Inductive power transmission and distribution apparatus using a coaxial transformer

• US 20030201862A1
• Filed: 04/29/2002
• Published: 10/30/2003
• Est. Priority Date: 04/29/2002
• Status: Active Grant

• Current Assignee: Murata Machinery Limited (Muratec)
• Original Assignee: PRI Automation, Inc. (Azenta, Inc.)
• Inventors: Roth, Ian S., Arntz, Floyd O., Doherty, Brian J., Gaudreau, Marcel P. J.
• Granted Patent: US 6,686,823 B2
• Time in Patent Office: Days
• US Class Current: 336/174
• CPC Class Codes: B60L 5/005 without mechanical contact between the collector and the power supply line
• CPC Class Codes: B60L 5/40 for collecting current from lines in slotted conduits
• CPC Class Codes: B60M 1/34 in slotted conduits
• CPC Class Codes: B60M 7/003 for vehicles using stored power (e.g. charging stations)
• CPC Class Codes: H01F 38/14 Inductive couplings for wireless supply or distribution of electric power using inductive coupling H02J50/10

Abstract

A coaxial inductive power transfer and distribution apparatus is disclosed that includes a primary conductor that is stationary and a mobile secondary coil magnetically coupled to the stationary primary conductor to provide an inductive power transfer therebetween. The primary and secondary coils are disposed within a return conductor that is stationary and acts as a return path for current flowing in the primary center conductor. The primary conductor is mechanically connected to the interior surface of the return conductor to ensure the position stability of the primary conductor with respect to the secondary coil. The return conductor also includes an air gap in which a support member for the mobile secondary coil and structure is disposed within. The mobile secondary coil and structure includes a toroidal core composed of a high permeability material that is coaxially disposed about, and spaced apart from, the primary conductor. A multi-turn coil is radially disposed about the high permeability toroidal core such that magnetic flux produced by a current flowing in the center conductor is coupled to the coil. The secondary structure includes a support element coaxially disposed about the high permeability toroidal core and the multi-turn coil. The support member extends through the air gap in the return conductor to the exterior of the return conductor, where it may be coupled to an electric vehicle. The low inductance of the primary conductor allows for low voltages to be used to power the vehicle electrically coupled to the mobile secondary coil and mechanically coupled to the mobile secondary structure.

Claims

1. An inductive power transfer apparatus for transferring power from a power source comprising:

a primary conductor extending in the longitudinal direction, the primary conductor having a first end and a second end;

a return conductor surrounding the primary conductor and spaced apart therefrom;

a first support element configured and arranged to secure the center conductor in place;

the primary conductor electrically coupled to the power source and receiving power therefrom and the primary conductor further electrically coupled to the return conductor, the return conductor being electrically coupled to the power source to provide a return path thereto;

a moveable secondary including a high permeability toroidal core coaxially disposed about the center conductor and spaced apart therefrom forming a first air gap, the toroidal core including a second air gap, the first support element disposed within the second air gap, the secondary further including a multi-turn coil disposed radially about the high permeability toroidal core;

a second support element configured and arranged to support the high permeability core and the multi-turn coil; and

whereby an alternating current imposed upon the primary conductor by the power source induces a voltage in the plurality of secondary coils.

2. The inductive power transfer apparatus of claim 1, wherein the first support element is coupled to the center conductor and connected to the inner surface of the outer conductor.

3. The inductive power transfer apparatus of claim 1, wherein the second support element includes a first support section coaxially disposed about the high permeability core and the plurality of coils, the support member further including a flange end and a connecting element connecting the first support section and the flange end, the connecting element disposed within the second air gap and extending beyond the exterior surface, wherein the flange end is spaced apart from the exterior surface.

4. The inductive power transfer apparatus of claim 1 wherein the outer conductor is composed of aluminum.

5. The inductive power transfer apparatus of claim 1 wherein the first support element is composed of aluminum, the first support element being electrically insulated from the outer conductor.

6. The inductive power transfer apparatus of claim 1 wherein the first high permeability toroidal core is composed of ferrite.

7. The inductive power transfer apparatus of claim 1 wherein the high permeability toroidal core is C-shaped.

8. The inductive power transfer apparatus of claim 1 wherein the support member is composed of aluminum.

9. The inductive power transfer apparatus of claim 1 wherein the center conductor is a Litz wire.

10. The inductive power transfer apparatus of claim 1 wherein the primary conductor is electrically coupled to the power source and receives power therefrom via a shielded coaxial conductor.

11. The inductive power transfer apparatus of claim 1 wherein the primary conductor is electrically coupled to the return conductor via a conductor having a large surface area and a thin cross sectional area.

12. A system for the inductive power transfer and distribution for an electric vehicle moveable on a track comprising:

a voltage source having a predetermined frequency and amplitude;

a power transformer primary coil coupled to the voltage source;

a power transformer secondary coil, magnetically coupled to the power transformer primary coil and providing a secondary voltage that is a function of the amplitude of the voltage source and the turns ratio between the power transformer primary coil and the power transformer secondary coil;

a capacitor coupled across the voltage source;

a plurality of transformer primary coils each having a first number of turns, the plurality of transformer primary coils connected in series with one another and with the power transformer secondary coil, wherein the plurality of transformer primary coils and the capacitor form a resonant circuit that is resonant substantially at the predetermined frequency of the voltage source;

a plurality of transformer secondary coils each having a second number of turns, each magnetically coupled to a corresponding one of the plurality of transformer primary coils, each of the plurality of transformer secondary coils providing a secondary voltage having the predetermined frequency and a magnitude that is a function of the amplitude of the voltage source and the first and second number of turns; and

a plurality of primary center conductors each coupled to a corresponding one of the plurality of transformer secondary windings, wherein the primary center conductors are oriented and positioned such that as the vehicle moves on the track, a secondary system mounted on the electric vehicle engages the primary center conductor receiving inductively transferred power therefrom.

13. The system of claim 12 wherein the secondary includes toroidal core having a center orifice, the toroidal core oriented to receive primary center conductor within the center orifice, the secondary further including a plurality of secondary coils disposed radially about the toroidal core, wherein the toroidal core and the secondary coils are coupled to the magnetic flux produced by a current in the center conductor.

14. The system of claim 12 further including a first inductor connected in series between the voltage source and the power transformer primary coil, the first inductor selected to provide a predetermined inductive reactance.

15. The system of claim 12 further including a tuning capacitor, the tuning capacitor placed in series with the plurality of transformer primary coils, the tuning capacitor selected to provide a capacitive reactance substantially equal to the inductive reactance of the plurality of transformer primary coils.

16. The system of claim 12 further including a plurality of tuning capacitor, each of the plurality of tuning capacitor placed in series with a corresponding one of the plurality of transformer primary coils, each tuning capacitor selected to provide a capacitive reactance substantially equal to the inductive reactance of the corresponding one of the plurality of transformer primary coils.

17. The system of claim 12 wherein the power transformer primary coil is coupled to the voltage source via shielded coaxial conductors.