 202b, and a third portion 202c. The first portion 202a, the second portion 202b, and the third portion 202c are coupled together, for example, by fasteners.

[0013] The hub 202 has three apertures 204, each for receiving an end portion 106 of a respective limb 102 of the electromagnetic core 100. The apertures 204 are formed across the second portion 202b and the third portion 202c of the hub 202. The retention mechanism 200 includes three jaws or wedges 206, each for engaging and / or retaining a respective limb of the electromagnetic core 100 in a respective aperture 204 of the three jaws or wedges 206. The hub 202 has an axis 208 coaxial with the axis 104 of the electromagnetic core 100.

[0014] Each jaw 206 has a shape that substantially corresponds to and matches the shape of the end portion 106 of the limb 102 with which it engages to maximize the contact area between the jaw 206 and the limb 102. Similarly, each aperture 204 has a shape that substantially corresponds to and matches the shape of the end portion 106 of the limb 102 with which it engages to maximize the contact area between the aperture 204 and the limb 102.

[0015] The radial distance of the jaws 206 from the axis 208 can be adjusted using an adjustment mechanism, thereby adjusting the position of the limbs 102 relative to the axis 104 when the limbs 102 are held by the holding mechanism 200. Adjusting the radial position of the jaws 206 thus allows the limbs 102 of the electromagnetic core 100 to intersect at the axis 104 of the electromagnetic core 100.

[0016] The adjustment mechanism includes a toothed key 210 for each jaw 206, a scroll plate 212, and three bevel gears 214. Each toothed key 210 is coupled to a respective jaw 206. Alternatively, each toothed key 210 may be integrally formed as part of a respective jaw 206. The hub 202, and specifically the second portion 202b, includes three slots for aligning and receiving the respective toothed keys 210.

[0017]

[0016] The scroll plate 212 has an annulus having a first side and a second side. The annulus has an axis coaxial with the axis 208 of the hub 202. The first side of the scroll plate includes a helical projection 216 for engaging with the toothed key 210. The helical projection 216 has a predetermined distance between the helical projections. The second side of the scroll plate includes a bevel gear 218. The teeth of each toothed key 210 form an arcuate projection configured to engage with the helical projection 216. In other words, the spacing and shape of the arcuate projections correspond to the spacing and shape of the helical projections 216.

[0018]

[0017] Each of the bevel gears 214 is configured to engage with a bevel gear 218 of the scroll plate. In other words, the spacing and shape of the gear teeth of the bevel gears 214 correspond to the spacing and shape of the gear teeth of the bevel gears 218. Each of the bevel gears 214 has a shaft. The hub 202 has three openings 220 formed between the first portion 202a and the second portion 202b. Each opening 220 is for receiving the shaft of a respective bevel gear 214. The openings 220 support the respective shaft while allowing the bevel gears 214 to rotate. A bearing may be located in each opening 220 to reduce friction as the shaft rotates. An end 222 of each shaft is accessible from the outside of the hub 202, for example, by a user. Each end 222 includes a head that can be driven by a tool. Although end 222 is shown as having a Robertson socket, any suitable driving socket may alternatively be used, such as a hex socket, a Phillips socket, a Torx socket, or a Pentalobe socket.

[0019]

[0018] Rotating the drive head of any one of the ends 222 with a suitable tool rotates the respective bevel gear 214 which engages the bevel gear 218, turning the scroll plate 212, which in turn rotates the helical projection 216, which in turn moves the toothed key 210 radially relative to the axis 208. Because the toothed key 210 is coupled to its respective jaw 206, when the end 222 of the bevel gear 214 is rotated, the jaw 206 also moves radially relative to the axis 208.

[0020] 2A-2D includes three bevel gears 214, any of which can be turned to adjust the radial distance between the jaws 206 and the axis 208, although it is clear that a single bevel gear 214 may also allow this adjustment. In a retention mechanism with multiple bevel gears, the radial distance between the jaws and the axis can be adjusted using any of the ends, which may be advantageous when it may be easier for a user to access one end of the bevel gears than the ends of the other bevel gears. Furthermore, multiple bevel gears 214 may allow the retention force on the scroll plate 212 to be evenly distributed to different locations in the scroll plate 212.

[0021] 4A-4C, a retention mechanism 300 retains an electromagnetic core having three limbs, such as the electromagnetic core 100. The retention mechanism 300 includes a hub 302. The hub 302 has three apertures 304, each for receiving an end portion 106 of a respective limb 102 of the electromagnetic core 100. The retention mechanism 300 includes three jaws 306, each for engaging and / or retaining a respective limb of the electromagnetic core 100 within a respective aperture 304 of the three jaws 306. The hub 302 has an axis 308 that is coaxial with the axis 104 of the electromagnetic core 100.

