Electric machine and method for operating the same

A method for operating an electric machine comprising a stator, a rotor, and a plurality of sub-machine systems formed by dividing windings for each phase on the stator or on the rotor into separately switchable winding sections, each said winding section being assigned to each said respective sub- machine system for each said phase and each said sub-machine system being configured to act as an electric machine, the method comprising:

• switching the winding sections of the sub-machine systems such that one or more of the sub-machine systems are operated, respectively depending on at least one of speed and torque requirements for the electric machine;
• wherein a connection between the winding sections takes place mechanically by a contact disc, and the connection between the winding sections of the electric machine comprises the following steps:
• moving the contact disc axially in a direction along an axis of rotation of the contact disc to interrupt an electrically conductive connection between contacts of the contact disc and at least one said winding section of at least one said sub-machine system;
• rotating the contact disc about the axis of rotation of the contact disc to select a type of interconnection between the winding sections of the sub- machine systems;
• and
• moving the contact disc axially in the direction along the axis of rotation of the contact disc to establish an electrically conductive connection between contacts of the contact disc and at least one said winding section of at least one said sub-machine system;
• wherein for switching between the winding sections of the electric machine initially demagnetizing at least one permanent magnet of the electric machine, and then magnetizing the at least one permanent magnet of the electric machine, wherein the demagnetizing comprises at least reducing the magnetization of the permanent magnet compared to before demagnetization of the permanent magnet.

An electric machine, comprising:

• a stator;
• a rotor, wherein the stator includes three sub-machine systems comprising separately switchable winding sections for each phase, and each of the three sub-machine systems being configured to act as an electric machine, and wherein the three sub-machine systems comprises a first sub-machine system, a second sub-machine system, and a third sub-machine system consecutively arranged in a repeating pattern around an outer surface of the rotor;
• and
• at least one permanent magnet, and a device for temporary demagnetization of the at least one permanent magnet, wherein demagnetization comprises at least reducing the magnetization of the permanent magnet compared to before demagnetization of the permanent magnet.