U.S. patent application number 13/882297 was filed with the patent office on 2013-08-29 for system for contactless power transfer between nacelle and tower of a windturbine.
This patent application is currently assigned to 3E. The applicant listed for this patent is Alex De Broe. Invention is credited to Alex De Broe.
Application Number | 20130224013 13/882297 |
Document ID | / |
Family ID | 43334508 |
Filed Date | 2013-08-29 |
United States Patent
Application |
20130224013 |
Kind Code |
A1 |
De Broe; Alex |
August 29, 2013 |
SYSTEM FOR CONTACTLESS POWER TRANSFER BETWEEN NACELLE AND TOWER OF
A WINDTURBINE
Abstract
The present invention relates to a transformer (100) for the
transfer of electrical power from a nacelle (250) of a
horizontal-axis wind turbine to a turbine tower (350) of said wind
turbine whereby the nacelle (250) is in revolute attachment to the
tower (350), comprising: a primary winding (200) adapted for
attachment to the nacelle (250), and a secondary winding (300)
adapted for attachment to the turbine tower (350), which windings
(200, 300) are in revolute alignment with each other, and
configured for transfer of electrical power by induction from the
primary winding (200) to the secondary winding (300). It also
relates to a method for assembly or disassembly of a wind
turbine.
Inventors: |
De Broe; Alex; (Asse,
BE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
De Broe; Alex |
Asse |
|
BE |
|
|
Assignee: |
3E
Brussel
BE
|
Family ID: |
43334508 |
Appl. No.: |
13/882297 |
Filed: |
October 29, 2010 |
PCT Filed: |
October 29, 2010 |
PCT NO: |
PCT/EP2010/066488 |
371 Date: |
April 29, 2013 |
Current U.S.
Class: |
415/213.1 ;
29/889.21 |
Current CPC
Class: |
Y10T 29/49321 20150115;
F01D 25/28 20130101; Y02E 10/72 20130101; F05B 2240/912 20130101;
H01F 38/18 20130101; Y02E 10/728 20130101; F03D 80/85 20160501 |
Class at
Publication: |
415/213.1 ;
29/889.21 |
International
Class: |
F01D 25/28 20060101
F01D025/28 |
Claims
1. A horizontal-axis wind turbine comprising turbine tower (350)
and a nacelle (250) in revolute attachment to the tower (350),
comprising a transformer (100) for the transfer of electrical power
from the nacelle (250) to the turbine tower (350), which
transformer comprises: a primary winding (200) adapted for
attachment to the nacelle (250), and a secondary winding (300)
adapted for attachment to the turbine tower (350), which windings
(200, 300) are in revolute alignment with each other, and
configured for transfer of electrical power by induction from the
primary winding (200) to the secondary winding (300), wherein the
revolute attachment comprises a mounting (150) into which the
transformer (100) is integrated, which mounting comprises a nacelle
part (230) and a tower part (330) that couple together, and the
primary (200) winding is integrated into the nacelle part (230) and
the secondary (300) winding is integrated into the tower part
(330). wherein one of said mounting parts (230, 330) comprising a
cylindrical pin, the other of said mounting parts comprising a
cylindrical cavity configured to slidably receive the cylindrical
pin.
2. Horizontal-axis wind turbine according to claim 1, wherein the
primary (200) and secondary (300) windings are in essentially
concentric alignment.
3. Horizontal-axis wind turbine according to claim 1, wherein the
primary (200) winding is outside of the secondary (300)
winding.
4. Horizontal-axis wind turbine according to claim 3, wherein the
primary winding (200) comprises an annular inductive coil (210) and
an annular magnetically permeable member (220, 222), whereby the
annular magnetically permeable member (222) is disposed around the
outside of the coil (210).
5. Horizontal-axis wind turbine according to claim 3 wherein the
secondary winding (300) comprises an annular inductive coil (310)
and a cylindrical magnetically permeable member (320, 322), whereby
the coil (310) is disposed around the outside of the cylindrical
magnetically permeable member (322).
6. Horizontal-axis wind turbine according to claim 1, wherein the
secondary (300) winding is outside of the primary (200)
winding.
7. Horizontal-axis wind turbine according to claim 1, wherein said
turbine tower (350) is at least partially hollow.
