TRANSFORMER

Description

[0001] Transformer design is often the art of compromising the conflicting requirements of electrical performance, space requirements and manufacturing and fabrication costs. The electrical performance requirements of the windings often conflict with the difficulties of winding the desired coils with the proper geometry and mechanical integrity at a reasonable cost. At the very least, a transformer winding must have the required number of turns, adequate current handling capacity and the necessary structural strength to withstand electrically induced mechanical stresses. Additional considerations include securing good coupling between the windings and maximizing utilization of the core windows. Many times the practical difficulties inherent in winding the transformer coils such as getting the coil to lay properly, getting proper tension, positioning in and filling the core windows require compromises that limit ultimate electrical performance.

[0002] A suitable technique for improving electrical performance while minimizing the aforementioned difficulties has been to use a preformed winding having a channel cross section into which another prewound winding is mechanically inserted. This solves many of the above mentioned constructional difficulties without compromising electrical performance. It also advantageously permits a low profile transformer design suitable for card-type circuit packs. Such an arrangement is disclosed in the PCT application WO 86/01333 and comprises a transformer having a one turn preformed secondary winding and further having the primary enclosed within a channel cross section of the secondary winding. This arrangement, however, is limited to situations where a single turn winding is appropriate since no arrangement exists permitting the preformed winding to have multiple turns.

[0003] According to this invention there is provided a transformer as claimed in claim 1.

[0004] In one embodiment of the invention a two-turn winding is formed of individual turns each having a channel cross section. The individual turns are stacked on top of one another to form a closed passageway. The two turns are electrically isolated from each other by a film of insulation coating the two channels that electrically isolates adjacent edges except for a series connection employed at the ends of the individual turns to form a two-turn winding. The other transformer winding is inserted into the enclosed passageway. An alternative embodiment of the invention uses two turns having a channel cross section with one cross section smaller than the other so that one turn may be nested within the other. The other transformer winding is located within the open channel cross section of the nested turn.

[0005] It is readily apparent that this multiwinding arrangement expands the range of applicability of preformed windings to a larger power range since the overall turns ratio permitted is increased. Furthermore, it permits a center tapped multiwinding where such an arrangement is desired.

[0006] This arrangement of a preformed winding also advantageously permits winding arrangements having close coupling and also fully utilizes the window area of the core.

[0007] The invention will now be described with reference to the accompanying drawings in which :

Fig. 1 is a perspective view of a transformer embodying the invention ;

Figs. 2, 3 and 4 are orthogonal projections of a component of the multiturn winding shown in Fig. 1 ;

Figs. 5, 6 and 7 are orthogonal projections of another component of the multiturn winding shown in Fig. 1 ;

Fig. 8 is a perspective view of another configuration of a multiturn winding which may be used in the invention ;

Figs. 9, 10 and 11 are orthogonal projections of a component of the multiturn winding shown in Fig. 8;

Fig. 12 is an exploded perspective view of another multitum transformer winding which may be used in the invention ;

Figs. 13, 14 and 15 are orthogonal projections of a component of the multiturn winding shown in Fig. 12, and

Figs. 16, 17 and 18 are orthogonal projections of another component of the multiturn winding shown in Fig. 12.

[0008] The transformer arrangement, shown in Fig. 1, is designed to be board-mounted and to have a very low profile so one circuit board may be mounted in a housing in close proximity with another circuit board. The transformer includes an elongated E shaped magnetic core 10 and a magnetic core cap 20. The cap 20 is secured to the core 10 and the entire assembly to the circuit board 1 by four clips 5 (one is shown) which are each connected into detents 21 in the cap 20 and snap into corresponding detents (not shown) located in the bottom surface of the core 10. The elongated ends 6 of the clip 5 fit into holes or receptacles 4 in the circuit board 1.

