I
`
`New Zealand No. 274939
`
`International
`No. PCT/NZ94/00115
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`•
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`......
`Date(s):
`Priority
`..........................................................................................................................
`Complote
`Specification
`Filed:
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`NEW ZEALAND
`
`PATENTS ACT 1953
`
`COMPLETE SPECIFICATION
`
`Title of Invention:
`Inductive
`power pick-up
`coils
`
`Name, address and nationality
`of
`applicant(s)
`as in international
`application form: � flltw 'br;l\Q.ld C.0"4fll�
`House, 58 Symonds Street,
`AUCKLAND UNISERVICES
`LIMITED,,.of
`UniServices
`Auckland 1001 , New Zealand
`
`,-
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`•
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`Momentum Dynamics Corporation
`Exhibit 1011
`Page 001
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`

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`W095/11545
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`•
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`- 1 -
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`PCT/NZ94/00115
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`274939
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`5
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`fl-· JO
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`INDUCTIVE POWER PICK-UP COILS
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`TECHNICAL FIELD OF THE INVENTION
`
`This invention relates to the field of inductive power transfer for loosely coupled
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`combinations and in particular to means to enhance the collection of said power at the
`15 receiving side.
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`BACKGROUND
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`Inductive power transfer is capable of providing electric power across a significant
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`20 space to often moving apparatus without a physical connection for the electricity (such
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`as sliding or rolling contacts). It c� be carried out at low or high frequencies, in a
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`loosely or a tightly coupled configuration, and with or without magnetically permeable
`materials.
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`25
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`
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`We have described such a system in om US Patent 5,293,308 (and in the corresponding
`International application filed as PCT/GB92/0220).
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`•
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`30
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`Advantages of the prefe:Ted loosely coupled inductive power transfer means over
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`various tightly coupled ttansfer amngements include that:
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`(a) Effective transfer is possible across a larger space, thus the primary and the
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`secondary need not be constrained in space to move within such close limits.
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`(b) The larger area results in a lower peak power density or a less tightly focused
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`35 field to carry power, which is less hazardous and places less sttess on components
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`or on incidental objects within the flux field
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`Momentum Dynamics Corporation
`Exhibit 1011
`Page 002
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`W09S/11545
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`PCT/NZ94/00115
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`(c) The pick-up coil need not smround the primary conductor so a system can be
`constructed in which a flat receiving swfacc containing secondary windings may
`be brought near another flat surface containing one or more embedded transmitting
`(primary) conductors. so permitting much freedom of moveme lt for vehicles over
`a roadway, for example.
`(d) Useful power conttol means applied to the secondary side may be implemented
`by shorting the secondary coil (which is generally a resonant inductor) without
`material effect on currents in the primary side. A shorted secondary coil ha3 little
`effect on primary current flow, so unaffected primary current can reach another
`consumer further from a power supply.
`Exploiting the above advantages of loosely coupled inductive power transfer systems to
`utilise IPT in an optimised way uncovers the inherent disadvantages between loosely
`and tightly coupled systems. mainly that the available power may be limited and that
`secondary pick-up coils are large, expensive, have unnecessary ohmic resistance, and
`have large magnetic fields of their own when in use. Means to make the transfer
`process more effective across wider gaps are required and therefore there is a need to
`enhance the ability of secondary windings to collect as much of the available flux as
`possible.
`
`DEFINITIONS
`
`IYr is used a s an abbreviation for "inductive power transfer".
`
`s
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`A tightly coupled pair of inductors exhibit a close correspondence or ratio between
`current in one and in the other. Substantially all of the magnetic flux generated by
`current in one inductor is coupled to the second inductor. An example is the relationship
`between windings in a power transformer. Thus a shorted tum in a typical power
`transformer secondary causes large and usually damaging currents to flow in the
`primary winding.
`
`A loosely coupled pair of inductors do not exhibit a close correspondence. Only a
`35 portion of the flux emanating from the primary conductor passes through the secondary
`conductor. Changes in the induced current in the secondary inductor has only a small
`
`Momentum Dynamics Corporation
`Exhibit 1011
`Page 003
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`

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`W09S/11545
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`•
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`-3-
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`effect in the primary inductor.
