AU675238B2

AU675238B2 - Adjustable-impedance choke coil

Info

Publication number: AU675238B2
Application number: AU47058/93A
Authority: AU
Inventors: Carsten Ruchholtz
Original assignee: Tridonic Bauelemente GmbH
Current assignee: Tridonic Bauelemente GmbH
Priority date: 1992-08-28
Filing date: 1993-08-02
Publication date: 1997-01-30
Anticipated expiration: 2013-08-02
Also published as: AU4705893A; ATE152854T1; WO1994006131A1; DE4228642A1; DE59306410D1; EP0657063A1; EP0657063B1

Abstract

The invention relates to a choke coil, the impedance of which can be matched within certain limits to a predetermined impedance, and a process for setting the impedance of the choke coil of the invention. The choke coil of the invention can be used, for instance, in fluorescent lamp ballasts. The core stack of the choke coil is constructed in layers with each layer made up of two C-shaped and one I-shaped lamination. The ends of the C-shaped lamination are in opposite pairs and bonded together on one side. The ends of the C-shaped laminations opposite the bonded ends have a stop device which ensures that, after these ends have been pressed together, they are at a fixed distance apart determined by the compressive force. The impedance of the choke coil can be matched to a predetermined value by pressing the C-shaped laminations of the core stack together.

Description

OPI DATE 29/03/94 APPLN. ID 47058/93 AOJP DATE 23/06/94 PCT NUMBER PCT/EP93/02052 INI1111~I 1111I AU9347fJ$8 INTERNATIONALE ANMELDUNG VEROFFENTLICHT NACH DEM VERTRAG OBER DIE INTERNATIONALE ZUSAMMENARBEIT AUF DEM GEBIET DES PATENTWESENS (PCT) (51) Internationale Patentklassifikation 5 HO1F3/14, 41/02 (11) Internationale Verdiffentlicliungsnummer: Al (43) Internadonales Veriiffentlichungsdatum: 17 WO 94/06131 Mfirz 1994 (17.03.94)

I

(21) Internationales Aktenzeichen: PCT/EP93/02052 (22) Internationales Anmeldedatum: 2. August 1993 (02.08,93) (81) Bestimmungsstaaten: AU, CZ, Fl, HU, JP, NZ, Pb, SK, US, europaiisches Patent (AT, BE, CH, DE, DK, ES, FR, GB, GR, LE, IT, LU, MC, NL, PT, SE), Veriiffentlicht Alit internationalen Recherczenbericlit.

Mit geiinderlen Ansprachen und Erkildrung.

Prioritaitsdaten: P 42 28 642.5 28. August 1992 (28.08.92) DE (71) Anelder (i~r alle Bestimrnnngsstaaten ausser US): TRIDO- NIC BAUELEMENTE GMBH [AT/AT]; Schmelzhiitterstrage 34, A-6850 Dornbirn (AT).

(72) Erfinder; und Erfinder/Anmelder (zurfiir US) RUCHHOLTZ, Carsten [DE/DE]; Bodenseestrage 15, D-88138 Sigmarszell

(DE).

(74) Anwalt: MITSCHERLICH, KORBER, SCHMIDT- EVERS, MELZER, SCHULZ, GRAF; Sonnenstrage 33, D-80331 MOnchen (DE).

fA"523 (54) Tit',e: ADJUSTABLE-IMPEDANCE CHOKE COIL (54) Bezeichnung: IMPEDANZJUSTIERBARE DROSSELSPULE t2-\3' LI3 fjZ'71 A hc4 The invention relates to a choke coil, the imped- 3 ance of which can be matched within certain limits to a 3 predetermined impedance, and a process for setting the 2L impedance of the choke coil of the invention, The choke coil of the invention can be used, for instance, in fluores- 2123 22 cent lamp ballasts. The core stack of the choke coil is constructed in layers with each layer made ujp of two C- 3 shaped and one I-shaped lamination. The ends of the C- 33 shaped lamination are in opposite pairs and bonded gether on one side. The ends of the C-shaped laminations opposite the bonded ends have a stop device which ensures that, after these ends have been pressed together, they are at a fixed distance apart determined by the compressive force. The impedance of the choke coil can be matched to a predetermined value by pressing the C-shaped laminations of the core stack together.

