Many applications require the use of RFI (Radio Frequency Interference ) X2 capacitors with high stability in harsh environmental conditions e.g. general-purpose applications in series to the mains (capacitive voltage dividers, energy meters) and automotive ones (battery chargers).
Although full agency approvals (UL, ENEC, CQC) are mandatory only on RFI components mounted in parallel to the line, customers often require X2 approval also for series-with-the-mains applications. While the electrical stress on components used in series and in parallel with the mains are comparable, the performance requirements in applications in series to the mains are much stricter. For both applications, environmental conditions (temperature and relative humidity) are the major factors affecting the expected life of components.
Severe working conditions are simulated in KEMET’s laboratories by means of accelerated life tests: climatic chambers replicate high temperature, high humidity, and AC voltage stress.
KEMET recently released a new fully-approved RFI X2 metallized film series, suitable for both series and parallel- to-the-mains connection, designed for high capacitance stability in harsh conditions.
This paper identifies the main root cause of capacitance instability in harsh environment applications and shows the features and performances of the most advanced KEMET capacitors suitable for RFI X2 applications.