A hybrid electric-power supply system (100, 100a), comprising: a three-phase rotary electric machine including an armature serving as a stator and a field element serving as a rotor, said armature having a first winding corresponding to a first phase, a second winding corresponding to a second phase, and a third winding corresponding to a third phase; a converter connected to the first winding, the second winding, and the third winding; a three-phase power source having a first terminal corresponding to the first phase, a second terminal corresponding to the second phase, and a third terminal corresponding to the third phase; a connecting part (40, 40a) for switching between a first state where power is fed from the three-phase rotary electric machine to the converter by a normal operation of the rotor while the first winding, the second winding, and the third winding are star-connected; and a second state where power is fed from the three-phase power source to the converter, wherein the first winding, the second winding, and the third winding are separated from one another (see section, page 7, 1. 14 to 16), wherein the first terminal is connected to the first winding, the second terminal is connected to the third winding, and the third terminal is connected to the second terminal, such that in the second state the second phase and third phase are interchanged as compared with the first state; and a reverse-rotation prevention mechanism for blocking rotation of the field element, during the second state, in a direction reverse to its normal direction of rotation in the first state. a three-phase rotary electric machine including an armature serving as a stator and a field element serving as a rotor, said armature having a first winding corresponding to a first phase, a second winding corresponding to a second phase, and a third winding corresponding to a third phase; a converter connected to the first winding, the second winding, and the third winding; a three-phase power source having a first terminal corresponding to the first phase, a second terminal corresponding to the second phase, and a third terminal corresponding to the third phase; a connecting part (40, 40a) for switching between a first state where power is fed from the three-phase rotary electric machine to the converter by a normal operation of the rotor while the first winding, the second winding, and the third winding are star-connected; and a second state where power is fed from the three-phase power source to the converter, wherein the first winding, the second winding, and the third winding are separated from one another (see section, page 7, 1. 14 to 16), wherein the first terminal is connected to the first winding, the second terminal is connected to the third winding, and the third terminal is connected to the second terminal, such that in the second state the second phase and third phase are interchanged as compared with the first state; and a first state where power is fed from the three-phase rotary electric machine to the converter by a normal operation of the rotor while the first winding, the second winding, and the third winding are star-connected; and a second state where power is fed from the three-phase power source to the converter, wherein the first winding, the second winding, and the third winding are separated from one another (see section, page 7, 1. 14 to 16), wherein the first terminal is connected to the first winding, the second terminal is connected to the third winding, and the third terminal is connected to the second terminal, such that in the second state the second phase and third phase are interchanged as compared with the first state; and a reverse-rotation prevention mechanism for blocking rotation of the field element, during the second state, in a direction reverse to its normal direction of rotation in the first state.