Insulation lifetime projection data is collected by using industry-standard Time Dependent Dielectric Breakdown (TDDB) test method. In this test, all pins on each side of the barrier are tied together creating a two-terminal device and high voltage applied between the two sides; See Figure 29 for TDDB test setup. The insulation breakdown data is collected at various high voltages switching at 60 Hz over temperature. For reinforced insulation, VDE standard requires the use of TDDB projection line with failure rate of less than 1 part per million (ppm). Even though the expected minimum insulation lifetime is 20 years at the specified working isolation voltage, VDE reinforced certification requires additional safety margin of 20% for working voltage and 87.5% for lifetime which translates into minimum required insulation lifetime of 37.5 years at a working voltage that's 20% higher than the specified value.
Figure 30 shows the intrinsic capability of the isolation barrier to withstand high voltage stress over its lifetime. Based on the TDDB data, the insulation withstand capability of DW-16 package is 1500 VRMS with a lifetime of 135 years as illustrated in Figure 30. Similarly, the insulation withstand capability of DWW-16 package is 2000 VRMS with a corresponding lifetime of 34 years. DBQ-16 package at 400 VRMS working voltage has a much longer lifetime than both DW-16 and DWW-16 packages. Factors, such as package size, pollution degree, and material group can limit the working voltage of a component.