U.S. patent application number 15/542138 was filed with the patent office on 2018-03-15 for winding for an electrical machine.
The applicant listed for this patent is UNIVERSITE CATHOLIQUE DE LOUVAIN. Invention is credited to Francois Baudart, Bruno Dehez.
Application Number | 20180076678 15/542138 |
Document ID | / |
Family ID | 52273032 |
Filed Date | 2018-03-15 |
United States Patent
Application |
20180076678 |
Kind Code |
A1 |
Dehez; Bruno ; et
al. |
March 15, 2018 |
Winding for an electrical machine
Abstract
Winding for an electrical machine having an inductor with pole
pitch .tau..sub.p, having a plurality of groups of turns
intercepting a fraction of a magnetic field, each group comprising
a first subgroup of turns and a second subgroup of turns of same
phase at a distance equal to .tau..sub.p, the turns of the first
subgroup being connected in such a way that a current may flow in
same direction in all turns of said subgroup, the turns of the
second subgroup being connected in such a way that a current may
flow in same direction in all turns of said subgroup, a turn of the
first subgroup being connected to a turn of the second subgroup in
such a way that the direction of said current in the first group is
opposite to the direction of the current in the second
subgroup.
Inventors: |
Dehez; Bruno; (Liernu,
BE) ; Baudart; Francois; (Bourlers, BE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
UNIVERSITE CATHOLIQUE DE LOUVAIN |
Louvain-la-Neuve |
|
BE |
|
|
Family ID: |
52273032 |
Appl. No.: |
15/542138 |
Filed: |
January 7, 2016 |
PCT Filed: |
January 7, 2016 |
PCT NO: |
PCT/EP2016/050229 |
371 Date: |
July 7, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H02K 2203/03 20130101;
H02K 3/26 20130101; H01F 27/323 20130101; H01F 27/2804 20130101;
H02K 3/28 20130101 |
International
Class: |
H02K 3/28 20060101
H02K003/28; H01F 27/28 20060101 H01F027/28; H01F 27/32 20060101
H01F027/32 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 7, 2015 |
EP |
15150392.7 |
Claims
1-20. (canceled)
21. A winding for an electrical machine adapted for interacting
with an inductor structure providing a sequence of at least one
pair of north and south magnetic poles along a length, producing a
magnetic field, the poles being separated by a pole pitch distance
r.sub.p along the length, the winding comprising: one or more
phases, the number of phases being n; and a plurality of groups of
pairs of conductors, each pair of conductors forming a turn
intercepting a fraction of the magnetic field, wherein a first
group of the plurality of groups includes: a first subgroup of
turns of one phase having a spread along the length inferior or
equal to .tau..sub.p/n; and a second subgroup of turns of same
phase having a spread along the length inferior or equal to
.tau..sub.p/n, at a distance equal to .tau..sub.p from first
subgroup along the length, the turns of the first subgroup being
connected such that a current may flow in same direction in all
turns of the first subgroup, the turns of the second subgroup being
connected such that a current may flow in same direction in all
turns of the second subgroup, and a turn of the first subgroup
being connected to a turn of the second subgroup such that the
direction of the current in the first subgroup is opposite to the
direction of the current in the second subgroup, and wherein the
winding is adapted for moving in relation to the inductor structure
along the length.
22. The winding according to claim 21, the first subgroup and the
second subgroup having same number t of turns.
23. The winding according to claim 21, a first conductor being
arranged in a first layer and a second conductor being arranged in
a second layer.
24. The winding according to claim 23, the first and second layer
being separated by an intermediate layer, the intermediate layer
having a height perpendicular to the length, an extremity of the
first conductor being connected to an extremity of the second
conductor through an opening in the intermediate layer.
25. The winding according to claim 24 wherein the first,
intermediate, and second layers are layers of a PCB.
26. The winding according to claim 24, wherein each of the pairs
conductors of a turn form a loop.
27. The winding according to claim 26, wherein a conductor of the
first layer of one turn is extended along its length and connected
through the intermediate layer to a conductor of the second layer
having a corresponding extension to form a connection between two
adjacent turns, the two adjacent turns being at a distance in the
length direction.
28. The winding according to claim 26, wherein each of the first
and second subgroups of turns have a number t of turns, first
conductors of the first layer being numbered from 1 to t in the
length direction, second conductors of the second layer being also
numbered from 1 to t in the length direction, and a first conductor
i of the first layer being connected at the upper end of the first
conductor i to a second conductor t-i of the second layer through a
horizontal shortcut connection extending along the length
direction, at decreasing heights, for i=1 to i=t-1; and the first
conductor i of the first layer being connected at the lower end of
the intermediate layer to a second conductor t-i+1 of the second
layer through a horizontal shortcut connection extending along the
length direction of the intermediate layer, at increasing heights,
for i=1 to i=t, the horizontal shortcut connections being in at
least one of the first layer or the second layer.
