Rotary electric machine

1. A rotary electric machine having at least one AC phase, the rotary electric machine comprising:

a rotor; and

a stator disposed around the rotor, including a stator core having a plurality of axially extending slots spaced along an inner periphery region of the stator core and armature windings accommodated in the slots;

wherein:

each slot contains four armature bars each extending in an axial direction of the stator core;

each armature winding is formed by electrically connecting at least one of the armature bars in a first slot and at least one of the armature bars in a second slot to each other;

the armature bars of a pair specified in accordance with a required output voltage of the rotary electric machine are connected to each other, via a connecting piece;

each armature winding is a one-turn winding formed by serially connecting one of the armature bars in the first slot and one of the armature bars in the second slot, via the connecting piece;

two of the one-turn windings are formed in parallel using two of the armature bars in the first slot and two of the armature bars in the second slot;

each AC phase has two parallel circuit branches each composed of the one-turn windings;

each armature bar has a coil end on its both ends; and

connections of two of the armature bars on each coil end have two types of connection configurations: a forward connection and a reverse connection.

2. The rotary electric machine according to claim 1 , wherein:

each AC phase has at least one pole;

each pole of each AC phase is formed by serially connecting a plurality of the one-turn windings; and

two of the armature bars in each slot used for forming the respective one-turn windings in each pole are insulated from each other.

3. The rotary electric machine according to claim 1 , wherein the connection of two of the armature bars is performed with an additional spacer sandwiched between each of the two armature bars and the connecting piece.

4. The rotary electric machine according to claim 1 , wherein the connection piece is of a step-wise form having at least two thicknesses, the portion connected to each armature bar having a thickness greater than the other portions thereof.

5. The rotary electric machine according to claim 1 , wherein:

pairs of the four armature bar layers on radially outward and inward sides in each slot respectively serve as a bottom coil and a top coil;

the forward connection connects a first layer of the bottom coil in a first slot and a first layer of the top coil in a second slot to each other, and also connects a second layer of the bottom coil in the first slot and a second layer of the top coil in the second slot to each other; and

the reverse connection connects a first layer of the bottom coil in a first slot and a second layer of the top coil in a second slot to each other, and also connects a second layer of the bottom coil in the first slot and a first layer of the top coil in the second slot to each other.

6. The rotary electric machine according to claim 1 , wherein:

the four armature bars are four radially layered armature bars;

the forward connection connects, in one slot, a first layer of the four radially layered armature bars and a third layer of the four radially layered armature bars to each other, and also connects a second layer of the four radially layered armature bars and a fourth layer of the four radially layered armature bars to each other; and

the reverse connection connects, in one slot, a first layer of the four radially layered armature bars and a fourth layer of the four radially layered armature bars to each other and also connects a second layer of the four radially layered armature bars and a third layer of the four radially layered armature bars to each other.