(57) Zusammenfassung Die Erfindung betrifft eine Drosseispule, deren Impedanz innerhaib gewisser Grenzen an einen vorgegebenen Impedanzwert angleichbar ist, und ein Verfahren zur Einstellung der lmpedanz der erfindungsgernflen Drosselspule. Die erfindungsgemiiIe Drosselspule findet z.B. bei Vorschaltgerfiten fflr Leuchtstoffr~hren Verwendung. Das Kernpaket der Drosselspule ist schichtweise aufgebaut, wobei jede Schicht aus zwei C-f6rmigen und einem I-f6rmigen Blech zusammengesetzt ist. Die Enden der C-f~rmigen Bleche stehen sich dabei paarweise gegentiber und sind auf einer Seite fest miteinander verbunden. Die den fest miteinander verbundenen Enden gegenflberliegenden Enden der C-f76rmigen Bleche weisen eine Arretierungs-Vorrichtung aug, die bewirkt, dags nach Zusammenpressen dieser Enden der C-f6rmigen Bleche diese einen fest arretierten Abstand zueinander ktafweisen, der durch die zusammenpressende Kraft bestimmt wird. Durch Zusammenpresseri der C-fl~rmigen Bleche des Kerntsis die Impedanz der Drosselspule an einen vorgegebenen Wert angleichbar.

DESCRIPTION

Adiustable-impedance choke coil The invention relates to a choke coil, the impedance of which is adjustable within certain limits to a predetermined impedance value, and a process for setting the impedance of the choke coil of the invention.

The choke coil according to the invention finds use eg. in fluorescent lamp ballasts. For the mentioned application, choke coils which take up little space, and have high inductance and Icw losses, are needed. The choke coil should also be suitable for mass production. To guide the magnetic flux the winding of the choke coil is in general surrounded and penetrated by a ferromagnetic core stack, which is constructed in layers from the avoidance of eddy currents.

On account of production tolerances of the lamination parts forming the core stack it is in general necessary to adjust the impedance of each choke coil manufactured in mass production, to the predetermined value, through a compensation measure. In this case a variation of the number of windings is not a measure appropriate for series production, on account of the great effort involved. However, an adaptation of the impedance of the choke coil, which is Ssuitable also for mass production, is afforded by variation of a gap which is arranged in the core stack, which gap is filled with a non-ferromagnetic material, 20 eg. air.

9**9 Cross-sections through core stack profiles of known choke coils are illustrated in Figures 1 and 2.

Figure 1 shows a two-part cross-sectional profile of a core a a: t, 9* 99a999 9 9 .e oea .e stack, whereby each layer of the core stack is composed of a U-shaped and a T-shaped lamination 1,2. The laminations of the core stack surround two winding windows 3 and 4 in which the winding body of the choke coil is arranged. In the lower region of the core stack the laminations of each layer are held together by means of a tension clamp 5. In the upper region of the core stack a gap 6 is arranged between the U-shaped lamination part 1 and the T-shaped lamination part 2, which gap is filled with a nonferromagnetic, plastically deformable material. By exerting a pressure 7 in the region of the gap 6 the width of this gap can be permanently reduced through deformation of the core stack. Through this measure the impedance of the choke coil is variable.

Similarly, it is also possible to arrange the gap 6 in the lower region of the choke coil. This leads to the cross section of the core stack shown in Figure 2, whereby each layer of the core stack is composed of an E-shaped lamination 10 and a I-shaped lamination 11. In the gap 12 a non-ferromagnetic, plastically deformable material is again arranged. Through exertion of a pressure 7 in the middle region of the core stack this is permanently deformable so that a variation of the impedance of the choke coil is made possible.

The configurations shown in Figures 1 and 2 have in common that the junctions 13 and 14 between the two laminations which form a layer of the core stack are located in the region of a great magnetic flux density of the magnetic field. It is disadvantageous that such a junction joint is associated with a stray field, which leads to losses at the choke coil.

It is therefore advantageous to arrange the junction between the laminations in a region through which the magnetic field flows only slightly. This is made possible if each layer of the core stack, as is shown in Figure 3, is assembled in three parts, two C-shaped laminations 21, 22 and an I-shaped lamination 23. The two C-shaped laminations 21 and 22 enclose the winding windows 24 and 25 as well as the I-shaped lamination 23 and are held together in the lower region by means of the tension clamp 5. Between one of the ends of the I-shaped lamination 23 and the two C-shaped laminations 21 and 22 a gap 26 filled with nonferromagnetic, plastically deformable material could be arranged with this configuration also. The effect of pressure in the middle region of the lamination steel stack does not, however, lead to a permanent deformation of the C-shaped laminations, as these spring back into their initial disposition after the pressure is released.

