This application is a 35 U.S.C. § 371 national phase application of PCT/NL2015/050551 (WO 2016/018149), filed on Jul. 28, 2015, entitled “Electrical Device, in Particular a Coil or a Transformer”, which application claims priority to Netherlands Application No. 2013277, filed Jul. 30, 2014, which is incorporated herein by reference in its entirety.
The invention relates to an electrical device, in particular a coil or a transformer.
Such a device is generally known in different embodiments. A coil comprises one electrically conductive winding, in particular of insulated copper wire, the ends of which arc externally accessible for the purpose of transmitting electric current, in particular alternating current. Such a coil can be a coreless coil or an air coil but can also comprise a ferromagnetic core, optionally with an external yoke forming a closed magnetic circuit with the core. The self-inductance of the coil is hereby increased substantially.
Such a device can also be embodied as transformer. A transformer comprises a minimum of two windings, in particular a primary winding and one or more secondary windings. It is for instance possible to envisage a transformer for transforming down from the mains voltage of for instance 115 V or 230 V AC, which is transformed down by the transformer to a voltage of for instance several volts. For this purpose the transformer comprises a primary winding with a relatively large number of turns and one or more secondary windings with a smaller number of turns. It is usual for such a transformer to comprise a ferromagnetic core with an external yoke.
The drawback of such a known device is that it is heavy, expensive due to the nature of the production technique and takes up much space.
It is an object of the invention to embody a device of the described type such that the device is suitable for mass production, can be manufactured at relatively low cost and can be given a very light form.
With a view to the above the invention provides an electrical device, in particular a coil or a transformer, comprising a stack of electrical elements, wherein:
in the stack a central axis is defined which extends perpendicularly of the electrical elements;
each element comprises an electrically insulating flat carrier;
the carrier carries at least one electrically conductive loop-shaped track;
both end zones of the or each track are located in the edge zone of the carrier;
the loop-shaped tracks each form a turn and are arranged around the central axis in the stack;
the end zones are connected to each other in electrically conductive manner such that the turns form one winding in at least groupwise manner and that the electric currents conducted through the turns during operation of the device generate summating magnetic fields in the zone enclosed by the turns;
the carriers are congruent and each have a form such that they can be rotated from a starting position through an angle α around the central axis to a rotated position in which they take up the same space as in the starting position;
adjacent elements with tracks which together form a winding are disposed rotated through an angle relative to each other such that only one end zone of the track of the one element is in register position relative to only one end zone of the track of the adjacent element, and these mutually registered end zones arc mutually connected by an electrical conductor extending transversely of the elements;
the free end zones of the tracks of the outermost elements of the stack of elements, or at least that part of the stack with tracks which together form one winding, form the externally accessible terminals of the or each winding;
the elements are connected non-releasably to each other, and
the stack has a peripheral surface with a form which is prismatic at least in its central zone, i.e. has the same cross-sectional form at any axial position.
According to an important aspect of the invention, the device has the special feature that
each track is located some distance from the peripheral edge of the carrier;
the end zones of the track are located close to the peripheral edge of the carrier in the edge zone thereof; and
situated on the outer side of the stack and extending over the full height thereof are electrical conductors which each connect two mutually registered end zones of the tracks of adjacent elements electrically to each other.
The adjacent elements with tracks which together form a winding cover an overall angle of rotation of n·α, wherein n·α must be less than 360°.
In respect of the foregoing the device can advantageously have the special feature that each carrier is round.
The device can alternatively be embodied such that each carrier has the form of a regular polygon. The polygon comprises a number of sides which equal 360°/α.
The device preferably has the special feature that a ferromagnetic core is located in the space of the stack enclosed by the turn. A greatly increased self-inductance is hereby achieved for a coil and achieved for a transformer is that the windings have a substantially stronger mutual electromagnetic coupling.
In a further practical embodiment the device has the special feature that
a ferromagnetic zone is located in the space enclosed by the turn of each electrical element;
each flat carrier comprises a plastic substrate; and
the ferromagnetic zone comprises a magnetic material in powder form which is mixed through the substrate material and is thus embedded therein in substantially homogenous distribution.
Such an embodiment can particularly be mass-produced in very simple manner on large industrial scale with a limited number of production steps.
A device of the latter type preferably has the feature that the end zones of the core are coupled at least magnetically to each other by a ferromagnetic yoke extending outside the stack such that the core and the yoke together form a closed magnetic circuit. Stray fields are hereby prevented and the effectiveness of the operation of the ferromagnetic core is substantially enhanced.
A further improvement is achieved with an embodiment in which the yoke comprises two yoke parts extending on either side of the stack.
