This paper presents an analytical evaluation of sensorless methods for the operation of permanent magnet synchronous machines. The influence of position estimation errors on the stability of a current controller and the deviation of the actual current value from the reference current are considered. Taking these effects into consideration, a flux estimator and a signal injection method are analyzed. Accuracy estimations and design guidelines for the implementation of the two methods are given.Index Terms-flux estimator, sensorless control, signal injection NOMENCLATURE i r d , i r q d-and q-axes currents in rotor frame u r d , u r q d-and q-axes voltages in rotor frame L d , L q d-and q-axes inductances L d ,L q estimated d-and q-axes inductances R s ,R s stator resistance and estimated value ω s r