LE COIL FLUX PAD
Field of the Invention
This invention relates to apparatus for generating or receiving magnetic flux. The invention has
particular, but not sole, application to a low profile, substantially fiat device such as a pad for
power transfer using an inductive power transfer (IPT) .
Background
lPT systems, and the use of a pad which includes one or more windings which may comprise
the primary or secondary windings for inductive power transfer, are reproduced in our
International Patent Publication No. WO 4033, the contents of which are incorporated
herein by reference.
One particular example application of lPT power transfer pads is electric vehicle charging, and
that application is discussed in this section to e the background to one application of the
invention. However, electric vehicle charging is an example of only one application, and the
invention has application to inductive power transfer in general. Electric vehicle charging may
occur while the vehicle is stationary, or atively while the vehicle is moving along a
roadway, for example. lPT power transfer pads can be used both in the vehicle as a power
“pickup" (i.e. the secondary side winding of the lPT ), and at a stationary location such as
a garage floor or a roadway for example as the “charging pad” (i.e. the primary side winding)
from which power is sourced.
The purpose of an lPT roadway system is to wirelessly transfer power to a stationary or moving
vehicle without physical t to the vehicle. The transmitting part of the system consists of a
power supply supplying a lumped coil (for example a pad as bed above) or a track with
many r lumped coils where such a system is tuned for operation at a suitable frequency,
usually anywhere from 10 kHz to 150 kHz. Where the receiver is placed underneath a vehicle
and d to receive power either when the vehicle is stationary above or near (in sufficiently
close proximity to couple power) to the primary transmitter. The pickup receiver also typically
comprises a lumped coll (such as a pad bed above) which is connected to a converter
and appropriate controller within the vehicle to regulate power. For convenience, the part of a
roadway from which power may be received inductively is referred to herein as a track.
The track may be formed by placing a plurality of pads along the centre of a lane in a roadway.
This results in the possibility of an essentially continuous supply of power to the vehicle as it
moves along the roadway in the immediate vicinity of the track.
In recent years such systems have received increasing attention due to their potential to allow
sustainable wireless powered personal transportation. For such a system to be useful it should
not only be able to transfer sufficient power over an airgap of able size (eg. 100—300mm)
it should also prove tolerant to any displacements between track and pickup, to avoid
dependency on a vehicle-to-track guidance system. in a roadway system such displacement will
most likely occur in the lateral ion (orthogonal to both vertical and the ion of
movement) for moving vehicles. For stationary vehicle charging the y to transfer
acceptable levels of power with suitable longitudinal displacement is of particular n in
order to ensure ease of parking. The power transfer profile in the pick~up pad is ideally a
smooth power profile which is ially constant (and sufficient) over as wide as possible a
ce laterally, with smooth drop-offs at each end. Such a power transfer profile eases the
demands on the electronic (primary and secondary) regulators in the system, enabling improved
operating performance for a comparable coupling over a system where during operation
significant ions are experienced in the coupling between the primary and receiver pads.
A further problem to be solved is the need to be able to couple to vehicles or appliances with
varying ground clearances, which y determines the distance between the charging pad on
the ground or as part of a primary structure (such as a mat or other surface) and the secondary
pad of a particular vehicle or other device. In such applications there will be significant changes
in coupling between the two pads that may require the primary inductive apparatus to operate
with substantially increased VA to meet the power demand. This operation will aiso increase
the magnetic field leakage t in the system, which may exceed allowable limits defined by
regulations.
A further problem may occur if the primary and secondary inductive pads are polarised but
oriented at an angle of 90 degrees to each other such that there is no coupling, and thus no
possibility of power transfer.
Yet a further problem arises due to the many different possible pad designs and operation
methods, and the potential mismatch between the charging and pickup pads. For example, the
pad on the ground may have a completely different structure to the vehicle pickup, and/or may
be ed as a single phase, two phase or hase system to produce substantially
different field flux shapes within the space between the two coupled pads under time varying
conditions. Under such conditions the y of a fixed magnetic structure to e power is
limited.
An ive power er apparatus which goes at least some way to addressing some of the
above problems was described in our international Patent Publication No. , the
contents of which are incorporated herein by reference. Embodiments of ?
provide a magnetic flux pad for ting or receiving magnetic flux, the pad including a
magnetically permeable core, two substantially flat overlapping coils magnetically associated
with the core whereby there is substantially no mutual coupling between the coils.
Object of the Invention
It is an object of the present ion to provide an improved apparatus for generating and/or
receiving magnetic flux for the es of inductive power transfer, or to at least provide the
public or the industry with a useful choice.
y of the Invention
in a first aspect the invention broadly provides a magnetic flux pad for generating or receiving
magnetic flux, the pad sing:
a magnetically permeable core, and
at least three overlapping coils ically associated with the core, the at least three
coils all being positioned such that the windings thereof are in substantially the same plane,
whereby there is substantially no mutual coupling n the coiis in use.
The coils are preferably positioned proximate to or to abut the core such that the surface of the
coils that abuts the core is substantially flat. For the avoidance of doubt, the coils may have a
thickness such that the coils do not lie entirely within a single ptane. Further, as will be
appreciated, at least in the region where the coils overlap, there will be some deviation out-of-
plane. References to being “in substantially the same plane" are to be interpreted subject to
these limitations throughout the specification.
Preferably each coil in use is substantially decoupled from all other coils of the at least three
coiis.
Preferably the coils are substantially completely magnetically decoupled in use.
Preferably the coils partially overlap.
Preferably the coils are substantially coplanar.
Preferably the coils are provided on one side of the said ble core, and a shielding means
is ed on the other side of the core.
Preferably the shielding means comprises a shielding plate made of a suitable material such as
aluminium.
Preferably a dielectric cover is provided on the side of the coils opposite the magnetic core.
Preferably the flux pad is d to receive currents from a power supply which are out of
phase with each other to produce a time varying magnetic field which also varies spatially.
Preferably the field produced by the -phase currents in the coils produces a time varying
magnetic field which moves spatially and ultimately between poles of the ic field.
In a second aspect. there is ed a magnetic flux pad for generating magnetic flux, the
magnetic flux pad being ured to be operable in a plurality of modes so as to control the
magnetic flux generated thereby.
Preferably the magnetic flux pad es three or more coils, any one or more of the coils
capable of being selectively energised, thereby enabling said control to be effected.
Preferably, the coils are substantially magnetically decoupled from one another.
Any one or combination (including all) of the coils may be selectively energised as desired and
depending on the particular implementation.