From EP 0 152 096 a choke coil is known with layers of the core stack each made up of two C-shaped laminations and an I-shaped lamination arranged in such a way that the two C-shaped laminations enclose two winding windows separated by the I-shap.:d lamination, the ends of one C-shaped lamination opposing the ends of the other C-shaped lamination. At the boundary surface between the C-shaped laminations and the I-shaped lamination the latter is conically shaped, whereas the C-shaped laminations have inclined surfaces which are matched to the I-shaped lamination. In gaps which are formed oSe.

20 between the I-shaped lamination and the two C-shaped laminations there are rsspective plastically deformable inserts of an insulating material or a metal.

Furthermore, the core stack is surrounded by a two-part casing in order to hold the C-shaped and I-shaped laminations in position. An adjustment of the gap width through variation of the force exerted by the casing onto the filing material e S 25 when the two parts of the casing are b'.ing connected during assembly seems,

S

however, to be scarcely possible. Further, it is questionable whether the described positioning of the lamination parts by means of the casing will be maintained under heat loading.

The object of the invention therefore is to provide an adjustable impedance choke coil with a core stack built up in layers each comprising two C-shaped laminations and an I-shaped lamination, and to provide a process which makes possible the adaptation of the impedance of the choke coil to a predetermined value.

The present invention accordingly provides an adjustable-impedance choke coil with a core stack constructed in layers, wherein each layer of the core stack is made up of two substantially C-shaped ferromagnetic laminations and a substantially I-shaped ferromagnetic lamination arranged in such a way that the two C-shaped laminations enclose two winding windows and the I-shaped lamination separates the winding windows, the ends of one C-shaped lamination opposing the ends of the other C-shaped lamination so as to form first and second pairs of mutually opposed ends, the C-shaped laminations being fixedly attached to one another at the first pair of mutually opposed ends and being held at a spacing from one another by means of a locking device at the second pair of mutually opposed ends, the spacing being settable in dependence upon a force pressing the second pair of mutually opposed ends together, the locking device including an inwardly opening recess in each end of the second pair of mutually opposed ends and a plastically deformable filling material arranged between the recesses such that the filling material, after pressing together of the second pair of mutually opposed ends, effects a fixed locking of the second pair of mutually opposed ends by cooperation with the recesses.

20 In one embodiment the recesses in each C-shaped lamination are in the eo Sshape of sectors of a circle. Alternatively the recesses in each C-shaped lamination may be of trapezoidal shape. The plastically deformable filling material is preferably copper or aluminium. Advantageously the locking device is arranged in a region of the core stack through which little magnetic flux passes. The fixed 25 attachment at the first pair of mutually opposed ends of the C-shaped laminations oa may be effected by a plate formed in the manner of a clamp.

The present invention also provides a process to set a predetermined impedance of the choke coil described above, including the following steps to be carried out successively or at the same time, if necessary several times: pressing together the second pair of mutually opposed ends of the Cshaped laminations of at least one layer of the core stack, electrically measuring the impedance of the choke coil, terminating the pressing together of the C-shaped laminations when the predetermined impedance is reached.

In one embodiment of the process the pressing together of the C-shaped laminations is begun at one end of the core stack and is continued in a direction laterally to the planes of the layers towards the other end of the core stack until the predetermined impedance of the choke coil is reached.

In another embodiment of the process, the layers of C-shaped laminations are pressed together one after another, whereby only a required number of layers are pressed together to obtain the predetermined impedance of the choke coil.

The invention will now be described in more detail with reference to the exemplary embodiments illustrated in the drawings, which show:- Figure 1 a cross-section through a core stack of a known choke coil, whereby each layer of the core stack is made up of a U-shaped and a T-shaped part; Figure 2 a cross section through the core stack of a known choke coil, whereby each layer of the core stack is made up of an E-shaped and an I-shaped part; Figure 3 a cross-section through the core stack of a choke coil, whereby each layer of the core stack is composed of two C-shaped parts and an I-shaped 20 part: Figure 4 a cross-section through the core stack of an embodiment of the choke coil according to the invention; Figure 5A and 5B two embodiments of the locking device of the .l choke coil according to the invention; Figure 6 a schematic arrangement for explaining the process according to the invention for the setting of the impedance of the choke coil according to the invention.

Figure 4 shows a cross-section through the core stack of an embodiment of the choke coil according to the invention.

