NOVELTY - The method involves applying one phase shift to multiple pulse width-modulated control signals, so that duration of switching states of inverter (102) is extended to generate one shift pattern for phases of inverter. Another phase shift is applied to signals to generate another shift pattern for phases of inverter. Patterns are selected to drive inverter. Multiple neutral point potentials are determined at neutral point (106) of synchronous machine (101) during drive of inverter. A rotor angle of machine is calculated in response to determined potentials.    USE - Method of determining rotor angle of three-phase synchronous machine such as electrical machine for use with control device of electric drive system (all claimed) of electrically powered vehicle, hybrid vehicle and electric vehicle. Can also be used in wind turbine and solar system.    ADVANTAGE - Since the rotor angle of the synchronous machine can be calculated in response to the determined neutral point potentials, the interference, temporary fluctuations and measurement inaccuracies can be taken into account during rotor angle determination process easily. The sensor less rotor angle determination for the synchronous machines can be implemented easily. The robustness and reliability of the rotor angle determination process can be improved. Since the generation of the additional suggestions by the test voltage pulses during the determination process can be avoided, the smoothness of the synchronous machine during operation can be improved.    DETAILED DESCRIPTION - The method involves generating multiple pulse width-modulated control signals for phases of inverter that supplies signals to synchronous machine, in response to voltage to be fed in the synchronous machine. An active voltage space vector is output in the inverter. INDEPENDENT CLAIMS are included for the following:    (1) a control device for determining rotor angle of a synchronous machine; and    (2) an electric drive system.    DESCRIPTION OF DRAWING(S) - The drawings show the circuit diagram of the electric drive system and the graphical view and the schematic view of the synchronous machine.    Synchronous machine (101)    Inverter (102)    Direct voltage intermediate circuit (103)    Strand (104)    Neutral point (106)