WO2006118474A1

WO2006118474A1 - Inductively coupled power transfer system

Info

Publication number: WO2006118474A1
Application number: PCT/NZ2006/000089
Authority: WO
Inventors: John Talbot Boys; Grant Anthony Covic; Dariusz Kacprzak
Original assignee: Auckland Uniservices Limited
Priority date: 2005-04-29
Filing date: 2006-04-28
Publication date: 2006-11-09
Also published as: TW200707877A; EP1884006A1; KR20080018875A; TWI434485B; KR101332488B1; US8581442B2; US20100289340A1; NZ539770A; JP2008539584A; EP1884006A4

Abstract

Abstract An inductively coupled power transfer system has a power pick-up that uses an asymmetrical magnetically permeable core (103, 105, 106, 107). Such cores have been found to provide a significant increase in the output power for given losses and given core volume when transferring power from a primary conductive path (101) to a secondary coil (104) provided on the core.

Description

INDUCTIVELY COUPLED POWER TRANSFER SYSTEM

Technical Field

The present invention relates to the field of inductively coupled power transfer systems. The invention may have particular utility for inductively coupled power transfer systems for vehicles travelling along a track.

Background

Inductive coupling is one known method for transferring power across coupled conductors without the need for physical connection between the conductors. An application of inductive coupling is to provide power to a movable vehicle running along a track.

Figures 1 and 2 show a schematic representation of a known inductively coupled power transfer (ICPT) system. Figure 2 is a cross-section through the system. A primary coil or conductive path 1 carries alternating current, typically at a very low frequency (VLF) of about 5-50 kHz. The primary coil 1 has first and second conductors extending along two spaced apart sides 1a, 1b. A power pick-up for such a system includes a secondary coil 2 wound about a magnetically permeable core 3 (preferably a ferromagnetic core) which is located between the sides 1a, 1 b. The ferromagnetic core concentrates the magnetic flux from the primary coil 1 and an electric potential is produced across the terminals of the secondary coil 2. The secondary coil 2 is typically tuned by a series or parallel capacitor. This electric potential is then rectified and converted to a required voltage. The ferromagnetic core 3 shown in Figure 1 is E-shaped. Alternatively, an H-shaped core can and has been used.

The ferromagnetic core 3 and coil 2 may be provided on an electric vehicle that can travel on tracks that follow the path of the primary coil 1 , or a set of primary coils 1. The output from the secondary coil 2 may be used to power the vehicle. United States patent number 5,293,308 (Boys et al.) describes an ICPT system for an electric vehicle and the contents of this patent are hereby incorporated herein by reference.

One problem with inductive power transfer is the relatively large losses that occur in comparison to power transfer methods involving a direct physical connection. These losses increase the cost of operating any apparatus. It would therefore be advantageous if these losses could be reduced. It is an object of the present invention to provide an ICPT system, or an ICPT system pickup that has reduced losses in comparison to existing systems, or at least to provide the public with a useful alternative.

Unless the context clearly requires otherwise, throughout the description, 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".

Summary of the Invention

In one aspect the invention consists in an ICPT system pick-up including an asymmetric magnetically permeable core.

In one embodiment the core comprises a first arm having first and second ends, a second arm that extends from the first arm at or closer to the first end in a direction substantially perpendicular to the first arm, and a third arm that extends from the first arm at or closer to the second end in an opposite direction to the second arm.

The core may further include a fourth arm extending parallel to the first arm from the second arm, so as to define a U-shape with the first and second arms.

A fifth arm may be provided extending from the first arm parallel to the third arm so as to define a U-shape with the first and third arms.

Alternatively or additionally a fifth arm may be provided extending from the third arm parallel to the first arm so as to define a U-shape with the first and third arms.

Preferably the pick-up includes a secondary coil wound about the first arm of the core.