Note that when used herein, “mode” or the like is to be interpreted broadly as not only meaning
that, say, the pad is capable of switching between two coils being energised and three coils
being energised, but onally or alternatively that different ones of the coils (but the same
number), may be energised. For example, different ones or different pairs of a three coil pad
may be selectively energised.
According to presently preferred embodiments, the flux pad includes three said coils. The
ion of three coils s a balance between the additional performance and flexibility
(provided by the adaptability of the flux) and the additional componentry and complexity thereof
(particularly in positioning of the le coils).
Further features of the second aspect may be taken from the features set out in relation to the
first aspect.
According to a third , there is ed a ferrite arrangement for a magnetic flux pad
having at least three coils, the ferrite arrangement comprising a ity of elongate ferrite
elements configured such that the elements are co—aligned with and/or parallel to an imaginary
line extending between the centres of at least two of said coils.
Preferably a plurality of arrays of elements are provided, each array being aligned with the
imaginary line between a different pair of coils. As will be appreciated, the imaginary lines
between different coil centres may be parallel in some arrangements (see, for e, Figure
). Consequently, the same array (but extended perpendicular to the orientation of the e
element lengths) may be used for different pairs of coils.
According to some embodiments, the arrangement comprises (or when assembled forms) one
or more raised and/or recessed portions provided on the surface of the ferrites configured to
receive the coils. For example, for ease of reference, consider an arrangement where coils are
positioned on the upper surface of a ferrite arrangement, raised ferrite portion(s) may be
provided at an outer edge of one or more of the coils. Additionally or alternatively, a raised
portion may be provided at a centre of one or more the coils. Other positions of raised portions
are also possible, as are recessed ns. The provision of raised and/or recessed portions
can be used to further adapt the flux to conform to a desired pattern.
According to one embodiment, the extent or combined operating area of the ferrite ement
is commensurate with that of the coils.
According to one embodiment, the ferrite material extends beyond the extent of the coils.
Preferably the increased extent of the provision of ferrites is provided at edges of the coils that
cross the imaginary line (or are proximate thereto) but that are at the outer extremities of the coil
/ ferrite arrangement. Elsewhere, the coils may extend beyond the extent of the ferrites. Such
arrangements of the es and coils can improve efficiency and reduce the amount of ferrite
al required because it is ed that only e provided substantially along the
imaginary lines will add to mutual inductance, ferrite material elsewhere simply adding to
inductance. ing the ferrite material beyond the extent of the coils along the imaginary
lines can serve to e flux spill out or over. This aspect of the invention may comprise only
two coils and is not to be limited as requiring three or more coils.
Preferably the ferrite arrangement is configured for use in the magnetic flux pad of the first and
second aspects.
in a fourth aspect the invention provides power supply apparatus for an inductive power transfer
system, the power supply apparatus comprising:
a ic flux pad for ting magnetic flux, the pad comprising:
a magnetically permeable core, and
at least three overlapping coils magnetically associated with the core, the at least
three coils ali being positioned such that the windings f are in substantially the
same plane; and
a power supply adapted to provide a current in one coil which has a different phase to a
t in the other coils.
Preferably, the power supply is adapted to e a current in any one coil so as to have a
different phase to a current in all respective other coils in use.
Providing currents with different phases in each coil and adjusting the overlap between the coils,
2O enables each coil to be ntially decoupled from all other coils.
Preferably the power supply is adapted to adjust the phase to produce a field that varies with
time and with spatial position on the pad.
Preferably the apparatus comprises means to detect where a field is or is not required in the
vicinity of the pad and adjust the phase and/or amplitude of the current in at least one of said
coils in response thereto.
More preferably. the means to detect is adapted to adjust a relative phase between at least a
first of said coils and at least a second of said coils.
ably the power supply comprises an inverter for each coil.
According to one embodiment, the power supply operates two of three inverters to be
synchronised with each other such that in one mode of operation the power supply produces a
current in a first one of said coils (preferably any one said coils) which is 90° out of phase with
the current in a second one of said coils.
ing to another embodiment, the power supply es one of three inverters to produce
a current in one of said coils, preferably any one said coils. Where different ones of said coils
may be driven independently of the other coils, preferably the current is produced in the coil that
is in closest proximity to a coil on a vehicle.
Preferably the magnetic flux pad produces a sliding time varying magnetic field.
According to one embodiment, the power supply operates at least one pair of the at least three
coils 180° out of phase with each other. In this embodiment a common inverter may be used,or
two inverters. one driving each coil.
Thus, the present invention provides all of the flexibility and functionality described in WC
2011/1673? but provides additional functionality and ility by enabling additional single coils
or pairs of coils that may be energised, as well as enabling higher numbers of coils to be
energised, thereby enabling the flux to be better tailored and improve power transfer. For
example, the coils sed may be selected at least in part on the required rate of power
transfer or the ve position between the pickup and the charging pad.
In a fifth aspect, the invention provides power supply apparatus for an inductive power transfer
, the power supply apparatus comprising:
a magnetic flux pad for generating ic flux, the magnetic flux pad being configured
to be le in a plurality of modes so as to control the magnetic flux generated thereby; and
a power supply adapted to provide a current to the magnetic flux pad.
Other features of the fifth aspect are readily derivable from features of the first through fourth
aspects without invention in light of the disclosure herein. For the avoidance of doubt, the
magnetic flux pad may be configured to be le in the plurality of modes by ively
energising any one or combination of at least three coils of the magnetic flux pad. Further, the
particular coils energised may be varied.
in a sixth aspect the invention broadly provides a method for providing an IPT magnetic flux pad
having at least three coils in which there is no mutual ic coupling n the coils, the
method comprising the steps of:
overlapping the coils; and
varying the overlap between the coils such that an overlap position is achieved whereby
there is substantially no mutual coupling between the coils.
Preferably the absence of mutual coupling is detected by detecting when an open t voltage
induced in a first one of the coils by energisation of at least one (but preferably all) of the other
coils is minimised.
Energisation of the other coils may comprise sing each coil in turn and/or energising
multiple coils simultaneously and/or energising each coil as they would be energised in normal
use, including with varying phases between the coils.
According to one embodiment, overlap determination is achieved by ering pairs of said at
least three coils in turn (i.e., for an arrangement having three coils, evaluating coil 1 against coil
2, coil 2 against coil 3, and coil 3 against coil 1).
According to one embodiment, the method comprises detecting an open circuit voltage induced
’15 in a second one of the coils ntially simultaneously (or at least subject to the same
operating conditions) as when the open t voltage is detected for the first coil. This may
rly be performed for the third (and more) of said plurality of coils.
