The packaging of low-voltage power supplies is driven by thermal considerations. Packaging of high-voltage power supplies on the other hand is dominated by "E" field gradients. MIL-STD-454 states that insulation systems having dielectric withstanding voltages over 300 volts are corona limited rather than dielectric strength limited.
Program management must recognize the special considerations that high voltage places on mechanical and electrical design disciplines.
Mechanical packaging of high-voltage power supplies directly impacts the ultimate reliability. The failure mechanisms which must be prevented by proper mechanical design are insulation breakdown, thermal stress and mechanical failure. The mechanical layout dictated by the "E" field analysis establishes the minimum packaging density. There is an iterative process involving mechanical layout, "E" field computation and selection of the insulation system to prevent insulation breakdown and corona in the development of a reliable design.
High-voltage power supplies designed to the guidelines
of Section 5 of this publication do not conform with the intent of Figure 3-4. However, the
dotted lines in Figures 3-2 and 3-3
are typical of high-voltage designs.