Environmental Challenges of Power Supplies, Part 2

Power supplies used in military applications must be able to operate in all types of environments, but any good student knows that environments are so much more than temperature. Temperature hardiness is important, but there are other factors that determine a military power supply’s environmental suitability as well.

One of these is moisture. From humidity to condensing atmospheres and from precipitation to ice, all forms of water can do considerable damage to a power supply unless it is designed to withstand that water. Unlike commercial power supplies, military power supplies are designed and built to tolerate water in all of the aforementioned forms.

That is because MIL-STDs, the military standards that govern the environmental testing that electrical systems in military applications must undergo, dictate that electronic equipment used in certain military applications must be able to hold up against various types of water penetration and damage. MIL-STD-810, the primary MIL-STD for environmental design and testing, instructs military power supply manufacturers to in ways to design and test equipment that will hold up against moisture-related conditions like wind-blown and freezing rain, 100% condensing atmosphere, salt-fog, and fungus. These high standards are required because military equipment often must be designed to accommodate any moisture level found on land, sea or air.

One technique sometimes used that is made for to combat atmospheric condensation is to filling the case of the power supply with a non-conductive, thermo-plastic material. Their methods involve tightly sealing the case and using proprietary techniques to handle any remaining internal moisture.

Another environmental condition that military power supplies must adapt to is radiation.  Military equipment could potentially enter fields of high radiation, including solar radiation or electromagnetic interference (EMI) or could be the emitter of EMI. For these reasons, MIL-STD-461 and MIL-STD-1553 outline a range of tests that a system may be required to undergo in order to meet the electromagnetic challenges it will encounter and safely accommodate the various radiation environments it may be immersed in, whether involving radiated emissions or conducted emissions. Commercial power supplies that are required to work in radiation or EMI environments are usually tested to MIL-STD-810 requirements rather than less-stringent civilian standards.  Radiation and EMI handling is one more way in which military power supplies are superior to commercial power supplies.

The challenges of manufacturing military power supplies that must face all types of environmental conditions present significant engineering and production difficulties, but overcoming these challenges ensures that equipment vital to military operations will work when it is most needed.