TECHNICAL FIELD
[0001] Aspects of the invention more generally relate to coil assembly designs for power
conversion circuits.
BACKGROUND
[0002] Power conversion circuits, such as power factor converters (PFC) used in alternating
current (AC) power systems, usually comprise an inductor element, such as a coil assembly
(e.g., a choke coil), designed to filter out unwanted frequency components from electrical
currents (e.g., to block higher frequencies and eliminate high-order harmonics).
[0004] Such coil assemblies typically comprise one or more windings, or coils, placed around
a core made from a metallic material, such as silicon steel. Cores of coil assemblies
made from silicon steel are relatively inexpensive to manufacture, but cannot be reliably
used for high frequency applications (e.g., with switching frequencies higher than
10kHz) due to high core losses and excessive overheating.
[0005] It is therefore desirable to provide low-cost coil assemblies capable of being used
in high frequency applications while being less prone to overheating.
SUMMARY
[0006] A coil assembly is defined in claim 1.
[0007] Advantageous but not obligatory aspects of the coil assembly according to the invention
are specified in claims 2 to 5.
[0008] According to another aspect, a power conversion circuit comprises a coil assembly
as defined above, as claimed in claim 6.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The invention will be better understood upon reading the following description, provided
solely as an example, and made in reference to the appended drawings, in which:
Fig. 1 is a simplified diagram of a power conversion circuit according to one or more
embodiments of the invention;
Fig. 2 is a simplified side view of a coil assembly according to one or more embodiment
of the invention;
Fig. 3 is another simplified side view of a coil assembly according to one or more
embodiment of the invention;
Fig. 4 is a simplified elevated view of a core portion of the coil assembly of Figs.
2 and 3;
Fig. 5 is a simplified perspective view of the coil assembly of Figs. 2 and 3.
DETAILED DESCRIPTION OF SOME EMBODIMENTS
[0010] Fig. 1 illustrates a coil assembly 2 part of an exemplary power conversion circuit
4 connected to an electrical device 6, such as a load or a power source.
[0011] According to some embodiments, the power conversion circuit 4 is a power factor converter,
or a power inverter, or any suitable AC power conversion system.
[0012] The coil assembly 2 is configured to filter out unwanted frequency components from
AC electrical currents, for example to block higher frequencies and eliminate high-order
harmonics. In other words, the coil assembly 2 acts as a low pass filter upon AC electrical
currents.
[0013] For example, the coil assembly 2 is a choke coil, such as a boost choke or a line
choke.
[0014] As illustrated on Fig. 2, Fig. 3 and Fig. 5, the coil assembly 2 comprises a plurality
of coils 10, or windings, and a metal core 12, preferably made from a magnetic material.
[0015] For example, the coils 10 are made of copper wire.
[0016] The coils 10 are placed around the metal core 12 and surround at least a portion
of said metal core 12.
[0017] The coils 10 are configured to be electrically connected to one or more elements
of the power conversion circuit 4, for example through connectors or leads.
[0018] According to some embodiments, each coil 10 is associated to a phase of the AC current.
[0019] In the illustrated example, the coil assembly 2 comprises three coils 10 and is configured
to operate in a three-phase electrical system.
[0020] This example is not limiting and, in alternative embodiments, the number of coils
10 could be different.
[0021] The metal core 12 is divided into a first core portion 14 and a second core portion
16 spaced apart from each other. Reference "18" denotes the space between the first
and second coil portions 14, 16.
[0022] The first and second core portions 14, 16 are made from laminated iron sheets, such
as silicon steel, although other suitable materials could be used instead.
[0023] The distance h18 separating the first and second core portions 14, 16 is comprised
between 1mm and 35mm, or preferably between 10mm and 30mm.
[0024] In some embodiments, the first and second core portions 14, 16 are superimposed vertically
on top of each other, for example along a vertical direction.
