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 provided along the circumferential direction in a surface, of the magnetic core, that is in contact with the through hole, the opening coupling the through hole and the cavity to each other;
• a first winding coupled to the inverter, provided in the cavity, and wound along the circumferential direction;
• a first rotary member provided at a location corresponding to the opening in an axial direction of the axis of rotation, the first rotary member being rotationally movable in the circumferential direction, inside the cavity, with a rotation of the shaft;
• a second winding provided on the first rotary member and wound along the circumferential direction;
• and
• one or more rectifiers provided in contact with the shaft, coupled to the second winding, and provided in a path coupling the second winding and the second motor winding to each other.