FIELD OF THE INVENTION
[0001] The present invention relates to an inductance device comprising at least two windings
wound on a common core and means for shielding a magnetic stray field. The invention
further relates to a filter device and a power converter comprising an inductance
device, in particular a coupled differential mode choke, with at least two windings
wound on a common core and means for shielding a magnetic stray field.
BACKGROUND OF THE INVENTION
[0002] In a power converter, for example an inverter for photovoltaic applications, an output
filter is used to reduce unwanted ripples in the output current to be fed into an
electrical supply grid. Such output filter usually comprises an inductance device
that may be configured as a coupled choke for differential currents. A coupled choke
comprises at least two windings wound on a common core and may be arranged at the
input and/or the output of the power converter such that a first winding of the coupled
choke is connected to a forward current path and a second winding is connected to
a return current path, wherein the forward and the return current path are configured
to transfer electric power input from a generator into the power converter or output
by the power converter into an electrical supply grid.
[0003] A magnetic flux is induced into the common core by a current input to or output by
the converter and running through the windings. Depending on the winding directions
of the windings and the current flow directions within the windings, the magnetic
flux induced by one winding may add either positively or destructively to the magnetic
flux induced by another winding. In particular, the coupled choke acts as a differential
mode choke having a significant inductance value for differential mode currents if
said magnetic fluxes add constructively for a differential current, i.e. for normal
currents running in anti-parallel direction through the input or output lines of the
converter and transferring the electrical power input to or output by the converter.
On the other hand, the coupled choke acts as a common mode choke having a significant
inductance value for common mode currents, if said magnetic fluxes add constructively
for common mode currents, i.e. for currents running in parallel through the input
or output lines of the converter.
[0004] In a known configuration of a coupled differential mode choke comprising a core of
rectangular cross section, two windings with identical number of turns and identical
winding directions relative to the perimeter of the core are placed on opposite legs
of the core. If the windings in such configuration carry differential mode currents
of the same magnitude, e.g. sinusoidal currents with π phase shift, the induced magnetic
flux produced by the first winding adds to the magnetic flux produced by the second
winding constructively. However, if the windings in such configuration carry common
mode currents, the induced magnetic flux produced by the first winding is compensated
by the opposite magnetic flux produced by the second winding. The latter situation,
in principle, is the same effect facilitated in a transformer wherein a current running
through a primary winding induces a current running through a secondary winding such
that the magnetic flux induced within the core by the current running through the
primary winding is compensated by the magnetic flux induced within the core by the
current running through the secondary winding
[0005] An inductance device such as a coupled differential mode choke may generate unwanted
magnetic stray fields in its periphery, in particular when being subjected to common
mode currents, and vice versa. Such stray fields may jeopardize the correct operation
of electronic components located close to the inductance device and have to be limited
according to electromagnetic interference (EMI) standards. Hence it is long known
that electromagnetic components in general may be shielded in order to minimize electromagnetic
interference with other components. A large variety of shielding setups to be applied
to chokes or transformers are described in the prior art, some of which are mentioned
in the following documents.
[0006] A very basic shielding setup was disclosed as early as 1944 in
CH230974, where an inductance device is enclosed by a shielding cage, said shielding cage
comprising electrically connected closed-loop windings which are oriented in parallel
to the magnetic stray field lines of the inductance coil. This setup may be considered
as a Faraday cage in a very basic version.
[0007] US3290634 discloses a transformer comprising a single band made of conductive material surrounding
a main core, yokes of the main core and a primary and a secondary coil, for reducing
the magnitude of magnetic stray fields generated by the transformer. Such magnetic
stray fields around the transformer are fields with a high energy density that mainly
arise from the power transfer mode during transformer operation. Hence the single
band experiences high amplitude currents and has to be dimensioned accordingly in
terms of material thickness and insulation means. Furthermore, in order to close an
electric path around the transformer, the end lines of the band have to be connected
to each other appropriately.
[0008] In view of the state of the art, there is still a need for an inductance device for
a power converter that comprises a sufficient shielding of magnetic fields generated
by currents flowing through coupled windings of the inductance device such that electromagnetic
compatibility of the inductance device is ensured, whereby the inductance device needs
to be easily manufacturable, reliably insulated and cost effective.