The C-shaped ferromagnetic laminations 21 and 22 enclose an I-shaped lamination 23 which is arranged between two winding windows 24 and 25. The winding windows 24 and serve for accommodating a coil body (not shown) of the choke coil. The two C-shaped laminations of the core stack are firmly connected with one another on one side. In the illustrated exemplary embodiment, this one-sided connection is effected by means of the base plate 5 which is formed in the manner of a clamp. For receiving this fastening clamp the C-shaped laminations can each have a corresponding groove 32 or 33. The base plate 5, formed in the manner of a clamp, can at the same time serve for the fastening of the choke in a housing, in particular a housing for accommodating a fluorescent lamp tube.

The two C-shaped laminations form, in their non-tensioned rest position, a gap 31 between their ends on the side away from the fastening clamp 5. Between the I-shaped lamination 23 and the C-shaped laminations 21, 22 a further gap 26 can be provided at least on one side, to facilitate the positioning of the I-shaped lamination relative to the C-shaped laminations. For the locking of the I-shaped lamination this gap can be filled with a non-ferromagnetic filling material. Further, the choke coil according to the invention has a locking device 30, which is significant for the invention, at the ends of the C-shaped laminations which are separated by an air gap 31. The locking device RA, 30 is so formed that the width of the gap 31 can be reduced T through the action of a pair of forces 34, 35 upon the two C-shaped laminations.

Furthermore, the locking device 30 is effective in such a way that after the action of the two forces 34, 35 the two C-shaped laminations 21, 22 do not spring back into their initial disposition. Through a reduction of the width of the gap 31 the impedance of the choke coil may be varied. The locking device 30 is thereby advantageously arranged in the vicinity of the peripheral side of the gap 31 away from the I-shaped lamination 23, as in this region the flux density of the magnetic field is particularly small.

In Figures 5A and 5B configurations of the locking device 30 are shown.

The end surfaces 40 and 41 of the two ends 42 and 43 of the C-shaped laminations 21 and 22 have inwardly opening recesses 44 and 45. Between the recesses 44 and 45 a filling material 46 is arranged, which bridges the gap 31. If the ends 42 and 43 of the two C-shaped laminations 21 and 22 are pressed against one another, the filling material 46 deforms in such a way that it increasingly occupies the regions of the recesses 44 and 45 indicated by oblique lines, which regions were not filled by the filling material 46 before the forces began to act. If that portion 47 of the filling material 46 which lies in the region of the gap 31 before the beginning of the deformation is equal in volume to the regions of the recesses 44, 45 (regions illustrated by oblique lines) which were 20 not yet filled with the filling material 46 before the beginning of the deformation, the recesses are thus just completely filled with the filling material after the process of pressing together is terminated, ie. after the disappearance of the gap 31. The cross-sectional surface of the filling material 46 has, after the deformation, a cross-section in the region of the recesses 44 and 45 larger than the cross-section of the openings of the recesses 44 and 45, so that a locking of S*the corresponding ends of the C-shaped laminations is effected.

*o re cz sSeq The nele-ies 44 and 45 can be formed as sectors of a circle in the manner shown in Figure 5A or formed in the shape of a trapezoid as shown in Figure 5B. However, other configurations of the dneei--s are also possible, which have in an inner region a cross-section which is larger than their opening cross-section.

The filling material can for example be a relatively soft material such as aluminium or copper. The filling material can e.g. be formed as a wire, which runs perpendicularly of the layer plane of the core stack.

The process according to the invention for the setting of the impedance of the choke coil according to the invention will now be described with reference to Figure 6. Figure 6 shows the choke coil according to the invention in a plan view, so that gap 31 is visible is its longitudinal direction.

The choke coil is fully assembled before commencement of the adjustment thereof, i.e. the lamination parts of the core stack are pushed onto the coil body and the fastening element 5 is mounted on the side of the choke away from the locking device 30. In the case of a clamp-like base plate this may be effected by means of a roller flanging machine With the process according to the invention for setting the impedance of the choke coil, the ends 42 and 43 of the Cshaped laminations separated by the gap 31 are slowly and continuously pressed together. At the same time the impedance of the choke coil is measured by means of an electric impedance measurement procedure. The chokce coil is thereby so dimensioned that before the C-shaped laminations are pressed together the choke coil has too low an impedance in comparison with the predetermined value.

Through the pressing together of the C-shaped laminations S the volume of the gap 31 is slowly reduced and the impedance of the choke coil is thus increased. The pressing together of the C-shaped laminations is completed when the electric measurement of the impedance of the choke coil indicates that the impedance of the choke coil coincides with the predetermined value. The pressing together of the C-shaped laminations and the electrical measuring of the impedance can be carried out alternatingly instead of simultaneously.

