Steady-state performance evaluations of three-phase brushless asynchronous excitation system for aircraft starter/ generator

This study proposes a novel mathematical model based on excitation system output equations (ESOEs) to evaluate the steady-state performance of the three-phase brushless asynchronous excitation system (BAES) of a wound-field synchronous aircraft starter-generator system. The steady-state performance could be used to evaluate the field current output capabilities of the BAES and provide a reference for the control schema of the BAES. However, the BAES has unknown multivariable non-linear characteristics, which give rise to difficulty in modelling the steady-state performance. Meanwhile, without closed-loop control of the main exciter stator current, the traditional methods fail to efficiently calculate the required excitation voltage and frequency for a desired field current. Steady-state performances are achieved for numerous discrete states with tedious simulations. This study develops the mathematical model of the ESOEs, which can be used to express the non-linear relationships among the main generator field current, main exciter (ME) rotor speed, ME excitation voltage, and frequency. The field current output capabilities could be evaluated in a time-efficient manner by solving these ESOEs. The proposed mathematical model and theoretical findings are verified by experimental results.