8. Horizontal-axis wind turbine according to claim 1, wherein said
nacelle (250) is dismountably attached to the tower (350).
9. A method of assembling a horizontal-axis wind turbine which
horizontal-axis wind turbine comprising a turbine tower (350) and a
nacelle (250) in revolute attachment to the tower (350), and a
transformer (100) for the transfer of electrical power from the
nacelle (250) to the turbine tower (350), which transformer
comprises: a primary winding (200) adapted for attachment to the
nacelle (250), and a secondary winding (300) adapted for attachment
to the turbine tower (350), which windings (200, 300) are in
revolute alignment with each other, and configured for transfer of
electrical power by induction from the primary winding (200) to the
secondary winding (300), comprising the steps: installing the wind
turbine tower (350) comprising a secondary winding (300) on a site,
and mounting the nacelle (250) comprising a primary winding (200)
on said tower (350), such that primary winding (200) and said
secondary winding (300) form the transformer (100) when said
nacelle and said tower are assembled.
10. A method of disassembling a horizontal-axis wind turbine which
horizontal-axis wind turbine comprising a turbine tower (350) and a
nacelle (250) in revolute attachment to the tower (350), and a
transformer (100) for the transfer of electrical power from the
nacelle (250) to the turbine tower (350), which transformer
comprises: a primary winding (200) adapted for attachment to the
nacelle (250), and a secondary winding (300) adapted for attachment
to the turbine tower (350), which windings (200, 300) are in
revolute alignment with each other, and configured for transfer of
electrical power by induction from the primary winding (200) to the
secondary winding (300), comprising the step of lifting the nacelle
comprising a primary winding (200) from the wind turbine tower
comprising the secondary winding (300).
11. Method according to claim 9, wherein the primary (200) and
secondary (300) windings are in essentially concentric
alignment.
12. Method according to claim 9, wherein the primary (200) winding
is outside of the secondary (300) winding.
13. Method according to claim 12, wherein the primary winding (200)
comprises an annular inductive coil (210) and an annular
magnetically permeable member (220, 222), whereby the annular
magnetically permeable member (222) is disposed around the outside
of the coil (210).
14. Method according to claim 12, wherein the secondary winding
(300) comprises an annular inductive coil (310) and a cylindrical
magnetically permeable member (320, 322), whereby the coil (310) is
disposed around the outside of the cylindrical magnetically
permeable member (322).
15. Method according to any claim 11, wherein the secondary (300)
winding is outside of the primary (200) winding.
Description
FIELD OF THE INVENTION
[0001] The present invention is in the field of wind turbines. More
in particular, it is in the field of power transfer between a wind
turbine nacelle and tower on which the nacelle is mounted
revolutely.
BACKGROUND TO THE INVENTION
[0002] The nacelle of a wind turbine is typically suspended at the
top of a tower in horizontal axis systems using a rotating
(revolute) mounting. The power produced by the generator in the
nacelle needs to be transferred to the base of the tower. For
larger turbines this is usually achieved using a cable connected to
the nacelle which passes through a passageway disposed within the
tower. Slack in the cable towards the upper part of the tower
allows for some degree of cable coiling due to rotation (yawing) of
the nacelle that follows any change in wind direction. A device
counting the number of turns is used to limit the maximum coiling
of the cable. Once this maximum has been reached, the turbine is
stopped and a yaw mechanism unwinds the cable by rotating the
nacelle in the opposite direction of the coiling, thereby restoring
the cable to its original unwound condition.
[0003] The system of the art is associated with several
disadvantages. Additional cable must be foreseen to allow for the
coiling, which adds to the expense of construction. The cable is
suspended through the aforementioned passageway using a net made of
steel cable; as the conducting cable is made from thick copper, and
is quite heavy, large forces are applied to the net, often leading
to fatigue and failure. The system needs a mechanism to count the
number of turns that the cable has been coiled; such a mechanism
requires maintenance and provides a potential source of failure and
expense. The system also requires an active yaw mechanism to unwind
the cable once the maximum allowed number of turns has been
reached; again this mechanism requires maintenance and provides a
potential source of failure and expense. Cable damage and
eventually short-circuits cause by failure of these systems lead to
additional expense. Downtime, while the turbine blade is stopped
and the nacelle rotated, leads to a loss of production and is
significant at sites where wind direction is variable.
