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.