The pressing together of the C-shaped laminations can occur homogenously over the entire length of the choke coil, in that all the C-shaped laminations of all layers of the core stack are pressed together at the same time. This procedure is however not very sensitive, as the width of the gap 31 is at the same time reduced over the entire length of the choke coil. It is more advantageous to begin with the pressing together of the C-shaped laminations at one of the ends of the gap 31 and to proceed in the direction of the other end of the gap 31 until the predetermined value of the impedance has been obtained, The pressing together of the C-shaped laminations of the core stack can thereby be advantageously performed by means of two rollers 51, 52 e.g. of a roller flanging machine.

With the above-described process for the pressing together of the C-shaped laminations of the core stack a V-shaped gap 31 is formed between the ends 42 and 43 of the C-shaped laminations. If the layers of the core stack can be displaced against one another with comparatively little force, a stepwise course of the slot 31 may also result.

Claims

1. Adjustable-impedance choke coil with a core stack constructed in layers, wherein each layer of the core stack is made up of two substantially C-shaped ferromagnetic laminations and a substantially I-shaped ferromagnetic lamination arranged in such a way that the two C-shaped laminations enclose two winding windows and the I-shaped lamination separates the winding windows, the ends of one C-shaped lamination opposing the ends of the other C-shaped lamination so as to form first and second pairs of mutually opposed ends, the C-shaped laminations being fixedly attached to one another at the first pair of mutually opposed ends and being held at a spacing from one another by means of a locking device at the second pair of mutually opposed ends, the spacing being settable in dependence upon a force pressing the second pair of mutually opposed ends together, the locking device including an inwardly opening recess in each end of the second pair of mutually opposed ends and a plastically deformable filling material arranged between the recesses such that the filling material, after pressing together of the second pair of mutually opposed ends, effects a fixed locking of the second pair of mutually opposed ends by i "cooperation with the recesses.

S2. Adjustable impedance choke coil according to claim 1, characterised in S 20 that, the recesses in each C-shaped lamination are in the shape of sectors of a circle.

3. Adjustable impedance choke coil according to claim 1, characterised in •that, the recesses in each C-shaped lamination are of trapezoidal shape.

4. Adjustable impedance choke coil according to any one of claims 1 to 3, 25 characterised in that, the plastically deformable filling material is copper or aluminium.

5. Adjustable impedance choke coil according to any one of claims 1 to 4, characterised in that, the locking device is arranged in a region of the core stack through which little magnetic flux passes.

6. Adjustable impedance choke coil according to any one of claims 1 to characterised in that, the fixed attachment at the first pair of mutually opposed ends of the C-shaped laminations is effected by a plate formed in the manner of a, clamp.

7. Process to set a predetermined impedance of the choke coil defined in any one of claims 1 to 6, including the following steps to be carried out successively or at the same time, if necessary several times: pressing together the second pair of mutually opposed ends of the C- shaped laminations of at least one layer of the core stack, electrically measuring the impedance of the choke coil, terminating the pressing together of the C-shaped laminations when the predetermined impedance is reached.

8. Process according to claim 7, characterised in that, the pressing together of the C-shaped laminations is begun at one end of the core stack and is continued in a direction laterally to the planes of the layers towards the other end of the core stack until the predetermined impedance of the choke coil is reached.

9. Process according to claim 7, characterised in that, the layers of C-shaped laminations are pressed together one after another, whereby only a required number of layers are pressed together to obtain the predetermined impedance of the choke coil.

Adjustable-impedance choke coil substantially as herein described with S.o 20 reference to any one of the embodiments shown in the accompanying drawings.

11. Process to set a predetermined impedance of a choke coil substantially as herein described with reference to any one of the embodiments shown in the accompanying drawings. 25 DATED: 26 November, 1996 S S' TRIDONIC BAUELEMENTE GMBH By their Patent Attorneys PHILLIPS ORMONDE FITZPATRICK ABSTRACT The invention relates to a choke coil the impedance of which can be matched within certain limits to a predetermined impedance, and a process for setting the impedance of the choke coil according to the invention The choke coil according to the invention finds use e.g. in ballasts for fluorescent light tubes. The core stack of the choke coil is constructed in layers, whereby each layer of the core stack is made up of two C-shaped and one I- shaped lamination. The ends of the C-shaped laminations oppose one another in pairs, and are fixedly attached to one another at one side. The ends of the of the C-shaped laminations lying opposite the ends fixedly attached to one another have a locking device which has the effect that after pressing together of these ends of the C-shaped laminations these ends have a fixedly locked spacing from one another, which is determined by the force pressing them together. By means of pressing together the C-shaped laminations of the core stack, the impedance of the choke coil can be matched to a predetermined value.