29. The winding according to claim 26, wherein each of the first
and second subgroup of turns have a number t of turns, first
conductors of a first subgroup being numbered from 1 to t in the
length direction, second conductors of the subsequent second
subgroup also being numbered from 1 to t in the length direction;
first conductor i of the first layer being replaced by a first
vertical shortcut extending in a vertical direction for an extent
of the first conductor i overlapping a second conductor 1 of the
second layer, for i going from the first conductor i having an
overlap to a last conductor t; second conductor i of the second
layer being replaced by a second vertical shortcut extending in the
vertical direction for an extent of the second conductor i
overlapping conductor t of the first layer, for i going from the
first conductor 1 to the last conductor having an overlap; the
first and second vertical shortcut connections being in at least
one of the first layer or the second layer, except for shortcut
number t of the first subgroup and shortcut number 1 of the second
subgroup, which are in the first layer and the second layer
respectively.
30. The winding according to claim 24, wherein each of the pairs of
conductors form a turn form a wave.
31. The winding according to claim 30, wherein a plurality of turns
are connected in series and a plurality of series of turns are
arranged successively at a distance in the length direction, a
first conductor of the first layer of one turn of one series is
extended along its length and connected through the intermediate
layer to a second conductor of a successive series of the second
layer, having a corresponding extension, so as to form a connection
between two successive series, the two successive series being at a
distance in the length direction.
32. The winding according to claim 30, wherein first conductors of
the first subgroup of turns are interrupted at mid height and
connected through the intermediate layer with corresponding second
conductors of the second subgroup, at both ends of the length to
form a continuous circuit.
33. The winding according to claim 30, wherein a plurality of
series of turns are arranged successively at a distance in the
length direction, the plurality of series is a number t of series,
adjacent conductors being numbered from 1 to t in both the first
and second layer, and first conductors 1 to t of the first layer
are connected at the upper end to second conductors t to 1
respectively of the second layer through t horizontal shortcut
connections extending along the length direction, at decreasing
heights, and second conductors 1 to t of the second layer being
connected at the lower end to first conductor t to 1 of the first
layer through a horizontal shortcut connections extending along the
length direction, at increasing heights, except for one of the
plurality of series where first conductors 1 to t-1 of the first
layer are connected at the upper end to second conductors t-1 to 1
respectively of the second layer through t-1 horizontal shortcut
connections extending along the length direction, at decreasing
heights, conductors t of the first and second layer being connected
to terminals.
34. The winding of claim 30, wherein a plurality of series of turns
are arranged successively at a distance in the length direction,
the plurality of series is a number t of series, adjacent
conductors being numbered from 1 to t in the length direction in
both the first and second layer, obtainable by: providing a
connection of part of the first conductor of the first subgroup
extending on upper part of the intermediate layer to part of the
second conductor of the second subgroup extending on lower part of
the intermediate layer, through the intermediate layer, at
mid-height of the intermediate layer; redirecting respectively (a)
part of first conductors 2 to t-1 of the first subgroup extending
on an upper part of the intermediate layer up to a point of overlap
with a second conductor 1 of the second subgroup to (b) part of
second conductors 2 to t-1 of the second subgroup extending on the
lower part of the intermediate layer from a point of overlap with a
first conductor 1 of first subgroup (c) through a vertical shortcut
connection extending in a vertical direction, the vertical shortcut
connection being in at least one of the first layer or the second
layer; redirecting (a) part of a first conductor t of the first
subgroup extending on the upper part of the intermediate layer up
to the point of overlap with the second conductor 1 of the second
subgroup to (b) part of the first conductor 1 of the first subgroup
extending on the lower part of the intermediate layer from the
point of overlap with a second conductor t of the second subgroup
(c) through the vertical shortcut connection extending in the
vertical direction, the vertical shortcut connection being in at
least one of the first layer or the second layer for conductors 2
to t-1 and in the first layer only for conductor t; and performing
same operations after a rotation of 180.degree. around a vertical
axis, the vertical shortcut being applied on first conductor t.
35. The winding according to claim 28, wherein a plurality of vias
connect at least one of corresponding vertical or horizontal
shortcut connections in the first and second layer of the
intermediate layer.
36. Use of the winding of claim 21, where the winding is in an
elongated configuration, in a linear electrical machine.
37. The use according to claim 36, where the winding is wound up in
a direction perpendicular to the length.
38. Use of the winding of claim 21, where the winding is wound up
in the length direction, in a cylindrical configuration, in a
rotating electrical machine.
39. Use of the winding of claim 21, where the winding is wound up
in a disc-shaped form, in a flat configuration, in a rotating
electrical machine having an axial field.
40. Use of the winding of claim 21, wherein one or more windings
are superposed with an insulating layer being located between two
superposed windings.
Description
FIELD OF THE INVENTION
[0001] The invention relates to a winding for an electrical
machine.
DESCRIPTION OF PRIOR ART
[0002] Electrical machines exist under many forms. These machines
can be generators, producing electrical energy from mechanical
energy, or motors, producing mechanical energy from electrical
energy. Rotating machines have a rotor rotating around an axis in
relation to a stator. Linear machines have a static element and a
moving element moving linearly with respect to the static element.