[0009] The transformer windings include a primary winding 30 formed of a prewound conductor and a secondary winding formed of two U channel cross sectioned conducting turns or units 41 and 42. Conducting units 41 and 42 are each oriented so that the open ends of the channel cross sections face one another. An insulating film or material 49 is applied by dipping the individual conducting units in a liquified insulative material that is then cured into a solid film so that when the edges 43 and 44 are substantially abutted against one another, the two units 41 and 42 remain electrically isolated along these edges. The thickness of the side walls 45 and 46 of the units 41 and 42 and of the bottom wall 47 and 48 may be varied as needed to accommodate an anticipated power range of the transformer. Each conducting unit 41 and 42 with the U channel cross section comprises one complete turn. Units 41 and 42 are stacked on top with the adjacent edges 43 and 44 electrically insulated from each other as described above. They are electrically joined at their ends to form two complete turns.

[0010] The ends of the lower conducting unit 42 are extended to form two L shaped shelves 51 and 52 on a plane with the bottom of the channel and with each shelf having a hole 53 and 54 at the end of the L shaped extension. Shelf 51 and hole 53 are used to facilitate an electrical connection with the upper conducting unit 41.

[0011] The extensions 55 and 56 of the channel bottom of the upper unit 41 are also L shaped shelves. Each shelf, however, includes a step bend so that the plane of the shelf is positioned substantially coplanar with the bottom shelf extensions 51 and 52. The shelf 56 is directly above the shelf 51 and the holes 58 and 53 are in register with each other. These two shelf extensions may be secured together to electrically join the two conducting units 41 and 42 and create a two-turn winding by a fastening device such as a bolt or by fusing or binding such as welding or soldering. When the two units 41 and 42 are electrically connected, they are positioned to enclose the primary winding 30. The other two free shelves 52 and 55 may be used as the end terminals of the secondary winding and may be secured by fasteners through holes 57 and 54 to conducting paths 2 and 3 on the circuit board or other conductive media. Bias windings 7 and 8 of the transformer are positioned in the bottom of core and may, as shown, comprise loose wire or may comprise a printed circuit winding.

[0012] The assembly of the transformer begins with placement of the bias windings 7 and 8 into the core cavity. The primary winding is inserted in the cavity of the lower conducting unit 42, and the upper unit 41 is placed in top of it enclosing the primary winding within the desired passageway formed by the upper and lower units 41 and 42. The two conducting units 41 and 42 are then secured together by suitable fastener hardwire passing through holes 53 and 58. The assembled winding is then dropped into place in core 10, and then core 10 and cap 20 are secured together by the clips 5, which facilitate mounting the unit on a circuit board 1.

[0013] The details of the lower conducting unit 42 and upper conducting unit 41 are shown in the orthogonal projections in Figs. 2, 3, 4, 5, 6 and 7, respectively. The bottom unit 42 has a channel cross section as shown in Fig. 4 and the base of the channel has two L shaped shelf extensions 51 and 54 as shown in Fig. 2. The shelf extensions are offset in length so that one 54 may serve as a winding terminal and the other 51 a midwinding connection of the two-turn winding. The upper unit 41 has a channel cross section as shown in Fig. 7 and two L shaped shelf extensions 55 and 56 as shown in Fig. 5. Each shelf extension has a step which is nearly coplanar with a mating surface of a shelf extension of the bottom unit 42.

[0014] A variation of a secondary winding arrangement is disclosed in Fig. 8 comprising two identical conducting units 141 and 142. The two units are joined together along their edges, with a primary winding positioned within the resulting enclosed passageway. An insulating film 144 coating the units electrically isolates the two windings from each other at the adjacent edges. The two windings 141 and 142 are electrically connected in series by a conductive spacer 150 conductively joining the L shaped shelf extensions 148 and 149 respectively to create a two-turn winding. The outer L shelves 146 and 147 are used to provide the start and finish termination leads of the completed secondary winding.

[0015] As is apparent from the detailed drawing of Figs. 9 through 11, the two individual units 141 and 142 are identical in geometry and are of the same handedness. They mate together, as shown in Fig. 8, form a two-turn winding with and enclosed passageway.

