TECHNICAL FIELD

The present disclosure relates to a coil winding apparatus.

BACKGROUND

Inductors are components widely used in electrical networks. It can for example be used to generate reactive power. The inductor can be designed in different ways. For example, an inductor can have an iron core or the inductor can be made with an air-core. When used to generate reactive power, the inductor can typically be referred to as a reactor. Typical applications include voltages of several kV such as 10 KV, 20 kV or 40 kV or above.

Reactors are typically used in high voltage power transmission, distribution and industrial applications. These reactors are typically placed in outdoor environments.

Irrespective of the type of inductor, a coil is typically used in the inductor. Manufacturing coils are generally difficult and can in most cases involve manual tasks that are time consuming. This is particularly so for larger coils used for kV applications. Moreover, some coils are not circular such as the coils used in WO2020171762 where a D-shaped coil is used in some embodiments.

SUMMARY

It is an object of the present invention to provide an improved apparatus for manufacturing coils. This object and/or others are obtained by the coil winding apparatus as set out in the appended claims. The coils manufactured can advantageously be used in reactors.

In accordance with the invention a coil winding apparatus is provided. The coil winding apparatus comprises a rotatable former with a perimeter surface onto which a wire can be wound. The coil winding apparatus further comprises a pair of rolls configured to press against the rotatable former with a predetermined force. The pair of rolls are configured to press against the perimeter surface of the rotatable former, such that the wire to be wound onto the rotatable former is configured to run between a first, leading, roll of the pair of rolls and a second, trailing, roll of the pair of rolls. The rotatable former can in some embodiments have a non-circular contour to form a non-circular coil. By employing the pair of rolls, the coil winding apparatus can wind the wire of the coil with a force that is evenly distributed also when the coil has a shape that deviates from a circular shape. This in turn makes the winding compact and robust.

In accordance with some embodiments, the width of at least the second, trailing roll corresponds to the width of the perimeter surface of the rotatable former. Hereby it can be ensured that the force applied when rolling the wire onto the former is evenly distributed over the width of the former.

In accordance with some embodiments, the rotatable former has a D-shaped contour to form a D-shaped coil. Hereby a D-shaped coil can be manufactured in an easy manner and be given a good performance.

In accordance with some embodiments the coil winding apparatus comprises a lever pivoted at a hinge. The pair of rolls are provided at one end of the lever. A weight can be provided attached to the lever on the side opposite to the side where the pair of rolls are located. Hereby an easy to implement mechanism that produces a constant force on the pair of rolls can be obtained. The weight can be exchangeable to allow for an easy change of force applied to the pair of rolls. In some embodiments the weight is movable along the lever. Hereby the force applied to the pair of rolls can be changed in an alternative manner.

In accordance with some embodiments, the coil winding apparatus comprises a guide element configured to move a wire laterally over the perimeter surface of the rotatable former. Hereby the coil winding apparatus can be configured to distribute the wire laterally over the width of the former so that a desired wire pattern can be achieved when winding the wire onto the former to produce the coil.

In accordance with some embodiments a flange or a stop element is provided at the edge of the perimeter surface of the former. Hereby the coil can be produced without risking that the wire slips off the former when winding the coil.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described in more detail by way of non-limiting examples and with reference to the accompanying drawings, in which:

- Fig. l is a view illustrating an apparatus for winding a coil is depicted,

- Fig. 2 is a view similar to Fig. 1 illustrating a wire wound into a coil, and

- Fig. 3 is a schematic view in perspective of a former for winding a coil.

DETAILED DESCRIPTION

In the following different embodiments of an apparatus 20 for winding a coil are described. In a typical application, an enameled copper wire or some other insulated wire is wound into a suitable shaped coil 10. The coil is formed by the apparatus 20 shown in Fig. 1. The apparatus 20 comprises a former 7. The former 7 has a contour shape corresponding to the desired shape of a coil to be manufactured. In Fig. 1, the former 7 has a generally D-shaped contour. The former 7 can have any desired form including circular and oval shapes. The former 7 can be rotated around an axle 6 as is indicated by the arrows in Fig. 1. The rotation of the former 7 can in accordance with one embodiment be made by connecting the axle 6 of the former to the shaft of a motor (not shown) and let the motor rotate the former 7 around the axle 6. However, it is also envisaged that the former 7 can be rotated manually around the axle 6.