The present invention relates to electrical machines having an
inductor producing a magnetic field and an armature winding wherein
currents may flow. When the inductor is the rotor of a rotating
electrical machine and is a permanent magnet, no brushes are needed
for accessing the current in the armature winding. Rotating
electrical machines may comprise an inductor producing a magnetic
field directed mainly radially, with a winding having a generally
cylindrical shape. Rotating electrical machines may also comprise
an inductor producing a field directed mainly axially, with a
winding having a generally disc-shape. Linear electrical machines
may comprise an inductor producing a magnetic field directed mainly
perpendicular to the direction of the movement and oriented towards
the armature winding, this winding having a generally rectangular
shape.
[0003] A winding for a slotless brushless-DC motor (BLDC motor) is
known from "B. Dehez, M. Markovic, Y. Perriard, "Analysis and
comparison of classical and flex-PCB slotless windings in BLDC
motors," Electrical Machines and Systems (ICEMS), 2012 15th
International Conference on, pp. 1-6, 21-24 Oct. 2012". This
document describes the general structure of a BLDC motor. A
comparison is made between a classic copper-wire winding, and a
Flex-PCB winding having a simple shape (a three segment either
skewed (wave) or rhombic (lap) winding) showing a potential 30%
improvement in power density of the Flex-PCB winding over the
classic copper-wire winding. However, no attempt is made at finding
a design with optimal performance.
SUMMARY OF THE INVENTION
[0004] It is an object of the present invention to provide a
winding for an electrical machine having an improved efficiency
or/and an improved torque density (rotating machine) or force
density (linear machine). The efficiency may be defined as the
ratio of delivered power to absorbed power. In a motor, the
delivered power is the mechanical power available at the motor
shaft (or Force X speed for a linear motor), and the absorbed power
is the electrical power absorbed by the winding. In a generator,
the delivered power is the electrical power provided at the winding
and the absorbed power is the mechanical power provided to the
shaft (or Force X speed for a linear generator). The losses are
mainly related to the electrical resistance of the winding. It is
therefore an object of the present invention to provide a winding
minimising these losses, while delivering a given high power when
used in an electrical machine. The torque or force density may be
defined as the ratio of the torque or force, respectively produced
by an electrical machine and its weight. The weight of an
electrical machine is mainly determined by the Joule losses arising
in the armature windings. For a current of given amplitude
circulating in the armature windings, the Joule losses are directly
proportional to their electrical resistance while the torque or
force is directly proportional to the amplitude of the magnetic
flux intercepted by these windings and generated by the inductor.
It is therefore an object of the present invention to provide a
winding minimising the electrical resistance, while maximising
amplitude of the magnetic flux intercepted by these windings and
generated by the inductor.
[0005] The invention is defined by the independent claims. The
dependent claims define advantageous embodiments.
[0006] According to a first aspect of the invention there is
provided a winding for an electrical machine adapted for
interacting with an inductor structure providing a sequence of at
least one pair of north and south magnetic poles along a length,
producing a magnetic field, said poles being separated by a pole
pitch distance .tau..sub.p along said length, the winding
comprising one or more phases, the number of phases being n. The
winding is adapted for moving in relation to the inductor structure
along said length. The winding has a plurality of groups of pairs
of conductors, each pair of conductors forming a turn intercepting
a fraction of the magnetic field. A group comprises a first
subgroup of turns of one phase having a spread along said length
inferior or equal to .tau..sub.p/n, and a second subgroup of turns
of same phase having a spread along said length inferior or equal
to .tau..sub.p/n, at a distance equal to .tau..sub.p from first
subgroup along said length. The turns of the first subgroup are
connected in such a way that a current may flow in same direction
in all turns of said subgroup, the turns of the second subgroup
being connected in such a way that a current may flow in same
direction in all turns of said subgroup, a turn of the first
subgroup being connected to a turn of the second subgroup in such a
way that the direction of said current in the first group is
opposite to the direction of the current in the second subgroup.
The first subgroup and the second subgroup may have same number t
of turns.
[0007] Preferably, said pairs of conductors comprise first
conductors arranged in a first layer and second conductors arranged
in a second layer.
[0008] Said first and second layers may be separated by an
intermediate layer. The intermediate layer may advantageously be
insulating. One extremity of a first conductor is connected to an
extremity of a corresponding second conductor through an opening in
said intermediate layer.
[0009] In a preferred embodiment of the invention, said first,
intermediate and second layers are layers of a PCB.
[0010] In the lap version of the invention, each of said pairs of
conductors of a turn form a loop. The entry and exit terminal of
the turns may be in close vicinity to each other. The conductors of
the winding may show a line of symmetry, the symmetry axis being a
line along the length of the intermediate layer, at mid-height of
the intermediate layer.
[0011] A conductor of the first layer of one turn may be extended
along its length and connected through said intermediate layer to a
conductor of the second layer, having a corresponding extension, so
as to form a connection between two adjacent turns, the two
adjacent turns being at a distance in the length direction.
[0012] In a first improvement of the invention, each of said first
and second subgroup of turns having a number t of turns, first
conductors of the first layer being numbered from 1 to t in the
length direction, second conductors of the second layer being also
numbered from 1 to t in the length direction, first conductor i of
the first layer is connected at the upper end of said conductor to
second conductor t-i of the second layer through a horizontal
shortcut connection extending along the length direction, at
decreasing heights, for i=1 to i=t-1; and first conductor i of the
first layer is connected at the lower end of said conductor to
second conductor t-i+1 of the second layer through a horizontal
shortcut connection extending along the length direction, at
increasing heights, for i=1 to i=t. Said horizontal shortcut
connections may be arranged in said first and/or in said second
layer.