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`PCI'/NZ94/00115
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`5
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`A primary winding is one which generally acts as a source of magnetic flux, some of
`the flux intersecting the windings of a secondary winding which then passes the power
`onwards for consumption. The direction of power transfer is of course reversible. In
`this specification we use the names primary and secondary to refer to the usual
`direction of power flow.
`
`OBJECT
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`10
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`It is an object of the present invcndon to provide an improved means for the transfer of
`electric power across a gap by inductive means. or one which will at least provide the
`public with a useful choice.
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`15
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`STATEMENT OF THE INVENTION
`
`In one aspect the invention provides an inductive power pick-up means comprising a
`plurality of pick•up coils mounted on a movable support said coils being spaced apart
`20 from ope another, each coil being adapted to pick-up inductive power from a primary
`conductor so that each coil can act as a secondary conductor when located relative to a
`
`said primary conductor, and control means capable of identifying from time to time the
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`25
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`pickup coil or coils in best alignment with a said primary conductor, said control
`means including switching means capable of switching "on" the identified pickup coil
`or coils which are best sited to collect inductive power from a said primary conductor,
`and to render functionally inactive the coil or coils (if any) which are remote from a
`said primary conductor.
`
`Preferably the control means is capable of determining from time to time the
`short-circuit current available at each pickup coil.
`
`Preferably the control means has means to measure the rate of voltage increase that
`occurs when the coil is released from a shorted state.
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`35 More preferably the control means maintains those coils which are not loaded, or only
`partly loaded, in a short-circuited state.
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`Momentum Dynamics Corporation
`Exhibit 1011
`Page 004
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`W095/1154S
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`PCI'/NZ94/00115
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`•
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`-4-
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`Preferably each pick-up coil is mounted on a ferromagnetic flux concentrator adapted
`for capturing flux lines and feeding them through the core of a said pickup coil
`
`In another aspect the invention provides a core for collecting magnetic flux from a
`space and concentrating the flux through a secondary winding of a loosely coupled
`inductive power transfer system; the core comprising an elongate mass of magnetically
`
`permeable material having a length, a width, and a height, and having low losses m. th�
`
`operating frequency.
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`5
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`10
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`Preferably the magnetic permeability of the magnetic core is relatively high, so that in
`use the magnetic core serves as a concentrator or collector of at least some of the flux
`generated by a primary conductor of the inductive power transfer system.
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`15
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`A preferred permeability is 1000 or greater - where air is 1.
`
`Preferably the magnetic core is flexible or at least capable of undergoing distortion
`without pennanent loss of function.
`
`In a related aspect the core is composed of a ferrite material, provided as a modular
`array comprising at least fom fingers of material, each finger having at least one shaped
`side, the fingers being laid side by side along the length of the elongate mass in an array
`with these shaped sides held in close contact with each other by a compliant force
`exerting a compression force along the length of the am.y, so that the permeability of
`the array is substantially similar to that of an equivalent single mass of the ferrite
`material.
`
`Preferably the shaped sides arc flat, although alternatively other mating shapes may be
`used.
`
`Preferably the flatness of the flat sides is such that, if two clean strips arc brought
`together, the magnetic permeability of the strips in contact is not substantially lower
`than that of the bulk ferrite material.
`
`Alternatively the ferrite material of the core may be made up of modules having shapes
`other than rectangles.
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`20
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`Momentum Dynamics Corporation
`Exhibit 1011
`Page 005
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`

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`W095/11545
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`•
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`-5-
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`PCl'/NZ94!00115
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`In a further related aspect the core is provided with one or more coil-carrying sections
`which support a coiled conductor wound as one or more t1D'DS around the core, which
`coil or winding is a secondary coil as herein defined and which comprises the inductive
`portion of a resonant tank circuit.
`
`Optionally more than one secondary coil may be provided on a single core.
`
`Preferably a conducting sheet is placed on the side of the magnetic core far from the
`source of magnetic flux and preferably this sheet is not in contact with the magnetic
`core or associated windings.
`
`Preferably the conductive sheet is capable of supporting the flow within it of significant
`eddy or reaction currents and for this reason a preferred material is aluminium
`substantially free of defects and smface scratches.