[0022] Each jaw 306 has a shape that substantially corresponds to and matches the shape of the end portion 106 of the limb 102 with which it engages to maximize the contact area between the jaw 306 and the limb 102. Similarly, each aperture 304 has a shape that substantially corresponds to and matches the shape of the end portion 106 of the limb 102 with which it engages to maximize the contact area between the aperture 304 and the limb 102.

[0023]

[0022] The radial distance of the jaws 306 from the axis 308 can be adjusted using an adjustment mechanism, thereby adjusting the position of the limbs relative to the axis 104 when the limbs are held by the holding mechanism. Adjusting the radial position of the jaws 306 thus allows the limbs 102 of the electromagnetic core 100 to intersect at the axis 104 of the electromagnetic core 100.

[0024] The adjustment mechanism includes a strap or band 310 that engages the radially outward side of the jaws 306. Each jaw 306 includes a flange 312 for holding the band 310 in place. The band 310 has a first end 314 and a second end 316. The first end 314 and the second end 316 are connected to one another using a closure means 318. The closure means 318 includes a threaded fastener configured to engage a threaded nut. For example, the threaded nut may be a barrel nut and the threaded fastener may be a bolt. Alternatively, the closure means 318 may include a biasing member, such as a spring, configured to bias the first end 314 and the second end 316 together. The closure means 318 exerts a radial force on the radially outward side of the jaws 306 toward the axis 308. The closure means 318 can be adjusted to tighten or loosen, for example in the case of a threaded fastener engaging a threaded nut, to adjust the amount of radial force applied radially outward of the jaws 306 toward the axis 308.

[0025] Further configurations of the retention mechanism are substantially identical to retention mechanism 200, with an adjustment mechanism comprising a scroll plate and a second adjustment mechanism comprising a strap or band substantially similar to band 310 that engages the radially outward side of the jaws of the retention mechanism. The jaws may each include a flange substantially similar to flange 312 to hold the band in place.

[0026] FIG. 5 illustrates a process 500 for manufacturing a core, such as electromagnetic core 100, using retention mechanism 200 or 300.

[0027]

[0026] In step 502, a set of magnetic steel strips are formed, one set of strips for one limb of the core. The strips may be formed, for example, by punching, stamping, or laser cutting the width and length of each strip from a sheet of magnetic steel. The magnetic steel may be, for example, Thyseen-Krupp powercore® C or powercore® H.

[0028]

[0027] At step 506, each set of straps is placed into a stack. At step 510, each stack is curved, for example using a jig, into arc-shaped limbs. The stack is curved by applying an external load in a direction perpendicular to the plane formed by the length and width of the straps.

[0029]

[0028] The magnetic strip may include a surface coating of an electrically insulating material. The surface coating may be hardenable, such as a varnish or paint. The hardenable surface coating on the strip stack may be hardened in step 514. For example, the hardenable surface coating may be hardened by heating the stack in an autoclave. The electrically insulating surface coating may be formed during annealing of the magnetic strip. For example, the magnetic strip may be annealed in an air atmosphere in a roller furnace at a maximum temperature of 860°C for a soak time of 1 to 2 minutes. Due to the air atmosphere, the cut edges of the magnetic strip oxidize and an insulating coating is formed. A coating thickness of 2 to 5 micrometers provides good electrical resistance and a high stacking factor.

[0030]

[0029] Each limb has a first end and a second end. In step 518, the ends of the limbs may be machined to produce angled ends that allow the limbs to fit closely together. For example, if the core being manufactured has three limbs, the ends are machined to a 120 degree angle. The machining may include one or more of sanding, grinding, milling, and cutting, such as water jet cutting or laser cutting. Alternatively or in addition to step 518, a band may be formed for the limbs with angled ends in step 502. In some examples, the ends of the limbs may be machined to create lap joints that allow the limbs to fit closely together.

[0031]

[0030] In step 522, the limbs may be annealed. If the hardenable surface coating is heat cured in step 514, the annealing of step 522 may be included in step 514. In some examples, the core may be annealed in step 534 after the limbs are joined. The annealing may be a magnetic anneal to improve the magnetic properties of the limbs. Additionally or alternatively, the annealing may be a stress relief anneal to relieve internal mechanical stresses in the limbs due to bending in step 510, for example. For example, the annealing may include a 2 hour soak at 820°C-850°C in a box furnace, preferably with a protective atmosphere of 100% nitrogen, followed by cooling to about 200°C-300°C in the furnace.

