Design and Control of a Two-Phase Brushless Exciter for Aircraft Wound-Rotor Synchronous Starter/Generator in the Starting Mode

The structure and control strategy of a novel two-phase brushless main exciter (ME) are proposed in this paper to solve the excitation problem of the main generator (MG) when the aircraft brushless wound-rotor synchronous starter/generator start up as a motor. Two-phase symmetrical winding is adopted as the field winding of the ME and is supplied with two-phase ac by a two-phase inverter in the starting mode and dc by the traditional generator control unit in the generation mode. In order to make the field current of the MG remain constant during the start-up process, the excitation control method for the two-phase ME in the starting mode is proposed, which contains the feedback control for the two-phase field currents and speed reference control for the excitation frequency. The proposed two-phase ME and excitation control method have the advantages of capability for higher and constant field current for the MG in the starting mode and unchanged structure and control methods in the generation mode. A two-phase ME prototype, based on an original single-phase ME, is designed, manufactured, and tested. Finite-element analysis (FEA)-based simulation and experimental results verify the feasibility and advantages of the novel two-phase brushless ME and excitation control method.

I. Introduction

Integrated starter/generator (ISG) system is becoming increasingly popular due to its less weight and volume in modern aircrafts [1]–[4] . A simple and efficient method to achieve the ISG system from a traditional separated starter and generator system is removing the special starter and making the generator also operate as a motor to start the aero engine in the starting mode. Various types of electric machines can be considered to operate as an ISG, such as switched reluctance machine [5], [6], permanent-magnet machine [7], [8], induction machine [9], [10], and wound-rotor synchronous machine [11]– [13]. Because of advantages such as high safety (possibility of canceling of the field current in case of short-circuit and high voltages in the generation mode) and low cost in maintenance, wound-rotor synchronous machine becomes an attractive candidate for ISG in aircrafts.