SUMMARY OF THE INVENTION
[0009] The invention provides an inductance device comprising the features of independent
claim 1, a filter device comprising the features of claim 7 and a power converter
comprising the features of claims 9 or 10. Preferred embodiments of the invention
are defined in the dependent claims.
[0010] An inductance device for a power converter comprises a core with a first leg, a second
leg oriented parallel to the first leg, a third leg and a fourth leg, wherein the
legs are in a rectangular arrangement. The inductance device further comprises a first
winding wound around the first leg and a second winding wound around the second leg.
An inductance device according to the present invention further comprises a third
winding comprising a short-circuited wire and being wound around an outer perimeter
of the inductance device as defined by the outer surfaces of the first winding and
the second winding, wherein a winding axis of the third winding is oriented parallel
to the first leg and the second leg of the core.
[0011] The third winding does not have any significant effect on the electrical or magnetical
properties of the inductance device if the first winding and the second winding are
subjected to a current that generates magnetic fields that sum up constructively within
the core. On the other hand, if the first winding and the second winding are subjected
to a current that generates magnetic fields that compensate each other within the
core, magnetic stray fields are generated outside the core which induce a current
in the third winding. Since the third winding is short-circuited, the current flowing
through the third winding generates a magnetic field outside the core that is oriented
in an opposite direction with regard to the magnetic stray field generated by the
current in the first winding and the second winding and thus compensates the magnetic
stray field. Hence, the resulting emission of magnetic stray fields by the inductance
device is significantly reduced by the third winding which may be implemented easily
at a very low design effort and low costs.
[0012] In other words, the third winding comprises a short-circuited wire and is wound around
the first leg and the second leg of the core onto the first winding and the second
winding, such that the third winding is oriented perpendicular to the first leg and
the second leg of the core. In such configuration, the inductance device comprises
a symmetry axis such that the first leg and the second leg are arranged axially symmetrical
with respect to the symmetry axis and the winding axis of the third winding coincides
or overlaps with the symmetry axis. The third winding does virtually not increase
the size of the inductance device and thus allows for compact design and cost reduction
of the inductance device as compared to conventional shielding methods.
[0013] In an embodiment of the inductance device the first winding and the second winding
each comprise a first end and a second end, wherein the respective first ends are
configured to be connected to respective input connections or to respective output
connections of the power converter such that magnetic fluxes generated inside the
core by a differential mode current flowing through the first winding and the second
winding add constructively. For example, the ends of the windings may be marked by
appropriate markings, geometrically encoded by comprising standardized connection
plugs, or geometrically arranged unambiguously, such that each end of the windings
may only be connected to a respective connection of a device the inductance device
is used in, e.g. a filter device or a power converter. Thereby a coupled differential
mode choke is obtained, wherein the third winding provides an effect in terms of a
magnetic shielding for common currents only and does not have any substantial effect
on the electrical or magnetical properties relevant to the regular operation of the
coupled differential mode choke for differential current.
[0014] In a further embodiment of the inductance device the individual turns of the third
winding are located directly adjacent to each other such that the third winding covers
the outer surfaces of the first winding and the second winding. By fully covering
the outer surfaces with respect to the symmetry axis of the inductance device, a third
winding with a maximum number of turns of the third winding is provided and an optimum
shielding effect is obtained.
[0015] In an alternative embodiment of the inductance device the third winding comprises
at least three turns equally spaced to each other, wherein the spacing between the
turns of the third winding is greater or equal to a wire diameter of the third winding.
While a third winding comprising a single turn only already provides a shielding effect
to a certain degree, a third winding with at least three turns provides a symmetrical
coverage of the perimeter of the inductance device and a significantly enhanced shielding
of the magnetic stray field.
[0016] The inductance device may comprises a casting compound covering the core, the first
winding, the second winding, and the third winding, wherein the third winding comprises
an insulation. The quality of the casting compound, especially the avoidance of any
voids within the casting compound, is ensured by tightly wrapping the turns of the
third winding such that spaces between the individual turn are provided where the
casting compound may freely flow into during the casting process.
[0017] In a further embodiment the inductance device comprises a fifth leg oriented parallel
to the first leg and the second leg such that the core is arranged in an El-type configuration,
wherein a fourth winding is wound around the fifth leg such that magnetic fluxes generated
by a three-phase differential mode current flowing through the first winding, the
second winding and the fourth winding add constructively. The first winding, the second
winding, and the fourth winding may be connected to a three-phase network, e.g. to
the three phase lines of a three phase power supply grid.
