GB1595083A

GB1595083A - Laminated core electrical devices

Info

Publication number: GB1595083A
Application number: GB46377/77A
Authority: GB
Original assignee: BERTOS AG
Current assignee: BERTOS AG
Priority date: 1976-11-08
Filing date: 1977-11-08
Publication date: 1981-08-05
Also published as: DE2650929C2; NO146040B; FR2370346B1; NO146040C; NO773802L; NL186411B; SE7712555L; IT1091718B; DE2650929A1; SE422635B; FR2370346A1; NL186411C; NL7711790A

Description

(54) IMPROVEMENTS IN OR RELATING TO LAMINATED CORE ELECTRICAL DEVICES (71) We, BERTOS AG, of Glarus, Switzerland, a Swiss Company do hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be performed to be particularly described in and by the following statement: This invention relates to electrical devices comprising an encased core that is built up from sheet-metal laminations, e.g. ballast devices and transformers, including autotransformers.

Ballast devices are already known, e.g. for the starterless operation of fluorescent lamps or auto-transformers, the dimensions of which are standardised, in which devices there is a core formed from substantially wastelessly stamped E-shaped and I-shaped core laminations that form two-part lamination layers surrounded by a two-part casing, so that the respective groups of E-shaped lamination parts and I-shaped laminations are each surrounded by a respective casing part, while the casing part of the E-shaped core laminations overlaps the casing part of the I-shaped core laminations. In this case, the I-shaped core laminations may be stamped wastelessly from between two juxtaposed E-shaped laminations, the inner surplus material of two E-shaped stampings producing two I-shaped stampings.

An earlier patent application (German P23 44 483.3) disclosing such arrangements illustrates how there can be obtained an economy of active material -- i.e. of copper and of core lamination material - by an enlargement of the inner core, because by this means fewer turns per winding are necessary for equal specific material stress. A particular geometry of the dimensions of the windings and of the core lamination layers is proposed in the patent application for this purpose.

The overlapping of the casing parts is also of importance, as will be explained further hereinbelow. However, in this earlier disclosure only the casing part surrounding the E-shaped core laminations overlaps the joints in the core lamination layers, whilst there is no overlapping of the joints by the other casing part surrounding the I- shaped core laminations.

It is known that a leakage field occurs at joints in a magnetic circuit, e.g. at the junctions of the E-shaped and I-shaped core laminations in this instance, depending upon the surface constitution. But said leakage fields are highly undesirable for specific applications of transformers and choke coils, e.g. in the case of hospital lamps because they may influence adjacent medical appliances. Even when iron parts are arranged in immediate proximity, these leakage fields can be found disturbing because they give rise to troublesome noise.

According to the present invention, there is provided an electrical device having a core comprising substantially wastelessly stamped core lamination layers which are surrounded by a two-part casing, each lamination layer being formed of two stamped laminations with each said lamination surrounded on the outer periphery of the lamination by a respective casing part, both casing parts overlapping the outer edges of the joints between the laminations of the lamination layers and at least one of said laminations being provided with recesses adjoining said joint outer edges and into which extends the casing part surrounding the other lamination.

In one form of the invention, the E-shaped core laminations have, in the region of their joints with the I-shaped core laminations, small stamped out portions in which the ends of the casing part surrounding the I-shaped core laminations are located.

As a result of these measures the joints of the magnetic circuit can be masked by both casing parts so that the magnetic leakage field at the joints is effectively reduced. Experiments have shown that a result of these measures the magnetic leakage field at the joints can be reduced by up to two thirds.

Conveniently, the depth of the stamped out portions coresponds approximately to the wall thickness of the casing part surrounding the I-shaped core laminations. It is also convenient to arrange the stamping operation so that the width of the stamped out portions has approximately twice the total dimension of the overlap of the two casing parts.

The additional stamped out portions can thus be comparatively very small parts, which if allowed to be scrap are so insignificant that it is still possible to speak of wasteless or substantially wasteless stamping.

The invention may provide that I-shaped core laminations having small stamped out portions are stamped wastelessly independently of the E-shaped core lamination parts.

In this manner such I-shaped core laminations can still be stamped totally wastelessly.

The stamping of the associated E-shaped core laminations can then be carried out independently of the I-shaped core laminations so that they are stamped wastelessly except for the small stamped out portions already referred to, while the width of the central limb of each E-shaped core lamination has double the dimension of the outer limbs. Thus in this case the E-shaped core laminations can also be stamped completely wastelessly, except for these small stamped out portions mentioned, from a strip of sheet-metal of appropriate width.

