There are power supplies in virtually every military system. They come in all shapes and sizes and power ratings, like missile power.
Getting it right, however, is not as simple. All the equipment has to be battle tested – literally. The reliability of military power supplies remains paramount, with the mean time between failures being much higher than commercial power supplies. I don’t have to explain just how different the optics are in case of failure between MIL power supplies and commercial power supplies. The former could lead to unnecessary loss of life.
Today, these power supplies are upgraded every two years, with every upgrade rendering previous generations obsolete – so much so that availability issues arise. The ability to recognize pending failure has become just as important as long-term reliability.
Designers of these power supplies have to design rugged equipment that can withstand any challenges that may threaten normal performance in the field of battle.
Commercial power supplies do face some environmental challenges in their work environment, say on the factory floor or out in the weather. The situation is replicated a hundredfold for military power supplies.
Just think of a missile cruising towards its target above the clouds or a torpedo torpedoing towards an enemy sub deep under the sea. You can see how different and complex the missile power supply needs to be to effectively do its job under all these challenging conditions. These power supplies are deployed everywhere, from deep seas to space, from deserts to swamps.
These are just some of the challenges they may encounter while out on the battlefield.
The Temperature range extends
Commercial power supplies are generally developed with an operating temperature range of zero to 70 degrees Celsius. Their more complex military counterparts need to accommodate temperatures of negative forty to eighty-five degrees Celsius – and that’s just at the very minimum.
Some special requirements may require the range to be from negative fifty-five to a hundred and fifty degrees Celsius. To achieve these rather extreme temperature ranges, a focus on component selection and environmental stress testing is required to determine how well or poorly they will perform in the field.
Shock and Vibration
Power supplies used in any military system must stand up to significant shock and vibration from a range of sources. Products used by the navy, for instance, must meet shock requirements, which can range up to 90 gs. Vibration testing has to be done for each product in accordance with its intended end use.
Sudden extreme temperature changes are an enemy to electronic systems, including power supplies. There are standards that provide a number of test regimens for cycling an assembly through rapidly changing temperatures.
Typical cycle tests involve temperature ranges of 0 to a hundred degrees Celsius. The maximum range is set at negative sixty-five degrees to one hundred and fifty degrees Celsius with a minimum interval between limits of 6 seconds.
Humidity, Moisture, and Condensation
This environmental challenge covers water in all its forms. Water in any form really is not an electronic system’s best friend. Water can significantly damage unprotected electronic equipment. As such, a MIL power supply needs to be ruggedized to deal with water and all water-related problems like fungus.
Traditional solutions for dealing with condensing atmospheres include potting the power assembly by filing its case with a non-conductive thermoplastic material. As helpful as this is, it brings in the issue of added weight. Added weight in the field is never good, especially for aero or mobile units. Extra weight is a severe design penalty for mobile military systems. Some newer techniques to solve this are coming up. Some of these techniques include employing light-weight circuit board coatings, which provide the environmental isolation for protection of electronic circuits from moisture. This technique comes with a lower weight penalty, which is good news for everyone.
EMI and Solar radiation
Military power supplies must be able to withstand radiation of all kinds. Electromagnetic interference and solar radiation are just some of the radiation issues they have to deal with and continue operating.