[0018] A filter device for a power converter according to the present invention comprises
an inductance device with the features as described in the preceding paragraphs, wherein
the first winding and the second winding of the inductance device are configured to
be connected to respective input connections and/or to respective output connections
of the power converter such that magnetic fluxes generated by a differential mode
current flowing through the first winding and the second winding add constructively.
For example, electrical connections of the filter device being connected to ends of
the windings of the inductance device may be marked by appropriate markings, geometrically
encoded by comprising standardized connection plugs, or geometrically arranged unambiguously,
such that each electrical connection of the filter device may only be connected to
a respective connection of a device the filter is used in, e.g. a power converter.
The filter device is thus configured as a differential mode filter that comprises
an inductance value effective to smooth a differential mode current. If the filter
device according to the invention is subjected to a common mode current, it generates
a significantly reduced magnetic stray field as compared to a conventional differential
mode filter without shielding being subjected to a common mode current. At the same
time, the filter device according to the invention is much smaller and easier to manufacture,
i.e. cheaper, than a differential mode choke comprising a shielding means as known
from the prior art.
[0019] A power converter according to the invention comprises an inductance device with
the features as described in the preceding paragraphs, wherein the first winding and
the second winding of the inductance device are connected to respective output connections
of the power converter such that magnetic fluxes generated by a differential mode
current flowing through the first winding and the second winding add constructively.
[0020] Besides the inductance device according to the invention, the power converter comprises
a variety of electronic components such as drivers, controllers, or communication
means. In a conventional power converter, these electronic components would either
have to be arranged at a distance to a inductance device generating magnetic stray
fields, such as a differential mode choke in an input or output filter, such that
the magnetic stray field does not harm the performance of the electronic devices,
or the inductance device would have to be shielded in order to prevent the magnetic
stray field to extent to the electronic devices in its vicinity. Using the inductance
device according to the invention within the power converter, the spatial separation
of electronic devices from the inductance device may be reduced, which enables a compact
design of the power converter. At the same time, the power converter may be build
much easier and cheaper due to the more compact design and due to the inductance device
itself being shielded appropriately such that the power converter does without bulky
shielding means around the inductance devices comprised in it.
[0021] In an embodiment of the invention, the power converter comprises a three-phase inductance
device comprising a fifth leg and a fourth winding as described above and a three-phase
inverter configured to output a three-phase current. The first winding, the second
winding, and the fourth winding of the inductance device are connected to respective
output connections of the power converter such that magnetic fluxes generated by a
differential mode current flowing through the first winding, the second winding and
the fourth winding add constructively. Using an inductance device according to the
invention in such three-phase power converter enables an even further reduction of
the size of the power converter as compared to a power converter comprising a conventional
three-phase inductance device such as an output filter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The invention may be better understood with reference to the following drawings.
The components in the drawings are not necessarily to scale, emphasis instead being
placed upon clearly illustrating the principles of the present invention. In the drawings,
like reference numerals designate corresponding parts throughout the several views.
- Fig. 1
- illustrates an power converter according to the prior art,
- Figs. 2a and 2b
- show an inductance device as known from the prior art being subjected to differential
mode currents and common mode currents, respectively,
- Fig. 3a and 3b
- show an inductance device according to the present invention being subjected to differential
mode currents and common mode currents, respectively,
- Fig. 4
- shows an embodiment of an inductance device according to the present invention in
an isometric view, and
- Fig. 5
- shows a further embodiment of an inductance device according to the present invention
in a top view.
DETAILED DESCRIPTION OF THE DRAWINGS
[0023] The power converter 10 depicted in
Fig. 1 comprises input connections 11 and output connections 12 and may be configured to
convert a direct current supplied at the input connections 11 into an alternating
current to be output via the output connections 12 and optionally vice versa. The
direct current may be supplied by a direct current source being connected to the input
connections 11. The alternating current may be fed into a power supply grid being
connected to the output connections 12. For that exemplary purpose, the power converter
10 further comprises a DC-DC converter 13 and an inverter 14. Furthermore, the power
converter 10 comprises buffer capacitors 15 for stabilizing an input voltage and an
intermediate voltage, respectively, a common mode choke 16 arranged at the input side
of the power converter 10, an output filter 17 comprising a filter capacitor 18 and
a coupled differential mode choke 19, and another common mode choke 16 arranged at
an output side of the power converter 10. If the power converter 10 is connected to
a power supply grid, the output filter 17 is configured to filter the output current
of the power converter 10 such that harmonics and common mode currents contained in
the alternating current generated by the inverter 14 are reduced to meet predefined
grid requirements.
