Evaluation of Capacitor Lifetime Based on EMI and Switch Characteristics

Aircraft electrical components are often misdiagnosed leading to high maintenance and upkeep costs. One potential method of increasing the accuracy of diagnostics is to use the system’s Electromagnetic Interference (EMI) to evaluate the systems condition. One of the least reliable components in electrical systems is capacitors. DC link capacitors are used as load-balancing energy storage devices used to mitigate voltage spikes and current surges subjecting them to significant stress. A model of a 3-phase inverter is analyzed to establish the impact of a capacitor’s age on its EMI. With the push for higher power in aircraft systems, the use of Wide BandGap (WBG) has increased. WBG devices are being used due their small size, greater thermal conductivity and efficiency. WBG devices offer higher switching frequencies, which can decrease the size of needed passive filtering components, thus saving in system size and cost. The faster voltage and current transients of WBG devices cause higher order harmonics in the system which may impact passive component lifetimes. Cuk and SEPIC converters utilizing both Si and SiC devices are used to evaluate the impact that WBG technology could cause in the aging of metalized film capacitors.