GB2048575A - Electrical choke or transformer - Google Patents

Abstract

In a choke or transformer a magnetic core is built up from J- laminations 12, which may be punched with little wastage in interengaging pairs from metal strip, and rectangular laminations 20, which may also be punched with little wastage from metal strip, the laminations being clamped together to include an air-gap 22 by casing members 34, 36. <IMAGE>

Description

SPECIFICATION Improved choke or transformer This invention relates to electrical chokes or transformers.

It is well-known to produce electrical chokes and transformers having cores made up from laminations which are punched from sheet metal. Such cores commonly include an air-gap, or insert of non-magnetic material, the dimensions of which are important in minimising hum and vibration in operation. The punching of laminations from sheet metal can be wasteful of raw material due to the particular shape of the laminations compared with the shape of the sheet.

It is an object of this invention to produce a core for a choke or transformer having laminations punched from metal strip with little wastage and having an air-gap which can be adjusted during manufacture in order to improve the performance of the choke or transformer.

According to the present invention there is provided an electrical choke or transformer having a laminated metal core each layer of which is made up from the combination of a pair of J-laminations and one rectangular lamination, each J-lamination comprising a basal portion from which a short limb extends perpendicularly at one end and a long limb extends perpendicularly in the same direction at the other end and being shaped and dimensioned so that two such J-laminations may be interengaged to form a rectangular shape, each pair of J-laminations being arranged in the choke with their short limbs in edge-to-edge contact to form an overall E-shape, the rectangular lamination being arranged in edge-toedge contact with both the long limbs with an air-gap between the rectangular lamination and the pair of short limbs, the laminations being held together by an external casing.

Preferably the casing of the choke or transformer comprises a pair of generally channel-shaped members having lips engaging notches cut in the Jlaminations, one member embracing the face of the core that includes the rectangular lamination and the other the opposite face.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 shows an arrangement of laminations in one layer of a core of an electrical choke, Figures 2 and 3 show patterns of punching laminations from metal strip, Figure 4 is a cross-section through an electrical choke, and Figure 5 shows a complete electrical choke.

Referring to Figure 1, this shows a pair of generally J-shaped laminations 12 each having a short limb 14, a basal portion 16 and a long limb 18 having semi-circular notches 24 cut in one edge. The J-laminations 12 are arranged to have their short limbs 14 in mutual edge-to-edge contact and a rectangular lamination 20 is positioned between the long limbs 18, in edge-to-edge contact each long limb 18 such that an air-gap 22 is created between it and the short limbs 14.

Referring now to Figure 2, this shows this manner in which J-laminations 12 are punched from a metal strip 26 with minimal wastage. Two interengaging J-laminations 12 form a rectangle having one side of equal length to the width of the strip 26. The notches 24 are formed by punching two circular holes 28 along each line at which the strip is cut across its full width. Figure 3 shows the manner in which the rectangular laminations 20 are formed by repeatedly cutting a metal strip 30 across its width.

Referring now to Figures 4 and 5 which show a choke assembled using J-laminations 12 and rectangular laminations 20. A winding 32 of electricallyconducting wire is wound around the short limbs 14 of the J-laminations 12. An upper casing 34 has lips 38 that engage the notches 24 formed in the long limbs 18 of the J-laminations 12. A lower casing 36 also has lips 38 that engage corresponding notches 24. The upper casing is formed at each end into a hollow box section 40 that encases the ends of the core and winding 32. A terminal block 42 for making an electrical connection to the winding 32 is fixed to the lower casing 36 and mounting-holes 44 are provided therein.Before final assembly of the choke, the position of the rectangular laminations 20 may be adjusted in order to alter the size of the air-gap 22 and so improve the performance of the choke by the minimisation of hum and vibration in operation.

1. An electrical choke or transformer having a laminated metal core each layer of which is made up from the combination of a pair of J-laminations and one rectangular lamination, each J-lamination comprising a basal portion from which a short limb extends perpendicularly at one end and a long limb extends perpendicularly in the same direction at the other end and being shaped and dimensioned so that two such J-laminations may be interengaged to form a rectangular shape, each pair of J-laminations being arranged in the choke with their short limbs in edge-to-edge contact to form an overall E-shape, the rectangular lamination being arranged in edge-toedge contact with both the long limbs with an air-gap between the rectangular lamination and the pair of short limbs, the laminations being held together by an external casing.