[0025] For example, the first core portion 14 and the second core portion 16 both have a
planar shape and lay parallel with each other along some geometrical plane, e.g. along
an horizontal geometrical plane. Core portions 14, 16 are offset from each other along
a direction perpendicular to said geometrical plane.
[0026] According to some embodiments, the first and second core portions 14, 16 have a similar
shape, and preferably have an identical shape.
[0027] In practice, the core 12 is configured to allow the passage of an airflow in the
space 18 between the first and second core portions 14, 16, as illustrated on Fig.
3 by the arrows "F". For example, the space 18 is open along the edges of the core
12.
[0028] This airflow F is advantageously used to naturally cool the core 12 during operation,
which improves the evacuation of heat generated by coils 10 and reduces the risk of
overheating.
[0029] In many embodiments, the core 12 is mounted atop a support structure 20.
[0030] For example, the support structure 20 include legs preferably arranged in a lower
region of the core assembly 2 and configured to be attached to a suitable reception
surface, such as a printed circuit board, e.g., for integrating the coil assembly
2 in the power conversion circuit 4.
[0031] The first and second core portions 14, 16 are held together by spacer elements 21.
[0032] Preferably, said spacer elements 21 are made from aluminum, although this example
is not limiting and other suitable nonmagnetic materials could be used instead.
[0033] For example, the spacer elements 21 are vertically arranged bars or plates fastened
to the first and second core portions 14, 16 by fastening elements such as screws,
or by welding, or by any appropriate means. The spacer elements 21 may also be fastened
to the support structure 20.
[0034] As illustrated on Fig. 4, each of the first core portion 14 and the second portion
16 comprise a plurality of arms 22, 24, 26. Said arms 22, 24, 26 may be separated
by hollow portions 28 and 30.
[0035] The arms 22, 24, 26 of the first core portion 14 are aligned with the arms 22, 24,
26 of the second core portion 16.
[0036] On Fig. 4, only the first core portion 14 is illustrated. However, it is understood
that, in many embodiments, the second core portion 16 has a similar or identical shape.
[0037] According to examples, each core portion 14, 16 has a square or rectangular shape
and includes rectilinear parallel arms 22, 24 and 26.
[0038] In the illustrated example, each core portion 14, 16 includes a first arm 22, a second
arm 24 and a third arm 26. The first arms 22 of both first and second core portions
14 are aligned with each other. Similarly, the second arms 24 of both first and second
core portions 14 are aligned with each other, and the third arms 26 of both first
and second core portions 14 are aligned with each other.
[0039] Each coil 10 is placed so as to surround an arm of the first core portion 14 and
an arm of the second core portion 16.
[0040] For example, a first coil 10 is mounted on the first arms 22 of both first and second
core portions 14, 16. A second coil 10 is mounted on the second arms 24 and a third
coil 10 is mounted on the third arms 26.
[0041] According to some embodiments 10, the coils may be wound directly onto the core 12,
or may be wound onto prefabricated coil holders mounted on said arms.
[0042] According to some embodiments, each arm 22, 24, 26 of the first and second core portions
14, 16 is divided into at least two subparts separated from each other by an air gap
32, 34, 36.
[0043] For example, the two subparts have each a longitudinal rod-like shape and are both
aligned essentially along a same longitudinal axis. The respective distal ends of
the two subparts face each other and are separated by said air gap.
[0044] For example, each arm 22, 24, 26 includes three air gaps 32, 34 and 36, preferably
having the same dimensions. However, this example is not limiting and, in alternative
embodiments, the number of air gaps and/or their dimensions could be chosen differently.
[0045] For example, the number and the dimensions of air gaps can be adjusted to manage
the magnetic flux coupling between the first and second core portions 14 and 16.
[0046] In the embodiments of the invention described herein, dividing the metal core 12
into two core portions 14 and 16 and allowing an airflow in the space 18 between said
core portions 14 and 16 provide a natural and efficient way of cooling the core assembly
2 and preventing overheating during operation.
