Sensorless Position Estimation for an Externally Excited Synchronous Machine over the Whole Speed Range

Inhalt:
This paper presents a sensorless position estimation method over the whole speed range for an externally excited synchronous machine using the rotor current. At standstill and low speeds, the ripple of the rotor current is used as carrier signal to estimate the rotor position. Above a certain minimum speed, the induced voltage is measurable, therefore it is used for the sensorless position estimation method. A switchover strategy between the two methods is presented in this paper. The functionality of the sensorless position estimation method and the switchover strategy is verified by measurements at a machine test bench.