[0013] In a second improvement of the invention, each of said first
and second subgroups of turns having a number t of turns, first
conductors of a first subgroup being numbered from 1 to t in the
length direction, second conductors of the subsequent second
subgroup being also numbered from 1 to t in the length
direction;
first conductor i of the first layer is replaced by a vertical
shortcut extending in the vertical direction for the extent of said
conductor overlapping second conductor 1 of the second layer, for i
going from the first conductor having an overlap, to the last
conductor t; and second conductor i of the second layer is replaced
by a vertical shortcut extending in the vertical direction for the
extent of said conductor overlapping conductor t of the first
layer, for i going from the first conductor 1 to the last conductor
having an overlap. These vertical shortcut connections may be
arranged in said first and/or second layer, except for shortcut
number t of first subgroup and shortcut number 1 of second subgroup
which are only in first and second layer respectively.
[0014] In the wave version of the invention, each of said pairs of
conductors of a turn form a wave. The entry and exit terminals of
the turns may be at a distance near 2*.tau..sub.p along said length
of each other. The conductors may show a point of symmetry, the
reflection point being at mid-height of the intermediate layer.
[0015] A plurality of turns may be connected in series and a
plurality of series of turns may be arranged successively at a
distance in the length direction, a first conductor of the first
layer of one turn of one series being extended along its length and
connected through said intermediate layer to a second conductor of
a successive series of the second layer, having a corresponding
extension, so as to form a connection between two successive
series, the two successive series being at a distance in the length
direction.
[0016] In a preferred version of the invention, first conductors of
the first subgroup of turns are interrupted at mid height and
connected through said intermediate layer with corresponding second
conductors of the second subgroup, at both ends of said length, so
as to form a continuous circuit.
[0017] In said first improvement of the invention, a plurality of
series of turns are arranged successively at a distance in the
length direction, said plurality of series is a number t of
series,
adjacent conductors being numbered from 1 to t in both the first
and second layer, and first conductor i of the first layer is
connected at the upper end to second conductor t+1-i of the second
layer through a horizontal shortcut connections extending along the
length direction, at decreasing heights, for i=1 to i=t, and second
conductor i of the second layer being connected at the lower end to
first conductor t+1-i of the first layer through a horizontal
shortcut connections extending along the length direction, at
increasing heights, for i=1 to i=t, except for one of the said
plurality of series where first conductor i of the first layer is
connected to second conductor t-i of the second layer through a
horizontal shortcut connection extending along the length
direction, at decreasing heights, for i=1 to i=t-1, conductors t of
the first and second layer being connected to terminals.
[0018] In said second improvement of the invention, wherein a
plurality of series of turns are arranged successively at a
distance in the length direction, said plurality of series is a
number t of series, adjacent conductors being numbered from 1 to t
in the length in both the first and second layer, the winding is
obtainable by modifications of the winding of the wave version of
the invention, the modifications comprising [0019] providing a
connection of part of first conductor number 1 of first subgroup
extending on upper part of intermediate layer to part of second
conductor number 1 of second subgroup extending on lower part of
intermediate layer, through said intermediate layer, at mid-height
of said intermediate layer; [0020] redirecting respectively [0021]
(a) part of first conductors number 2 to number t-1 of said first
subgroup, extending on upper part of intermediate layer up to the
point of overlap with second conductor number 1 of second subgroup
to [0022] (b) part of second conductors number 2 to number t-1 of
second subgroup extending on lower part of intermediate layer from
the point of overlap with first conductor number 1 of first
subgroup [0023] (c) through a vertical shortcut connection
extending in a vertical direction said a vertical shortcut
connection being in first and/or in second layer; [0024]
redirecting [0025] (a) part of first conductor number t of said
first subgroup, extending on upper part of intermediate layer up to
the point of overlap with second conductor number 1 of second
subgroup to [0026] (b) part of first conductor number 1 of first
subgroup extending on lower part of intermediate layer from the
point of overlap with second conductor number t of second subgroup
[0027] (c) through a vertical shortcut connection extending in a
vertical direction said a vertical shortcut connection being in
first layer; [0028] Performing similar operations after a rotation
of 180.degree. around a vertical axis being the vertical shortcut
applied on first conductor t. The above connections and
redirections, with respect to both the wave and lap version of the
winding, are such that a current flowing in a conductor will flow
to a conductor whereto it is connected or redirected. Unused parts
of conductors of the original wave or lap winding wherefrom the
winding according to the second improvement are obtained are
removed.
[0029] Preferably, in the winding according to the first and second
improvement of the invention, i.e. the windings having vertical
and/or horizontal shortcuts, these shortcuts may extend on first
and second layer, except where explicitly not allowed. Having two
shortcut conductors in parallel reduces the overall resistance of
the winding, and therefore improves the efficiency. In these cases,
a plurality of vias may be connecting said corresponding vertical
and/or horizontal shortcut connection in the first and second
layer.