In a seventh aspect, the invention es a method of generating magnetic flux. the method
comprising:
ively energising one or more coils of at least three coils of a magnetic flux pad.
For the avoidance of doubt, said selectively energising may comprise energising any subset of
the coils, or all of the coils.
Preferably said selectively energising comprises switching between energising a first subset of
) and a second subset of coil(s).
The first and second subsets may comprise the same or a different number of coils. Further,
one or more coils may be common to both subsets.
Additional or alternative subsets of coils may additionally or alternatively be energised. Further,
one or more of said subsets may comprise all said coils.
Further features of the method of the seventh aspect may be derived from analogous features
of the first through sixth aspects.
In an eighth aspect the invention may broadly be said to consist in a magnetic flux pad for
generating or receiving magnetic flux, the pad comprising:
at least three coils oned such that the windings thereof are in substantially the
same plane; and
a power supply or pickup ller operable to selectively conduct with two or more of
the coils such that a magnetic field is produced or power is received by at least one of a plurality
of pairs of the at least three coils.
Preferably the power supply or pickup controller is operable to operable to selectively conduct
with the coils to energise or receive power from any one or more of the coils.
Preferably the power supply or pickup controller is operable to sequentially energise or receive
power from the at least three coils.
ably the power supply or pickup ller is operable to independently control the phase,
magnitude and/or frequency of current in each of the at least three coils.
Preferably the at least three coils are substantially mutually decoupled from one another.
Preferably the at least three coils partially overlap.
Preferably the at least three coils are spaced substantially equidistantiy from one another.
Preferably the magnetic flux pad comprises three substantially mutually decoupled coils.
ably the magnetic flux pad is operable in a plurality of modes comprising at least two of:
~phase modes, wherein one or more of the coils are energised in phase with each
other;
two-phase modes, wherein one or more of the coils are simultaneously energised out of
phase with one or more other coils; and
a multiphase mode, wherein three or more of the coils are simultaneously energised out
of phase with each other.
Preferably the magnetic flux pad further comprises a ically permeable core, wherein the
at least three coils are ically associated with the core.
Preferably the magnetic flux pad comprises a further coil disposed substantially centrally and
ling or partially overlapping the at least three coils.
ably the further coil is substantially mutually decoupled from the at least three coils in at
least one mode of operation.
Preferably the ic flux pad comprises:
three overlapping and substantially mutually decoupled coils each spaced substantially
equidistantly from one r, and
a magnetically permeable core providing a low reluctance magnetic path between poles
of the three coils.
Preferably the power supply or pickup controller is operable to independently controi the
magnitude, phase, and/or frequency of current in each coil.
Preferably the flux pad is operable in at least a three-phase mode.
In a ninth aspect the invention may broadly be said to t in a magnetic flux pad for
receiving magnetic flux and supplying power to a load, the magnetic flux pad being configured
to be operable in a plurality of modes so as to control the magnetic flux received thereby, and
sing three or more coils capable of being selectively operated to enable said control to be
effected.
in a ninth aspect the invention may broadly be said to consist in a pickup apparatus for an
inductive power transfer system. the pickup tus comprising:
a magnetic flux pad for ing magnetic flux, comprising at least three coils positioned
such that the windings thereof are in substantially the same plane; and
a pickup controller adapted to operate one coil with a different phase to the other coils.
Further aspects of the invention will become apparent from the following description.
Drawing Description
One or more embodiments of the invention will be described with reference to the
anying drawings in which:
Figure 1: is a side view and a plan view respectively of a magnetic flux pad;
Figure 2: is a side view and plan view respectively of the pad of Figure 1 including a
quadrature coil;
Figure 3: is a side view and plan view respectively of an alternative form of ic flux
Pad;
Figure 4: (a) is a plan view of a magnetic flux pad according to a first embodiment of the
invention; and (b) is a plan view of a ion of the first embodiment;
Figure 5: is a plan view of a magnetic flux pad according to a second embodiment of the
invention;
Figure 6: is a schematic power supply circuit for a known 2 coil pad with mutually
decoupled coils;
Figure 7: is a schematic power supply circuit for a three coil mutually decoupled pad;
Figure 8: is a schematic receiver circuit for a three coil pad with mutually decoupled coils
which can both receive and reverse power flow to and from the load;
Figure 9: is a schematic circuit for a three coil pad with mutually decoupled coils which can
independently decouple any of the coils and l power flow to the load;
Figure 10: is a plan View of a ic flux pad according to a third embodiment of the
invention;
Figure 11: is a plan view of a magnetic flux pad according to a fourth embodiment of the
invention;
Figure 12: shows plan views of two further embodiments of magnetic flux pads ing to
the invention;
Figure 13: shows plan views of five further ments of ic flux pads according to
the invention, comprising ions of the embodiments of Figure 4; and
Figure 14: shows plan views of four further embodiments of magnetic flux pads according to
the invention, comprising sub-optimal variations of the embodiments of Figure 4.
Detailed Description
Figures 1 to 3 are prior art arrangements taken from the aforementioned International Patent
Publication No. .
Referring to Figure 1, a prior art magnetic flux pad construction is shown. For convenience, this
general construction is referred to herein as a DDP pad, and is generally referenced DDP in the
relevant drawing figures.
The DDP pad shown in Figure 1 generally comprises two substantially coplanar coils referenced
2 and 3 which are magnetically associated with, and sit on top of, a core 4. As can be seen, the
core 4 may consist of a plurality of individual lengths of permeable material such as ferrite strips
or bars 5 which are arranged el to each other but spaced apart. The pad construction may
include a spacer 6 on which the core is located, and a plate 7 below the spacer. A cover 8 may
be provided on the other surface of the flat coils 2 and 3. Padding 9 may be provided about the
periphery of the pad. As can be seen, the coils 2 and 3 each define a pole area 10 and 11
respectively. This DDP pad construction shows very good characteristics suitable for IPT power
transfer applications such as vehicle charging. The coils 2, 3 may be connected out of phase
and driven by a single inverter to produce a stationary time varying magnetic field to couple to a
receiver (which may for example be of substantially the same magnetic design) at distances
suitable for electric vehicle power transfer with good coupling.
