The invention relates to a method for controlling an optimal operating point in a synchronous machine and to an inverter-fed synchronous machine, wherein in a first method step according to the invention for the synchronous machine by means of a FEM method or by means of a measurement method a functional dependency of the voltage components Ud, Uq, UE upon the current components ld, lq, lE is determined, and from this according to formula (I) the respective dependency of the flux linkage components ?d, ?q, ?? upon the current components ld, lq, IE is determined, wherein R1 and R2 are the ohmic resistances of the corresponding windings of the synchronous machine. In a second method step according to the invention the synchronous machine is operated in regulated operation and an optimal operating point is controlled, (1) wherein a desired value of the exciting current is ascertained by solving the non-linear optimisation problem, formula (II), (2) wherein the ascertained desired value of the exciting current is used as desired value for an exciting current regulator, (3) wherein an actual value of the exciting current is ascertained by measurement or modelling, (4) wherein desired values of the stator current are ascertained using the ascertained actual value of the exciting current by solving the non-linear optimisation problem, formula (III), (5) wherein the desired values of the stator current are supplied to the stator current regulators.