A preferred embodiment has a special feature that
the yoke comprises two ferromagnetic plates at least magnetically coupled to the end zones of the core and a ferromagnetic jacket at least magnetically coupled to these plates; and
situated in the jacket and/or in at least one of the plates is a passage for allowing through electrical conductors connected to both terminals of the or each winding.
In an important variant the device has the special feature that
the ferromagnetic yoke comprises a plastic substrate into which magnetic material in powder form is mixed and is thus embedded therein in substantially homogenous distribution; and
the yoke is manufactured by injection moulding.
According to yet another aspect of the invention, the device has the feature that respective electrically conductive pins are connected to both terminals of the or each winding, which pins extend outside the peripheral surface of the device.
According to an important aspect of the invention, the device can have the special feature that the pins are located in a zone forming part of a flat part of the peripheral surface of the device extending in longitudinal direction, and the pins extend perpendicularly of this flat part.
A device designed as transformer, for instance power supply transformer, can have the feature that
the tracks of the elements of the stack together form at least two windings, wherein a primary winding is configured to receive a relatively high alternating voltage and the or each other secondary winding is configured to generate a relatively low alternating voltage; and
the pins connected to the primary windings are located at the one axial end zone of the device, and the pins connected to the or each secondary winding are located at the other axial end zone of the device.
According to an important aspect, the above specified device according to the invention serving as transformer has the special feature that the pins are located in a zone forming part of a flat part of the peripheral surface of the device extending in axial direction, and the pins extend perpendicularly of this flat part. Such a transformer can be easily arranged on a printed circuit board or other carrier, the carrier being provided beforehand with for instance through-holes or other connecting provisions for correct positioning and electrical connection of the transformer and the electric connecting pins.
According to a further practical aspect of the invention, the device can have the special feature that the tracks of the or each secondary winding have a larger cross-section than the tracks of the primary winding. In such an embodiment the generation of heat per volume unit in the tracks of the primary winding or in the or each secondary winding can be substantially the same during operation, whereby temperature differences can be reduced to negligible proportions.
It is known that for instance power supply transformers for electronic units which convert the available mains voltage to a lower voltage must generally have a large mass because of the relatively low mains frequency, in particular 50 or 60 Hz. With a view to a still further miniaturization according to the invention an embodiment is recommended in which a frequency converter is added to the device embodied as transformer which converts the frequency of the alternating current to be supplied to the primary winding from a relatively low value, for instance 50 or 60 Hz, to a relatively high value of a minimum of 100 kHz.
The device still more preferably has the special feature that the relatively high value of the frequency amounts to a minimum of 1 MHZ.
According to an important aspect of the invention, the device can have the special feature that thermally conductive protrusions are situated on the outer side of the device, for instance pins, wires or fins, which at least partially relinquish heat generated in the device to the surrounding area.
Such protrusions can be embodied in per se known manner in a suitable thermally conductive material, for instance a metal such as copper, aluminium, silver.
As practical alternative the device can be embodied such that the protrusions consist together or in groups of a plastic substrate through which thermally conductive material in powder form, for instance aluminium powder, copper powder, silver powder, carbon powder, diamond powder, is mixed and thus embedded therein in substantially homogenous distribution; and
the protrusions are manufactured together or in groups by injection moulding or extrusion.
According to yet another aspect of the invention, the device has the special feature that each flat carrier consists of film material with a thickness of a maximum of about 100 μm.
It is particularly possible to envisage film thicknesses of 50 μm or less, and even to the order of 10 μm.
A practical choice in the context of the invention is that where the film material is PI (polyimide) or PEI (polyetherimide).
Polyimide and polyetherimide are materials with an extremely good temperature loadability. Melting of the materials and degeneration due to heating occur only at extremely high temperatures, i.e. above 400° C.
The device according to the invention is highly suitable for miniaturization. It is thus possible to envisage an embodiment in which the maximum linear dimension of the device, for instance the diameter of a cylindrical device, transversely of the central axis amounts to 10 mm, preferably 8 mm, still more preferably 6 mm.
The invention will now be elucidated with reference to the accompanying drawings. In the drawings:
As shown particularly clearly in the top view of
The adjacent elements 2 of the complete stack 9 are placed such that each end zone 4, 5 of an element is registered with only one end zone of the adjacent element 2. The registered zones of the complete stack, which are all designated with the reference numeral 10, thus acquire the linear helical form shown clearly in, among others,
Realized with the described coupling in each case of an end zone 4 to the subsequent end zone 5 is that the windings of a coil and of a winding of a transformer are respectively connected in series to each other.
Positioned in grooves 12 in a manner to be described below with reference to
As shown in
The coil according to
Coil 15 is of the type which does not have a ferromagnetic core. Only the plastic of carriers 6 is located in the space present defined by the tracks 3 operating as turns.
