Coil switching circuit for linear electric generator

• US 20050218728A1
• Filed: 01/07/2005
• Published: 10/06/2005
• Est. Priority Date: 03/16/2004
• Status: Active Grant

• Current Assignee: Ocean Power Technologies, Inc.
• Original Assignee: Ocean Power Technologies, Inc.
• Inventors: Stewart, David B., Schanzer, Henry I., Smalser, Paul
• Granted Patent: US 7,362,003 B2
• Time in Patent Office: Days
• US Class Current: 310/12.120
• CPC Class Codes: F03B 13/1845 and the wom slides relative to the rem
• CPC Class Codes: F05B 2220/7068 equipped with permanent magnets
• CPC Class Codes: H02K 3/28 Layout of windings or of connections between windings windings for pole-changing H02K17/06, H02K17/14, H02K19/12, H02K19/32
• CPC Class Codes: H02K 41/031 of the permanent magnet type
• CPC Class Codes: H02P 25/06 Linear motors
• CPC Class Codes: H02P 9/00 Arrangements for controlling electric generators for the purpose of obtaining a desired output Ward-Leonard arrangements H02P7/34; vector control H02P21/00; feeding a network by two or more generators H02J; for charging batteries H02J7/14
• CPC Class Codes: Y02E 10/30 Energy from the sea, e.g. using wave energy or salinity gradient

Abstract

In a linear electric generator (LEG) which includes apparatus for passing a permanent magnetic assembly (PMA) along linearly disposed sections of coils of an induction coil assembly (ICA) for generating voltages and power, a switching arrangement for coupling only selected sections of coils of the ICA across the power output lines of the LEG. The selected coil sections include the sections of coils of the ICA in close proximity to the passing PMA. In accordance with different embodiments, the non selected coils of the ICA may be either short circuited or disconnected (open circuited) from the power output lines.

Claims

1. A linear electric generator (LEG) comprising:

a coil assembly comprising N sections of induction coils disposed linearly along a distance dl;

the coils exhibiting inductance and resistance along their length;

a magnetic assembly of length d2, where d2 is smaller than d1;

means for passing the magnetic assembly along and over the linearly disposed induction coils while maintaining a small gap between the magnetic assembly and the coils, the passing of the magnetic assembly over a particular coil section causing that particular coil section to be excited in that it produces a voltage across the coils in that particular section;

first and second output points for producing therebetween a voltage corresponding to the voltage generated across the coils due to the passing magnetic assembly; and

switching means coupled between the coils and the first and second output points for selectively coupling only sections of coils in close proximity to the passing magnetic assembly between the first and second output points.

2. The LEG as claimed in claim 1, wherein said switching means includes N selectively enabled switches, one switch per coil, each switch connected across its coil section for selectively shorting out its corresponding coil section when not in close proximity to the magnetic assembly;

said switches exhibiting a very low impedance when turned-on or closed and a high impedance when turned-off or open; and

wherein a load is coupled across said first and second output points; and

wherein excited coils are coupled between said first and second outputs points and said load via a low impedance path provided by said switching means.

3. The LEG as claimed in claim 2, wherein the switches corresponding to the coil sections in close proximity to the magnetic assembly are opened for enabling a voltage to be developed across the coil sections in close proximity to the magnetic assembly;

and wherein the switches associated with the coil sections not in close proximity to the magnetic assembly are closed for shorting out their corresponding coil section and concurrently providing a path for the selected excited coils producing a voltage.

4. The LEG as claimed in claim 2, wherein the N coil sections are connected end to end between said first and second output points.

5. The LEG as claimed in claim 4 wherein said switching means includes means for sensing at least one of the position and direction of the magnetic assembly relative to the coil sections for producing signals to control the turn-on and turn-off of the switches, for enabling only selected coils in close proximity to the magnetic assembly to be coupled across the first and second output points.

