Electrical transmission or interconnection systems – Electromagnet or highly inductive systems
Patent
1996-05-16
1998-10-13
Shoop, Jr., William M.
Electrical transmission or interconnection systems
Electromagnet or highly inductive systems
336178, 336212, 336233, H01F 4100
Patent
active
058216383
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to the field of inductive power transfer for loosely coupled combinations and in particular to means to enhance the collection of said power at the receiving side.
DESCRIPTION OF THE RELATED ART
Inductive power transfer is capable of providing electric power across a significant space to often moving apparatus without a physical connection for the electricity (such as sliding or rolling contacts). It can be carried out at low or high frequencies, in a loosely or a tightly coupled configuration, and with or without magnetically permeable materials.
We have described such a system in our U.S. Pat. No. 5,293,308 (and in the corresponding International application filed as PCT/GB92/0220).
Advantages of the preferred loosely coupled inductive power transfer means over various tightly coupled transfer arrangements include that: and the secondary need not be constrained in space to move within such close limits. focused field to carry power, which is less hazardous and places less stress on components or on incidental objects within the flux field. can be constructed in which a flat receiving surface containing secondary windings may be brought near another flat surface containing one or more embedded transmitting (primary) conductors, so permitting much freedom of movement for vehicles over a roadway, for example. 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 has 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
IPT is used as an abbreviation for "inductive power transfer".
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 turn 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 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 effect in the primary inductor.
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.
SUMMARY OF THE INVENTION
It is an object of the present invention 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.
In one aspect the invention provides an inductive power pick-up means comprising a secondary conductor capable of collecting power from an inductively powered primary conductor characterised-in-that the secondary conductor comprises one or more pick-up coils, each coil being mounted on a ferromagnetic flux concentrator adapted for capturing flux lines and feeding them through the core of each pickup c
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Boys John Talbot
Green Andrew William
Auckland UniServices Limited
Ganjian Peter
Shoop Jr. William M.
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