[0047] As a result, the core assembly 2 can be suitably used in high frequency operations
(e.g., with frequencies higher than 10 kHz) without being prone to excessive overheating,
even though the core 12 is made of a low cost material such as silicon steel.
[0048] If needed, air gaps 32, 34 and 36 can be suitably shaped and arranged in the arms
of the core portions 14, 16 to mitigate or eliminate possible unwanted magnetic losses
and/or coupling that might occur between the core portions 14 and 16.
[0049] In accordance with some embodiments, the width of each air gap 32, 34 and 36 is higher
than or equal to 1mm, to avoid any unwanted magnetic saturation of the metal core
12 due to the proximity effect. Preferentially, the width of each air gap 32, 34 and
36 is higher than or equal to 2mm, to ensure a sufficient airflow and provide adequate
cooling.
[0050] However, the width of each air gap 32, 34 and 36 is preferentially lower than or
equal to 10mm, in order to limit the size of the metal core 12.
[0051] The embodiments and alternatives described above may be combined with each other
in order to generate new embodiments of the invention within the scope of the claims.
1. A coil assembly (2) comprising a plurality of coils (10) and a metal core (12), wherein
the core (12) is divided into a first core portion (14) and a second core portion
(16) spaced apart from each other by a space (18), the first and second core portions
(14, 16) having a planar shape and laying parallel with each other along a geometrical
plane, the first and second core portions (14, 16) being made from laminated iron
sheets, the first core portion (14) and the second portion (16) each comprising a
plurality of arms (22, 24, 26), the arms of the first core portion being aligned with
the arms of the second core portion, each coil surrounding an arm of the first core
portion and an arm of the second core portion, characterized in that the core (12) is configured to allow the passage of an air flow in the space (18)
between the first and second core portions (14, 16), in that the space (18) defines a distance (h18) separating the first and second core portions,
the distance (h18) being comprised between 1mm and 35mm, and in that the first and second core portions (14, 16) are held together by spacer elements
(21), said spacer elements (21) being preferably made from aluminum.
2. The coil assembly of claim 1, wherein the first and second core portions are offset
from each other along a direction perpendicular to said geometrical plane.
3. The coil assembly according to any of the previous claims, wherein the first and second
core portions (14, 16) are superimposed vertically on top of each other.
4. The coil assembly according to any of the previous claims, wherein the first and second
core portions (14, 16) have an identical shape.
5. The coil assembly according to any of the previous claims, wherein each arm (22, 24,
26) of the first and second core portions (14, 16) is divided into at least two subparts
separated from each other by an air gap (32, 34, 36).
6. A power conversion circuit (4) comprising a coil assembly (2), wherein said coil assembly
(2) is according to any of the previous claims.
1. Spulenanordnung (2), die eine Vielzahl von Spulen (10) und einen Metallkern (12) umfasst,
wobei der Kern (12) in einen ersten Kernabschnitt (14) und einen zweiten Kernabschnitt
(16) unterteilt ist, die durch einen Zwischenraum (18) voneinander beabstandet sind,
wobei der erste und der zweite Kernabschnitt (14, 16) eine ebene Form haben und parallel
zueinander entlang einer geometrischen Ebene liegen, der erste und der zweite Kernabschnitt
(14, 16) aus laminierten Eisenblechen hergestellt sind, wobei der erste Kernabschnitt
(14) und der zweite Abschnitt (16) jeweils eine Mehrzahl von Armen (22, 24, 26) umfassen,
wobei die Arme des ersten Kernabschnitts mit den Armen des zweiten Kernabschnitts
ausgerichtet sind, jede Spule einen Arm des ersten Kernabschnitts und einen Arm des
zweiten Kernabschnitts umgibt, dadurch gekennzeichnet, dass der Kern (12) so konfiguriert ist, dass er den Durchgang eines Luftstroms in dem
Raum (18) zwischen dem ersten und dem zweiten Kernabschnitt (14, 16) ermöglicht, dass
der Raum (18) einen Abstand (h18) definiert, der den ersten und den zweiten Kernabschnitt
trennt, wobei der Abstand (h18) zwischen 1 mm und 35 mm liegt, und dass der erste
und der zweite Kernabschnitt (14, 16) durch Abstandselemente (21) zusammengehalten
werden, wobei die Abstandselemente (21) vorzugsweise aus Aluminium hergestellt sind.