6. The LEG as claimed in claim 5 wherein said switching means includes voltage sensing means coupled across the coil sections for sensing the voltages induced across the coils as a function of their proximity to the magnetic assembly and for producing signals to control the turn-on and turn-off of the switches, for enabling only selected coils in close proximity to the magnetic assembly to be coupled across the first and second output points.

7. The LEG as claimed in claim 6, wherein said switching means includes switch control circuitry coupled to said voltage sensing means for applying turn-on signals to selected shorting switches connected across the coil sections;

and wherein each switch is controlled by a switch control circuit; and

wherein each switch control circuit is in turn controlled by a voltage sensing circuit.

8. The LEG as claimed in claim 5, wherein there is a switch connected across each coil section;

and wherein each switch is controlled by a switch control circuit; and

wherein each switch control circuit is coupled to a control logic module for selectively turning on the switch to short out its corresponding coil section or for maintaining a switch associated with a coil section turned-off to enable a voltage to be developed across the coil section and to be coupled across the first and second output points.

9. The LEG as claimed in claim 8, wherein said switching means includes sensing means for supplying signals to said control logic module pertaining to at least one of:

(a) the position of the magnetic assembly relative to the coil assembly;

(b) the direction of the magnetic assembly relative to the coil assembly; and

(c) outputs of coil voltage sensing circuits.

10. The LEG as claimed in claim 2, wherein each one of said N selectively enabled switches is one of a silicon controlled rectifier (SCR), a TRIAC, a relay contact, a triggered solid-state switch, a latching switch and a non-latching switch.

11. The LEG as claimed in claim 1, wherein a position sensing coil for sensing the position of the magnetic assembly relative to the coil assembly is disposed along the N sections of induction coils for providing signals pertaining to the position of the magnetic assembly relative to the coil assembly for controlling the switching means and enabling only the voltages developed across the coils in close proximity to the magnetic assembly to be coupled between said first and second points.

12. The LEG as claimed in claim 1, wherein light emitting elements are attached to one of the magnetic assembly and the coil sections and light sensors are connected to the other one of the magnetic assembly and the coil sections for sensing the position of the magnetic assembly and for providing signals for controlling the switching means and enabling only the voltages developed across the coils in close proximity to the magnetic assembly to be coupled between said first and second points.

13. The LEG as claimed in claim 1, wherein optical light sensing means are disposed along the coils and a corresponding light emitting means is disposed on the magnetic assembly for sensing the position of the magnetic assembly and for providing signals for controlling the switching means and enabling only the voltages developed across the coils in close proximity to the magnetic assembly to be coupled between said first and second points.

14. The LEG as claimed in claim 1, wherein said N sections of coils are connected end to end across said first and second output points;

and wherein said switching means includes a selectively enabled/disabled switch connected across each one of said N sections of coils.

15. The LEG as claimed in claim 1, wherein each section of coil has first and second terminals;

and wherein said switching means includes;

(a) a first set of selectively enabled switches connected between the first terminals of each one of said coil sections and said first output point; and

(b) a second set of selectively enabled switches connected between the second terminals of each one of said coil sections and said second output point.

16. The LEG as claimed in claim 15 wherein selected coils in close proximity to the magnetic assembly are coupled via a selectively enabled switch from said first set to said first output point and via a corresponding selectively enabled switch from said second set to said second output point.

17. The LEG as claimed in claim 16, wherein the non selected coils which are not in close proximity to the magnetic assembly are open circuited and wherein the selected coils in close proximity to the magnetic assembly are connected in series via a switch from said first set and a switch from said second set across said first and second output points.

18. The LEG as claimed in claim 1, wherein the means for passing the magnetic assembly over and along the coils includes disposing the coils along one of a float and column of a wave energy converter (WEC) intended to be placed in a body of water and wherein the magnetic assembly is attached to the other one of the float and column;

and wherein the float and column can move relative to each other and are part of the wave energy converter (WEC).

