A Voltage and Current Estimation Method for Wirelessly Excited System Based on Phasor Transformation

Electrically Excited Synchronous Motors (EESM) can effectively eliminate friction losses caused by brushes and reduce maintenance costs by adopting Inductive Power Transfer (IPT) technology. However, the introduction of IPT technology makes it difficult to directly measure the field current and voltage, posing challenges for precise control and condition monitoring of EESM. Traditional current and voltage estimation methods require the acquisition of exciter-side signals or rely on rotor winding parameters during monitoring, limiting the adaptability of field system state observation. To address the difficulty in observing field current and voltage in EESM, this paper proposes an indirect estimation method based on phasor transformation. First, the electrical relationships of the system compensation network are simplified through phasor transformation. On this basis, a reduced-order model for field current and voltage is established using two-port network functions, enabling indirect estimation of field voltage and current from the primary side of the IPT system. Compared with traditional methods, this approach offers greater adaptability.Finally, an experimental platform for the IPT-EESM system was constructed, The estimation errors of current and voltage are maintained below 5% and 7% respectively, demonstrating the validity and accuracy of the theoretical analysis.