METHOD FOR STARTING A SYNCHRONOUS MOTOR

The invention relates to a method (600) for starting a synchronous motor (102). The synchronous motor (102) comprises a rotor (112) for creating a first magnetic field and a stator (108) with stator windings (110) connected to an electrical energy converter (104) for converting a supply voltage (Vcc) into a stator voltage (Vsx, Vsy, Vsz) to be applied to the stator windings (110) to create a rotating second magnetic field interacting with the first magnetic field. The method (600) comprises the following steps: applying (610) reference stator voltages ([ Vsx*Vsy*Vsz*]) to the stator windings (110), wherein the reference stator voltages ([ Vsx*Vsy*Vsz*]) are determined from a reference current vector ([ isd**isq**]) and a reference rotor speed ( ωr**); measuring (620) stator currents (isx, isy) in the stator windings (110); calculating (630) an estimated rotor speed (ω̃r) and an estimated rotor position (θ̃r) of the rotor (112) from the applied stator voltages (Vsx, Vsy, Vsz) and the measured stator currents (isx, isy); calculating (640) a speed error (ωe) by subtracting the estimated rotor speed (ω̃r) from the reference rotor speed ( ωr**); determining (650) a reference torque producing current component ( isq**) from the speed error (ωe) and modifying the reference current vector isd**isq** with the reference torque producing current component ( isq**); calculating (660) a position error (θe) by subtracting the estimated rotor position (θ̃r) from a reference rotor position ( θr*), wherein the reference rotor position ( θr*) is determined from the reference rotor speed ( ωr**) and a reference rotor speed correction (ωc), wherein the reference rotor speed correction (ωc) increases and decreases with the position error (θe); correcting (670) the reference current vector isd**isq** by transforming the reference current vector isd**isq** into a corrected reference current vector isd*isq* by the position error (θe), wherein a rotating coordinate system (dq) of the corrected reference current vector isd*isq* is aligned with the estimated rotor position (θ̃r); determining (680) switching signals (s1, s2, s3) for the electrical energy converter (104) from the reference stator voltages Vsx*Vsy*Vsz* and applying the switching signals (s1, s2, s3) to the electrical energy converter (104).