A reconfigurable brushless AC electric motor, operating in both asynchronous and synchronous modes, the motor comprising: a stator receiving an AC power signal and generating a rotating stator magnetic field; a rotating motor shaft (11, 23); a rotor (12, 12a, 12b, 12c, 12d, 12e, 12f, 12g, 12h, 12i, 12j) rotating with the motor shaft (11, 23), the rotor (12, 12a, 12b, 12c, 12d, 12e, 12f, 12g, 12h, 12i, 12j) comprising: inductive elements for cooperation with the rotating stator magnetic field, providing the asynchronous mode of operation for motor startup; pole pieces (20, 20a,20b, 20c) fixed to the rotor, carrying the inductive elements; and at least one rotatable magnetic circuit element (16, 16a, 16b, 16c, 16d, 72, 70) residing inside and extending along substantially the entire length of the rotor (12, 12a, 12b, 12c, 12d, 12e, 12f, 12g, 12h, 12i, 12j) and configured to magnetically cooperate with the pole pieces (20, 20a,20b, 20c) and the stator, having a first position resulting in a weak magnetic field to allow the inductive motor startup; and being rotatable with respect to the rotor (12, 12a, 12b, 12c, 12d, 12e, 12f, 12g, 12h, 12i, 12j), around an axis of rotation parallel with the motor shaft (11, 23), to a second position resulting in a strong magnetic field for cooperation with the rotating stator magnetic field for efficient synchronous operation; wherein said at least one rotatable magnetic circuit element (16, 16a, 16b, 16c, 16d, 72, 70) comprises at least one rotatable permanent magnet (16, 16a, 16b, 16c, 16d, 72) or a rotatable shunting piece comprising non-magnetically conducting material, magnetically cooperating with at least one fixed permanent magnet. a stator receiving an AC power signal and generating a rotating stator magnetic field; a rotating motor shaft (11, 23); a rotor (12, 12a, 12b, 12c, 12d, 12e, 12f, 12g, 12h, 12i, 12j) rotating with the motor shaft (11, 23), the rotor (12, 12a, 12b, 12c, 12d, 12e, 12f, 12g, 12h, 12i, 12j) comprising: inductive elements for cooperation with the rotating stator magnetic field, providing the asynchronous mode of operation for motor startup; pole pieces (20, 20a,20b, 20c) fixed to the rotor, carrying the inductive elements; and at least one rotatable magnetic circuit element (16, 16a, 16b, 16c, 16d, 72, 70) residing inside and extending along substantially the entire length of the rotor (12, 12a, 12b, 12c, 12d, 12e, 12f, 12g, 12h, 12i, 12j) and configured to magnetically cooperate with the pole pieces (20, 20a,20b, 20c) and the stator, having a first position resulting in a weak magnetic field to allow the inductive motor startup; and being rotatable with respect to the rotor (12, 12a, 12b, 12c, 12d, 12e, 12f, 12g, 12h, 12i, 12j), around an axis of rotation parallel with the motor shaft (11, 23), to a second position resulting in a strong magnetic field for cooperation with the rotating stator magnetic field for efficient synchronous operation; wherein said at least one rotatable magnetic circuit element (16, 16a, 16b, 16c, 16d, 72, 70) comprises at least one rotatable permanent magnet (16, 16a, 16b, 16c, 16d, 72) or a rotatable shunting piece comprising non-magnetically conducting material, magnetically cooperating with at least one fixed permanent magnet. inductive elements for cooperation with the rotating stator magnetic field, providing the asynchronous mode of operation for motor startup; pole pieces (20, 20a,20b, 20c) fixed to the rotor, carrying the inductive elements; and at least one rotatable magnetic circuit element (16, 16a, 16b, 16c, 16d, 72, 70) residing inside and extending along substantially the entire length of the rotor (12, 12a, 12b, 12c, 12d, 12e, 12f, 12g, 12h, 12i, 12j) and configured to magnetically cooperate with the pole pieces (20, 20a,20b, 20c) and the stator, having a first position resulting in a weak magnetic field to allow the inductive motor startup; and being rotatable with respect to the rotor (12, 12a, 12b, 12c, 12d, 12e, 12f, 12g, 12h, 12i, 12j), around an axis of rotation parallel with the motor shaft (11, 23), to a second position resulting in a strong magnetic field for cooperation with the rotating stator magnetic field for efficient synchronous operation; wherein said at least one rotatable magnetic circuit element (16, 16a, 16b, 16c, 16d, 72, 70) comprises at least one rotatable permanent magnet (16, 16a, 16b, 16c, 16d, 72) or a rotatable shunting piece comprising non-magnetically conducting material, magnetically cooperating with at least one fixed permanent magnet.