Turning to Figure 2, the DDP construction of Figure 1 is shown but further including a
ture coil 12 (referred to herein as a DDPQ pad). The quadrature coil extends the power
transfer profile when there is lateral movement of the construction shown in Figure 2 with
respect to a flux generator such as the DDP pad of Figure 1 when energised by an appropriate
inverter. The quadrature coil allows power to be extracted from the “vertical" component of the
magnetic field that the receiver pad intercepts while the other coils 2, 3 facilitate power
extraction from the “horizontal” ent of the flux intercepted. Therefore, the construction of
Figure 2 is suited as a flux receiver.
Turning to Figure 3. another uction is shown which is ed to in this document as a bi-
polar pad or, alternatively, as a BPP pad. The BPP pad has a similar construction to the DDP
pad discussed with respect to Figures 1 and 2 above as it enables excellent coupling to
secondary receivers at distances suitable for charging and powering of electric vehicles.
The BPP pad ts, from bottom up, of an aluminium plate 7, a dielectric spacer 6, a core 4
comprising four rows of ferrite bars 5 (referred to herein as ferrites), two flat substantially
ar, yet overlapping and ideally “rectangular" shaped coils 2, 3 (although in practice these
are more oval due to the ease in winding Litz wire) spread out in the lateral ion, and a
dielectric cover 8. The core 4 acts as a shield so that ideally all flux is ed away form the
core 4 through the top of the pad. The plate 7 merely acts to a) eliminate any small stray or
spurious fields that may be present beneath the core 4 in certain environments, and b) provide
additional structurai th. Table A1 provides example ions of a working prototype of
a BPP pad. Tabies A2 and A3 provide example dimensions of the DPP pad of Figure 1 and the
DDPQ pad of Figure 3, respectively.
The magnetic structure of the BPP of Figure 3 is ed so that there is substantially no
mutual coupling between either of the coils 2, 3 in the primary, as described later. This allows
the coils to be driven independently at any magnitude or phase without ng voltage into
each other which if t would oppose the power output of such a coil.
In one mode of operation, the two coils within the BPP can be driven using two separate but
synchronised inverters operating with known current magnitude and phase difference as shown
conceptually in Figure 6. The switches in the H-bridge inverter of Figure 6 are shown as FETs.
In practice these switches may comprise an lGBT with a suitable inverse parailel diode, or SiC
JFET and SiC diode or other suitable arrangement as desired. The power supply tuning
arrangement of Figure 6 uses a known LCL topology (see, for example, ) at
the output of the each inverter‘s H-bridge. The inductances in each of the coils of Figure 3 are
assumed to be cal based on them having the same shape and turns ratio. This inductance
(as seen by the supply and including lead lengths and any other sation elements such
as a series capacitor which may be required to limit voltage across the power suppiy tuning
capacitor CD) is given a value of L1. The primary inductor (Lp) is chosen to be identical to L1,
and the tuning capacitor CD has an identical reactance at the designed frequency of the supply.
Subscripts 2 and 3 represent the circuit attached to coils labelled 2 and 3 in the BPP of Figure 3.
if the coils are completely magnetically decoupled, ideally there will be no power transfer
between the primary inverters to limit power transfer to the secondary receiver, although due to
small loading differences on the coils from a receiver there may be some small mutual coupling
which may cause a small residual current to flow between the ers. Because the DC bus of
each inverter is common, this residual current simply circulates between the inverters and does
not cause any issue or loss of performance during operation.
The two inverters shown in Figure 6 may be onised but operated so as to produce
currents with the same RMS ude, but operating 90 s out of phase in each of the
coils 2, 3. By having a 90" phase separation between the currents in the coils 2, 3, a spatially
varying and time varying magnetic fieid is created rather than the stationary time varying
magnetic field of the DDP. The spatial variation in the field of the BPP may appear as a siiding
nt in alternate ions between the poles of the coils 2, 3.
Other relative phase and/or magnitude variations between the currents in the coils could be
used to shape the field if there is a need to reduce the field emissions on one side of the
transmitter to avoid leakage during operation due to an offset nature of the d receiver, for
example to meet ICNIRP regulations. Thus the field may be directed in response to the output
of a sensor for example which may sense where greater field strength is required, or where the
field strength should be reduced. Also, the field strength may be time varying but lly
nary ent on where across the pad the field is required.
it is also possible to operate the coils 2, 3 180 degrees out of phase using the circuit of Figure 6,
or they could be simply connected to one inverter (as in the DDP operation). This particular
single phase operating mode is a second possible mode of ion to simplify the onic
control and power conversion that will produce a stationary time varying fieid as for the DDP.
further provides guidance on red configurations of the ferrite strips 5
above which the coils 2, 3 are placed in the BPP pad. The ferrite strips 5 are used to enhance
power transfer and ensure that a predominately single sided flux field is created to best couple
to the secondary power receiver, while ensuring that a minimal amount of ferrite is used to keep
weight to a minimum and restrict the inductance of the pad. In such a sliding field it is shown
that the ferrite strips should preferably extend under the winding coils otherwise the field may
not be forced s towards the receiver.
When the two primary coils 2, 3 of the BPP are placed with an arbitrary overlap (or substantially
nt with no overlap) with respect to each other, there will be a mutual coupling between
the coils. However for a certain ratio of overlap to coil width, denoted r0, this mutual coupling is
almost zero. The ideal overlap required to ensure no mutual coupling exists between each
y coil is not simple due to the presence of the ferrite but can be determined by simply
fixing one coil and sing this with a ermined current at fixed frequency (either via a
suitable 3D simulator or using a suitable experimental setup, for example). The open t
voltage induced in the second primary coil can then be measured. If the second coil is moved
so as to change the overlap there will be a change in coupled voltage. When this is minimised
(ideally zero) the ideal configuration can be set. The optimal overlap is dependent on the length
of the ferrite strips eath the coils.
In ? it was noted that there was a significant se in power when the ferrite
under the coils was extended, and it was clear that the ferrite should extend at least under the
entire extent of coils 2, 3 for the BPP pad arrangement of Figure 3. The reason for this is that
the field close to the BPP pad can best be described as a sliding wave across the surface.
Figure 4(a) shows a plan View of a ion of the Figure 3 arrangement according to an
embodiment of the invention. The magnetic flux pad of Figure 4(a) includes three coils 2, 3, 3a
and a modified ferrite 5 arrangement. Otherwise, the construction of the pad of Figure 4(a) is
generally in accordance with that of the BPP pad of Figure 3, including, from the bottom
upwards (when comparing with the upper drawing of Figure 3), base plate 7 (preferably
aluminium), spacer 6 (preferably tric), a core 4 comprising ferrite material 5, substantially
co-planar coils 2, 3, 3a and a cover 8 (preferably dielectric). The key difference is that an
additional coil 3a is placed above or below coil 2 or above coil 3 such that the centres or poles
of all three coils are spaced substantially equidistantly from one r in a triangular
arrangement. rmore, the configuration of the core 4 has been adapted and includes three
sets of ferrites 5 arranged with an offset of or substantially of 60“ between each set, wherein
each the three ferrite sets extends substantially parallel with an axis extending between the
centre of respective pairs of coils 2, 3 and Ba.