[0030] Preferably, one or more windings are superimposed with an
insulating layer being located between two superimposed
windings.
[0031] According to a second aspect, the invention is related to
the use of these windings in electrical machines. Windings in an
elongated configuration may be used in a linear electrical machine.
When wound up in a direction perpendicular to the length, the
linear electrical machine may be a cylindrical winding travelling
along a linear magnet having a radial field, inside the cylinder.
When the winding is wound up in the length direction, in a
cylindrical configuration, the winding may be used in a rotating
electrical machine, having a radial field. When wound up in a
disc-shaped form, in a flat configuration, the winding may be used
in a rotating electrical machine having an axial field.
SHORT DESCRIPTION OF THE DRAWINGS
[0032] These and further aspects of the invention will be explained
in greater detail by way of examples and with reference to the
accompanying drawings in which:
[0033] FIG. 1 is a schematic representation of a lap winding
according to the prior art.
[0034] FIG. 2 is a schematic representation of a wave winding
according to the prior art.
[0035] FIG. 3 is a schematic representation of a lap winding
according to an embodiment of the invention.
[0036] FIG. 4 is a schematic representation of a wave winding
according to an embodiment of the invention.
[0037] FIG. 5 is a schematic representation of a lap winding
according to a first improvement of the embodiment of the
invention.
[0038] FIG. 6 is a schematic representation of a wave winding
according to same first improvement of the embodiment of the
invention.
[0039] FIG. 7 is a schematic representation of a lap winding
according to a second improvement of the embodiment of the
invention.
[0040] FIG. 8 is a schematic representation of a wave winding
according to same second improvement of the embodiment of the
invention.
[0041] FIG. 9 is a schematic representation of a lap winding
combining first and second improvements of the embodiment of the
invention.
[0042] FIG. 10 is a schematic representation of a wave winding
combining first and second improvement of the embodiment of the
invention.
[0043] FIG. 11 is a schematic representation of a wave winding
having a third improvement of the embodiment of the invention.
[0044] FIG. 12 is a schematic representation of a wave winding
having a third improvement of the embodiment of the invention in
combination with the first and second improvement of the
invention.
[0045] FIG. 13 is a schematic representation of a lap winding
combining first and second improvement of the embodiment of the
invention for use in a rotating electrical machine having an axial
field.
[0046] The drawings of the figures are neither drawn to scale nor
proportioned. Generally, identical components are denoted by the
same reference numerals in the figures.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0047] In all the examples of the prior art and of the invention
discussed herein, a first conductor 61, represented as a continuous
line is connected to a second conductor 62, represented as dashed
lines so as to form a turn. Conductors 61, 62 may be straight
lines, broken lines or curves.
A pair of conductors 61, 62 of a turn may for a loop. In this case,
the conductors may show a line of symmetry, with respect to a line
passing through their midpoint, and form lap windings, as shown in
FIGS. 1, 3, 5, 7, and 9. The line at mid-height of the windings is
represented on the drawings as a dotted line at the left and right
end of the windings. Alternatively, a pair of conductors 61, 62 of
a turn may for a wave. In this case, the conductors may show a
point of symmetry, and form wave windings, as shown on FIGS. 2, 4,
6, 8, 10, 11 and 12. In a first embodiment of the invention, the
conductors may be wires or rods insulated from each other by many
means known in the art. For example, the conductors may be coated
with an insulating material. Also, the conductors may be wrapped
around or in a support that may be insulating. In a second
embodiment of the invention, the first conductors 61 are in one
layer and the second conductors 62 are in a second layer,
preferably separated from each other by an insulating layer. These
conductors may be obtained by cutting out from sheets of conductive
material. The cut-out may be performed by known techniques such as
mechanical cutting, laser cutting or chemical attack. The
connection of a first conductor 61 of the first layer to a second
conductor 62 of the second layer may then be obtained by an opening
in the insulating layer through which the conductors are contacted
or soldered. These conductors may also be tracks printed on both
sides of a printed-circuit board (PCB). The connection of a first
conductor 61 on a first side of the PCB to a second conductor 62 on
the second side of the PCB may then be realised by a via 43, i.e. a
hole through the PCB, containing conductive material. The term
"via" is used herein for designating the different connecting means
of a first conductor 61 to a second conductor 62. Vias 43 are
represented on the figures by a little circle. All these solutions
are well knows in the art. In all the examples discussed, the
length direction will be the direction from left to right of the
figure and the height direction, the direction from the bottom to
the top of the figure. The windings are represented as flat
structures, as this will be the case for linear motors or
generators. The windings may also be wound up in a cylindrical
fashion one or more times along the length direction, for use in a
rotating electrical machine having a radial magnetic field. The
windings may also be wound up in a cylindrical fashion one or more
times along a direction perpendicular to the length direction, for
use in a linear tubular electrical machine having a radial magnetic
field. The winding may also be wound up in a disc fashion, for use
in an electrical machine having an axial magnetic field. The
"length" is then to be understood as the azimuthal angular
distance. When the winding is wound up more than one time, or when
a plurality of windings are superimposed, a fourth insulating, and
optionally adhesive, sheet may be inserted between each winding
layer in order to avoid unwanted electrical short circuits between
winding turns/loops.