19. The LEG as claimed in claim 1, wherein the means for passing the magnetic assembly over and along the coils includes disposing the coils along one of a float and column and wherein the magnetic assembly is attached to the other one of the float and column for enabling at least one of the following:

(a) the coils to be stationary and the magnetic assembly to move up and down relative to the coils;

(b) the magnetic assembly to be stationary and the coils to move up and down relative to the magnetic assembly; and

(c) the magnetic assembly and the coils to move relative to each other.

20. A combination comprising:

a coil assembly including N sections of induction coils extending along a support structure for a distance d1;

the coils exhibiting inductance and resistance along their length;

a permanent magnetic assembly (PMA) of length d2, where d2 is smaller than d1,

means for passing the PMA along and over the induction coils while maintaining a small gap between the magnet and the coils, the passing of the PMA over a coil section causing that coil section to be excited in that it produces a voltage across the coils in that coil section; and

switching means coupled to the coils for selectively coupling only selected sections of coils in close proximity to the passing PMA between first and second output points via said selected switching means.

21. The combination as claimed in claim 20, wherein a load is connected between said first and second output points, and wherein said selected sections of coils produce a voltage across said load.

22. The combination as claimed in claim 21, wherein said switching means includes N selectively enabled shorting switches, one switch per coil, each switch being connected across its corresponding coil section for selectively shorting out its corresponding coil section.

23. The combination as claimed in claim 22, wherein the shorting switches connected across the coils in close proximity to the PMA are opened and the shorting switches across the coils which are not in close proximity to the PMA are closed for shorting out their corresponding coil section.

24. The combination as claimed in claim 20, wherein the means for passing the magnetic assembly over and along the coils includes disposing the coils along one of a float and column of a wave energy converter (WEC) and wherein the magnetic assembly is attached to the other one of the float and column of the WEC;

and wherein the float and column can move relative to each other.

25. The combination as claimed in claim 20 wherein each coil section has first and second terminals, and wherein each coil terminal is coupled via a first selectively enabled switch to said first output point and via a second selectively enabled switch to said second output point for enabling each terminal to be selectively coupled to one of said first and to second output points.

26. The combination as claimed in claim 25 wherein selected coil sections are coupled via selectively enabled switches between said first and second output points;

and wherein the non selected coil sections are disconnected from said first and second output points by disconnecting at least one of their first and second terminals from one of said first and second output point.

27. The combination as claimed in claim 20 wherein the N coil sections define a tapped coil configuration.

28. The combination as claimed in claim 20 wherein the N coil sections define a segmented coil configuration.

29. The combination as claimed in claim 20 wherein said switching means includes switches for selectively coupling selected active coils in series between said first and second output points and for disconnecting non-selected inactive coils from said first and second output points, whereby the non-selected coils are effectively open circuited.

30. The combination as claimed in claim 20, wherein each one of said N induction coils has first and second terminals;

and wherein adjacent coils share a common terminal, the second terminal of one coil being common to the first terminal of an adjacent coil, whereby the N sections of induction coils are physically and electrically connected in series between said first and second output points.

31. The combination as claimed in claim 30 wherein there are N-1 taps formed between said first and second output points to enable said switching means to be connected to said N sections of coils.

32. The combination as claimed in claim 20 wherein said switching means includes means for sensing at least one of position and direction for controlling the coupling of the coil sections between the first and second output points.

33. A combination comprising:

a coil assembly including N sections of induction coils extending along a support structure for a distance d1;

the coils exhibiting inductance and resistance along their length;

a permanent magnetic assembly (PMA) of length d2;

means for passing the PMA along and over the induction coils while maintaining a small gap between the magnet and the coils, the passing of the PMA over a coil section causing that coil section to be excited in that it produces a voltage across the coils in that coil section; and

switching means coupled to the coils for selectively coupling only selected sections of coils in close proximity to the passing PMA between first and second output points via said selected switching means.