Figure 4(b) illustrates a variation of the embodiment of Figure 4(a), in which the core ses
a single ferrite strip or bar 5 along each of the ary lines between the centres of the coils,
1O forming at equilateral triangle in the centre. The plate 7 in this embodiment has a shape
corresponding substantially with the outer perimeter of overlapping coils 2, 3 and 3a, including
padding.
Figure 5 shows a plan view of another embodiment of the ion. The ement of Figure
5 is substantially the same as those of Figure 4 but includes four coils 2, 3, 3a, 3b and a
ed ferrite 5 arrangement within the core 4. The additional coil 3b may be placed above,
below or between coils 2, 3 and 3a. In the arrangement shown, a ferrite lattice is used with one
set of ferrites offset from the other by or substantially by 90° to form a grid.
As with the arrangement of Figure 3, the extent of overlap between the coils may be varied to
obtain the desired decoupling. More particularly, one or more of the at least three coils may be
energised with a ermined current at a fixed or respective fixed frequency and the overlap
with the other or other ones of the at least three coils varied so as to minimise the voltage in the
other or other ones of the at least three coils. To e such an overlap in practice, preferably
the ferrites 5 should first be fixed in place (since any change to the position and shape of ferrites
will impact on the overlap required between the coils necessary to ensure mutual coupling is
minimised). The shape and size of each of coils 2, 3 and 3A should preferably be identical
(although the invention is not limited o). If coil 2 is fixed in position, then coil 3 can be
moved into the relative position shown while energising coil 2. The open circuit voltage coupled
into coil 3 from the sation of coil 2 can be easily measured and with suitable movement of
coil 3 ve to coil 2 can be reduced to a minimum (ideally zero), to determine the ideal
relative position of both coils. Once the position of coils 2 and 3 have been fixed, then coil 3a
can be added generally in the position shown on Figure 4(a). Coil 3a can now be energised
and the voltages coupled into coils 2 and 3 monitored. By adjusting the position of coil 3a
relative to both coils 2 and 3 the coupled voltages should be reduced to a minimum (ideally
zero), at which point its position is fixed.
While circular coils are shown in Figures 4 and 5, the invention is not d to coils of that
shape. By way of example only, the coils may alternatively have a generally oval, square or
rectangular configuration. Further, different coils within the same pad may have different
configurations. For example, referring to the Figure 4(a) ement, coil 2 may be oval and
coils 3, 3a circular. Furthermore, while the lateral spacing of the circular coils of the Figures
may be substantially equidistant such that imaginary lines or axes extending between the
centres of adjacent coils may form a substantially equilateral triangle or square shape, this need
not necessarily be the case.
Further, while particular e 5 arrangements have been shown in Figures 4 and 5, the
ion is not limited thereto. Other ements may be devised to direct the field in a
desired manner, or more particularly to provide a path of low magnetic reluctance between the
poles of the three or more mutually decoupled coils, including a single sheet of ferrite material
of sufficient size. However, it has been found that the use of e strips as opposed to a sheet
of ferrite material provides similar performance in terms of lling the flux and so
appropriately ured strips may be favoured to reduce the cost and weight f. On the
other hand, a core comprising a sheet of ferrite material may be thinner and preferred in other
applications, and may be shaped to ensure that it provides a path of low magnetic reluctance
only between the poles.
As shown in Figures 4 and 5, where ferrite strips are used, it is preferable that these are
arranged to pass through or be parallel to an imaginary line or axis extending between the
centres of adjacent coils. Thus, arrays of ferrite strips may be provided, each array being
configured to be so aligned with one or more pairs of said coils (i.e., with the ary lines or
axes extending between coil centres).
Generally, it is able for the ferrite material to extend beyond the edges of the coils (as
shown in at least Figures 4 and 5). However, the invention is not limited thereto and may be
configured differently depending on the particular application and the coils may in fact extend
over a larger area than the ferrite material.
According to one embodiment, the ferrite material extends beyond the outer extremity of the
coils in selected regions of the coils only, the selected regions being at or proximate to where
said ary lines cross said cells (see Figure 3). Additionally or alternatively, one or more of
the coils may extend beyond the extent of the ferrites, preferably outside of said previously
mentioned ed regions (again, see Figure 3).
Referring to s 4 and 5, while it is possible for the ferrites to include arrays of strips one
above the other as shown, preferably, the es are configured to form the desired pattern in a
single layer. For example, referring to Figure 5, the ferrites may be arranged such that the
ferrites extending up and down the page (the vertical ferrites) are as shown and the left to right
ferrites (the horizontal ferrites) are then each formed by a plurality of shorter ferrites that extend
across the gap between the vertical ferrites, preferably such that the ends of the horizontal
elements abut or substantially abut the adjacent vertical ferrites.
Forming the ferrites in this manner reduces the thickness and weight of the core.
It will be appreciated that the ferrites may be otherwise configured. For example, referring again
to the Figure 5 example, the strips may have a varying thickness such that they are thinner at
the s of overlap. Reducing the thickness as a step enables the ent ferrite ts
to interlock.
The examples of e ements bed in relation to Figure 5 in the preceding three
paragraphs are not intended to be limited to the Figure 5 arrangement and may be adapted
without invention to other required ferrite arrangements such as those similar to the Figure 4
arrangement or those requiring a more complicated ferrite arrangement where additional coils
are added.
Further, each strip of ferrite may be formed from more than one piece of ferrite material. Thus,
smaller strips or pieces of ferrite material may abut or substantially abut one another to form
each larger piece.
Additionally or alternatively, the degree of integration between adjacent ferrite portions may be
sed. For example, a ferrite arrangement may be formed from one or more sheets of
ferrite material with portions thereof d as desired.
Further coils may also be added, as desired.
Figure 7 shows a possible power supply arrangement necessary for driving the pad shown in
Figure 4. As shown subscripts 2, 3 and 3A represent the inverter topology connection to coils 2,
3 and 3A in Figure 4.
