Finite-Element-Informed Analytical Modelling of an EESM Drive Under Constant Field Current Excitation

This paper presents a finite-element-informed analytical modelling framework for an electrically excited synchronous machine (EESM) drive under constant-field-current excitation. The aim is to extend operating-point-dependent electromagnetic data obtained from a detailed finite-element-based machine model into a dynamic, drive-level analytical model, while preserving the interactions among current regulation, torque production, and mechanical speed dynamics. The proposed framework combines an analytical dq-axis EESM model with a cascaded speed–current control structure, where the outer speed loop generates the torque reference and the inner current loops regulate the d–q current components. Operating-point-dependent quantities, including d- and q-axis currents, inductances, mutual field–armature inductance, and torque, are extracted under multiple phase-advance-angle conditions and incorporated into the dynamic model. A separate transient finite-element field solution was used to validate the analytical torque predictions. The results show that the proposed model captures the main operating-point-dependent trends of the reference machine. Speed-reference tracking and load-disturbance tests further demonstrate its ability to analyse transient drive-level behaviour beyond steady-state operating-point comparison. Mechanical output power, reactive power, power factor, and efficiency are also used as supplementary indicators. The framework provides a structured and extendable basis for analysing EESM drive behaviour without relying on predefined machine blocks.