`
`Preferably each secondary coil is tuned with its own resonating capacitor and each has
`its own rectifier so that a DC output can be taken from it.
`
`In another aspect this invention provides a magnetic flux enhancement controller
`capable of sensing the relative magnitude of the current flowing in any one shotted
`pick-up or secondary coil and capable of controlling each shorting switch, and provided
`
`with a controlling set of instructions to utilise, by opening the shorting switch for, or
`
`unshon that coil exhibiting the highest short-circuit cm:rent.
`
`Preferably the choice is made amongst one set of coils on a shared core and so several
`coils may be in simultaneous use in an installation having several cores.
`
`In a related aspect the controller also includes means to sense the output voltage, means
`
`to short out all coils if the output voltage is higher than a predetermined limit. and
`means to unshort the selected coils if the output voltage i s lower than another
`predetermined limit.
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`Optionally both predetermined limits may be the same voltage.
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`Momentum Dynamics Corporation
`Exhibit 1011
`Page 006
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`

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`W095/11545
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`•
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`-6-
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`PCT/NZ94/0011S
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`In a further aspect this invention provides a magnetic flux enhancement controller
`capable of sensing the relative magnitude of the cutTent flowing in any shorted coil
`wound over a single magnetic core, and capable of ci�ti,:mining by a logic process
`based on relative magnitudes of all coil short-circuit currents the position of the
`elongated source of magnetic flux or primary conductive pathway which is providing
`magnetic flux passing through the or each magnetic core.
`
`In another aspect this invention provides a movable vehicle equipped with a magnetic
`flux enhancement controller and with one or more magne tic cores capable of
`concentrating a magnetic flux, built onto or into a surface of the vehicle close to the
`primary conductive pathway.
`
`DRAWINGS
`
`The following is a description of a preferred form of the invention, given by way of
`example only, with refe�nce to the accompanying diagrams.
`
`is an illustration of a prior art inductive power transfer anangement
`using a vertical field.
`
`is an illustration of a ferrite core according to the present invention,
`using a horizontal field from conductors below a smface.
`
`is an illustration of a ferrite module or finger of the present invention.
`
`is an illustration of a ferrite core assembly of the present invention,
`including three pick-up coils.
`
`is a section along a fCilitc core showing one secondary winding in place.
`
`is a wiring diagram for an IPT controller for the vehicle of Fig 13
`
`is a circuit diagram for a pick-up coil controller for the vehicle of Fig 13
`
`Ei&.,2.:
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`Eia,.3.:
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`Hu:
`Eu:
`Ei&.,6:
`Eiu:
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`5
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`Momentum Dynamics Corporation
`Exhibit 1011
`Page 007
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`

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`W095/11545
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`PCT/NZ94/00115
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`•
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`Eid:
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`5
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`10
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`-7-
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`is an illustration to show the placing of cores and coils as they would be
`installed beneath a vehicle.
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`is a block diagram for instructions for estimating the position of the
`primary conductor in relation to the array of secondary coils for the
`controller of Fig 6.
`
`Fi& 10:
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`Fi& 11:
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`is an illustration of the present invention in principle; in an idealised,
`solid-ferrite form.
`
`is an illustration of a preferred embodiment of the present invention
`constructed from discrete fenite elements as seen from below.
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`15
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`Fi& 12:
`
`is an illustration of a preferred embodiment of the present invention
`constructed from discrete fenite elements as seen from one end.
`
`Fi& 13:
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`20
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`is an illustration from below of a prcfetred embodiment of the present
`invention, comprising a vehicle having ten separate pickup units
`embedded in the underneath surface adjacent to the road
`
`is an illustration of a preferred embodiment of the present invention
`showing how a pickup coil within a pickup unit may be controlled.
`25 INTRODUCTION
`
`In our loosely coupled inductive power transfer (]Pr) systems, we prefer to use:
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`30
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`35
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`(a) Alternating currents of medium frequency; using presently available semiconductor
`switches it is possible to generate effective power at around 10 KHz and while higher
`frequencies would result in more compact IPT systems, losses within tuning capacitor
`dielectrics, switching-duration delays and the generation of radio-frequency
`interference becomes more likely. Hence, at present 10 KHz is the centre of the
`preferred frequency range. Furthermore we prefer to use reasonably pure sine waves;
`that is. alternating currents having a low harmonic content, as these radiate less
`electromagnetic interference and dissipate less energy than do waveforms with added
`
`Momentum Dynamics Corporation
`Exhibit 1011
`Page 008
`
`

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`WO9S/11545
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`•
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`harmonics.
