Rotating electric machine or wind power generation system

1. A rotating electric machine comprising:

a rotor having a rotor iron core;

a field winding provided on the rotor iron core; and

a neutral ring supported independently of the field winding, wherein

the field winding and the neutral ring electrically connect with each other through a connecting wire, a radially innermost portion of the connecting wire connected to the neutral ring and a radially outermost portion of the connecting wire connected to the field winding,

the neutral ring is spaced from the rotor iron core,

the connecting wire absorbs a stress difference between the field winding and the neutral ring when a centrifugal force is applied,

the neutral ring is supported independently of the field winding so as not to move in a radial direction,

the neutral ring is supported by a supporting portion fixed to a shaft of the rotor so as not to move in a radial direction, and

the supporting portion is disposed between the rotor iron core and the neutral ring in a rotational axis direction.

2. The rotating electric machine according to claim 1 , wherein a length of the connecting wire between a connected position on the field winding and a connected position on the neutral ring is longer than a length of a straight line connecting the connected position on the field winding and the connected position on the neutral ring.

3. The rotating electric machine according to claim 2 , wherein the connecting wire includes a slack.

4. The rotating electric machine according to claim 1 , wherein the connecting wire is flexible.

5. The rotating electric machine according to claim 1 , wherein the connecting wire includes a part along the neutral ring, and is connected with the neutral ring in the part along the neutral ring.

6. The rotating electric machine according to claim 5 , wherein the connecting wire is formed in a stepped shape.

7. The rotating electric machine according to claim 1 , wherein the connecting wire extends straight from a connected position on the field winding toward a rotation center, includes only one right-angled bent part, and is connected with the neutral ring along a circumferential direction at a location at which the connecting wire is connected with the neutral ring.

8. The rotating electric machine according to claim 1 , wherein the connecting wire includes a bent part that is symmetric with respect to a circumferential direction.

9. The rotating electric machine according to claim 8 , wherein the connecting wire is one of a plurality of connecting wires, and the neutral ring and the connecting wires are disposed in a line symmetric manner with respect to a straight line extending toward a rotation center.

10. A wind power generation system comprising the rotating electric machine according to claim 1 , wherein

the rotating electric machine is an alternating-current excitation synchronous electric generator, and the field winding is supplied with excitation current through an electrical power converter,

the rotor is a rotor of the alternating-current excitation synchronous electric generator that rotates when a blade receives wind and rotates, and

the alternating-current excitation synchronous electric generator is housed in a nacelle supported on a tower.

11. The rotating electric machine according to claim 1 , wherein the radially innermost portion and the neutral ring define a connected location at which the connecting wire and the neutral ring are joined.

12. The rotating electric machine according to claim 1 , wherein the radially outermost portion and the field winding define a connected location at which the connecting wire and the field winding are joined.

13. A rotating electric machine comprising:

a rotor having a rotor iron core;

a field winding provided on the rotor iron core; and

a neutral ring supported independently of the field winding, wherein the field winding and the neutral ring electrically connect with each other through a connecting wire,

the neutral ring is spaced from the rotor iron core,

the connecting wire absorbs a stress difference between the field winding and the neutral ring when a centrifugal force is applied,

the neutral ring is supported independently of the field winding so as not to move in a radial direction,

the neutral ring is supported by a supporting portion fixed to a shaft of the rotor so as not to move in a radial direction, and

the supporting portion is disposed between the rotor iron core and the neutral ring in a rotational axis direction.

14. A rotating electric machine comprising:

a rotor having a rotor iron core;

a field winding provided on the rotor iron core;

a neutral ring supported independently of the field winding;

a cantilever electrically connected with the neutral ring and having one end supported by the neutral ring; and

a connecting wire connected with the cantilever, wherein

the field winding and the neutral ring electrically connect with each other through the connecting wire, a radially innermost portion of the connecting wire connected to the cantilever and a radially outermost portion of the connecting wire connected to the field winding,

the neutral ring is spaced from the rotor iron core,

the connecting wire absorbs a stress difference between the field winding and the neutral ring when a centrifugal force is applied,

the neutral ring is supported independently of the field winding so as not to move in a radial direction,

the neutral ring is supported by a supporting portion fixed to a shaft of the rotor so as not to move in a radial direction, and

the supporting portion is disposed between the rotor iron core and the neutral ring in a rotational axis direction.

15. The rotating electric machine according to claim 14 , wherein the connecting wire is one of multiple connecting wires, and a length L of the cantilever satisfies L<2πR/m where R is an outside diameter of the neutral ring and m represents a number of the connecting wires in the rotating electric machine.