Therefore the application demand requiring a highly reliable AC film capacitor operating under harsh conditions is at the heart of EPCOS’ new “heavy duty” product series. The key requirement was to develop a film capacitor which has stable capacitance value even under sever conditions such as elevated temperatures and high relative humidity, while working under AC voltage for an extended period of time. As shown on the previous slide, the AC capacitor is typically positioned in series with the power line. In this case, there is no requirement for safety certified capacitors, however X2 rated capacitors are preferred as they are approved according to IEC60384-14 and UL60384-14. However, the X2 capacitor is designed specifically to operate, in parallel with the power line, not in series as demanded by the capacitive power supply. To sum up, the challenge was to combine the high capacitance stability under AC load and severe environmental conditions within relatively small dimensions and maintain the safety certification to ensure the X2 rating.