An electric power supply system configured to supply electric power to an electrical load device being a motor that requires a current that can be variable, the electric power supply system comprising: an engine configured to output rotational power, the engine including an engine output adjustment unit configured to adjust the rotational power; a generator (10, 20, 30) configured to receive the rotational power from the engine and configured to supply a current to the electrical load device, the generator (10, 20, 30) including a rotor (11, 21, 31), a stator (12, 22, 32), and a supply current adjustment unit (131, 231, 331), the rotor (11, 21, 31) connected to the engine, the rotor (11, 21, 31) including a permanent magnet, the stator (12, 22, 32) arranged opposite to the rotor (11, 21, 31), the stator (12, 22, 32) including a winding (121, 221, 321) and a stator core (122, 222, 322), the winding (121, 221, 321) wound around the stator core (122, 222, 322), the supply current adjustment unit (131, 231, 331) configured to adjust the current to be supplied to the electrical load device, the adjustment implemented by changing an inductance of the winding (121, 221, 321), the change implemented by changing a magnetic resistance of a magnetic circuit (F2, F22, F32) for the winding (121, 221, 321), which passes through the stator core (122, 222, 322); and a control device configured to, upon a requirement of increasing the current to be supplied to the electrical load device, control the current to be supplied to the electrical load device by controlling both the engine output adjustment unit and the supply current adjustment unit (131, 231, 331) configured to adjust the current by changing the inductance of the winding (121, 221, 321), wherein the supply current adjustment unit (13, 23, 33) is configured to change the state of the generator (10, 20, 30) from one of a high-resistance state and a low-resistance state to the other, wherein in the low-resistance state, the magnetic resistance of the magnetic circuit for the winding, which passes through the stator core, is lower than that in the high-resistance state, wherein at an equal rotation speed the generator (10, 20, 30) in the high-resistance state and the generator (10, 20, 30) in the low-resistance state outputs an equal magnitude of current, wherein, to further increase the drive source output while the electrical load device is rotating at a relatively high rotation speed, the supply current adjustment unit (13, 23, 33) is configured to change the state of the generator (10, 20, 30) from the low-resistance state to the high-resistance state, the generator (10, 20, 30) in the high-resistance state outputting a first current when rotating at a first rotation speed (M+) higher than the equal rotation speed, the first current being larger than a maximum current output by the generator (10, 20, 30) in the low-resistance state rotating at the first rotation speed (M+), and wherein at a relatively low rotation speed the supply current adjustment unit (13, 23, 33) is configured to change the state of the generator (10, 20, 30) from the high-resistance state to the low-resistance state, the generator (10, 20, 30) in the low-resistance state outputting a second current when rotating at a second rotation speed (M-) lower than the equal rotation speed, the second current being larger than a maximum current output by the generator (10, 20, 30) in the high-resistance state rotating at the second rotation speed (M-). an engine configured to output rotational power, the engine including an engine output adjustment unit configured to adjust the rotational power; a generator (10, 20, 30) configured to receive the rotational power from the engine and configured to supply a current to the electrical load device, the generator (10, 20, 30) including a rotor (11, 21, 31), a stator (12, 22, 32), and a supply current adjustment unit (131, 231, 331), the rotor (11, 21, 31) connected to the engine, the rotor (11, 21, 31) including a permanent magnet, the stator (12, 22, 32) arranged opposite to the rotor (11, 21, 31), the stator (12, 22, 32) including a winding (121, 221, 321) and a stator core (122, 222, 322), the winding (121, 221, 321) wound around the stator core (122, 222, 322), the supply current adjustment unit (131, 231, 331) configured to adjust the current to be supplied to the electrical load device, the adjustment implemented by changing an inductance of the winding (121, 221, 321), the change implemented by changing a magnetic resistance of a magnetic circuit (F2, F22, F32) for the winding (121, 221, 321), which passes through the stator core (122, 222, 322); and a control device configured to, upon a requirement of increasing the current to be supplied to the electrical load device, control the current to be supplied to the electrical load device by controlling both the engine output adjustment unit and the supply current adjustment unit (131, 231, 331) configured to adjust the current by changing the inductance of the winding (121, 221, 321),