A Brief Guide to Defense Power Supplies

Military power conversion solutions are specially made power supplies for ground, airborne, and naval military equipment. They have higher performance, higher reliability, and more ruggedness. Ruggedness means that they can withstand harsh conditions like extreme weather or the heavy vibration and shock that is experienced during combat in the field. Not only can they withstand such conditions but they can also continue operating at full capacity. 

Such solutions can also be used for non-military applications in other industries, especially where ruggedness and reliability are priorities. 

A military power supply, or MIL power supply, will always conform to several military standards, depending on where it is meant to be used. Different defense use-cases, which include communication and naval applications, have specific standards. Such standards ensure the high performance of military equipment in mission-critical applications. 

There are several options in the procurement of defense power supplies. A client can use fully-customized military power supply units when they have unique requirements. But this option is expensive and has a long time-to-market. 

The more popular options are lightly-customized military power supplies and commercial off-the-shelf (COTS) solutions that are made for military use. 

Each of these options comes with pros and cons, as we’ll see below. 

Types of Military Power Supplies

COTS Units

COTS power supply units are a popular choice among defense contractors not because they are the best but because they are often good enough. Military contractors often have to work within budgets and COTS power supplies are appropriate because they are more cost-effective than the alternatives. 

Another plus for COTS units is the modularity and ease in case upgrades are required. A modular power unit can stay for long without becoming obsolete. This is because obsolete parts can easily be swiped out for new ones. This makes upgrades much easier, unlike in custom power supplies. 

In addition, COTS units have the shortest time to market because they’re usually readily available and no modifications are needed. 

Lightly Customized Units 

In some cases, it happens that due to one or two unique requirements, military power contractors aren’t satisfied by the COTS options available in the market. Some of these requirements are simple. A contractor could need a customized unit simply because no existing unit fits in the intended location. In such a case, the form or size of an existing unit would have to be modified. 

Such a modification is light. Most MIL power supply companies use the building-block system, where they simply use a new combination of existing building blocks to come up with a suitable customization. As such, most lightly customized units have a short time to market. 

Fully Custom Military Power Conversion Solutions 

There are some military use-cases that are so unique that they require fully-customized power supplies. This of course depends on the designers. Usually, for clients to resort to fully-customized units, it is because there are multiple unique requirements. It may be that the output power characteristics required simply aren’t available on the market. It may also be that the form and size required are not available. 

Even with the use of readily available building blocks, fully custom solutions are more expensive than other alternatives. They also have the longest time to market. 

Military Standards 

MIL-STD 461

This standard deals with electromagnetic interference (EMI), and specifies requirements for the EMI characteristics of military equipment, including emission and susceptibility. It also specifies the test methods to be used for the determination and measurement of the said characteristics. 

Compliance with these standards ensures the integrity of data, which is important, especially due to the critical nature of military operations. 

MIL-STD-1399

This standard deals with electrical equipment. It defines the required electrical interface characteristics, enabling compatibility between equipment and the power system. A subset of this standard goes ahead to define the navy and industrial medium voltage systems, including power characteristics and tolerances. 

The standard also defines test methods for ensuring the compatibility of electronic devices with electric power systems. 

MIL-STD 810

This standard defines the environmental engineering considerations that should guide the manufacture of military electric equipment. It also specifies the tests to be used to ensure compliance with set standards. 

In accordance with this standard, military equipment should be tested in the conditions to which it will eventually be exposed. Such conditions include altitude, vibration, extreme temperatures, humidity, dust, and shock. This ensures that flaws are determined before the equipment ever gets used, minimizing the chances of performance failure. 

MIL-STD 704

This defines standards for aircraft electrical power characteristics. It lays out the specifications for power factor, ripple, voltage, frequency, maximum current, and EMI. It also specifies features for dealing with abnormal power conditions such as undervoltage and overvoltage. 

MIL-STD 1275

This standard defines specifications that ensure military equipment has higher immunity to power events such as spikes, surges, and ripples. It also specifies thorough tests for both normal and generator-only modes as well as limits for transient voltage characteristics. It applies to military ground vehicles.