[0016] A third winding arrangement is disclosed in a perspective view in Fig. 12 in which the two winding units 241 and 242 are sized differently so that the upper conducting unit 241 may be nested into or fit within the channel cross section of the bottom conducting unit 242 with the opening of the channels facing in the same direction for both conducting units. The conductive cross sectional area of both conducting units is selected so that both units have the same conductive cross sectional area. Hence, a thinner conductive material is used for the lower shell winding. This matching of conductive area allows for equalization of dissipative losses in each individual conducting unit. The two turns are insulated from each other by a layer of insulation (possibly epoxy) on the surfaces of the two units.

[0017] Each turn has the base of its channel extended into L shaped shelves 251-254. The shelf extensions 251-252 of the top unit 241 are oriented in a direction opposite to the extension direction of shelves 253 and 254 of the bottom unit 242. Holes are in shelves 252 and 253 permit attachment of the conducting units to each other to form two series connecting turns. Holes in shelves 251 and 254 are used for terminating the two turns.

[0018] The prewound primary winding is inserted in the open channel 246 of the upper turn 241 which is left uncovered. The arrangement has very low leakage inductances between the two turns and is eminently suitable for application when the individual turns of the secondary conduct alternately when the winding is center tapped and current is switched between the two turns.

[0019] The two winding units 241 and 242 differ in handedness as shown in Figs. 13, 14, 15, 16, 17 and 18, respectively. This permits the shelf extensions 251 and 254 to clear each other and be used as winding termination connections.

[0020] It is readily apparent that by successive nesting arrangements the arrangement of Fig. 12 may be extended beyond two turns to multiple turns. Such arrangements will be readily apparent to those skilled in the art.

Claims

1. A transformer comprising a core (10) having first and second windows around a central core leg, a first conductor unit (42, 142, 242) extending through the first and second windows to encircle the central core leg and having a channel shaped cross section, a conductor (30) encircling the core leg, characterised by a second conductor unit (41, 141, 241) extending through the first and second windows to encircle the central core leg and having a channel shaped cross section, the first (42, 142, 242) and second (41, 141, 241) conductor units being positioned adjacent to one another with an open edge (44, 43) of the channel cross section of each of the first and second conductor units being substantially adjacent to one another, the said conductor (30) being within the channel cross section of each of the first and second conductor units, means for electrically insulating the first and second conductor units from each other, and a conducting mechanism (55, 56; 147, 149; 251, 252) electrically connecting the first (42, 142, 242) and second (41, 141, 241) conductor units in a series connection.

2. A transformer as claimed in claim 1 wherein the second conductor unit (241) is nested within the first conductor unit (242).

3. A transformer as claimed in claim 2 wherein the first and second conductor units have equal cross section areas of conducting material.

4. A transformer as claimed in claim 1 wherein the first and second conductor units (142, 141) are positioned so that channel cross sections are joined to form a closed passageway.

5. A transformer as claimed in any preceding claim wherein each conductor unit includes two extensions (51, 52, 55, 56 ; 146, 148, 147, 149; 251, 252, 253, 254) extending beyond a channel cross section of the unit, one extension (51, 56 ; 148, 149; 252, 253) at each unit being operative to connect the units in series to form a two-turn winding.

Ansprüche

1. Transformator mit einem Kem (10) der ein erstes und ein zweites, einen zentralen Kemschenkel umgebendes Fenster besitzt, ferner eine erste Leitereinheit (42, 142, 242), die sich durch das erste und zweite Fenster erstreckt, den zentralen Kemschenkel umgibt und einen kanalförmigen Querschnitt besitzt, sowie einen Leiter (30), der den Kemschenkel umfaßt, dadurch gekennzeichnet, daß eine zweite Leitereinheit (41, 141, 241) vorgesehen ist, die sich durch das erste und zweite Fenster erstreckt, den zentralen Kernschenkel umgibt und einen kanalförmigen Querschnitt besitzt, daß die erste (42, 142, 242) und zweite (41, 141, 241) Leitereinheit nahe beieinander so angeordnet ist, daß eine obere Kante (44, 43) des kanalförmigen Querschnitts der ersten und zweiten Leitereinheit im wesentlichen dicht aneinanderliegen, daß der Leiter (30) sich innerhalb des kanalförmigen Querschnitts sowohl der ersten als auch der zweiten Leitereinheit befindet, daß eine Einrichtung zur elektrischen Isolation der ersten und zweiten Leitereinheit gegeneinander vorgesehen ist, und daß eine leitende Einrichtung (55, 56 ; 147, 149 ; 251, 252) die erste (42, 142, 242) und zweite (41, 141, 241) Leitereinheit elektrisch in Reihe miteinander schaltet.