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`PCT/NZ94/00115
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`-8-
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`5
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`(b) A primary conductor carrying resonant current This provides a higher circulating
`current than that actually passing through the semiconductor switches which provide
`the power at any moment, and enhances the sine-wave nature of the circulating current.
`A typical primary Q is of the order of 3, in a lightly loaded state. We also prefer to use
`t. heavy litz wire to carry the primary current as this type of wire provides a good ratio
`of surface (skin) to volume. In its most commonly used form, the primary conductor
`laid out along or within a substrate is formed as a closed loop with the outward wire
`running parallel to the return wire at a reasonab�y constant spacing, �though other
`configurations such as open loops are possible. In order to extend the length of track
`that can be driven with a limited voltage we use pi-coupling and zero-inductance
`coupling methods as described in our PCT applications published as W093/23908 and
`W093/23909.
`
`(c) A secondary conductor (pick-up coil) also carrying resonant current. Again we
`prefer to use litz wire for the windings and as a typical secondary Q is of the order of 10
`a significant secondary current can flow in the pick-up coil and through its resonating
`capacitor.
`
`(d) Secondary power control means. We have found that one convenient way to control
`circulating current, which if too high can interfere with propagation of primary CUITCnt,
`is to shon out the secondary coil. Only a small quantity of electricity is dissipated at the
`moment of shorting or while being shoned, in a loosely coupled IPT system. The
`shorting action is typically under the control of a controller seeking to provide a steady
`voltage, so that if the (usually rectified) output voltage available at a certain load is in
`excess of a first threshold value the coil is shorted until the output voltage is under a
`second threshold value. In this way, the resonating current in a secondary coil does not
`rise to high levels if the consumption of power from it happens to be light
`
`PREFERRED EMBODIMENT
`
`Originally we used a relatively large coil having its axis orientated verticdly (assuming
`a vehicle operating on a substantially flat surface) and wound on a low-permeability
`former (equivalent to an "air-cored" coil ) to pick up the flux from the primary
`
`Momentum Dynamics Corporation
`Exhibit 1011
`Page 009
`
`

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`W095/US45
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`PC.T/NZ94/001 15
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`•
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`- 9 -
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`conductor, relying on a reasonable length of parallel conductors to intersect a useful
`amount of flux. While an air core is unsaturable its permeability is only one. The
`preferred form of this invention is concerned with means to overcome several problems
`associated with that approach, including :Lat as the pick-up coil is inherently large its
`series resistance is significant, leading to power dissipation and inefficiency, and that
`its physical size is inconvenient and leads to wastage of resources. In addition those
`portions of the pick-up coil bridging between the actively collecting portions that run
`parallel to the primary conductor arc not used to pick up flux and in a sense are wasted
`copper.
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`5
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`10
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`The invention will now be described in general tenns with reference to figures 10-14,
`then in more detail with reference to figures 1-9.
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`15
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`Example 1:
`Various embodiments of our earlier inventions directed towards the transfer of electric
`power from a fixed primary element to a mobile or at least portable secondary element
`have generally involved the use of a rectangular, air-cored pickup coil which is
`constructed and placed so that its long sides are, during use, placed as close as
`20 reasonably possible to the one or more turns of the primary inductor. Our more recent
`embodiments have used ferritcs which have projections that practically swround the
`primary inductor which for the purpose has been mounted so as to project from a
`surface. The _close tolerances and projecting components involved are somewhat
`undesirable for applications involving road vehicles or even for railway vehicles which
`use switches or points.
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`25
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`It has smprisingly l ecn found that an arrangement as shown conceptually at 1 100 in Fig
`11. essentially consisting of a large sheet of fenitc oriented more or less tangentially to
`the direction of CUl'l'ent flow, or in other words, in a plane that would intersect along the
`length of the conductor were it not shifted away at right angles from the conductor, acts
`as a flux collector and is capable of channeling flux from a relatively large space about
`the primary conductor through one or more relatively small secondary coils. A suitable
`ferrite would be cheap, have a relatively large saturation point, and would have low
`losses at the operation frequency. The secondary coil has no "waste copper" bridging
`gaps between active pickup areas - a problem in air-only rectangular coils.