[0048] FIG. 1 is a schematic representation of an example of a lap
winding for an electrical machine according to the prior art. A
first conductor 61 having a line symmetry with respect to a line
represented by the dots at the left and at the right of the figure
is connected to a second conductor 62 through a via 43 at the
bottom of the figure to form a turn. A plurality of such turns (in
this example 10 turns) are connected in series so as to form a
group of turns, having a current entry terminal 44 and a current
exit terminal 45. Successive turns are displaced with respect to
each other in the length direction. This may be obtained by
extending the first and second conductors beyond their height L1 up
to a height L2, and connecting a turn to an adjacent turn through a
via 43 at the height L2. FIG. 1 displays a three phase winding, a
first phase being drawn in bold line and the other two phases in
thin lines. The inductor structure providing a magnetic field is
represented schematically as a bar, and shows two North poles and
two South poles. This inductor structure is represented for clarity
at the bottom of the winding, but is overlapping the winding, so
that the turns intercept the magnetic field. The electrical machine
is designed in such a manner that the winding may move in relation
to the magnet structure in the length direction. The separation
distance in the length direction between a north pole and a south
pole is .tau..sub.p. As can be seen in FIG. 1, the distance between
two successive groups of a phase in a conventional winding is 2
.tau..sub.p such that these two groups intercept the same field,
both in sign and amplitude. The extent of a group in the length
direction is 2 .tau..sub.p divided by the number of phases. This
condition is required for preventing an overlap of successive
groups of turns. Current exit terminal 45 of one group may be
connected to current entry terminal 44 of a successive group of
same phase, so that currents in the conductors flow in the
directions suggested by the arrows. The prior art winding of FIG. 1
is discussed more in detail at paragraphs [0030] and FIG. 7a of
WO2014/207174.
[0049] FIG. 2 is a schematic representation of an example of a
winding for an electrical machine according to the prior art,
similar to FIG. 1 with the difference that the conductors 61, 62
form wave turns. The conductors 61, 62 are formed as straight
lines, but may also be formed as polygonal lines or curves, as
shown in other examples. Here, as in FIG. 1, the distance between
two groups is 2 .tau..sub.p, and the extent of a group in the
length direction is 2 .tau..sub.p/3
[0050] FIG. 3 is a schematic representation of a lap winding
according to an embodiment of the invention. With respect to the
winding of FIG. 1, the winding of FIG. 3 has been modified as
follows: the group of turns has been divided in a first subgroup 81
of turns, and a second subgroup of turns 82. Second subgroup 82 is
located from first subgroup 81 at a distance .tau..sub.p in the
length direction. The extent of a subgroup in the length direction
is .tau..sub.p divided by the number of phases, i.e half the extent
of a group in the winding of FIG. 1. This condition is required for
preventing an overlap of successive subgroups of turns. Current
entry/exit terminals 44/45 of the first subgroup, and 44'/45' of
the second subgroup are in opposite orders so that a current
flowing in conductor 61 of first subgroup would flow in opposite
direction in corresponding conductor 61' of second subgroup. This
condition can be met when current exit terminal 45 of one subgroup
is connected to current entry terminal 44' of another successive
subgroup of same phase. As can be seen on FIG. 3, when a first
subgroup intercepts the field of a north pole, a subsequent second
subgroup of same phase intercepts the field of a south pole. The
inventors have determined that this winding according to the
invention has an torque or force density improved by approximately
15% with respect to corresponding winding of the prior art of FIG.
1 having same characteristics, for a three-phase winding. This
improvement results from the fact that the turns of a phase
intercept a magnetic flux, and therefore generate an electromotive
force, whose phase spreading is reduced by a factor of two with
respect to the prior art winding. The spreading factor linking the
electromotive force amplitude of a winding to the electromotive
force amplitude of one turn multiplied by the number of turns and
given by the mathematical formula:
2 sin(.alpha./2)/.alpha.
where .alpha. is the maximum phase difference, increases therefore
from 0.827 to 0.955, in a three phase winding. The phase spreading
is reduced from 120 to 60 electrical degrees.
[0051] FIG. 4 is a schematic representation of a wave winding
according to an embodiment of the invention. The modifications of
the winding of FIG. 1 to the winding of FIG. 3 have been applied
similarly to the winding of FIG. 2. Same improvement of efficiency
is obtained.