[0024] Each of the common mode chokes 16 and the differential mode choke 19 may comprise
two windings placed on the same magnetic path, i.e. sharing the same core. For example,
the differential mode choke 19 may comprise one winding that may be connected to a
forward output current path of the power converter 10 and the other winding may be
electrically in series with a return current path. Such configuration provides current
path symmetry with regard to magnetic coupling of the windings of the coupled differential
mode choke 19.
[0025] In a configuration known from the prior art, the common mode chokes 16 as well as
the coupled differential mode choke 18 may comprise an inductance device 20 according
to the
Figs. 2a and 2b. The inductance device 20 comprises a core 21 comprising a magnetic material. The
core 21 comprises four legs 21 a, 21 b, 21 c, 21 d in a rectangular arrangement. A
first winding 22a comprising a first end 23a and a second end 24a is wound around
the first leg 21a. A second winding 22b comprising a first end 23b and a second end
24b is wound around and the second leg 21 b.
[0026] The first end 23a of the first winding 22a and the first end 23b of the second winding
22b are configured to be connected to the input connections 11 or to an output of
the inverter 14 of the power converter 10. The second end 24a of the first winding
22a and the second end 24b of the second winding 22b are configured to be connected
to the output connections 12, to an input of the DC-DC converter 13, or to an input
of the inverter 14 of the power converter 10. Since the inductance device 20 is setup
symmetrically with respect to the electrical properties of the first winding 22a and
the second winding 22b, it is apparent that the assignment of the first ends and the
second ends to the input side and the output side of the power converter 10 may be
exchanged as long as such exchange is done pairwise.
[0027] The inductance device 20 may be subjected to a differential mode current I
DM according to Fig. 2a, e.g. a current I
DM flowing through the first winding 22a from its first end 23a to its second end 24a
and, at the same time and with substantially the same amplitude, flowing through the
second winding 22b from its second end 23b to its first end 23a. The winding directions
of the windings 22a and 22b are configured such that said differential mode current
I
DM flowing through the windings 22a and 22b generates magnetic fields in the core 21
that are oriented in the same direction as seen along the perimeter of the core 21
and said magnetic fields add to each other constructively. This constructive addition
is depicted in Fig. 2a by arrows 25 representing a magnetic flux being substantially
confined within the legs 21a-d of the core 21. In other words, the differential mode
current I
DM produces cumulative magnetic flux that is closed in the magnetic core 21 while negligible
stray fields are produced outside the inductance device 20.
[0028] The inductance device 20 may alternatively or additionally be subjected to a common
mode current according to Fig. 2b, e.g. a current I
CM flowing through the first winding 22a from its first end 23a to its second end 24a
and, at the same time and with substantially the same amplitude, flowing through the
second winding 22b from its first end 23a to its second end 23b. If the inductance
device is connected at the output of the inverter 14 according to Fig. 1, such common
mode current may be generated in operation of the power converter 10 as a side effect
of periodic switching of power switches of the inverter 14. The common mode current
I
CM flowing through the windings 22a and 22b generates magnetic fields in the first leg
21 a and in the second leg 21b of the core 21, respectively, that are oriented in
the opposite direction as seen along the perimeter of the core 21 such that said magnetic
fields add to each other destructively. These magnetic fields are depicted in Fig.
2b by arrows 26a representing the magnetic flux within the legs 21 a and 21 b, respectively,
of the core 21. Note that there is substantially no magnetic flux within the legs
21c and 21 d of the core 21. Furthermore, since the magnetic flux lines 26a have to
be closed due to fundamental laws of electromagnetism, a substantial magnetic stray
field represented by the magnetic flux lines 26b is generated outside the core 21.
For the sake of comparison, the magnetical behaviour of the inductance device 20 when
being subjected to common mode currents is an equivalent to a rod inductor as the
surface integral of the current density within the winding cross section is 0. By
default, a rod inductor produces substantial stray field in its vicinity.
