An open-loop and/or closed-loop control device for operating a rotary current machine, which is fed by a 3-phase converter, wherein • the device comprises a structure, specifically an open-loop and/or closed-loop control structure, • the structure comprises a stator flux controller and a slip frequency controller or the structure comprises a stator flux controller and a torque controller, • the structure comprises a first limiter, which is adapted to limit a setpoint value ω Sl * fed to the slip frequency controller or the torque controller to a slip frequency maximum value ω Sl _ i _ max * or torque maximum value in order to limit a torque-forming fundamental oscillation current component ( i Sq) of the stator current ( i S), i.e. the current through the stator of the machine, • the structure comprises a second limiter, which is adapted to limit the speed at which a setpoint value fed to the stator flux controller changes to a maximum value (ΔΨ S,max) in order to limit a flux-forming fundamental oscillation current component ( i Sd) of the stator current ( i S), • the structure is adapted to calculate the slip frequency maximum value ( ω Sl _ i _ max *) or torque maximum value depending on - a predefined current maximum value ( i S,max) for a stator current fundamental oscillation value of the stator current, - an actual value ( i Sd, mod) formed by filtering measured current values of the stator current ( i S) in accordance with the flux-forming fundamental oscillation current component of the stator current ( i S) and - an actual value (| i Sd | f) formed by filtering measured current values of the stator current ( i S) in accordance with the flux-forming fundamental oscillation current component of the stator current ( i S), wherein the structure is adapted to feed a first difference which is a difference of the actual value (| i Sq | f) formed by filtering measured current values of the stator current ( i S) in accordance with the torque-forming fundamental oscillation component of the stator current ( i S) and a maximum value ( i Sq,max) of the torque-forming fundamental oscillation current component of the stator current formed by the predefined maximum current value ( i S,max) and a filtered actual value ( i Sd, mod) of the flux-forming fundamental oscillation current component of the stator current to a first closed-loop control device (401 - 409) with a proportional, integral controller and wherein the structure is adapted to feed a second difference, which is a difference of an actual value (| i Sd | f) formed by filtering measured current values of the stator current ( i S) in accordance with the flux-forming fundamental oscillation current component of the stator current ( i S) and a maximum value ( i Sd,max) of the flux-forming fundamental oscillation current component of the stator current to a second closed-loop control device (201 - 209) with a proportional controller, wherein an output of the first closed-loop control device (401 - 409) is connected to an input of the first limiter and wherein an output of the second closed-loop control device (201 - 209) is connected to an input of the second limiter. • the device comprises a structure, specifically an open-loop and/or closed-loop control structure, • the structure comprises a stator flux controller and a slip frequency controller or the structure comprises a stator flux controller and a torque controller, • the structure comprises a first limiter, which is adapted to limit a setpoint value ω Sl * fed to the slip frequency controller or the torque controller to a slip frequency maximum value ω Sl _ i _ max * or torque maximum value in order to limit a torque-forming fundamental oscillation current component ( i Sq) of the stator current ( i S), i.e. the current through the stator of the machine, • the structure comprises a second limiter, which is adapted to limit the speed at which a setpoint value fed to the stator flux controller changes to a maximum value (ΔΨ S,max) in order to limit a flux-forming fundamental oscillation current component ( i Sd) of the stator current ( i S), • the structure is adapted to calculate the slip frequency maximum value ( ω Sl _ i _ max *) or torque maximum value depending on - a predefined current maximum value ( i S,max) for a stator current fundamental oscillation value of the stator current, - an actual value ( i Sd, mod) formed by filtering measured current values of the stator current ( i S) in accordance with the flux-forming fundamental oscillation current component of the stator current ( i S) and - an actual value (| i Sd | f) formed by filtering measured current values of the stator current ( i S) in accordance with the flux-forming fundamental oscillation current component of the stator current ( i S), - a predefined current maximum value ( i S,max) for a stator current fundamental oscillation value of the stator current, - an actual value ( i Sd, mod) formed by filtering measured current values of the stator current ( i S) in accordance with the flux-forming fundamental oscillation current component of the stator current ( i S) and - an actual value (| i Sd | f) formed by filtering measured current values of the stator current ( i S) in accordance with the flux-forming fundamental oscillation current component of the stator current ( i S),