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`30
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`Momentum Dynamics Corporation
`Exhibit 1011
`Page 010
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`

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`W0 95/US15
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`•
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`- 10 -
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`PCT/NZ94/00115
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`Advantages of this flux collector in inductive power pickup applications include that, as
`the spacing and orientation of the vehicle (sec Fig 13) is not closely constrained, it is
`possible to lay an &mly of conductors beneath a roadway to allow powering of vehicles
`whether they are proceeding in a direct path or involved in passing or parking
`s
`manoeuvres or the like. Therefore this application provides for the electric powering of
`vehicles from stationary power sources without unduly altering driving style.s.
`Furthermore, the relatively high frequency of the power provided ;,n the primary
`conductors (ca 10 KHz} cJimioatcs the need for ferromagnetic aids at the primary side -
`as used in 120 Hz installations. Simple slits cut as parallel pairs in the roadway with a
`diamond saw or the like, to accommodate the preferred litz wire array, are all that are
`needed.
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`10
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`In a warehouse, an inductively powered vehicle used for shifting goods may pick up
`15 power from anywhere if an may of cables carrying primary inductive current is laid
`over the floor.
`
`In Fig 10 the entire ferrite sheet is 1 101 - 1 104 - 1 106, wherein the raised portions
`1 102, 1105 have been raised in order to accommodate the turns of the pickup coil
`(indicated as 1103) wrapped around the ferrite at that point. An aluminium cover sheet
`1107 is applied relatively closely to the upper surface of the ferrite - herein the primary
`conductors arc located beneath the lower surface of the ferrite. The aluminium cover
`sheet may be made structurally and electrically continuous with an outer r 1n of the
`vehicle. It serves to further restrict spread of the flux and to screen the interior of the
`vehicle from stray induced currents.
`
`A large single sheet of ferrite such as shown in Fig 10 is a relatively impractical
`solution. Effective fcrrites are extremely brittle and SIC hard to fabricate as single units
`in the form shown. A unit cost of at least NZ$4000 is likely. On the other hand, ferrite
`slabs and bars are already available as standard products and Figs 1 1 and 12 illustrate a
`preferred embodiment of our "flux concentrator", made from standard slabs and bars
`(fingers). The advantages of this approach include that the ferrite elements are
`protected, there is freedom to slip within the ferrite mass if the assembly is distorted,
`and replacement of individual modular elements is easy, should there be breakage. The
`unit cost of an assembly made from discrete ferrite elements is of the order of NZ$400.
`Preferably at least the adjacent surfaces between individual elements of the ferrite
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`20
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`Momentum Dynamics Corporation
`Exhibit 1011
`Page 011
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`W095/11545
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`PCT/NZ94/00115
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`elements are finished by grinding so that the adjacent surfaces have little or no air gap
`between �m. Preferably the entixe assembly is held in compression by spring pressure
`from end to end, and by downwards pressure against the bridged from (for example) a
`sponge rubber sheet or other 1esilient material.
`
`In Fig 11, 1200 indicates the entilc assembly as seen from below, within a ttansparent
`s upport 1206. In fact a support made from "Tufnol" - a dimensionally stable
`engineering plastics comprising a resin in which layers of cloth are embedded - is
`preferred. In any case the support should not be of a material liable to interact with the
`magnetic flux. The preferred embodiment support comprises a sheet of 15 mm thick
`"Tufnol" into which a 10 mm deep depression has been milled to accommodate the
`several arrays of ferrite fingers (1201, 1204, 1205) and two non-magnetic (perhaps
`"NylGn") spacers ( 1202, 1203) which underlie the two bridges 1309, 1 3 10 in Fig 12)
`carrying the pickup coils. The aluminium backing plate (1 107 or 131 1; not visible in
`this view) would preferably be screwed to the sheet 1206 by an array of fasteners. As
`an alternative to milling, an may of strips may be laminated onto a baseplate and glued
`or otherwise held in place, or an inert structure may be pressed, cast or otherwise
`fonned from, for example, polycarbonate, polyethylenetercphthalate, or acrylic plastics.