[0029] This magnetic stray field is relevant for EMI considerations and potentially hazardous
to the correct operation of electronic devices located in the periphery of the inductance
device. Hence there is a need to reduce the magnetic stray field outside the inductance
device as far as possible.
[0030] Figs. 3a and 3b show an inductance device 30 according to an embodiment of the present invention.
The inductance device 30 comprises a core 21 comprising four legs 21 a, 21 b, 21 c,
21 d in a rectangular arrangement. A first winding 22a comprising a first end 23a
and a second end 24a is wound around the first leg 21 a, and a second winding 22b
comprising a first end 23b and a second end 24b is wound around and the second leg
21 b. A third winding 31 is wound around an outer perimeter of the inductance device
30 such that the third winding 31 is wound around respective outer surfaces of the
first winding 22a and the second winding 22b. The winding axis of the third winding
31 is oriented parallel to the first leg 21a and the second leg 21b. Hence, the winding
axis of the third winding 31 is oriented parallel to the winding axes of the first
winding 22a and the second winding 22b, too.
[0031] The third winding is short-circuited by connecting the short-circuiting connection
points SC to each other; this connection is omitted in Figs. 3a and 3b for the sake
of clarity but rather implied by denoting the short-circuiting connection points SC
with the same reference sign SC.
[0032] Fig. 3a shows the inductance device 30 being subjected to a differential mode current
I
DM flowing through the first winding 22a and the second winding 22b. In comparison to
the inductance device 20 according to Fig. 2a, magnetic fields of similar strength
and orientation are generated in the core 21 by both windings. Hence, the third winding
31 has substantially no effect on the operation of the inductance device 30. In particular,
the inductivity of the inductance device 30 for differential mode currents is the
same as the inductivity of the inductance device 20 without the third winding 31.
[0033] In contrast, Fig. 3b illustrates the effect of the third winding 31 on the magnetic
fields generated in the periphery of inductance device 30 being subjected to a common
mode current I
CM flowing through the first winding 22a and the second winding 22b. The magnetic field
generated by the common mode current I
CM, in particular the magnetic field inside the legs 21a and 21b of the core 21 represented
by the magnetic flux lines 32a, induces a current I
S in the short-circuited third winding 31. This current I
S in turn generates a magnetic field represented by the magnetic flux lines 33 substantially
extending outside the inductance device 30. Such interaction of the common mode currents
I
CM in the first winding 22a and in the second winding 22b with induced currents I
S in the third winding 31 is similar to transformer operation.
[0034] A major part of the magnetic field 33 generated by the current I
S is located outside the inductance device 30. This part of the magnetic field 33 is
oriented in an opposite direction as compared to the magnetic stray field represented
by the magnetic flux lines 32a and 32b. The resulting total magnetic field strength
of the magnetic field located outside the inductance device 30 is the sum of the magnetic
stray field generated by the common mode current I
CM and the magnetic field generated by the current I
S within the short-circuited third winding 31. As a result of this summation, the total
magnetic field strength in the periphery of the inductance device 30 is significantly
reduced as compared to the magnetic field strength of the magnetic stray field as
represented by magnetic flux lines 26b generated by the common mode current I
CM outside the inductance device 20 according to Fig. 2b.
[0035] For an ideal implementation of the inductance device 30, the current density induced
in the third winding 31 should be equal to the current density of the common mode
current I
CM in the first winding 22a and in the second winding 22b, but in opposite direction,
such that the stray field of the inductance device 20 according to Fig. 2b and the
counteracting magnetic field generated by the current I
S induced in the third winding 31 completely eliminate each other. In a practical setup
an identity of the magnetic stray field and the magnetic field generated by the third
winding 31 is hardly achievable and the inductance device 30 will still generate a
residual stray field, but the strength of the residual stray field is significantly
reduced to a value that will not impede operation of other components in the vicinity
of the inductance device 30.
[0036] In order to further decrease high frequency radiated field emission, the short-circuiting
connection point SC may additionally be connected to one of the ends 23a, 23b, 24a,
24b of the first winding 22a or the second winding 22b. Additionally, a magnetic material,
e.g. a sheet or foil, may be arranged between the perimeter of the inductance device
30 and the third winding 31, i.e. between the outer surfaces of the first winding
22a and the second winding 22b and the inner surface of the third winding 31. Such
additional material may increase the common mode inductance value of the inductance
device 31 while the differential mode inductance value of the inductance device 31
is unaffected.
