A power plant with a driven part, wherein the power plant is configured to drive the driven part by motive power, comprising: a heat engine; and a first rotating machine including a stator, and a first rotor and a second rotor which are relatively rotatable with respect to said stator, in which one of said first rotor and said second rotor is mechanically connected to said heat engine, and the other of said first rotor and said second rotor is mechanically connected to said driven part, wherein said stator includes an armature row which is formed by a plurality of armatures arranged in a circumferential direction of the stator, and configured to generate a rotating magnetic field which rotates in the circumferential direction, by armature magnetic poles generated in the plurality of armatures in accordance with supply of electric power, wherein said first rotor includes a magnetic pole row disposed in a manner opposed to said armature row, said magnetic pole row being formed by a plurality of magnetic poles which are arranged in a manner spaced from each other in the circumferential direction and each two adjacent ones of which have polarities different from each other, wherein said second rotor includes a soft magnetic material element row disposed between said armature row and said magnetic pole row, said soft magnetic material element row being formed by a plurality of soft magnetic material elements which are arranged in a manner spaced from each other in the circumferential direction, and characterized in that a ratio of the number of the armature magnetic poles to the number of the magnetic poles to the number of said soft magnetic material elements is set to 1 to m to(1+m)/2 provided m≠1. a heat engine; and a first rotating machine including a stator, and a first rotor and a second rotor which are relatively rotatable with respect to said stator, in which one of said first rotor and said second rotor is mechanically connected to said heat engine, and the other of said first rotor and said second rotor is mechanically connected to said driven part, wherein said stator includes an armature row which is formed by a plurality of armatures arranged in a circumferential direction of the stator, and configured to generate a rotating magnetic field which rotates in the circumferential direction, by armature magnetic poles generated in the plurality of armatures in accordance with supply of electric power, wherein said first rotor includes a magnetic pole row disposed in a manner opposed to said armature row, said magnetic pole row being formed by a plurality of magnetic poles which are arranged in a manner spaced from each other in the circumferential direction and each two adjacent ones of which have polarities different from each other, wherein said second rotor includes a soft magnetic material element row disposed between said armature row and said magnetic pole row, said soft magnetic material element row being formed by a plurality of soft magnetic material elements which are arranged in a manner spaced from each other in the circumferential direction, and characterized in that a ratio of the number of the armature magnetic poles to the number of the magnetic poles to the number of said soft magnetic material elements is set to 1 to m to(1+m)/2 provided m≠1.