[0032]

[0031] In step 526, one or more of the primary winding, secondary winding, and modulation winding may be applied to each limb. The application of the windings to the limbs may be performed at any time before the ends of each limb are connected together in step 538, in other words, when there is at least one open end. Applying the windings around the limbs may include winding a wire around the limb to form a winding. Alternatively, applying the windings around the limbs may include spinning a wire onto a bobbin and inserting the limb into the bobbin. By winding the limbs before joining them together, the winding process is simplified. The windings may be distributed onto the limbs with or without spacers.

[0033] In step 534, the first ends of the limbs are inserted into respective apertures of a first retention feature, such as retention feature 200 or 300. In step 536, jaws of the first retention feature are inserted into respective apertures of the first retention feature, and an adjustment mechanism of the first retention feature is employed to adjust the radial position of the jaws relative to the axis of the hub of the first retention feature to intersect the first ends of the limbs of the electromagnetic core with the axis of the electromagnetic core.

[0034]

[0033] In step 538, the second ends of the limbs may be inserted into respective apertures of a second retention feature, such as retention feature 200 or 300. In step 540, jaws of the second retention feature may be inserted into respective apertures of the second retention feature, and an adjustment mechanism of the second retention feature may be employed to adjust the radial position of the jaws relative to the axis of the hub of the second retention feature to intersect the second ends of the limbs of the electromagnetic core with the axis of the electromagnetic core.

[0035]

[0034] Connecting the limb ends together in steps 534 and 538 may include using an adhesive, such as a metal-to-metal structural adhesive. Steps 534 and 538 may be performed sequentially or simultaneously. Steps 536 and 540 may be performed sequentially or simultaneously.

[0036]

[0035] Although the present invention has been described in relation to several embodiments, it is not intended that the present invention be limited to the specific form described herein. Rather, the scope of the present invention is limited only by the appended claims. Furthermore, although features may appear to be described in relation to specific embodiments, those skilled in the art will recognize that various features of the described embodiments may be combined in accordance with the present invention. In the claims, the term "comprises" or "includes" does not exclude the presence of other elements.

[0037] Exemplary embodiments

[0036] As previously mentioned, the techniques described herein can be implemented in various ways. In this regard, the above is intended to include, but is not limited to, the apparatus, methods, combinations and subcombinations thereof described in the following exemplary embodiments. The following paragraphs disclose preferred embodiments. [Paragraph 1] 1. A retention mechanism for an electromagnetic core having a number of limbs disposed about a central axis, comprising: A hub, Axis line, and a plurality of apertures corresponding to the predetermined number of limbs, each of the apertures configured to receive an end portion of a respective limb in a radial direction about the axis, the axis coinciding with the central axis when the predetermined number of limbs are received within the plurality of apertures; a hub comprising: a plurality of jaws corresponding to the predetermined number of limbs, each of the jaws configured to maintain the end portion of a respective limb within a respective aperture when the predetermined number of limbs are received within the plurality of apertures; an adjustment mechanism configured to adjustably move the plurality of jaws radially relative to the axis of the hub; A retention mechanism comprising: [Paragraph 2] 2. The retaining mechanism of paragraph 1, wherein the adjustment mechanism comprises a plurality of toothed keys corresponding to the predetermined number of limbs, and a scroll plate having a first side and a second side, the first side comprising a helical projection for engaging the toothed keys of each of the jaws, and the second side comprising a first bevel gear, each toothed key coupled to a respective jaw. [Paragraph 3] 3. The retention mechanism of paragraph 2, comprising a second bevel gear having an axle and configured to engage the first bevel gear, the hub comprising an opening for rotatably supporting the second bevel gear, and an end of the axle engageable with a tool to rotate the second bevel gear. [Paragraph 4] 4. A retention mechanism as described in paragraphs 2 or 3, wherein the hub includes a plurality of slots corresponding to the predetermined number of limbs, the toothed key of each of the jaws being received within a respective one of the plurality of slots. [Paragraph 5] 5. The retaining mechanism of any of paragraphs 2-4, wherein each toothed key of each of the jaws includes a plurality of teeth, the plurality of teeth having an arcuate projection for engaging the helical projection of the scroll plate. [Paragraph 6] 6. The retention mechanism of any of paragraphs 1-5, wherein the adjustment mechanism engages a radially outer side of the jaw. [Paragraph 7] 7. The retention mechanism of paragraph 6, wherein the adjustment mechanism comprises a band for engaging the radially outer side of the jaw, the band having a first end and a second end, the first end and the second end being joined using a closure means. [Paragraph 8] 8. The retention mechanism of paragraph 7, wherein the closure means includes a threaded fastener configured to engage a threaded nut. [Paragraph 9] 8. A retention mechanism as described in paragraph 7, wherein the closure means includes a biasing member arranged to bias the first end and the second end together. [Paragraph 10] 10. A retention mechanism as described in any of paragraphs 7 to 9, wherein each jaw includes a flange for retaining the band on the radially outer side of the jaw. [Paragraph 11] an electromagnetic core having a number of legs disposed about a central axis; A retention mechanism according to any one of paragraphs 1 to 10; Equipped with the predetermined number of limbs being received within the plurality of apertures of the retention mechanism. [Paragraph 12] 12. The assembly of paragraph 11, wherein the predetermined number of limbs is three. [Explanation of symbols]