An advantage of using at least three coils of the t invention is that the pad may be used
in multiple modes. For example, for a stationary vehicle ng application, a singie coil of at
least three coils of a charging pad may be activated to couple power to a small receiver on a
small utility vehicle, where the chosen coil to be activated depends on the coil which is best
coupled (i.e. best aligned) to the receiver on the vehicle. Alternatively, all coils may be
energised in phase with each other, creating a larger stationary time g field to power a
large vehicle or one requiring faster charge. Further, said coils rably three) may be used
in a three phase system (i.e. each 120 degrees out of phase) to create a g spatially varying
and time g field or multiple selected coils may be energised in a single phase system (i.e.,
to create a stationary time varying field).
In another mode, coils of the charging pad may be energised dependent on the orientation
and/or alignment of the p (e.g. on the vehicle to be charged). In this mode, all or a subset
of the coils may be sed in use. For example, pairs of coils may be sed, per the
BPP pad arrangement of Figure 3, to produce a field most effectively received by a pickup. The
pair of coils energised may be varied, for example, to modify the field to compensate for
movement of the pickup. According to one embodiment, pairs of coils of a pad containing at
least three coils may be selectively energised (including sequentially) if that produces the most
effective field.
The presence of at least three coils further enables improved steering of the field generated by
the charging pad. in addition or as an alternative to energising only selected coils of the
plurality of coils, different coils may be energised to ent levels, y “steering" the field
in a selected direction to, say, accommodate misalignment of a pickup with a charging pad,
such as due to variations in parking of vehicles to which a charge is to be provided.
The use of at least three coils can additionally or alternatively assist in g a location of a
vehicle pickup so that an appropriate (ideally optimal) charging regime can be implemented,
depending at least in part on the detected location. While this is achievable to some extent
using the arrangements described in WC 2011/16737, the inclusion of additional coils provides
greater accuracy of detected position and enables position to be ined in at least two
dimensions.
Thus the use of additional, decoupled coils provides for increased ility in the manners in
which the apparatus of the invention may be used by enabling all or a subset of the coils to be
used and further provides for improved power er by varying the mode of operation and/or
through the improved ng / positioning of the field achieved (improved in terms of being
controllable in multiple dimensions and/or across a larger area and/or better determination of
pickup position and/or adaptation of the field as a result thereof).
Operating the triangular ements of Figure 4 in a three-phase mode is particularly useful,
as it is capable of high power transfer, possesses the ability to cope with variable secondary
alignments, and has inherent field cancellation (i.e. low/no leakage) in the far field.
It will be noted from the foregoing that embodiments of the invention have particular ation
for use as a "charging pad" (i.e., the primary side winding) but the same or similar arrangements
may be used for the pickup, again with improved power transfer characteristics as a result of the
decoupling between coils of the pickup. in such embodiments, the coils would be electrically
coupled to and controlled by a pick-up controller, rather than a power supply, the pickup
ller being operable to deliver power received from the pickup coils to a load. The
controller would typically comprise a controllable rectifier or rectifiers, rather than the inverters of
a power supply.
For example, the circuit of Figure 8 which is essentially identical to the that of Figure 7, could
also be used at the output of a pad to enable power transfer to a load ted across the DC
capacitor which in such a case could also be across the battery of an electric vehicle. The
power available from each receiver coil can be monitored, and if small, the bottom switches in
each inverter bridge can be closed to decouple that receiver coil and remove any losses which
wouid ise occur from its operation.
In yet other ments of the invention, the y and/or secondary pads may be
reversible, wherein the pad may be operated to selectiveiy conduct with the coils to receive or
deliver power from/to another pad. The circuit of Figure 8 could easily be used to reverse the
power flow back to the primary but in order to synchronise this power flow back into mains utility
supply, the three phase rectifier of Figure 7 would need to be repiaced with a suitable ible
ier.
Where reversible power flow is unnecessary, a simpler secondary circuit can be used, an
3O example of which is shown in Figure 9. At the output of each coil a tuning capacitor can be
used either in series or parallel or both to bring each AC circuit to resonance. Here a parallei
resonant circuit is shown with optional series capacitance to boost the current from each coil if
required at design. The output of each of these tuned circuits is then ied, filtered (using the
common de and Cdc) and regulated using switch 8 to the load. If the coupled power to any of
the coils is determined to be low, then the two switches at the base of each ier can be
turned on and used to decouple that coil from the circuit without ing the power transfer in
either of the remaining coils, thereby substantially removing any loss associated with that circuit.
This power transfer from each coil can be easily determined by measuring the ude of the
AC current in each of the rectifiers. The output diode ensures that the energy in Cdc is not
discharged undesirably through any of the es in the circuit when these switches are
turned on. Switch 8 is used to both regulate the total power flow and decouple all three coils if
and when required.
In any ment where the lPT pad of the present invention is configured as a primary side
magnetic apparatus generating a magnetic field, it preferably couples power to the secondary or
receiving pad as effectively as possible, irrespective of the secondary pad’s ic
configuration, orientation, and displacement (lateral or otherwise). The secondary pad may be
integrated within a vehicle, mobile telephone, laptop or other such electrical device, providing
little if any control over these variable factors. That is, the primary pad is preferably ed to
be sal or near—universal in that it is adapted to transfer power to a range of le
secondary pads and/or under a wide range of conditions which could be ably anticipated
in a particular application.
When a device with a circular secondary pad is in proximity with varying ground clearance or
displacement with respect to the primary, for example, there will be a need to configure the
system to best couple power from the primary to the secondary. If the device is in close
proximity to the ground, then the coil which is in best alignment might be selected, whereas if
the secondary is r away a group of coils may be energised either together in phase or as a
multiphase system to produce a better coupling n the primary and secondary. Another
important consideration is limiting or minimising magnetic field leakage at distances of concern,
such as where there are foreign s which may heat up or humans or animals which may be
subjected to these leakage fields.
For secondary s which have polarised magnetics such as those sed in International
Patent Publication Nos. or , then the orientation of this
device is of equal concern. In such situations the primary coils may be energised to ensure best
coupling and in the case where the coils are separately controlled either a singie phase
polarised coil with best orientation can be energised, or multiphase operation can be used to
transfer power while ensuring greatest coupling and power transfer with minimal leakage for the
designated application. Variations in ground clearance, alignment and rotation may all affect
the choice of which coils are selected under what conditions. Preferably the coils in the primary
ground side have minimal mutual coupling n them, so that any configuration is
acceptable and can be used without detrimental effects such as coupled voltages from the
energising of neighbouring coils appearing in nearby coils and disrupting power flow and the
generation of the desired flux shape. However some mutual cross—coupling may be ble in
certain configurations if is sufficiently small, ed the power coupling between the apparatus
is controllable and leakage is contained as required for the application.