[0037] Figs. 4 and 5 show another embodiment of an inductance device according to the present invention.
In addition to the illustrative examples shown in Figs. 3a and 3b, it can be seen
from Figs. 4 and 5 that the third winding 31 comprises a wire being wrapped around
the first winding 22a and the second wining 22b. The third winding 31 is short-circuited
by connecting the ends of the wire at the short-circuiting connection point SC. An
electrically conductive joining of the two ends of the wire of the third winding 31
is much easier than, e.g. for a copper foil as known from the prior art.
[0038] While for an optimum shielding effect it is preferred to select the diameter of the
wire and the number of turns of the third winding 31 such that the third winding 31
completely covers the outer surfaces of the first winding 22a and the second winding
22b, such optimum shielding and hence such complete coverage may not be necessary
in each case. In contrast, the advantage of reduced effort, material and costs achievable
by wrapping the third winding 31 such that the individual turns are separated by a
significant distance may outweigh the disadvantage of a reduced shielding effect.
[0039] Moreover, the inductance device 30 may be completely encapsulated in a casting compound,
e.g. an electrically insulating material. While the first winding 22a and the second
winding 22b may be already enclosed in a proper casting, it may be beneficial to leave
a significant space between the individual turns of the third winding 31 in order
to enable the potting material to flow freely and cover the inductance device 30 completely,
i.e. without leaving voids which may occur between the third winding 31 and the first
winding 22a and/or the second winding 22b, respectively, if the third winding 31 completely
covers outer surfaces of the first winding 22a and the second winding 22b. The problem
of voids within the casting is especially eminent when using a third winding 31 made
of a single foil since a foil reduces the free flow of the potting material significantly
and may cause a problem with the potting adhesion while a third winding 31 made of
a wire does not constitute a significant barrier for the potting material.
[0040] The wire constituting the third winding 31 may be insulated by a non-conductive coating.
The diameter of the wire and the number of turns of the third winding 31 may be selected,
as a rule of thumb, such that the distance between adjacent turns of the third winding
31 at least equals the diameter of the wire such that the relevant perimeter of the
inductance device 30 is covered by the third winding 31 by 50 percent at most.
[0041] Simulations and laboratory tests were conducted with an inductance device 31 according
to the model depicted in Figs. 4 and 5 being subjected to common mode currents I
CM of 100 mA and frequency 100 kHz. The results showed that the magnetic field strength
in the vicinity the inductance device 30, i.e. at a distance where other electronic
components may be located, is reduced by 90 % as compared to the magnetic field strength
generated by a conventional inductance device 20 without a third winding 31. The magnetic
field strength may be further reduced by 99,5 % as compared to the conventional setup
when using a short-circuited copper foil wrapped around the inductance device 20;
however, the drawbacks of using a copper foil in terms of manufacturability and costs
by far outweigh the advantages achievable in terms of better shielding. In other words,
using a third winding 31 made of a short-circuited wire already provides a sufficient
shielding of the magnetic stray field of the inductance device 30 and additionally
provides a robust solution that is much easier to manufacture and thus significantly
cheaper.
[0042] Many variations and modifications may be made to the preferred embodiments of the
invention without departing substantially from the spirit and principles of the invention.
All such modifications and variations are intended to be included herein within the
scope of the present invention, as defined by the following claims. In particular,
preferred further developments of the invention result from the claims, the description
and the drawings. Advantages of features and of combinations of several features mentioned
in the introduction of the description are only exemplary and may come into effect
alternatively or cumulatively, without the necessity that the advantages have to be
achieved by embodiments of the invention. Further features may be taken from the drawings
- particularly from the depicted relative arrangement and operational connections
of several parts. The combination of features of different embodiments of the invention
and of features of different claims is also possible and is encouraged herewith. This
also applies to such features which are depicted in separate drawings or mentioned
in their description. These features may also be combined with features of different
claims.