As alternative the carriers 6 can be embodied in their central zone, i.e. in the zone within the conductive tracks 3, such that ferromagnetic material in powder form is embedded in the plastic of the usually film-like carriers 3. By assembling and curing stack 9 under high temperature and optionally pressure a non-releasable unit is thus formed which is provided with a ferromagnetic core.
The electromagnetic coupling between the primary winding and secondary winding is substantially improved in this embodiment in that a core and a yoke co-acting therewith are added to the transformer. Ferromagnetic core 16 is formed as monolithic unit with a ferromagnetic bottom plate 22 and a ferromagnetic jacket 23. The thus resulting magnetic circuit is closed on the upper side after placing of a ferromagnetic cover 24 which has an edge recess 25 through which the terminals of the primary winding and those of the secondary winding extend. Edge recess 25 co-acts for positioning purposes with a correspondingly formed elevation 37 which protrudes from end surface 26.
The coupling between end surface 26 of the jacket and end surface 27 of the core and the lower surface of cover 24 can be realized by making use of a very thin adhesive layer.
Attention is drawn to the fact that copper tracks 3 of primary winding 18 have a smaller cross-sectional area than those of secondary winding 19. As is after all generally known from transformer technology, the cross-sectional area of a turn must be selected in the light of the current to be transmitted. For a secondary winding which generates a voltage of for instance 1 V, this is substantially greater than is the case for the primary winding, which is for instance intended for an alternating voltage of for instance 230 V.
The terminals of the primary winding are designated with reference numeral 128, while the terminals of the three secondary windings are jointly designated with reference numeral 29.
A ferromagnetic core with yoke is constructed symmetrically and via a thin electrically insulating jacket 30 can be arranged from both sides over the ends of stack 9 and subsequently fixed with for instance a small quantity of adhesive.
It is important to note that the two ferromagnetic yoke parts 31, 32 together define on their outer side a flat surface 33, 34 perpendicularly of which the connecting pins 35 of the primary winding extend at the one axial end zone, while connecting pins 36 of the three secondary windings extend perpendicularly thereof on the other axial side. As a result of the presence of this flat surface and the fact that pins 35, 36 extend perpendicularly thereof, transformer 28 can be easily positioned on a carrier of an electronic unit, after which pins 35, 36 are fixed, for instance with a welding or soldering process, to electrically conductive tracks.
For purposes of comparison a match 51 is placed next to electronic unit 45. This has the particular purpose of indicating the small dimensions of transformers 48, 49, 50.
All transformers are provided with cooling fins. Transformers 48 can he by and large of type as according to
It will be apparent from
Situated on the underside of transformer 50 is a flat placing surface with which in the mounted situation as according to
As a result of the usual application of a forced cooling airflow along an electronic unit of the type according to
Ferromagnetic cover 70 with filler block 76 and coupling surfaces 75 on the underside of connecting pins 35 takes place via the electrically insulating plate 72, which can for instance be embodied as film. Attention is drawn to the fact that, with a view to good positioning and a reliable electrically conductive connection between pins 35 and end zones 74, the coupling surfaces are provided with shallow grooves lying in the direction of the roughly radially extending upper parts of wires 13.
Number | Date | Country | Kind |
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2013277 | Jul 2014 | NL | national |
Filing Document | Filing Date | Country | Kind |
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PCT/NL2015/050551 | 7/28/2015 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2016/018149 | 2/4/2016 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
316354 | Gaulard | Apr 1885 | A |
728038 | Stowe | May 1903 | A |
2911605 | Wales, Jr. | Nov 1959 | A |
3089106 | Saaty | May 1963 | A |
4517540 | McDougal | May 1985 | A |
5038104 | Wikswo, Jr. | Aug 1991 | A |
20060278963 | Harada | Dec 2006 | A1 |
20110074397 | Bulumulla | Mar 2011 | A1 |
20120068693 | Ocket | Mar 2012 | A1 |
20120094555 | Calverley | Apr 2012 | A1 |
20120299685 | Yokota | Nov 2012 | A1 |
20160163445 | Bertels | Jun 2016 | A1 |
Number | Date | Country |
---|---|---|
390 600 | May 1990 | AT |
0 035 964 | Sep 1981 | EP |
0 435 461 | Jul 1991 | EP |
0 601 791 | Jun 1994 | EP |
0 953 993 | Nov 1999 | EP |
1 260 998 | Nov 2002 | EP |
1 353 436 | Oct 2003 | EP |
H06 325948 | Nov 1994 | JP |
Entry |
---|
International Search Report from PCT/NL2014/050459 dated Jul. 8, 2014. |
International Search Report from PCT/NL2015/050551 dated Jan. 1, 2016. |
Number | Date | Country | |
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20170213635 A1 | Jul 2017 | US |