[0004] Smaller turbines (e.g. below 50 kW rated power) sometimes
employ slip-ring units to transfer the power from the rotating
nacelle to the fixed tower. A slip ring unit consists of a set of
brushes and a set of rings that form rotating contacts. Uniformly
distributed pressure for a contact between the brush and the ring
is usually assured using springs. This system has numerous
disadvantages. Dependent upon the yaw rate and the amount of
current transferred, the brushes, usually made out of carbon, wear
down regularly and need to be replaced, which contributes to
running costs which includes downtime. The slip-ring unit needs to
be mounted so that the alignment between the brushes and the
contact rings is correct, to avoid that the brushes wear unduly;
this alignment process requires time and specialist equipment. The
slip ring assembly generates carbon dust caused by wearing of the
brushes; therefore an evaluation system is required to prevent
short-circuits caused by the conductive carbon; such a system
requires maintenance and provides a potential source of failure and
expense.
[0005] Contact-less power transmission is a generally known method
used in mechanical and electrical engineering fields with
particular use in consumer devices. In U.S. Pat. No. 7,622,891
(Cheng et al., Nov. 24 2010) a general device is described to
inductively power a secondary unit. The device eases manipulation
for the user as it is not necessary to place the power-receiving
unit in mechanical or other registration with the
power-transmitting device. U.S. Pat. No. 7,717,619 (Karch et al.,
May 18 2010) describes contactless data transmission for CT imaging
purposes. US 2007/0007857 (Cullen et al., Jan. 11 2007) describes a
wind-turbine architecture eliminating the problem of slip-rings and
cable wind-up.
SUMMARY OF THE INVENTION
[0006] The present invention is a system for contactless,
(zero-wear) power transfer from a wind turbine nacelle to a wind
turbine tower on which the nacelle is attached. The nacelle is
preferably a horizontal axis system i.e. the axle of the turbine
blades is aligned essentially horizontally. The wind turbine tower
is preferably longitudinal, and vertically mounted. The wind
turbine nacelle is attached to a wind turbine tower using a
revolute (rotatable or yawing) mounting. The tower may be fixed to
the ground or to the seabed, or be floating on water.
[0007] In general the tower is not able to rotate around its
longitudinal axis, while the nacelle is able to rotate around the
longitudinal axis of the tower in order to track the wind direction
and keep the rotor perpendicular to the dominating wind flow. The
relative motion between the nacelle and the tower is known as the
yawing or yaw motion, and is in most cases facilitated by a yaw
bearing. The power generated by the wind turbine electrical
generator thus has to be transmitted from the rotating nacelle that
is connected to the fixed tower.
[0008] One aspect provides a transformer comprising a primary
winding and secondary winding arranged in concentric alignment. The
primary winding is configured for attachment to the nacelle; the
secondary winding is configured for attachment to the turbine
tower. The secondary winding and the primary winding are also in
rotatable (revolute) alignment. In the wind turbine, the primary
windings in the tower and the secondary windings in the nacelle
align such that they form a transformer.
[0009] Alternating current (AC) provided by the generator housed in
the nacelle is transferred wirelessly via the transformer to the
tower, without the need for an arrangement of slip-rings or a
direct cable connection. The operation of the transformer is such
that it is independent of the relative (revolute) orientation of
the primary and secondary windings. The nacelle can thus rotate
freely and track the wind direction without having to take into
account its rotational position in relation with the tower. On
other words, the system permits an infinite number of turns. This
invention is thus particularly well suited in combination with a
free yaw system where there is no active system controlling the yaw
motion but rather the aerodynamic forces are used to ensure proper
orientation of the nacelle in the wind flow.
[0010] The generator housed in the nacelle may supply alternating
current at a fixed-frequency. The generator housed in the nacelle
may supply alternating current at a variable-frequency. The
transformer will wireless transfer power to the tower, regardless
of the frequency of the alternating current. It will be appreciated
that higher alternating current output frequencies allow for a more
compact transformer. One aspect provides a power converter for
transforming the low-frequency alternating current provided by the
generator into a higher-frequency current, for instance in the kHz
range (e.g. at least 1 kHz, 10 kHz, 50 kHz, 100 kHz or a value in
the range between any two of the aforementioned values). This would
reduce the size and thus the weight of the rotating transformer
arrangement thereby reducing costs.