The casing parts of a device according to the invention may consist of multiple-layered sheet metal at least in the region of the said overlaps. Although there may be only two layers of sheet metal at said overlapping of the casing parts, if still more layers are provided, possibly with the individual layers having a smaller thickness, the said shielding effect can be further strengthened.

Further advantages and particulars of the invention will emerge from the description given hereinbelow of some embodiments, by way of example, with reference to the accompanying drawing, wherein: Fig. 1 shows an end elevation of a ballast device or a transformer according to a first embodiment, without the winding; Fig. 2 shows a stamping section for the production of the core laminations of the transformer according to Fig. 1; Fig. 3 is an illustration, similar to Fig. 1, of another embodiment of the invention; Fig. 4 shows a stamping section for the production of the E-shaped core laminations for the embodiment according to Fig. 3; Fig. 5 shows a stamping section for the I-shaped core laminations for the embodiment according to Fig. 3; Fig. 6 is an illustration, similar to Fig. 1 and Fig. 3, of a third embodiment of the invention; and Fig. 7 shows a stamping section for the production of the core laminations of the embodiment according to Fig. 6.

Fig. 1 shows an E-shaped core lamination 1 which is adjoined below by an I-shaped core lamination 2 at the two joints 5 and 6.

This device comprises, in known manner, a bundle or stack of such lamination layers which are surrounded by an upper casing part 3 and a lower casing part 4.

In the region of the joints 5 and 6 an overlapping of the casing parts 3 and 4 is provided, and in fact not only the upper casing part but also the lower casing part 4 overlaps the two joints 5 and 6 with its two ends 7 and 8.

As will be seen, the total width of the ballast device is designated A and that of the E-shaped core lamination parts a, whilst the sheet-metal thickness of the casing parts is indicated as s. In this case the length of the I-shaped core lamination 2 = a - 2s, whilst the height is indicated on the right of Fig. 1 as H. The said overlapping by the ends 7 and 8 of the casing part 4 is indicated by the dimension u.

Fig. 2 shows the stamping section from which the E- and I-shaped laminations used in the ballast device according to Fig. 1 are stamped. As will be seen, from a strip of the width a, two E-shaped core laminations la and lb, which are mutually separated by the centreline 13, and two I-shaped core laminations 2a and 2b are stamped out wastelessly each time from the sheet-metal. This stamping technique is known in principle.

In the present instance, however, it is provided that small cavities or recesses 9 and 10 approximately with thickness s and length c = 2u are additionally stamped out, so that the said arrangement according to Fig. 1, namely the overlapping of the joints 5 and 6, is possible. According to the prior patent application referred to above, said joints were merely overlapped by the upper casing part 3 according to Fig. 1.

Figs. 3 to 5 show another embodiment, wherein the E-shaped and I-shaped core laminations 1 and 2 are stamped out, not from a common sheet-metal strip but from two different strips, as is illustrated in Figs. 4 and 5. The central limb of the E-shape in this case has a width d which is twice as great as the width e of the externally located limbs of the E-shape, so that the wasteless stamping of two interlaced E-shaped core laminations according to Fig. 4 is possible.

Here again, the very small stamped out recesses 9a and 10a are provided additionally, so that the ends 7 and 8 of the lower casing part 4 can fit in there. In this case the vertical dimension in Fig. 4 of the stampings has only the dimension u, whereas the width is 2s, as indicated in the case of the stamping 9a.

Fig. 5 shows the wasteless stamping of the I-shaped core laminations 2 in the manner that the recesses 11 and 12 according To Fig. 3 are produced. The length of the I shaped core laminations is here again a - 2s as according to Fig. 1.

Fig. 6 shows a third embodiment, wherein air gap 14 is moved further upwards, as shown. Otherwise the construction and the designations are the same as in the previous figures. In this case the stamping section according- to Fig. 7 can be used analogously to the scheme shown in Fig. 2.

In another unillustrated embodiment, the casing parts 3 and 4 consist, at least in the region of the overlaps 7 and 8, of multiplelayered sheet metal, whilst the individual layers are preferably constructed with a smaller wall thickness s compared to the previously illustrated embodiments. They may therefore, inter alia, be formed from foil-like metal sheets, each casing part comprising a number of such sheets in layers, which will be understood by one skilled in the art without further illustration.

Reference is directed to our co-pending application No. 46378/77 (Serial No.

