Patent ID: 8922086

Claim:
An electric machine, comprising: a fixed stator, which carries a multi-phase stator winding; a rotor, which cooperates with the stator via an operating air gap, and which has multiple poles over its circumference in a predefined sequence which are excited by permanent magnets and by at least one field coil; wherein the number of poles of the rotor is changeable as a function of an intensity and a direction of a field current in the at least one field coil, wherein the rotor has a core which is a laminated core laminated in the axial direction which is provided with grooves on its circumference for accommodating the at least one field coil and the at least one field coil, having a step size which corresponds to a pole pitch of the lower number of poles, is situated on the circumference of the rotor, wherein winding overhangs of the at least one field coil pass by below at least one radially magnetized permanent magnet situated on the rotor circumference, on the faces of the laminated core in a chord-like manner, and wherein the rotor has only one field coil, inserted into grooves diametrically opposite one another, which is wound around a rotor shaft split at the winding overhangs and cooperates with at least two permanent magnets situated between the grooves on the rotor circumference diametrically opposite one another.