[0011] Cables connected to the primary winding conduct power
generated by the wind tower to an electrical collector network of a
wind farm or to a grid, optionally via one or more power
converters.
[0012] The invention does not add any unnecessary components to the
conversion process of a wind turbine. Turbines with rated powers
starting at several hundreds of kilowatts are usually connected to
the distribution grid and thus use step-up transformers to convert
the lower output voltage of the generator to the voltage level of
the grid. In turbines that have tall towers, it is commonplace to
do this transformation in the nacelle to limit the conduction
losses in the cables that descend from the tower. Such modern-day
turbines already include a Low-voltage-to-Medium-voltage
transformer in the nacelle. Hence the invention does not add any or
significant weight to the tower-top mass (the total mass of the
turbine placed on top of the tower). In addition may make the
nacelle more compact as transformer can now be integrated in the
tower top, as opposed to occupying space within the nacelle.
[0013] One aspect of the invention relates to a transformer (100)
for the transfer of electrical power from a nacelle (250) of a
horizontal-axis wind turbine to a turbine tower (350) of said wind
turbine whereby the nacelle (250) is in revolute attachment to the
tower (350), comprising: [0014] a primary winding (200) adapted for
attachment to the nacelle (250), and [0015] a secondary winding
(300) adapted for attachment to the turbine tower (350), which
windings (200, 300) are in revolute alignment with each other, and
configured for transfer of electrical power by induction from the
primary winding (200) to the secondary winding (300).
[0016] The primary (200) and secondary (300) windings may be in
essentially concentric alignment. The primary (200) winding may be
outside of the secondary (300) winding. The primary winding (200)
may comprise an annular inductive coil (210) and an annular
magnetically permeable member (220, 222), whereby the annular
magnetically permeable member (222) is disposed around the outside
of the coil (210). The secondary winding (300) may comprise an
annular inductive coil (310) and a cylindrical magnetically
permeable member (320, 322), whereby the coil (310) is disposed
around the outside of the cylindrical magnetically permeable member
(322). The secondary (300) winding may be outside of the primary
(200) winding. The transformer (100) may be configured for
inductive transfer of high-frequency alternating current.
[0017] Another aspect of the invention relates to a horizontal-axis
wind turbine comprising turbine tower (350) and a nacelle (250) in
revolute attachment to the tower (350), comprising a transformer
(100) describe herein. The revolute attachment may comprise a
mounting (150) into which the transformer (100) is integrated. The
mounting (150) may comprise a nacelle part (230) and a tower part
(330) that couple together, and the primary (200) winding is
integrated into the nacelle part (230) and the secondary (300)
winding is integrated into the tower part (330).
[0018] One of said mounting parts (230, 330) may comprise a
cylindrical pin, the other of said mounting parts may comprise a
cylindrical cavity configured to slidably receive the cylindrical
pin. Said turbine tower (350) may be at least partially hollow.
Said nacelle (250) may be dismountably attached to the tower
(350).
[0019] Another aspect of the invention relates to a method of
assembling a horizontal-axis wind turbine as described herein,
comprising the steps: [0020] installing the wind turbine tower
(350) comprising a secondary winding (300) on a site, and [0021]
mounting the nacelle (250) comprising a primary winding (200) on
said tower (350), such that primary winding (200) and said
secondary winding (300) form the transformer (100) when said
nacelle and said tower are assembled.
[0022] Another aspect of the invention relates to a method of
assembling a horizontal-axis wind turbine as described herein
comprising the step of lifting the nacelle comprising a primary
winding (200) from the wind turbine tower comprising the secondary
winding (300).
FIGURE LEGENDS
[0023] FIG. 1 is a schematic perspective view of a transformer
described herein.
[0024] FIG. 2 is a cross sectional view through a plane parallel
and adjacent to the central axis of the transformer. Hatched
shading indicates magnetically permeable material while horizontal
shading indicates inductive coil.