In accordance with some embodiments, the wire wound to form a coil can have non-circular cross section. In particular wire with a square or rectangular cross-section can be used to form a coil. Hereby the shaping of the coils can be made easier since there is more freedom to select the shape of the wire. Also, the fill factor, i.e. the space used to form the turns can be reduced if a square /rectangular profile is used.

The coil winding apparatus 20 comprises a pair of rolls 2 to roll the wire onto the former 7. The pair of rolls 2 can be pressed against the former with a desired pressure when winding the wire onto the former 7. The pair of rolls 2 forms a bogie to even the pressure that is applied when winding the wire onto the former. Hereby the rolls can be used to apply the required force to bend the wire to its desired form. The pair of rolls 2 comprises a first, leading, roll 9, and a second, trailing roll 11.

When a wire is rolled onto the former 7, the wire is pressed against the former 7 by the trailing roll 11. Because both the leading roll 9 and the trailing roll 11 are pressed towards the former as a bogie, the pressure applied between the trailing roll and the former 7 can be kept constant or nearly constant, even if the shape of the former 7 is not circular. Thus, the pair of rolls 2 acts to even out the pressure applied when rolling the wire onto the former as the former 7 rotates. It is also envisaged that additional rolls can be provided; both additional leading rolls and additional trailing rolls can be used. For example, at least two leading rolls can be used and/or at least two trailing rolls can be used to further improve the distribution of pressure applied when rolling the wire onto the former 7 such that the pressure is constant and even both along the contour of the former and also along the width of the former when rolling the wire into the shape of the former 7.

To apply a pressure force onto the pair of rolls 2, a number of different mechanisms can be used. For example, a spring force can be used or a motor pressing the pair of rolls to the former 7 can be used. In Fig. 1, a pivoted lever 5 is used to apply the pressure force onto the pair of rolls 2. In such an embodiment the apparatus can comprise a fixed hinge 4. The lever 5 pivots on the hinge 4. At one side of the hinge 4 the pair of rolls 2 is located. The lever can have a bent portion 13 between the hinge 4 and the pair of rolls 2. The bent portion 13 allows for an easier feed of wire between the pair of rolls 2. At the other side of the hinge 4, i.e., the side where the pair of rolls 2 are not located, a weight 16 can be provided. The weight 16 can be selected to provide a desired pressure force to the rolls against the former. Also, the weight 16 can be changed to provide the user with an option to change the pressure force onto the pair of rolls 2. In accordance with one embodiment the weight 16 can be moved along the lever 5. Moving the weight 16 provides another or additional way to change the pressure force onto the pair of rolls 2 against the former 7.

In Fig. 2, the apparatus of Fig. 1 is shown when a wire 18 is wound onto the former 7. The wire 18 is fed from a bobbin 22. As set out above, the wire 18 can be selected to have a suitable diameter and cross-section. When the wire 18 is wound onto the former 7, a coil 10 is formed. As set out above, the coil can be made into a suitable shape such as a D-shape. The shape can be determined by designing the former 7 accordingly. For example, circular or oval shapes can be used. The number of turns of wire and how the wires of each turn are located in relation to each other is a design parameter that the user can select. In Fig. 2, a guide element 12 is shown. The guide element 12 is useful when a coil comprising a number of wires located next to each other along the width of the former 7 is produced. Thus, by moving the guide element 12 laterally (in the direction of the axle 6), the wire 18 can be located at a suitable location along the width of the former 7. Thus, a coil with a suitable number of turns which is determined by the number of turns the former is rotated and the coil can also have the wires located in any suitable pattern by moving the guide element 12 when rotating the former so that each turn of the produced coil is placed laterally (i.e., in the direction of the axle of the former) in a desired location to obtain a desired coil. In Fig. 3, an exemplary former 7 is schematically shown in perspective. The former 7 has a suitable contour and a perimeter surface 24 with a suitable width W. The former 7 typically has a uniform width all around the contour of the former 7. Here the contour is generally D shaped. In order to facilitate winding of the wire onto the former 7, at least one flange 23 or some other stop element can be provided at the side, the edge, of the former 7. The at least one flange 23 can be provided on one or both sides of the former 7. Also, the flange can cover parts of the perimeter the former 7 as shown in Fig. 3 or the at least one flange can extend all around the perimeter of the former 7. By providing a flange 23 or some other stop element at the side of the former 7, the coil can be produced without risking that the wire slips off the former when winding the coil on the former 7.

By using the coil winding apparatus as described herein coils can be produced more efficiently and with improved performance.