`
`Fig 12 illustrates the view 1300 fro� one end of the assembly of Fig 1 1. Two primary
`conductors 1312 and 1313 arc indicated. The pickup coils 1307 and 1318 are indicated
`wrapped around a "bridge" made of ferrite slabs 1309, 1310 which are free to side over
`the raised bars at each end bat which are pressed downwards against them. In practice
`the coils would preferably comprise thicker conductor - e.g. litz wire in a bundle of
`about S mm diameter. Also in practice some form of thermal connection between the
`windings of the coil and the aluminium sheet may be included in order to provide for
`the dissipation of heat from within the metal of the coil. Sections through ferrite bars or
`fingers are shown at 1301, 1304, and 1305.
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`A spring (not shown) may compress the bars along the length of the assembly from one
`end. One possibility for such a spring is to form the spacers 1 302, 130 3 out of a
`resilient material. The overa..U aluminium cover is indicated as 1 31 1 . It may be
`
`continuous with the underside of the vehicle, so that this assembly protrudes slightly, t ·:
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`35
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`the lower surface of the "Tufnol" or other sheet may be flush or even slightly depressed
`below the smrounding smface.
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`Momentum Dynamics Corporation
`Exhibit 1011
`Page 012
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`W0 95/1154S
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`PCT/NZ9�/00115
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`- 12-
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`It has been found that effective power transfer occurs over primary-to-ferrite spacings
`of up to 75 mm ± 25 mm, whereas earlier designs had preferred spacings of only 20
`mm, ± 10 mm.
`
`Fig 13 shows at 1400 an underneath view of a vehicle 1401 bearing a number of pickup
`assemblies or flux concentrators 1404, 1405, 1406; the units 1406 being inclined as
`they are near the steering wheels 1402. It will be evident that only some of the pickup
`coils will at a given time be suitably orientated with respect to the pair of primary
`conductors 1403.
`
`Use of the preferred resonant, or tuned, primary and secondary inductive clements for
`the sake of greatly improved effectiveness carries the potential disadvantage that any
`lightly loaded or unloaded secondary resonant coil, because it will then develop a high
`resonating current within it, will interfere with the primary inductor and effectively
`prevent the transfer of inductive power to other consumers located further from the
`position where power is injected into the primary inductor. In effect, a closely coupled
`and lightly loaded coil terminates the primary inductive pathway at its present position.
`
`It has been found that this disadvantage may be negated by shorting any lightly loaded
`pickup coils, thereby halting the flow of resonant currents and causing the coil to
`resemble a conducting sheet in which only eddy currents may circulate.
`
`In a practical vehicle (or other such installation such as a boat or cntenainment
`conveyance or the like), electronic means is provided to instantaneously and
`repetitively:
`(a) determine which is the most appropriate coil or coils to use for power collection,
`(b) to hold any unused coil or coils in a shorted state, and
`(c) to control circulating currenta within coils in use by shoning the flowing current
`from time to time so that the rectified output voltage remains within predetermined
`limits.
`
`Pan (a) is preferably carried out by periodically measuring the short-circuit current
`from any pickup unit or coil/rectifier assembly, and selecting the one pickup unit (or
`more, if high power tra:.mfcr is required) having the highest short-circuit currcnL This
`process selects the coil capable of supplying the power at the lowest Q factor; each
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`10
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`15
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`20
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`25
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`30
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`35
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`Momentum Dynamics Corporation
`Exhibit 1011
`Page 013
`
`

`

`W0 95/11S45
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`•
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`- 13 -
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`PCT/NZ94/00115
`
`pickup coil 501 being resonant in combination with its parallel capacitor S02.
`
`5
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`10
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`Parts (b) and (c) may be carried out at each pickup coil by a simple local comparator
`circuit with hysteresis driving a solid-state switch as illustrated in Fig 14, or
`alternatively by electronic means linking all the coils of a vehicle.