[0025] FIG. 3 is a cross sectional view through a plane parallel
and adjacent to the central axis of the tower. One transformer is
shown.
[0026] FIG. 4 is a cross sectional view through a plane parallel
and adjacent to the central axis of the tower. Three transformers
are shown.
[0027] FIG. 5 is a cross sectional view through a plane parallel
and adjacent to the central axis of the tower. Three transformers
are shown that are magnetically coupled.
DETAILED DESCRIPTION OF THE INVENTION
[0028] Before the present system and method of the invention are
described, it is to be understood that this invention is not
limited to particular systems and methods or combinations
described, since such systems and methods and combinations may, of
course, vary. It is also to be understood that the terminology used
herein is not intended to be limiting, since the scope of the
present invention will be limited only by the appended claims.
[0029] As used herein, the singular forms "a", "an", and "the"
include both singular and plural referents unless the context
clearly dictates otherwise.
[0030] The terms "comprising", "comprises" and "comprised of" as
used herein are synonymous with "including", "includes" or
"containing", "contains", and are inclusive or open-ended and do
not exclude additional, non-recited members, elements or method
steps. It will be appreciated that the terms "comprising",
"comprises" and "comprised of" as used herein comprise the terms
"consisting of", "consists" and "consists of".
[0031] The recitation of numerical ranges by endpoints includes all
numbers and fractions subsumed within the respective ranges, as
well as the recited endpoints.
[0032] Whereas the terms "one or more" or "at least one", such as
one or more or at least one member(s) of a group of members, is
clear per se, by means of further exemplification, the term
encompasses inter alia a reference to any one of said members, or
to any two or more of said members, such as, e.g., any .gtoreq.3,
.gtoreq.4, .gtoreq.5, .gtoreq.6, or 24 7 etc. of said members, and
up to all said members.
[0033] Unless otherwise defined, all terms used in disclosing the
invention, including technical and scientific terms, have the
meaning as commonly understood by one of ordinary skill in the art
to which this invention belongs. By means of further guidance, term
definitions are included to better appreciate the teaching of the
present invention.
[0034] In the following passages, different aspects of the
invention are defined in more detail. Each aspect so defined may be
combined with any other aspect or aspects unless clearly indicated
to the contrary. In particular, any feature indicated as being
preferred or advantageous may be combined with any other feature or
features indicated as being preferred or advantageous.
[0035] In the following detailed description of the invention,
reference is made to the accompanying drawings that form a part
hereof, and in which are shown by way of illustration only of
specific embodiments in which the invention may be practiced. It is
to be understood that other embodiments may be utilised and
structural or logical changes may be made without departing from
the scope of the present invention. The following detailed
description, therefore, is not to be taken in a limiting sense, and
the scope of the present invention is defined by the appended
claims.
[0036] With reference to FIG. 1, one aspect of the invention
relates to a transformer 100, (rotating transformer), for the
transfer of electrical power from a nacelle of a horizontal-axis
wind turbine to a turbine tower of said wind turbine, whereby the
nacelle is in revolute attachment to the tower, comprising a
primary winding 200 adapted for attachment to the nacelle and a
secondary winding 300 adapted for attachment to the tower which
windings 200, 300 are revolute (rotatable) and optionally in
essentially concentric alignment with each other, configured for
transfer of electrical power by induction from the primary winding
200 to the secondary winding 300. The rotation is about an axis of
rotation R-R'. One winding is generally static, while the other
winding rotates around that axis of rotation. In FIGS. 1 to 3, the
primary winding 200 is on the outside and rotates, while the
secondary winding 300 is on the inside and is static relative to
the primary winding 200. It will be appreciated that other
configurations are possible e.g. the primary winding 200 may be on
the inside. The primary winding 200, the secondary winding 300 or
both windings 200, 300 may incorporate one or more magnetically
permeable members (e.g. core) such as iron for guidance of the
flux, particularly across an annular air gap between the primary
200 and secondary 300 windings.