2. Spulenbaugruppe nach Anspruch 1, wobei der erste und der zweite Kernabschnitt in einer
Richtung senkrecht zur geometrischen Ebene gegeneinander versetzt sind.
3. Spulenanordnung nach einem der vorhergehenden Ansprüche, wobei der erste und der zweite
Kernabschnitt (14, 16) vertikal übereinander angeordnet sind.
4. Spulenanordnung nach einem der vorhergehenden Ansprüche, wobei der erste und der zweite
Kernabschnitt (14, 16) eine identische Form aufweisen.
5. Spulenanordnung nach einem der vorhergehenden Ansprüche, wobei jeder Arm (22, 24,
26) des ersten und zweiten Kernteils (14, 16) in mindestens zwei durch einen Luftspalt
(32, 34, 36) voneinander getrennte Unterteile unterteilt ist.
6. Leistungswandlerschaltung (4) mit einer Spulenanordnung (2), wobei die Spulenanordnung
(2) einem der vorhergehenden Ansprüche entspricht.
1. Ensemble de bobines (2) comprenant plusieurs bobines (10) et un noyau métallique (12),
dans lequel le noyau (12) est divisé en une première partie de noyau (14) et une deuxième
partie de noyau (16) espacées l'une de l'autre par un espace (18), les première et
deuxième parties de noyau (14, 16) ayant une forme plane et reposant parallèlement
l'une à l'autre le long d'un plan géométrique, les première et deuxième parties de
noyau (14, 16) étant fabriquées à partir de feuilles de fer laminées, la première
partie de noyau (14) et la deuxième partie (16) comprenant chacune une pluralité de
bras (22, 24, 26), les bras de la première partie de noyau étant alignés avec les
bras de la deuxième partie de noyau, chaque bobine entourant un bras de la première
partie de noyau et un bras de la deuxième partie de noyau, caractérisé en ce que le noyau (12) est configuré pour permettre le passage d'un flux d'air dans l'espace
(18) entre les première et deuxième parties de noyau (14, 16), en ce que l'espace (18) définit une distance (h18) séparant les première et deuxième parties
de noyau, la distance (h18) étant comprise entre 1 mm et 35 mm, et en ce que les première et deuxième parties de noyau (14, 16) sont maintenues ensemble par des
éléments d'espacement (21), lesdits éléments d'espacement (21) étant de préférence
fabriqués en aluminium.
2. Ensemble de bobines selon la revendication 1, dans lequel les première et deuxième
parties de noyau sont décalées l'une de l'autre le long d'une direction perpendiculaire
audit plan géométrique.
3. Ensemble de bobines selon l'une quelconque des revendications précédentes, dans lequel
les première et deuxième parties de noyau (14, 16) sont superposées verticalement
l'une sur l'autre.
4. Ensemble de bobines selon l'une quelconque des revendications précédentes, dans lequel
les première et deuxième parties de noyau (14, 16) ont une forme identique.
5. Ensemble de bobines selon l'une quelconque des revendications précédentes, dans lequel
chaque bras (22, 24, 26) des première et deuxième parties de noyau (14, 16) est divisé
en au moins deux sous-parties séparées l'une de l'autre par un espace d'air (32, 34,
36).
6. Circuit de conversion de puissance (4) comprenant un ensemble de bobines (2), dans
lequel ledit ensemble de bobines (2) est conforme à l'une quelconque des revendications
précédentes.