[0052] FIG. 5 is a schematic representation of a lap winding
according to a first improvement of the embodiment of the
invention. The improvement lies in the manner of interconnecting
turns of a subgroup with respect to the manner of interconnecting
the turns of a subgroup in FIG. 3. With reference to FIG. 5, first
conductor 61, numbered 3 in the first subgroup is connected to
second conductor numbered 2 in the same subgroup through a
horizontal shortcut connection 46. For reducing the phase
resistance, this horizontal shortcut connection may be made in
parallel in the first layer and in the second layer. Similar
shortcut connections are made for all turns of a subgroup both at
the top and at the bottom of the winding. As is well known by the
man skilled in the art, only the component of currents
perpendicular to the relative movement (i.e. axial currents in a
cylindrical electrical machine) will generate a torque or force in
a motor. Therefore, in the nearly triangular regions at the bottom
and at the top of the winding of FIG. 3 where first conductors 61
if the front layer and second conductors 62 of the second layer
overlap, the resulting torque will be nil. This explains why the
improved mode of inter-turn connection, represented in FIG. 5
represents no loss in torque or force when the electrical machine
is a motor while reduces the phase resistance. For a same geometry
and currents, the winding of FIG. 5 will produce the same torque or
force as the winding of FIG. 3. Compared to the winding of FIG. 3,
the winding of FIG. 5 has shorter tracks, and therefore a reduced
phase resistance R.sub.ph. For the same reasons, when the
electrical machine is a generator, the emf generated with the
winding of FIG. 3 and FIG. 5 will be equivalent.
[0053] FIG. 6 is a schematic representation of a wave winding
according to same first improvement of the embodiment of the
invention. The improvement corresponds to the modifications made to
the winding of FIG. 3 for obtaining the winding of FIG. 5 but
applied to the winding of FIG. 4. Horizontal shortcut connections
46 reduce the overall length of the conductors, without reducing
the torque or force of the electrical machine. The applicants have
observed that, for a conventional design, the resulting torque or
force density is improved by more than 10% with respect to the
winding without horizontal shortcuts.
[0054] FIG. 7 is a schematic representation of a lap winding
according to a second improvement of the embodiment of the
invention. The improvement lies in a modification of the shape of
conductors 61, 62 in the median region of their height. With
reference to FIG. 7, as an example, first conductor 61, numbered 3
in the first subgroup 81 is shortcut beginning from the point of
overlap with conductor 62 numbered 1 of second subgroup 82, with a
vertical shortcut connection 47.
Second conductor 62 of second subgroup 82 is also shortcut with a
vertical shortcut connection 47' from the point of overlap with the
last conductor 61 of preceding first subgroup (conductor number 2
in the example shown). Except for the last vertical shortcut of the
first subgroup and first vertical shortcut of the second subgroup,
these shortcuts may extend in parallel in the first and second
layer, which further reduces the phase resistance. The last
shortcut of the first subgroup and the first vertical shortcut of
the second subgroup overlap, and, being part of different circuits,
may not be combined in parallel, but must remain in the first and
second layer respectively. For reasons similar to the reasons
explained in relation to the horizontal shortcuts and FIG. 5, the
winding of FIG. 7 will produce same torque or force as the
corresponding winding of FIG. 3 without vertical shortcut. It has
be determined, that, for the conductor shape of FIG. 7, the
resulting torque or force efficiency is improved by more than 1%
with respect to the winding of FIG. 3, without vertical
shortcuts.
[0055] FIG. 8 is a schematic representation of a wave winding
according to same second improvement of the embodiment of the
invention. The improvement corresponds to the modifications made to
the winding of FIG. 3 for obtaining the winding of FIG. 7, but
applied to the winding of FIG. 4. Vertical shortcut connections 47
reduce the overall length and resistance of the winding, without
reducing the torque or force of the electrical machine
[0056] FIGS. 9 and 10 are schematic representations of a lap and a
wave winding, respectively, combining first and second improvements
of the embodiment of the invention, where the conductors have three
linear segments. This example shows that the invention and its
improvements apply similarly to windings where the conductors are
straight lines, broken lines or curves.
[0057] The conception of a wave winding according to the second
improvement of the invention (i.e. having the vertical shortcuts)
will be described by describing the modifications to be performed
on the winding of FIG. 4 for obtaining the winding of FIG. 10, and
focusing only on the vertical shortcut improvement, located in a
diamond (lozenge) shaped area at mid-height of the winding.
First conductors 61 (continuous lines) of first subgroup are
numbered sequentially from left to right and noted 61/1 to 61/t (t
being equal to 5 in FIG. 10). Similarly, second conductors 62'
(represented as dashed lines) of second subgroup are numbered 62'/1
to 62'/t. In a first modification (a), first conductor 61/1 is
interrupted at mid-height of the winding, and connected through a
via to the part of conductor 62'/1 on the lower part of the
winding. The remaining parts of conductors 61/1 and 62'/1 will be
discussed below. In a second modification (b), upper parts of
conductors 61/2 to 61/t-1 are kept up to the point where they
overlap second conductor 62'/1 of second group. From that point of
overlap, they are interrupted and prolonged downwards by a vertical
shortcut 47 up to the point where conductor 62'/2 to 62'/t-1
overlap conductor 61/1. From that second point of overlap, the
vertical shortcuts are connected to the parts of conductors 62/'2
to 62'/t-1 extending downwards, respectively. In a third
modification (c), upper part of conductor 61/t is kept up to the
point where it overlaps second conductor 62'/1 of second group.
From that point of overlap, it is interrupted and prolonged
downwards by a vertical shortcut 47 up to the point where conductor
62'/t overlaps conductor 61/1. From that second point of overlap,
the vertical shortcuts are connected to the part of first conductor
61/1 of first group, extending downwards. Unused parts of
conductors of original, unmodified winding are removed. Vertical
shortcuts 2 to t-1 may extend in parallel on both sides of
intermediate layer, thereby reducing the resistance of the winding.