[0037] With reference to FIGS. 2 and 3, the primary winding 200
comprises a primary winding inductive coil 210 that is electrically
connected directly or indirectly to the generator housed in the
nacelle. The primary winding coil 210 preferably forms an annular
(circular) ring, having a central axis. The central (A-A') axis of
the coil 210 is essentially co-axial with the axis of rotation of
the transformer 100. The primary winding 200 may further comprise
at least one magnetically permeable member 220, having a
cylindrical or annular shape 222 and having a central axis. The
central axis of the magnetically permeable member 222 is
essentially co-axial with the axis of rotation of the transformer.
The coil 210 and magnetically permeable member 222 are preferable
in concentric and optionally co-axial alignment. The coil 210 may
be made from copper or aluminum formed into wire or foil. It may be
form-wound for higher power ratings. The primary winding 200 is in
fixed relation to the nacelle 250, and thus rotates as the nacelle
250 rotates around the longitudinal axis of the tower 350.
[0038] With reference to FIGS. 2 and 3, the secondary winding 300
comprises an inductive coil 310 that is electrically connected to
the output of the wind tower located in the wind tower. The
secondary winding coil 310 preferably forms an annular (circular)
ring, having a central axis. The central (A-A') axis of the coil
310 is essentially co-axial with the axis of rotation of the
transformer 100. The secondary winding 300 may further comprise at
least one magnetically permeable member 320, having a cylindrical
or annular shape and having a central axis. The central axis is
essentially co-axial with the axis of rotation of the transformer
100. The secondary winding coil 310 and magnetically permeable
member 320 are preferable in concentric and optionally co-axial
alignment. The coil 310 may be made from copper or aluminum formed
into wire or foil. It may be form-wound for higher power ratings.
The secondary winding 300 is in fixed relation to the tower, and
thus stationary.
[0039] The primary 200 and secondary 300 windings are preferably in
essentially concentric alignment. In this arrangement, the primary
winding 200 (the outer winding) may be disposed around the outside
of the secondary winding 300 (the inner winding) as illustrated in
FIG. 2. Alternatively, the secondary winding 300 (the outer
winding) may be disposed around the outside of the primary winding
200 (the inner winding) (not illustrated). The arrangement will
depend on the configuration of the rotatable mounting used to
attach the nacelle 250 to the tower 350. Generally, the primary
winding 200 is integrated into the one part of the mounting and the
secondary winding 300 is integrated into the another reciprocating
part of the mounting, such that the primary 200 and secondary
windings 300 are in concentric (overlapping) alignment when the
nacelle 250 is mounted on the tower 300.
[0040] As mentioned elsewhere, the primary winding 200, the
secondary winding 300 or both windings may incorporate an
arrangement of one or more of magnetically permeable members 230,
320, made, for instance from iron for conductance of the flux,
particularly across an air gap between the primary and secondary
winding. A magnetically permeable member (sometimes known as a
core) is made from magnetically conductive material. It provides a
path of minimum resistance to magnetic flux generated by the coil.
A magnetically permeable member may be made from any high
permeability magnetically conductive material. In one example, a
magnetically permeable member may be made from iron. Preferably a
magnetically permeable member is made from non-grain oriented iron
to reduce the weigh of the transformer and to reduce the losses.
Depending on the function of the transformer, frequency and its
rated power, other materials such as ferrites or iron powder may be
used.
[0041] According to one aspect, magnetically permeable members 220,
320 are arranged to give rise to a shell-type transformer. In a
shell-type transformer, the outer winding comprising an annular
cylinder of magnetically permeable material 220, 320 that encloses
the coil of the outer winding, and the coil is flanked by a pair of
end plates of magnetically permeable material. The central axis
(A-A') of annular ring of magnetically permeable material is
essentially co-axial with the axis of rotation of the transformer.
Exemplified in FIG. 2, the primary winding 200 is on the outside
and comprises an annular cylinder 222 of magnetically permeable
material that encloses the coil 210, and the coil 210 is flanked by
a pair of end plates 224, 226 of magnetically permeable material.
The shell-type transformer has the advantage that no coil is
apparent outside the permeable members. The magnetically permeable
material encloses the coil, which provides robustness to short
circuit and transportation efforts, and compactness of the design
to match transportation and hauling restrictions. It is appreciated
that magnetically permeable members may be arranged to give rise to
a core-type transformer in the outer winding i.e. the coil of the
outer winding is arranged around an annular ring of magnetically
permeable material.