2. Transformator nach Anspruch 1, bei dem die zweite Leitereinheit (241) innerhalb der ersten Leitereinheit (242) untergebracht ist.

3. Transformator nach Anspruch 2, bei dem die erste und die zweite Leitereinheit gleiche Querschnittsflächen aus leitendem Material besitzen.

4. Transformator nach Anspruch 1, bei dem die erste und die zweite Leitereinheit (142, 141) so angeordnet sind, daß die kanalförmigen Querschnitte unter Bildung eines geschlossenen Durchgangs aneinanderliegen.

5. Transformator nach einem der vorhergehenden Ansprüche, bei dem jede Leitereinheit zwei Verlängerungen (51, 52, 55, 56; 146, 148, 147, 149 ; 251, 252, 253, 254) besitzt, die sich über den kanalförmigen Querschnitt der Einheit hinaus erstrecken, wobei eine Verlängerung (51, 56 ; 148, 149 ; 252, 253) so ausgebildet ist, daß sie die Einheiten unter Bildung einer Wicklung mit zwei Windungen in Reihe schaltet.

Revendications

1. Un transformateur comprenant un circuit magnétique (10) qui présente des première et seconde fenêtres autour d'une branche de circuit magnétique centrale, un premier élément conducteur (42, 142, 242) qui s'étend dans les première et seconde fenêtres de façon à entourer la branche de circuit magnétique centrale, et qui présente une section transversale en forme de U, et un conducteur (30) entourant la branche de circuit magnétique, caractérisé par un second élément conducteur (41, 141, 241) qui s'étend dans les première et seconde fenêtres de façon à entourer la branche de circuit magnétique centrale et qui présente une section transversale en forme de U, les premier (42, 142, 242) et second (41, 141, 241) éléments conducteurs étant positionnés de façon mutuellement adjacente, avec un bord ouvert (44, 43) de la section transversale en U de chacun des premier et second éléments conducteurs placé de façon pratiquement adjacente à celui de l'autre élément conducteur, le conducteur précité (30) se trouvant à l'intérieur de la section transversale en U de chacun des premier et second éléments conducteurs, des moyens pour assurer l'isolation électrique mutuelle des premier et second éléments conducteurs, et des moyens conducteurs (55, 56; 147, 149 ; 251, 252) qui connectent électriquement les premier (42, 142, 242) et second (41, 141, 241) éléments conducteurs en une connexion série.

2. Un transformateur selon la revendication 1, dans lequel le second élément conducteur (241) est emboîté à l'intérieur du premier élément conducteur (242).

3. Un transformateur selon la revendication 2, dans lequel les premier et second éléments conducteurs ont des aires de section droite de matériau conducteur égales.

4. Un transformateur selon la revendication 1, dans lequel les premier et second éléments conducteurs (142, 141) sont positionnés de façon que leurs sections transversales en U soient réunies pour former un passage fermé.

5. Un transformateur selon l'une quelconque des revendications précédentes, dans lequel chaque élément conducteur comprend deux prolongements (51, 52, 55, 56 ; 146, 148, 147, 149 ; 252, 252, 253, 254) qui s'étendent au-delà d'une partie de l'élément qui présente une section transversale en U, un prolongement (51, 56 ; 148, 149 ; 252 ; 253) de chaque élément ayant pour. fonction de connecter les éléments en série pour former un enroulement à deux spires.

Drawing