1,595,084) in which there is described and claimed an electrical device having a laminated core comprising substantially wastelessly stamped E- . and I-shaped core laminations which are surrounded by a two-part casing, so that the E- and I-shaped core laminations are surrounded by respective casing parts while the casing part of the E-shaped core laminations overlaps the casing part of the I-shaped core laminations wherein the respective groups of E-shaped core laminations and I-shaped core laminations are wastelessly stamped independently of each other and are assembled to form a common core arrangement.

WHAT WE CLAIM IS:- 1. An electrical device having a core comprising substantially wastelessly stamped core lamination layers which are surrounded by a two-part casing, each lamination layer being formed of two stamped laminations with each said lamination surrounded on the outer periphery of the lamination by a respective casing part, both casing parts overlapping the outer edges of the joints between the laminations of the lamination layers and at least one of said laminations being provided with recesses adjoining said joint outer edges and into which extends the casing part surrounding the other lamination.

2. A device according to claim 1 wherein the depth of the recesses transverse to the adjacent peripheral region of the core lamination layer corresponds aprpoximately to the wall thickness of the casing part of said other lamination.

3. A device according to claim 1 or claim 2 wherein the lamination layers comprise at least one form of lamination that is stamped out in opposed pairs from a sheet metal blank and the width of the recesses stamped out in the direction of the adjacent periphery of the paired lamination stampings is approximately twice the total dimension in the same direction of the overlap that the casing part surrounding said other lamination has with said one form of lamination.

4. A device according to any one of claims 1 to 3 wherein each core lamination layer comprises a substantially E-shaped lamination and a substantially I-shaped lamination, and the E-shaped laminations are provided in the region of their joints with the I-shaped laminations with small recesses in which lie the ends of the casing part surrounding the I-shaped laminations.

5. A device according to claim 4 wherein the I-shaped core laminations with recesses are wastelessly stamped out independently of the E-shaped laminations.

6. A device according to claim 5 wherein the E-shaped laminations stamped out independently of the I-shaped laminations are formed wastelessly except for small peripheral recesses of the completed laminations, the width of the central limb of each Eshaped core lamination being double the width of each of the outer limbs of said lamination.

7. A device according to any one of the preceding claims wherein at least in the regions of overlap, the casing parts each consist of a plurality of layers.

8. An electrical device having a laminated core in a casing comprising two casing parts having overlapping ends, the core lamination layers being formed by substantially wastelessly stamped plates with a plurality of said plates forming complementary laminations of each lamination layer of the core, each lamination layer being provided with recesses at its outer periphery at the joints between the laminations into which extend said overlapping ends of at least one of the casing parts.

9. An electrical device constructed and arranged for use substantially as described herein with reference to any of the embodiments illustrated in the accompanying drawing.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. Fig. 3 are produced. The length of the I shaped core laminations is here again a - 2s as according to Fig. 1. Fig. 6 shows a third embodiment, wherein air gap 14 is moved further upwards, as shown. Otherwise the construction and the designations are the same as in the previous figures. In this case the stamping section according- to Fig. 7 can be used analogously to the scheme shown in Fig. 2. In another unillustrated embodiment, the casing parts 3 and 4 consist, at least in the region of the overlaps 7 and 8, of multiplelayered sheet metal, whilst the individual layers are preferably constructed with a smaller wall thickness s compared to the previously illustrated embodiments. They may therefore, inter alia, be formed from foil-like metal sheets, each casing part comprising a number of such sheets in layers, which will be understood by one skilled in the art without further illustration. Reference is directed to our co-pending application No. 46378/77 (Serial No. 1,595,084) in which there is described and claimed an electrical device having a laminated core comprising substantially wastelessly stamped E- . and I-shaped core laminations which are surrounded by a two-part casing, so that the E- and I-shaped core laminations are surrounded by respective casing parts while the casing part of the E-shaped core laminations overlaps the casing part of the I-shaped core laminations wherein the respective groups of E-shaped core laminations and I-shaped core laminations are wastelessly stamped independently of each other and are assembled to form a common core arrangement. WHAT WE CLAIM IS:-

1. An electrical device having a core comprising substantially wastelessly stamped core lamination layers which are surrounded by a two-part casing, each lamination layer being formed of two stamped laminations with each said lamination surrounded on the outer periphery of the lamination by a respective casing part, both casing parts overlapping the outer edges of the joints between the laminations of the lamination layers and at least one of said laminations being provided with recesses adjoining said joint outer edges and into which extends the casing part surrounding the other lamination.