[0042] In a standard transformer, the amount of magnetic flux
passing through each of the primary and secondary windings is
similar or the same by disposing both windings on the same
continuous magnetically permeable member (core). In the present
case, the magnetically permeable members 220, 320 are arranged in a
discontinuous manner, i.e. there is an air gap between magnetically
permeable members (core) of the primary 200 and secondary 300
windings of the transformer in order to allow for relative
rotational movement. The air gap in between the inner and outer
part of the magnetic core is minimised in order to limit the
leakage inductance of the transformer. In FIG. 2 the air gap 160
between the primary 200 and secondary 300 windings has an annular
cylindrical shape.
[0043] According to one aspect, magnetically permeable members 220,
320 are arranged to give rise to a reel shape, around which reel
the coil is wound. The reel has a cylindrical core 322 that is
flanked by a pair of disc-shaped end plates 324, 326. The central
axis of the reel is essentially co-axial with an axis of the
rotation of the transformer. In FIG. 2, the a secondary winding 300
is an inner winding, and which the magnetically permeable members
320 are arranged to give rise to said reel shape, around which reel
the coil 310 is wound.
[0044] A cylindrical magnetically permeable member of the inner
winding of a transformer may comprise one or more longitudinal
grooves on the surface for the passage of conductive wires from
transformers located above to grid interconnection at the base of
the tower. Preferably, three longitudinal grooves are evenly
arranged around the cylindrical surface of the magnetically
permeable member. In other words, they are circumferentially
distributed at intervals of 120 deg. Where there are three
transformers in a wind turbine, the grooves may be offset in order
to have a balance in magnetic forces in all relative positions of
the primary and secondary windings and thus no preferred positions.
It will be appreciated that the groove arrangement may be achieved
using three segments of magnetically permeable material which
together form essentially a cylindrical shape.
[0045] The magnetically permeable members can be prolonged to be in
contact with the outer surface of the tower in order to have a
better cooling and/or to fit with the mechanical support
structure.
[0046] As mentioned elsewhere herein, the coil 210, 310 of one or
both windings may be made from a foil. In other words, from an
insulated strip of conductive metal, as opposed from a conventional
strand of wire. A foil coil can be used with some advantage. For
instance, with respect to the inner winding, a foil can be easily
wound around magnetically permeable member when it forms the shape
of a reel, as shown in FIG. 2. A polyester layer is bonded to the
foil to provide mechanical strength and for insulation.
[0047] With respect to the outer winding, a foil coil can form a
ring onto which the segments of annular magnetically permeable
member can be fitted. The conductive metal may be a flat strip. For
high voltage, rectangular conducting strips are preferred.
[0048] As mentioned earlier, the nacelle 250 is in revolute
attachment to the tower 350 using a rotatable (revolute) mounting
150. As the invention allows for relative rotation of the primary
200 and secondary 300 windings of the transformer 100, the mounting
is configured for integration of the transformer components, namely
these primary and secondary windings. The windings may be
integrated into the mounting 150 by virtue of a mechanical support
structure. The mounting preferably comprising a bearing that
transfer the weight of the nacelle onto the wind tower while
allowing yawing
[0049] With reference to FIG. 3, the mounting 150 may comprise a
nacelle part 230 and a tower part 330, one of said mounting parts
comprising a cylindrical pin, the other of said mounting parts
comprising a cylindrical cavity configured to slidably receive the
cylindrical pin. In other words, the pin and cylindrical cavity are
in slidable relation. In FIG. 3, the nacelle part 320 of the
mounting comprises a cylindrical cavity while the tower part 330
comprises the cylindrical pin. It is understood that other
configurations are possible, for instance, the nacelle part 320 of
the mounting may comprise a cylindrical pin while the tower part
330 may comprise the cylindrical cavity. According to one aspect,
the nacelle 250 is dismountably attached to the tower 350.
According to another aspect, the nacelle part 320 is dismountably
attached to the tower part 330 of the mounting. A dismountable
attachment is configured for reversible attachment (e.g. for ease
of attachment and unattachment) of the respective elements.
