Method and device for determining the position angle of a rotor in an electric synchronous machine

A device (10) for determining the position angle of a rotor (2) of an electric synchronous machine (1), the device comprising:

• a voltage generating device (12) which is configured to generate (S10) in each case at least one electrical voltage pulse at predetermined electrical angles in a stator-fixed coordinate system, referred to as a stator (3) of the electric synchronous machine (1), when the rotor (2) of the synchronous machine (1) is stationary, the at least one electrical voltage pulse being generated in such a way that the rotor is not made to rotate;
• a measuring device (14) which is configured to measure (S20) in each case at least one respective electrical current value which arises from the electrical voltage pulses generated by the voltage generating device (12);
• and
• a computing device (16) which is configured:
• to store a current signal profile of the measured current values corresponding to each of the predetermined electrical angles;
• to generate a mean-value-free current signal profile by shifting the current signal profile and/or the measured current values;
• to calculate an integral function (83) of the mean-value-free current signal profile;
• and
• to determine the position angle of the rotor (2) on the basis of the calculated integral function (83)
• wherein the determination of the position angle of the rotor (2) includes determining a mean value (84) of the calculated integral function (83) and determining a first angle value (85) at which the calculated integral function (83) intersects the determined mean value (84) of the calculated integral function (83), and wherein the determination of the position angle of the rotor (2) is carried out on the basis of the determined first angle value (85).