`
`The electronic means in question may be integrated into a single digital controller unit
`including an embedded microprocessor, with gate drivers corresponding to the number
`of pickup coils as its outputs, and a corresponding number of A-to-D input channels to
`read voltage outputs as inputs to �c microprocessor. The actual design of such a
`controllei: will be immediately apparent to a designer skilled in the art of electronic
`design.
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`15
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`Fig 14 indicates at 1500 one form of the circuitry that may be used. 1501 is a pickup
`coil with a piefcrrcd ferrite core, and 1502 is a capacitor which together form a resonant
`or tank circuit. Bridge rectifier 1503 rectifies the resonant current which is smoothed
`by capacitor 1507 and presented at the output terminals 1508. The solid-state switch
`(here a NPN tranSistor 1504 but preferably a low ON-resistance MOSFBT device) may
`20 be controlled through its gate terminal 1505 and when closed will shon the pickup coil
`1S0 1 . Surprisingly, very little power is dissipated on closing such a switch. A
`stand-alone controller capable of overcoming the lightly-loaded pickup coil effect
`typically compares the output voltage with a reference voltage by means of a
`comparator preferably including some hysteresis, and closes the switch 1504 whenever
`the output is too high, and conversely opens the switch when the output is too low.
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`25
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`A preferred controller for use with a number of such coils within one installation may
`use a single embedded microcontroller to manage the entire system, taking voltage
`measurements from the terminals 1508 and returning control signals to the base/gate
`input 1505.
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`30
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`D---pJe"'·•
`.E,A,IIIU _ ,._.
`We have made use of materials with a high magnetic permeability to gather or
`concentrate the available flux into a smaller space, so that the secondary coil can be
`made smaller (both in its dimensions and in its length) and so that flux can be sucked
`into the core from a greater area. At the preferred operating frequencies (such as 10
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`35
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`Momentum Dynamics Corporation
`Exhibit 1011
`Page 014
`
`

`

`W0 9S/1 154S
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`•
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`- 14 -
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`PCT/NZ94/00115
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`KHz) laminated metal cores and the like exhibit significant losses. We prefer to use
`ferritcs, some preferred types of which have a permeability (µ) of 2000 to 3000.
`
`For om moving vehicle projects, a secondary pick-up unit may be built around a slab of
`ferrite, for example 30 cm long, 2 cm thick and 10 cm wide. This slab is preferably
`orientated with its flat face parallel to the length of a primary conductor, and its long
`a.xis at right angles to the primary conductor. The pick-up coil is wound closely around
`the central part of the fenite slab. Practical units are several times longer and have
`several coils wound around separate sections (as in Fig 2) and in use a controller may
`be instructed to select the most productive coil at any one instant.
`
`As ferritcs are a type of ceramic, slabs of this size are quite difficult and therefore
`expensive to make. They are brittle and may be broken easily during use. An air-filled
`crack of even 25 microns (1/1000 inch) width will substantially detract from the
`magnetic advantages of the fenitc. We have therefore developed a type of modular
`ferrite core which is easy to configure in various sizes, to make (and repair), and which
`may flex in use without suffering permanent damage.
`
`Our flux concentrator is comprised of a stack of modules hel d together in a
`magnetically inert tray b;r means of spring pressure using a leaf spring or the like
`
`exerting pressure along the length of the core.
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`5
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`10
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`15
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`20
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`Each module (see Fig 3) is preferably a squBJ"".; or rectangular bar 300 of solid ferrite
`25 having a length (along the edge 303) equal to the desired width of the fenite core and a
`height equal to the desired thickness of the core. The wjdth (from side to side) of each
`module is of less importance and typically it is the same as the height. A ferrite core is
`made up by stacking a number of these modules side by side with the precision-ground
`edges 302 in close contact. Precision grinding is commonly applied to femte cores. As
`internal air gaps detract from the permeability of the assembled ferrite core it is
`desirable to form the sides of each module so that when one touches another there is
`substantially no air gap. Preferably any remaining air gap is less than one micron in
`thickness. Thus the typical smfacc finish required for the sides 302 of each module is
`"flat to within one micron over the length of the module" which is not far short of an
`optically flat surface . A typical price for finished modules according to our
`requirements is of the order of NZ$4 to $6, and so an example ferrite core using 20
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`30
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`Momentum Dynamics