[0050] The primary winding 200 is integrated into the nacelle part
230 of the mounting 150. Preferably it is integrated so that the
outer cylindrical profile is maintained. The secondary winding 300
is integrated into the tower part 330 of the mounting 150.
Preferably it is integrated so that the outer cylindrical profile
is maintained. The primary 200 and secondary 300 windings may each
be disposed in a housing configured to withstand the bending loads
due to the aerodynamic forces and gravity.
[0051] One or more yaw bearings 170, 175 (FIG. 3) may be provided
where the nacelle part 230 and a tower part 330 of the mounting are
in mechanical contact, preferably where the weight of the nacelle
250 is supported by the tower 350. Typically they are provided at
the longitudinal end of the cylindrical pin (see bearing 170) and
around the mouth of the cylindrical cavity (see bearing 175). The
former bearing may assure the exact spacing between the two parts
of the rotating transformer. The yaw bearing may be a sliding or
rolling bearing.
[0052] A wind turbine may be provided with one or more (e.g. 2, 3,
4 or more) transformers 100. FIG. 4 depicts a wind turbine disposed
with three separate transformers 100, 100' 100'', one for each
phase. Also shown is the nacelle 250 and turbine blades 252 and
wind tower 350.The transformers are arranged in longitudinal
displacement along the mounting. Their central axes are preferably
essentially co-axial. The transformers are preferably spatially
separated from each other. Where there are two or more
transformers, they may be arranged adjacently i.e. without air gaps
in the longitudinal direction, so that at least some of the flux
circuits of one transformer pass through an adjacent transformer.
More in particular, at least some of the flux conducted by the
magnetically permeable members of one transformer extends through
magnetically permeable members of adjacent transformers. By
magnetically coupling the transformers so, the number of
magnetically permeable members may be reduced, thus allowing a more
compact mounting and, therefore, facilitating a more economically
produced wind turbine. FIG. 5 depicts a wind turbine disposed with
three separate transformers 100, 100' 100'', one for each phase,
arranged in the longitudinal direction without air gaps between
adjacent magnetically permeable members 224, 226, 324, 326 in the
longitudinal direction.
[0053] Another aspect described is the horizontal-axis wind turbine
described herein comprising the turbine tower 350 and a nacelle 250
in revolute attachment to the tower 350, comprising the transformer
100 as described herein. The revolute attachment may comprise the
mounting 150 into which the transformer 100 is integrated. The
mounting 150 may comprise a nacelle part 230 and a tower part 330
that couple together, and the primary 200 winding may be integrated
into the nacelle part 230 and the secondary 300 winding may be
integrated into the tower part 330. One of said mounting parts 230,
330 may comprise a cylindrical pin, the other of said mounting
parts comprising a cylindrical cavity configured to slidably
receive the cylindrical pin. The turbine tower 350 may be at least
partially hollow. The nacelle 250 may be dismountably attached to
the tower 350.
[0054] The above described transformer 100 and system would be
suitable for a three-phase 100 kW wind turbine and may have a
capacity of 105 kVA. The system is not necessarily limited to the
aforementioned parameters. The invention is applicable over a range
of wind turbine rated powers from small (e.g. several hundreds of
watts) turbines to very large (e.g. tens of MW's) turbines.
[0055] The present invention allows for easy removal of the nacelle
250 from a tower 350 that is fixed to the ground, the seabed or
floating in sea. A lifting device (crane or even a helicopter)
removes the complete nacelle structure 250 and separate primary 200
and secondary 300 side of the transformer 100 by lifting the
nacelle 250 vertically. By making both sides of the mounting
completely enclosed and weather resistant, the tower 350 together
with the secondary winding 350 of the transformer 150 may be left
in place for indefinite time while the nacelle 250, and the primary
winding 200 of the transformer 100, undergo maintenance. Repairs
may be performed by replacing a complete nacelle 250 to ensure
rapid resuming of power production while the faulty nacelle 250 is
being investigated and repaired onshore.
[0056] Although the preferred embodiments of the invention have
been disclosed for illustrative purposes, those skilled in the art
will appreciate that various modifications, additions and
substitutions are possible, without departing from the scope and
spirit of the invention as disclosed in the accompanying
claims.
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