2. A choke or transformer according to claim 1 in which the casing comprises a pair of generally channel-shaped members having lips engaging notches cut in the J-laminations, one member embracing the face of the core that includes the rectangular laminations and the other the opposite face.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (2)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Improved choke or transformer This invention relates to electrical chokes or transformers. It is well-known to produce electrical chokes and transformers having cores made up from laminations which are punched from sheet metal. Such cores commonly include an air-gap, or insert of non-magnetic material, the dimensions of which are important in minimising hum and vibration in operation. The punching of laminations from sheet metal can be wasteful of raw material due to the particular shape of the laminations compared with the shape of the sheet. It is an object of this invention to produce a core for a choke or transformer having laminations punched from metal strip with little wastage and having an air-gap which can be adjusted during manufacture in order to improve the performance of the choke or transformer. According to the present invention there is provided an electrical choke or transformer having a laminated metal core each layer of which is made up from the combination of a pair of J-laminations and one rectangular lamination, each J-lamination comprising a basal portion from which a short limb extends perpendicularly at one end and a long limb extends perpendicularly in the same direction at the other end and being shaped and dimensioned so that two such J-laminations may be interengaged to form a rectangular shape, each pair of J-laminations being arranged in the choke with their short limbs in edge-to-edge contact to form an overall E-shape, the rectangular lamination being arranged in edge-toedge contact with both the long limbs with an air-gap between the rectangular lamination and the pair of short limbs, the laminations being held together by an external casing. Preferably the casing of the choke or transformer comprises a pair of generally channel-shaped members having lips engaging notches cut in the Jlaminations, one member embracing the face of the core that includes the rectangular lamination and the other the opposite face. An embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 shows an arrangement of laminations in one layer of a core of an electrical choke, Figures 2 and 3 show patterns of punching laminations from metal strip, Figure 4 is a cross-section through an electrical choke, and Figure 5 shows a complete electrical choke. Referring to Figure 1, this shows a pair of generally J-shaped laminations 12 each having a short limb 14, a basal portion 16 and a long limb 18 having semi-circular notches 24 cut in one edge. The J-laminations 12 are arranged to have their short limbs 14 in mutual edge-to-edge contact and a rectangular lamination 20 is positioned between the long limbs 18, in edge-to-edge contact each long limb 18 such that an air-gap 22 is created between it and the short limbs 14. Referring now to Figure 2, this shows this manner in which J-laminations 12 are punched from a metal strip 26 with minimal wastage. Two interengaging J-laminations 12 form a rectangle having one side of equal length to the width of the strip 26. The notches 24 are formed by punching two circular holes 28 along each line at which the strip is cut across its full width. Figure 3 shows the manner in which the rectangular laminations 20 are formed by repeatedly cutting a metal strip 30 across its width. Referring now to Figures 4 and 5 which show a choke assembled using J-laminations 12 and rectangular laminations 20. A winding 32 of electricallyconducting wire is wound around the short limbs 14 of the J-laminations 12. An upper casing 34 has lips 38 that engage the notches 24 formed in the long limbs 18 of the J-laminations 12. A lower casing 36 also has lips 38 that engage corresponding notches 24. The upper casing is formed at each end into a hollow box section 40 that encases the ends of the core and winding 32. A terminal block 42 for making an electrical connection to the winding 32 is fixed to the lower casing 36 and mounting-holes 44 are provided therein.Before final assembly of the choke, the position of the rectangular laminations 20 may be adjusted in order to alter the size of the air-gap 22 and so improve the performance of the choke by the minimisation of hum and vibration in operation. CLAIMS

1. An electrical choke or transformer having a laminated metal core each layer of which is made up from the combination of a pair of J-laminations and one rectangular lamination, each J-lamination comprising a basal portion from which a short limb extends perpendicularly at one end and a long limb extends perpendicularly in the same direction at the other end and being shaped and dimensioned so that two such J-laminations may be interengaged to form a rectangular shape, each pair of J-laminations being arranged in the choke with their short limbs in edge-to-edge contact to form an overall E-shape, the rectangular lamination being arranged in edge-toedge contact with both the long limbs with an air-gap between the rectangular lamination and the pair of short limbs, the laminations being held together by an external casing.

2. A choke or transformer according to claim 1 in which the casing comprises a pair of generally channel-shaped members having lips engaging notches cut in the J-laminations, one member embracing the face of the core that includes the rectangular laminations and the other the opposite face.