In a further aspect the invention consists in an ICPT system including:

- a primary conductive path connectable to a power source for providing alternating current to the primary conductive path, the primary conductive path in use supplying electrical energy, the primary conductive path having first and second spaced apart conductors that extend along the path; - a pick-up having a secondary coil provided about a magnetically permeable core, the secondary coil in use receiving electrical energy from the primary conductive path through inductive coupling; wherein, at least when the secondary coil is coupled to the primary conductive path, the ferromagnetic core comprises a first arm that extends between the first and second conductors, the first arm having first and second ends, a second arm that extends from the first arm at or closer to the first end in a direction substantially perpendicular to the first arm, and a third arm that extends from the first arm at or closer to the second end in an opposite direction to the second arm.

Preferably the core includes one or more additional arms to allow a part of the core to define a U-shape about at least one of the first and second conductors.

Alternatively or additionally the core includes one or more additional arms to allow a part of the core to define a U-shape about both of the first and second conductors.

A fourth arm may be provided extending parallel to the first arm from the second arm, so as to define a U-shape about the first conductor.

The core may further include a fifth arm extending from the first arm parallel to the third arm so as to define a U-shape about the second conductor.

Alternatively or additionally a fifth arm may be provided extending from the third arm parallel to the first arm so as to define a U-shape about the second conductor.

In a further aspect the invention consists in an ICPT system comprising:

- a primary conductive path connectable to a power source for providing alternating current to the primary conductive path, the primary conductive path in use supplying electrical energy, the primary conductive path having spaced apart conductors defining first and second sides that extend along a first axis;

- a pick-up including a secondary coil wound about a magnetically permeable core, the secondary coil in use receiving electrical energy from the primary conductive path through inductive coupling; wherein the ferromagnetic core comprises a first arm that extends between the first and second sides and is asymmetrical about an imaginary plane extending transverse to a plane through the conductors of the first and second sides. Preferably the core comprises three, four or five arms.

In a preferred embodiment the core is shaped to define a U-shape about at least one of the conductors.

Alternatively or additionally the core is shaped to define a U-shape about both of the conductors.

In a further aspect the invention consists in a vehicle including an ICPT system pick-up as set forth in the preceding statements.

In a further aspect the invention consists in a vehicle powered by an ICPT system as set forth in the immediately preceding statements.

Further aspects of the present invention will become apparent from the following description, which is given by way of example only.

Brief Description of the Drawings

A description of preferred embodiments of the present invention, at least as presently contemplated, will now be provided with reference to the accompanying drawings, in which:

Figures 1-2 show schematic representations of part of a known inductive power transfer system; and

Figures 3-6 show representations of four embodiments of a ferromagnetic core according to the present invention.

Description of One or More Preferred Embodiments of the Invention

Figure 3 is a schematic representation of a cross-section through part of an inductively coupled power transfer (ICPT) system 100 according to a first embodiment of the invention.

The ICPT system 100 includes a primary conductive path having conductor parts 101a and 101b extending into and out of the page. The primary conductive path 101 is connected to an alternating current source (not shown), which supplies power to the ICPT system 100. The first and second conductor parts 101a and 101 b are supported by a suitable support structure (not shown).

A pick-up includes a secondary coil 102 wound about a ferromagnetic core 103, more particularly about a first arm 103a of the ferromagnetic core 103. As shown in Figure 2, the first arm 103a may include a recess 104 into which the conductor of the secondary coil 102 is wound. At least during the time that the ICPT system 100 is transferring power from the primary conductive path 101 to the secondary coil 102, the first arm 103a is located between the conductors 101a and 101 b, preferably centrally to the conductors 101a and 101 b.

Power may be taken from the secondary coil of the pick-up using known circuits and methods. The secondary coil may be tuned by a capacitor, rectified and converted to the required voltage. Appropriate circuits for achieving this are described in United States patent no. 5,293,308.

