Electric power transmission device and motor apparatus

A motor apparatus comprising:

• a motor including a motor stator and a motor rotor, the motor stator including a first motor magnetic core and a first motor winding, the motor rotor including a second motor magnetic core and a second motor winding;
• a shaft coupled to the motor rotor;
• an inverter;
• a magnetic core having a ring shape including a through hole through which the shaft extends, the magnetic core including therein a cavity along a circumferential direction about an axis of rotation of the shaft, and having an opening to the cavity, the opening being provided along the circumferential direction in a surface of the magnetic core different from a surface thereof in contact with the through hole;
• a first winding coupled to the inverter, provided in the cavity, and wound along the circumferential direction;
• a rotary member coupled to the shaft through the opening, the rotary member being rotationally movable, inside the cavity, in the circumferential direction with a rotation of the shaft;
• a second winding provided on the rotary member and wound along the circumferential direction;
• and
• a rectifying circuit provided in a path coupling the second winding and the second motor winding to each other.