[0038] 100...electromagnetic core, 102...arc-shaped limb, 104...central axis, 105...bobbin, 106...first end, end portion, 108...second end, 200...retention mechanism, 202...hub, 202a...first portion, 202b...second portion, 202c...third portion, 204...aperture, 206...jaw or wedge, 208...axis, 210...toothed key, 212...scroll plate, 214...bevel gear, 216...spiral projection, 218...bevel gear, 220...opening, 22 2...end, 300...retention mechanism, 302...hub, 304...aperture, 306...jaw, 308...axis, 310...strap or band, 312...flange, 314...first end, 316...second end, 318...closure means, 500...process, 502...step, 506...step, 510...step, 514...step, 518...step, 522...step, 526...step, 534...step, 536...step, 538...step, 540...step

Claims

1. 1. A retention mechanism for an electromagnetic core having a number of limbs disposed about a central axis, comprising: a hub, a plurality of jaws corresponding to the predetermined number of limbs, and an adjustment mechanism; The hub includes: Axis line, and a plurality of apertures corresponding to the predetermined number of limbs, each of the apertures configured to receive an end portion of a respective limb in a radial direction about the axis, the axis coinciding with the central axis when the predetermined number of limbs are received within the plurality of apertures; Equipped with the plurality of jaws are configured such that each of the jaws engages the end portion of a respective one of the limbs to retain the end portion of each of the limbs within a respective one of the apertures when the predetermined number of limbs are received within the plurality of apertures; The adjustment mechanism is configured to adjustably move the jaws radially relative to the axis of the hub and adjustably move the limbs relative to the central axis when the jaws are engaged with the limbs.

2. the adjustment mechanism comprising: a plurality of toothed keys corresponding to the predetermined number of limbs; and a scroll plate having a first side and a second side; 2. The retention mechanism of claim 1, wherein the first side includes a helical projection for engaging the toothed key of each of the jaws, and the second side includes a first bevel gear, each toothed key coupled to a respective jaw.

3. a second bevel gear having an axis and configured to engage the first bevel gear; 3. The retention mechanism of claim 2, wherein the hub includes an opening for rotatably supporting the second bevel gear, and an end of the shaft is engagable with a tool for rotating the second bevel gear.

4. 3. The retention mechanism of claim 2, wherein said hub includes a plurality of slots corresponding to said predetermined number of limbs, said toothed key of each of said jaws being received within a respective one of said plurality of slots.

5. 3. The retention mechanism of claim 2, wherein each toothed key on each of said jaws includes a plurality of teeth, said plurality of teeth comprising an arcuate projection for engaging said helical projection of said scroll plate.

6. The retention mechanism of claim 1 , wherein the adjustment mechanism engages a radially outward side of the jaws.

7. 7. The retention mechanism of claim 6, wherein the adjustment mechanism comprises a band for engaging the radially outer side of the jaw, the band having a first end and a second end, the first end and the second end being joined using a closure means.

8. The retention mechanism of claim 7 , wherein the closure means comprises a threaded fastener configured to engage a threaded nut.

9. The retention mechanism of claim 7 , wherein the closure means includes a biasing member arranged to bias the first end and the second end together.

10. The retention mechanism of claim 7 , wherein each of the jaws includes a flange for maintaining the band on the radially outer side of the jaw.

11. an electromagnetic core having a number of legs disposed about a central axis; The holding mechanism according to any one of claims 1 to 10. An assembly comprising: the predetermined number of limbs being received within the plurality of apertures of the retention mechanism.

12. The assembly of claim 11 , wherein the predetermined number of limbs is three.

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