Method and device for controlling an operation of an electric motor

A method for controlling an operation of an electric motor, the method comprising:

• in a modulation, generating electric voltages which are applied to electric phases of the electric motor and outputting the electric voltages in a controlled fashion as a function of a rotor position of the electric motor and as a function of a setpoint/actual comparison of at least one first variable that characterizes a load of the electric motor or of an actual rotational speed of the electric motor;
• when a field-weakening range of the electric motor is reached, adding a predefined pilot-control angle and a further regulated pilot-control angle component to a rotor position angle, which characterizes a rotor position, to form a composite angle;
• and
• when the field-weakening range is reached, using the composite angle to characterize the rotor position in the modulation.

A device for controlling an operation of an electric motor, the device comprising:

• a supply unit for a controlled outputting of electric voltages at electric phases of the electric motor;
• at least one detection unit coupled to said supply unit and configured for detecting a rotor position of the electric motor;
• at least one closed-loop controller for carrying out a setpoint/actual comparison of a first variable that characterizes a load of the electric motor;
• a memory having stored therein a pilot-control angle characteristic diagram;
• a control unit connected to said memory and configured for determining a pilot-control angle from the pilot-control angle characteristic diagram, in order to add a pilot-control angle and a further regulated pilot-control angle component to a rotor position angle, which characterizes the rotor position, to form a composite angle, for determining the voltages as a function of the composite angle when a field-weakening range of the electric motor is reached, and for controlling the outputting of the electric voltages to the electric phases of the electric motor by said supply unit.