Last vertical shortcut t may extend only on one side. Modifications
(a) (b) and (c) address the left hand side of the diamond region of
FIG. 10. Similar modifications are performed for the right hand
side of the diamond region of FIG. 10: the winding is rotated
180.degree. around the vertical diagonal of the diamond, and same
connections and redirections are performed on conductors now
occupying locations of former conductors Same operations may be
performed on all diamonds occurring in the winding. It can be seen
from the drawing that e.g. the currents in conductors 61/1 to
61/t-1 of first subgroup in upper part of winding, and flowing
downwards, will flow in the natural direction, also downwards, in
conductors 62'/1 to 62'/t-1, producing the same motor or generator
effect as with the winding of FIG. 4, but with a reduced
resistance, and therefore an improved efficiency. In the present
discussion "to overlap" it is to be understood as meaning "to be on
same position but on different sides of an intermediate layer"
[0058] All examples discussed in relation to FIGS. 3 to 10 have
been described without discussing the connections at the left and
right ends of the winding. For the lap windings of FIGS. 3, 5, 7,
and 9, the situation is simple: each of the subgroups form coils,
each having one current entry terminal 44 and current exit terminal
45. These may be connected to external means or interconnected so
as to form a number of phases each having a current entry terminal
and a current exit terminal. The winding may be of any length and
have a plurality of groups of turns and may be wound up in a
cylindrical fashion, with an insulating layer between two folds, in
such a way that corresponding groups and subgroups of same phase
overlap. In the case of a PCB winding, all of the conductors,
including the interconnections between subgroup at the top height
of the PCB may be produced with a single PCB, without requiring any
additional wiring.
[0059] In the wave winding of FIG. 4, the second conductors 62 at
the right hand end may be connected to corresponding first
conductors 61 at the left hand end of the winding. This may be
performed with external wiring or additional tracks at the top of
the PCB. FIGS. 11 and 12 show examples of a third improvement of
the invention where the need for these external wiring or
additional tracks is avoided. Referring to FIG. 11, a conductor 61
of the first subgroup 81 of turns in the first layer, at the right
hand end of the winding is interrupted at mid height of the
intermediate layer and connected through said intermediate layer
with via 43 to corresponding lower half of conductor 62 of the
second subgroup 82 in the other layer. This is performed for all
conductors of this subgroup, and is performed in a similar fashion
at the left hand side of the winding. This results in having for
each phase a closed circuit having current entry terminal 44 and
current exit terminal 45. The resulting winding can be produced as
a single PCB, without requiring any additional wiring or
connections. Although FIG. 11 shows a winding having three turns in
each phase and each subgroup, a winding having an arbitrary number
of turns may be produced, according to the needs of the electrical
machine for which it is intended. FIG. 12 shows an example of a
winding having same end-wraps of conductors in a winding having
both horizontal and vertical shortcuts. The winding of FIG. 12
combines all improvements of the invention.
[0060] FIG. 13 is a schematic representation of a lap winding
combining first and second improvement of the embodiment of the
invention for use in a rotating electrical machine having an axial
field. This winding is adapted for interacting with an inductor
having two north poles and two south poles producing a magnetic
field oriented along the axis, i.e. perpendicularly to the figure.
The poles are distributed at 90 degrees from each other. The
winding has two first subgroups 81 and two second subgroups 82 at
90 degrees angular distance from each other.
[0061] The present invention has been described in terms of
specific embodiments, which are illustrative of the invention and
not to be construed as limiting. More generally, it will be
appreciated by persons skilled in the art that the present
invention is not limited by what has been particularly shown and/or
described hereinabove.
[0062] Reference numerals in the claims do not limit their
protective scope. Use of the verbs "to comprise", "to include", "to
be composed of", or any other variant, as well as their respective
conjugations, does not exclude the presence of elements other than
those stated. Use of the article "a", "an" or "the" preceding an
element does not exclude the presence of a plurality of such
elements.
[0063] The invention may also be described as follows: the
invention provides a winding for an electrical machine adapted for
interacting with an inductor structure providing a sequence of at
least one pair of north and south magnetic poles along a length,
producing a magnetic field, said poles being separated by a pole
pitch distance .tau..sub.p along said length. The winding may
comprise one or more phases, be adapted for moving in relation to
the inductor structure along said length, and have a plurality of
groups of pairs of conductors, each pair of conductors forming a
turn intercepting a fraction of said magnetic field. According to
the invention, a first subgroup of turns of one phase have a spread
along the length inferior or equal to .tau..sub.p/n, a second
subgroup of turns of same phase have a spread along said length
inferior or equal to .tau..sub.p/n, at a distance equal to
.tau..sub.p along said length, the turns of the first subgroup
being connected in such a way that a current may flow in same
direction in all turns of said subgroup, the turns of the second
subgroup being connected in such a way that a current may flow in
same direction in all turns of said subgroup, a turn of the first
subgroup being connected to a turn of the second subgroup in such a
way that the direction of said current in the first group is
opposite to the direction of the current in the second subgroup.
The first subgroup and the second subgroup may have the same number
t of turns.
* * * * *