The ferromagnetic core 103 includes a second arm 103b and a third arm 103c, which extend in opposite directions from opposite ends of the first arm 103a. Unlike the known E-shaped and H-shaped ferromagnetic cores that have been used in the past, the ferromagnetic core 103 is asymmetrical about a plane BB that extends through a midpoint between the first and second sides, transverse to the plane in which the primary conductive path is located.

The ferromagnetic core 103 may be provided on a vehicle (not shown), which moves along tracks (also not shown) that follow the path of the primary conductive path 101. To accommodate this travel, the support structure for the primary conductive path 101 and the support structure for the ferromagnetic core 103 needs to be appropriately shaped to allow the ferromagnetic core 103 to clear the support structure(s) for the primary conductive path 101.

Figures 4-6 show three alternative ferromagnetic cores 105, 106 and 107. While the primary conductive path 101 remains unchanged, for each alternative ferromagnetic core, different support structures for the primary conductive path 101 and ferromagnetic core will be required to enable the ferromagnetic core to move along the primary conductive path 101. The secondary coil of the ICPT system is not shown in Figures 4-6, but is in practice provided on the first arm 103a. Referring specifically to Figure 4, a ferromagnetic core 105 includes first, second and third arms 105a-105c in the same configuration as the first to third arms 103a-103c of the ferromagnetic core 103. The ferromagnetic core 105 further includes a fourth arm 105d extending parallel to the first arm 105a from the end of the second arm 103b. The first arm 105a, second arm 105b and fourth arm 105d together form a U-shape about conductor part 101a.

Referring specifically to Figure 5, a ferromagnetic core 106 includes first, second, third and fourth arms 106a-106d in the same configuration as the first to fourth arms 105a-105d of the ferromagnetic core 105. The ferromagnetic core 106 further includes a fifth arm 106e extending parallel to the third arm 106c. The first arm 106a, third arm 106c and fifth arm 106e together form a U-shape about conductor part 101 b.

Referring specifically to Figure 6, a ferromagnetic core 107 includes first, second, third and fourth arms 107a-107d in the same configuration as the first to fourth arms 105a-105d of the ferromagnetic core 105. The ferromagnetic core 107 further includes a fifth arm 107e extending parallel to the first arm 107a from the end of the third arm 107c. The first arm 107a, third arm 107c and fifth arm 107e together form a U-shape about conductor part 101b.

In two further alternative embodiments, the arm 107d may be omitted from the ferromagnetic core shown in Figure 6, or both the arms 107d and 107b may be omitted.

The secondary coil 104 is preferably wound on the first arm of the ferromagnetic cores 105-107. The first arm may include a recess to receive the secondary coil 104.

From the foregoing description and Figures 3-6, it is clear that all the ferromagnetic cores 103, 105, 106 and 107 are asymmetrical. Specifically, the cores may be considered as being asymmetrical about an imaginary plane bisecting the primary conductive path 101. This asymmetrical characteristic of the ferromagnetic cores results in an increase in the output power for given losses and given core (e.g. ferrite) volume when transferring power from the primary conductive path 101 to the secondary coil 104, or equivalents reduced power input to the primary conductive path 101 is required to obtain the same power output from the secondary coil 104.

In the preferred embodiment of the invention, each ferromagnetic core 103, 105-107 is a single integrated component. Alternatively a ferromagnetic magnetic core may comprise two or more parts that abut each other or have a small air gap between them. Where the ferromagnetic core is provided in multiple parts, one part may be provided on a movable vehicle, the other part being stationary, located next to the primary conductive path 101 and extending along at least a portion of the primary conductive path 101 , preferably the entire length of the primary conductive path 101 where inductive power transfer is to occur.

It will also be appreciated that the ferromagnetic cores 103, 105-107 may be inverted without affecting their operation.

The shape of the ferromagnetic cores may be varied from those shown in Figures 3-6 without departing from the scope of the present invention. For example, the arms may be of different length or shape, but the asymmetrical nature of the ferromagnetic core as described herein above should be retained. Vehicles that receive some or all of their power from an ICPT system may make use of the invention to improve operating efficiency.