It will be iated that numerous other ments or variations of the coil arrangements of
Figures 4 and 5 are possible without departing from the scope of the t invention. A
number of such embodiments and variations are briefly described below by way of example.
While a backing sing the core and/or conductive plate is useful to ensure that the fields
1O are single sided and can be oriented in space such that they enhance the coupling to a
secondary magnetic device, the ferrite strips 5 are not essential to the present invention, and
may in particular be omitted where a double—sided flux field may be tolerable or even desirable.
Figures 10 and 11 show variations of the embodiments of Figures 4 and 5, tively, in
which the ferrite strips 5 are omitted. Without the core a backplate made of a conductive
material such as aluminium or copper ed a suitable distance from the coils may act as a
shield while minimising losses. The plate 7 may therefore comprise a ferrite loaded printed
circuit board (PCB) and/or an aluminium plate, for example. Alternatively there may be
applications where there is a desire to have fields in both directions, such as in a primary pad
which may need to couple to two or more secondary's which are situated both above and below
the coils. [n such cases the ferrite or shields can be removed entirely to enable such coupling.
in other cases, the fields below the structure may not be able to couple undesirably to any
ure, and therefore wili not cause any losses. While having fields present on both sides of
the primary reduces ng to a secondary device, it does not produce any significant loss and
may therefore be preferred in some circumstances to minimise the cost of producing the y
pad.
Figures 12(a) and 12(b) show two ions of a further embodiment of an iPT pad according to
the present invention, with and without ferrite strips 5. The pad according to this embodiment
comprises four coils 2, 3, 3a and 3b with a quadrature coil 12. if the four circular coils 2, 3, 3a
and 3b are thought of as each having a centre collectively defining the vertices of a square,
diagonally opposing coils of the square abut each other without pping to form two
orthogonal DDP pairs (as described above with respect to Figures 1 and 2) ing as
dipoles. Each coil of the DDP pairs overlaps both the coils of the orthogonal DDP pair, and the
two DDP pairs are accordingly mutually decoupled. The quadrature coil 12 is also mutuaiiy
decoupled from both of the DDP pairs. As a primary structure the DDP pairs and the
quadrature coil are ail independent and may also be operated with different magnitude, phase
or frequency without interfering with each other, to shape the field as required. As a secondary
structure the DDP or quadrature coils can be separately tuned at different or similar frequencies
and power can be extracted as and when desired based on the application.
In one le mode of operation of the ments of Figure 12, the DDP pairs may be
operated in phase with each other, generating a stationary time varying magnetic field. In
another mode, one pair of diagonally opposing DDP coils may be energised out of phase with
the other pair. In yet another mode, only one DDP may be energised. In yet further modes,
the quadrature coil 12 may be energised simultaneously with either or both of the DDP pairs.
The mode of operation and, where riate, coils energised are preferably chosen to
produce a field most effectively received by a pickup. The lPT system is preferably capable of
switching between any such mode as required to operate in the most efficient way, but may be
limited to a single mode or a selection of modes to simplify the power supply design and/or
control.
Figures 12(c)-(e) show r variations of the embodiments of Figures 12(a) and (b). The
embodiment of Figure 12(0) omits the quadrature coil. Figure 12(d) illustrates that the coils of
each DDP pair need not necessarily be the same size, yet are still capable of being mutually
decoupled. A quadrature coil 12 can also be added to this embodiment as shown in Figure
2O 12(e). Because the DDP pairs of coils are operated as dipoles, the quadrature coil 12 is
mutually decoupled from both DDP pairs in this embodiment.
While the coils of an lPT pad according to various embodiments of the present ion are
y completely decoupled from one another, some l coupling may be inevitable. The
IPT pad of Figure 4(b), with the dimensions listed in Table A4, under testing was shown to have
an optimum mutual coupling or coupling coefficient k of 0.15% between coils 2 and 3, and
0.08% between coils 2 and 3a, for example. However, any significant mutual coupling between
coils will severely impact the efficiency of the system and the mutual coupling should y be
as close to zero as practically possible. It should be noted that the mutual coupling measured
between coils will generally increase under load or in the presence of an external e
material. An lPT pad according to the present invention is thus ably designed to have a
mutual coupling of less than about 10% in the absence of a load or external ferrite material, and
more particularly less than about 2% or even 1%. For the purpose of the description and
claims, the phrases "mutually decoupled”, “no mutual ng” and the like are intended to
ass such mutual couplings.
For such apparatuses to have coils which are mutually decoupled requires proper spacing of the
coils relative to each other so that the flux generated from one device enters and exits in
approximately equal proportion with neighbouring coils in the primary (or secondary), wherein
the net flux through neighbouring coils is approximately zero.
Nevertheless, a higher level of coupling between the coils, such as up to about 20%, may be
acceptable in at least some applications without departing from the scope of the invention.
Even higher levels of mutual decoupling may be tolerable for some applications, in particular
where the spacing between the y and secondary pads is low. Figures 13 and 14 show
embodiments of the invention in which there may be a low level of mutual coupling, of up to
about 20% for e.
Figures 13(a)-13(e) show embodiments comprising further variations of the three~coil IPT pad of
Figure 4.
The lPT pad of Figure 13(a) further comprises a further coil 13 which is not ideally ly
decoupled, in this case entirely encircling coils 2, 3 and 3a. The further coil 13 in this
embodiment is preferably ed such that its centre or pole is substantially central with
respect to coils 2, 3 and 3a which are, preferably, mutually led from one r.
Although the central coil 13 in this embodiment encircles the other coils, in other embodiments
the substantially central coil 13 may circumscribe or partially overlap the three or more other
coils, as described below.
As the central coil 13 les or partially overlaps all of the other coils, it will not be mutually
decoupled from those coils in all possible modes of operation. In ular, the central coil 13
of Figure 13(a) will be substantially mutually decoupled from coils 2, 3 and 3a when all three of
those coils are energised, but will not lly be mutually decoupled when only coils 2 and 3
are energised, for example,
The IPT pad of Figure 13(a) also omits the core or ferrite strips 5 of the embodiment of Figure 4.
The square shape of the plate 7 can also be seen to differ from the triangular plate 7 of Figure 4
to accommodate the central coil 13.
