In direct grid tied synchronous motors (no inverter and rotor position sensor), how do we guarantee that stator flux is 90 degree electrically displaced with rotor flux as in vector control. If stator flux is NOT 90 degree displaced, then stator may support or oppose the field (rotor flux). This may change motor characteristics wholly, max speed, torque etc. Do damper windings achieve such thing? IN SHORT, do direct grid tied synchronous motors represents natural vector control behavior?

Am I right in thinking when you say about grid and a synchronous motor ? Well the grid refers to be vast generation or combination of sync machines. Coming to a synchronous motor is is refer to a machine ?