Design and Analysis of Hybrid Excitation Generators for Aircraft Applications Under Limiting Open-Circuit Voltage

A hybrid excitation generator is proposed as a brushless solution for aircraft low-voltage dc power system applications. This topology distinguishes itself from the commonly used electrically excited generator in aircraft power systems because it features an open-circuit voltage without field current. This feature is an advantage, but it also includes a risk. As a too high open-circuit voltage has detrimental influences on the generation system, the limitation of this open-circuit voltage needs to be guaranteed at all times. The key design parameters, such as the slot–pole combination, stack length, and number of turns of the armature winding, are determined to make sure that generators meet the open-circuit voltage limitation. These key design parameters also influence the inductance characteristics of the generator and put consequences on the load characteristics thereby. Therefore, this article also analyzes the load and short-circuit characteristics of these hybrid excitation generators as a function of these parameters. Theoretical deduction and simulation are conducted to reveal the influence law of the parameters on the performance of the hybrid excitation generator under the limitation of open-circuit voltage. A 12300-r/min 12-kW prototype is developed. The experiments verify the analysis and show that the hybrid excitation generator is appropriate for aircraft applications.