The embodiment of Figure 13(b) is similar to that of Figure 13(a), but ses a lattice or grid
of substantially orthogonal ferrite strips 5. It will be apparent that the ferrite strips 5 thus need
not arily extend parallel to imaginary lines between the centres of coils 2, 3 and 3a as
shown in Figure 4. As previously described, the core may alternatively comprise a sheet of
ferrite material.
The embodiment of Figure 13(0) comprises a r modification with respect to Figure 13(b), in
that the ferrite strips 5 extend beyond the outer circumference of central coil ‘13. If the ferrite
strips 5 terminate within the central coil 13 then the field wiil radiate, and the elongated ferrite
strips 5 of this embodiment will thus generally be preferred.
Figures 13(d) and 13(e) show further variations of the three—coil pad of Figure 4, further
comprising a central coil 13 which partially encircles coils 2, 3 and 3a. Figure 13(d) shows an
embodiment of an tPT pad t e strips 5, while Figure 13(e) ses a lattice of
ferrite strips 5 extending to, or slightly beyond, the outer circumference of coils 2, 3 and 3a.
s 14(a) to 14(d) illustrate some sub-optimal variations of the three-coil embodiments of
Figure 4, by way of example. In these embodiments, the coils 2, 3 and 3a do not overlap, and
will therefore have mutual coupling.
in the case where the coii structure of the present invention is used as a secondary pad to
receive power, y the coils will all be mutually led from each other to ensure that
each coil can be easily tuned to receive power at a selected frequency, and that power transfer
is maximised. Under such conditions, when a coil is not receiving power it can be switched off
without impacting the ion of the other coils, to reduce any operating loss. Nevertheless, if
the secondary coils are not perfectly mutually coupled (independent), then provided the
operating circuit tuning Q (reactance of the coil divided by the load of the circuit) is iow, then
nominal tuning can be ed and operation can still arise despite there being some mutual
coupling between neighbouring coils. Such coils can also be switched out and while this may
ly impact the power transfer in adjacent coils, this can be compensated for by operation of
the primary ground coils sing or decreasing its driving VA or by adjusting a secondary
3O regulator to modify the power to the load.
In a further embodiment of the present invention comprising three or more mutuaily decoupled
coils, it may in some applications be desirable to tune one or more of the various coils to
different frequencies to enable coupled operation with secondary devices which have different
tunings. For example, for high power transfer some of the coils may be designed and tuned for
operation at 40kHz while others may be tuned at SOkHz, enabling coupling to different magnetic
structures at different tuned frequencies. Alternatively, for lower power transfer some coils may
be tuned at 800 MHz while others may be tuned to 2.4 GHz (both unlicensed bands) to achieve
the same for smaller appliances or mobile consumer electronics devices, for example.
Table A1: Dimensions of the EFF
Common Dimensions
Winding width 80 mm
Ferrite g 32 mm
Ferrite width 28 mm
Y coil spacing 50 mm
Y padding 46 mm
Cover thickness 6 mm
Coil height 4 mm
Ferrite height 16 mm
Spacer thickness 6 mm
Plate thickness 4 mm
Variations based on number of ferrites
A: BBPG: using 6 e slabs to make each e strip
(BPPB) Ferrite length 558 mm
(BBP6) Overlap 156 mm
X coil spacing 10 mm
X padding 10 mm
B: BBP8: using 8 ferrite slabs to make each ferrite strip
Ferrite length 774 mm
p 74 mm
X coil spacing — 83 mm ( — represents an p)
3O X padding 10 mm
C: BBP10: using 10 ferrite slabs to make each ferrite strip
Ferrite length 930 mm
Overlap 39 mm
X coil spacing —174 mm (— represents an overlap)
X padding 110 mm (nb: 200mm added overall to padding to fit extra
ferrites)
40 Table A2: Dimensions of the DDP
Winding width 80 mm
Inner g width 120mm
Ferrite spacing 32 mm
45 Ferrite width 28 mm
Y coil spacing 10 mm
Y padding 46 mm
Cover thickness 6 mm
Coil height 4 mm
50 Ferrite height 16 mm
Spacer thickness 6 mm
Plate thickness 4 mm
Ferrite length 558 mm
X coil spacing 10 mm
X padding 10 mm
Table A3: Dimensions of the DDQP
Winding width 80 mm
Inner winding width 120mm
Ferrite spacing 32 mm
Ferrite width 28 mm
Y coil Spacing 10 mm
Y padding 46 mm
Cover thickness 6 mm
Coil height 4 mm
e height 16 mm
Spacer thickness 6 mm
Plate thickness 4 mm
Ferrite length 558 mm
X coil spacing 10 mm
X padding 10 mm
Quadrature coil length 534 mm
Table A4: Dimensions of the IPT Pad of Figure 12
Ferrite length 520 mm
Ferrite width 28 mm
Ferrite height 16 mm
Each side of the equilateral triangle formed by e structure 200 mm
Inner diameter of each coil 130 mm
Outer diameter of each coil 150 mm
Optimum ce from centre point of one coil to the other 172 mm
Mutual coupling k between coils 2 and 3 0.15%
Mutual coupling k between coils 2 and 3a 0.08%
While the invention has been described primarily with reference to applications in ng or
charging electric vehicles, it is to be noted that the invention has application to inductive
power transfer in general, and may ore be applied in a range of industrial or
er applications including, but not limited to, wireiessly powering or charging
high— or low-power nces or consumer electronics such as mobile telephones,
40 computer devices, and/or computer peripherals. By way of example with reference to a
human interface device (HID), a primary magnetic flux pad according to the present
ion may be provided in a mouse pad to power or charge a wireless mouse, or
may be integrated in the mouse to receive power from a known primary pad.
45 Unless the context clearly requires otherwise, hout the description and the claims, the
words “comprise", "comprising”, and the like, are to be construed in an inclusive sense as
opposed to an exclusive or exhaustive sense, that is to say, in the sense of “including, but not
limited to”.
Reference to any prior art in this specification is not, and should not be taken as, an
acknowledgement or any form of suggestion that that prior art forms part of the common general
knowledge in the field of endeavour in any country in the world.
The invention may also be said broadly to consist in the parts, elements and features referred to
or indicated in the specification of the application, dually or collectively, in any or all
combinations of two or more of said parts, elements or features.
Where in the foregoing description, reference has been made to specific components or
rs of the invention having known equivalents then such lents are herein
orated as if individually set forth.
Although this invention has been described by way of example and with reference to possible
embodiments thereof, it is to be understood that modifications or improvements may be made
thereto without departing from the scope or spirit of the invention.