LIST OF REFERENCE NUMERALS
[0043]
- 10
- Power converter
- 11
- Input connections
- 12
- Output connections
- 13
- DC-DC converter
- 14
- Inverter
- 15
- Buffer capacitor
- 16
- Common mode choke
- 17
- Output filter
- 18
- Filter capacitor
- 19
- Differential mode choke
- 20
- Inductance device
- 21
- Core
- 21a, 21b
- Leg
- 21c, 21d
- Leg
- 22a, 22b
- Winding
- 23a, 23b
- First End
- 24a, 24b
- Second End
- 25
- Magnetic flux line
- 26a, 26b
- Magnetic flux line
- 30
- Inductance device
- 31
- Shield Winding
- 32a, 32b
- Magnetic flux line
- 33
- Magnetic flux line
- IDM
- Differential mode current
- ICM
- Common mode current
- IS
- Shielding current
- SC
- Short circuit connection
1. Inductance device (30) for a power converter (10) comprising
- a core (21) with a first leg (21 a), a second leg (21 b) oriented parallel to the
first leg (21 a), a third leg (21c) and a fourth leg (21 d), wherein the legs (21a,
21b, 21c, 21 d) are in a rectangular arrangement; and
- a first winding (22a) wound around the first leg (21a) and a second winding (22b)
wound around the second leg (21 b),
characterised in that the inductance device (30) further comprises
a third winding (31) comprising a short-circuited wire and being wound around an outer
perimeter of the inductance device (10) as defined by the outer surfaces of the first
winding (22a) and the second winding (22b), wherein a winding axis of the third winding
(31) is oriented parallel to the first leg (21 a) and the second leg (21 b) of the
core (21).
2. Inductance device (30) according to claim 1, characterised in that the first winding (22a) and the second winding (22b) each comprise a first end (23a,
23b) and a second end (24a, 24b), wherein the respective first ends (23a, 23b) are
configured to be connected electrically in series to respective input connections
(11) or to respective output connections (12) of the power converter such that magnetic
fluxes (25) generated inside the core (21) by a differential mode current (IDM) flowing through the first winding (22a) and the second winding (22b) add constructively.
3. Inductance device (30) according to claim 1 or claim 2, characterised in that individual turns of the third winding (31) are located directly adjacent to each
other such that the third winding (31) covers the outer surfaces of the first winding
(22a) and the second winding (22b).
4. Inductance device (30) according to claim 1 or claim 2, characterised in that the third winding (31) comprises at least three turns equally spaced to each other,
wherein the spacing between the turns of the third winding (31) is greater or equal
to a wire diameter of the third winding (31).
5. Inductance device (30) according to any of the preceding claims, characterised in that the inductance device (30) comprises a casting compound covering the core (21), the
first winding (22a), the second winding (22b), and the third winding (22c), wherein
the third winding comprises an insulation.
6. Inductance device (30) according to any of the preceding claims, characterised in that the core (21) of the inductance device (30) comprises a fifth leg oriented parallel
to the first leg (21 a) and the second leg (21 b) such that the core (21) is arranged
in an El-type configuration, wherein a fourth winding is wound around the fifth leg
such that magnetic fluxes generated by a three-phase differential mode current (ICM) flowing through the first winding (22a), the second winding (22b) and the fourth
winding add constructively.
7. Filter device (17) for a power converter (10) comprising an inductance device (30)
according to any of the preceding claims, wherein the first winding (22a) and the
second winding (22b) of the inductance device (30) are configured to be connected
to respective input connections (11) and/or to respective output connections (12)
of the power converter (10) such that magnetic fluxes (25) generated by a differential
mode current (IDM) flowing through the first winding (22a) and the second winding (22b) add constructively.
8. Power converter (10) comprising an inductance device (30) according to any of the
claims 1 to 5, wherein the first winding (22a) and the second winding (22b) of the
inductance device (30) are connected to respective output connections (12) of the
power converter (10) such that magnetic fluxes (25) generated by a differential mode
current (IDM) flowing through the first winding (22a) and the second winding (22b) add constructively.
9. Power converter (10) comprising an inductance device (30) according to claim 6, wherein
the power converter (10) comprises a three-phase inverter (14) configured to output
a three-phase current and wherein the first winding (22a), the second winding (22b),
and the fourth winding of the inductance device (30) are connected to respective output
connections (12) of the power converter (10) such that magnetic fluxes (25) generated
by a differential mode current (IDM) flowing through the first winding (22a), the second winding (22b) and the fourth
winding add constructively.