Arrangement comprising a rotation member, a case enclosing the rotation member and a brushless winding field rotational electric machine positioned between the rotation member and the case, wherein the brushless winding field rotational electric machine comprises: a stator, which is held to the case, including an alternating-current coil configured to generate a rotation magnetic field by alternating current; a field core, which is held to the case, including a field coil to be excited by direct current; and a rotor disposed on an outer periphery of the rotation member and rotatably held about a rotational axis relative to the stator and the field coil, wherein the field coil includes a plurality of coil winding layers stacked in a radial direction of the rotational axis, and a) a cross-sectional area along an axial direction of the rotational axis, of a coil winding layer (204, 206) closest to the rotational axis in the radial direction of the rotational axis 87) among the plurality of coil winding layers is smaller than a cross-sectional area along the axial direction of the rotational axis, of a coil winding layer farthest from the rotational axis in the radial direction of the rotational axis, or b) the plurality of coil winding layers include: a first coil winding layer (202; 204); and a second coil winding layer (203; 205) adjacent to the first coil winding layer (202; 204) in the radial direction of the rotational axis and having a dimension different from a dimension of the first coil winding layer in an axial direction of the rotational axis, wherein a magnetic path formed when the field coil is excited by direct current and magnetic flux flows around the field coil includes a first magnetic path and a second magnetic path characterized in that the field coil is shifted relative to the stator and the rotor in the axial direction of the rotational axis and the first magnetic path extends in the axial direction of the rotational axis so that magnetic flux flows axially from the rotor toward the field core, the second magnetic path extends in the axial direction of the rotational axis, disposed from the first magnetic path in the radial direction of the rotational axis with a gap therebetween so that magnetic flux flows axially from the field core toward the rotor, and the field coil is disposed from a first end portion of the gap closer to the rotor to a second end portion farther from the rotor in the axial direction of the rotational axis. a stator, which is held to the case, including an alternating-current coil configured to generate a rotation magnetic field by alternating current; a field core, which is held to the case, including a field coil to be excited by direct current; and a rotor disposed on an outer periphery of the rotation member and rotatably held about a rotational axis relative to the stator and the field coil, wherein the field coil includes a plurality of coil winding layers stacked in a radial direction of the rotational axis, and a) a cross-sectional area along an axial direction of the rotational axis, of a coil winding layer (204, 206) closest to the rotational axis in the radial direction of the rotational axis 87) among the plurality of coil winding layers is smaller than a cross-sectional area along the axial direction of the rotational axis, of a coil winding layer farthest from the rotational axis in the radial direction of the rotational axis, or b) the plurality of coil winding layers include: a first coil winding layer (202; 204); and a second coil winding layer (203; 205) adjacent to the first coil winding layer (202; 204) in the radial direction of the rotational axis and having a dimension different from a dimension of the first coil winding layer in an axial direction of the rotational axis, wherein a) a cross-sectional area along an axial direction of the rotational axis, of a coil winding layer (204, 206) closest to the rotational axis in the radial direction of the rotational axis 87) among the plurality of coil winding layers is smaller than a cross-sectional area along the axial direction of the rotational axis, of a coil winding layer farthest from the rotational axis in the radial direction of the rotational axis, or b) the plurality of coil winding layers include: a first coil winding layer (202; 204); and a second coil winding layer (203; 205) adjacent to the first coil winding layer (202; 204) in the radial direction of the rotational axis and having a dimension different from a dimension of the first coil winding layer in an axial direction of the rotational axis, wherein a magnetic path formed when the field coil is excited by direct current and magnetic flux flows around the field coil includes a first magnetic path and a second magnetic path characterized in that the field coil is shifted relative to the stator and the rotor in the axial direction of the rotational axis and the first magnetic path extends in the axial direction of the rotational axis so that magnetic flux flows axially from the rotor toward the field core, the second magnetic path extends in the axial direction of the rotational axis, disposed from the first magnetic path in the radial direction of the rotational axis with a gap therebetween so that magnetic flux flows axially from the field core toward the rotor, and the field coil is disposed from a first end portion of the gap closer to the rotor to a second end portion farther from the rotor in the axial direction of the rotational axis.