Where in the foregoing description reference has been made to specific components or integers of the invention having known equivalents then such equivalents are herein incorporated 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 of the invention as defined in the appended claims.

Claims

1. An ICPT system pick-up including an asymmetric magnetically permeable core.

2. A pick-up as claimed in claim 1 wherein the core comprises a first arm having first and second ends, a second arm that extends from the the first arm at or closer to the first end in a direction substantially perpendicular to the first arm, and a third arm that extends from the first arm at or closer to the second end in an opposite direction to the second arm.

3. A pick-up as claimed in claim 2 wherein the core further includes a fourth arm extending parallel to the first arm from the second arm, so as to define a U-shape with the first and second arms.

4. A pick-up as claimed in claim 2 or claim 3 wherein core further includes a fifth arm extending from the first arm parallel to the third arm so as to define a U-shape with the first and third arms.

5. A pick-up as claimed in claim 2 or claim 3 wherein core further includes a fifth arm extending from the third arm parallel to the first arm so as to define a U-shape with the first and third arms.

6. A pick-up as claimed in any one of claims 2 to 5 including a secondary coil wound about the first arm of the core.

7. A pick-up as claimed in any one of the preceding claims wherein the core comprises a single integral component.

8. An ICPT system including:

- a primary conductive path connectable to a power source for providing alternating current to the primary conductive path, the primary conductive path in use supplying electrical energy, the primary conductive path having first and second spaced apart conductors that extend along the path;

- a pick-up having a secondary coil provided about a magnetically permeable core, the secondary coil in use receiving electrical energy from the primary conductive path through inductive coupling; wherein, at least when the secondary coil is coupled to the primary conductive path, the core comprises a first arm that extends between the first and second conductors, the first arm having first and second ends, a second arm that extends from the first arm at or closer to the first end in a direction substantially perpendicular to the first arm, and a third arm that extends from the first arm at or closer to the second end in an opposite direction to the second arm.

9. An ICPT system as claimed in claim 8 wherein the core includes one or more additional arms to allow a part of the core to define a U-shape about at least one of the first and second conductors.

10. An ICPT system as claimed in claim 8 wherein the core includes one or more additional arms to allow a part of the core to define a U-shape about both of the first and second conductors.

11. An ICPT system as claimed in claim 8 wherein the core further includes a fourth arm extending parallel to the first arm from the second arm, so as to define a U-shape about the first conductor.

12. An ICPT system as claimed in claim 8 or claim 11 wherein the core further comprises a fifth arm extending from the first arm parallel to the third arm so as to define a U-shape about the second conductor.

13. An ICPT system as claimed in claim 8 or claim 11 wherein the core further comprises a fifth arm extending from the third arm parallel to the first arm so as to define a U-shape about the second conductor.

14. An ICPT system as claimed in any one of claims 8 to 13 wherein the secondary coil is wound about the first arm of the core.

15. An ICPT system comprising:

- a pick-up including a secondary coil wound about a magnetically permeable core, the secondary coil in use receiving electrical energy from the primary conductive path through inductive coupling; wherein the ferromagnetic core comprises a first arm that extends between the first and second sides and is asymmetrical about an imaginary plane extending transverse to a plane through the conductors of the first and second sides.

16. An ICPT system as claimed in claim 15 wherein the core comprises three, four or five arms.

17. An ICPT system as claimed in claim 16 wherein the core is shaped to define a U- shape about at least one of the conductors.

18. An ICPT system as claimed in claim 16 wherein the core is shaped to define a U- shape about both of the conductors.

19. A vehicle including an ICPT system pick-up as claimed in any one of claims 1 to 7.

20. A vehicle powered by an ICPT system according to any one of claims 8 to 18.

21. An ICPT system pick-up substantially as herein described with reference to any embodiment shown in the accompanying drawings.

22. An ICPT system substantially as herein described with reference to any embodiment shown in the accompanying drawings.