Amrhein, M., Wells, J., Walters, E., McNeal, S. et al., "Impact of Transient Operating Conditions on Electrical Power System and Component Reliability," SAE Int. J. Aerosp. 7(1):99-108, 2014, doi:10.4271/2014-01-2144.
Transient operating conditions in electrical systems not only have significant impact on the operating behavior of individual components but indirectly affect system and component reliability and life. Specifically, transient loads can cause additional loss in the electrical conduction path consisting of windings, power electronic devices, distribution wires, etc., particularly when loads introduce high peak vs. average power ratios. The additional loss increases the operating temperatures and thermal cycling in the components, which is known to reduce their life and reliability. Further, mechanical stress caused by dynamic loading, which includes load torque cycling and high peak torque loading, increases material fatigue and thus reduces expected service life, particularly on rotating components (shaft, bearings). This article investigates the aforementioned stress mechanisms and provides analysis techniques and metrics to quantify the impact of transient operating conditions onto system and component reliability and life. It is shown that reducing transient loading in an electrical power generation system of a more-electric aircraft, for example through the inclusion of an appropriately controlled energy storage device, can have a significant impact on reliability and life of the power generating system and its components. Specifically, winding insulation, power electronic devices, rotating shaft structures, and bearings benefit from the reduced exposure to transient loading.