Large power supply manufacturers specialize in producing commercial-off-the-shelf (COTS) uninterruptible power supplies (UPS). These COTS products are designed for use in indoor, air-conditioned spaces and operate from clean power provided by the same local electric-utility provider that power our homes and businesses.

While these products are inexpensive and perform well in commercial and residential applications, they were not designed nor manufactured for the harsh environments and strict operational requirements particularly military applications. To meet the requirements of these more demanding applications, it is essential that a high-quality, rugged product, which is designed to pass strict military standards and made specifically for harsh operating environments, is deployed.

Understanding the Differing Technologies
There are several different types of UPSs available. The most common are Standby or Offline, Line-Interactive, or True Online, Double Conversion. COTS UPSs are typically designed to operate using the clean, stable electricity provided to commercial and residential buildings. Standby (Off-line) and Line-interactive UPSs can be a suitable selection for these applications, but Online UPSs should be used when the input power is neither clean nor reliable, in harsh environments, and when the load equipment absolutely cannot fail.

Standby or Offline Ups
A Standby or Offline UPS typically offers only surge protection and battery backup capability. This type of UPS spends most of its life in Standby Mode, or Offline, waiting for a power loss event. It passes input power through to the output and performs little, if any, power conditioning during normal operation. When a power loss event occurs, the inverter is switched on and the inverter, supplied by the batteries, provides output power. The time to switch from input power to inverter/battery power is typically 8-10 msec, so the term “uninterruptible” isn’t accurate, and this interruption can cause load equipment to shut down. Additionally, the inexpensive inverter design in Standby (Offline) and Line Interactive UPSs often produces a square wave (Figure 1) and not a true sine wave output. The lack of a pure sine wave output waveform may cause sensitive load equipment to constantly cycle on and off, or just not operate properly.

Line Interactive UPS
A Line Interactive UPS is similar to a Standby UPS in that Line Interactive also passes input power through to the output with little or no power conditioning, and the inverter only provides power during an input power loss event. The primary difference between a Standby and Line Interactive UPS is that a Line Interactive may also feature an autotransformer on the system input. The autotransformer allows the UPS to ride through brownouts and a wider range of sags, swells and events on the input line voltage before switching to inverter/battery backup power.

Online UPS
An Online UPS is superior to Standby and Line Interactive UPS designs because an Online UPS works 100% of the time. Input AC electricity is continuously rectified to a DC voltage and inverted back to AC (Double Conversion) where a true sine wave AC output waveform (Figure 2) is provided. The AC-DC rectification stage eliminates electrical disturbances on the input power line, and the pure sine wave output waveform generated by the inverter provides the clean, reliable output power. A True Online, Double Conversion UPS is truly uninterruptible because the inverter is online all the time so there is no interruption (0 msec) in the output power waveform when the AC input source is lost. The inverter seamlessly transitions from AC input utility power to battery backup power without any interruption or disturbances in the true sine wave output waveform.

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How does NOVA’s UPS Meet Military Standards?
Most military applications are not afforded the luxury of having a clean, stable power source. Electricity for military applications can be generated
many ways including but not limited to: shipboard turbine diesel or nuclear generators, gasoline-powered field generator, vehicular battery power, or from a foreign electrical grid. In these instances, a True Online, Double Conversion UPS should be used to ensure clean, reliable power is provided. Products used in defense systems must meet certain standards to ensure survivability in harsh environments. These military standards and specifications outline the minimum requirements products must meet for use in defense systems:

  • MIL-STD-461E, Electromagnetic Interference
  • MIL-STD 167, Mechanical Vibration
  • MIL-STD 1399 Section 300, AC Electrical Power
  • MIL-STD 901, Shock
  • MIL-STD 810, Environmental (Section 501.4, High Temperature, Section 510.4, Blown Sand and Dust, Sections 516.4 and 514.5, Shock and Vibration)

Military applications require compliance to at least some part of the eighteen different sections, so electromagnetic interference; vibration, electricity, shock, temperature and blown sand/dust should be a design consideration of any defence electronics manufacturer.

What is the True Lifecycle Cost?
The initial investment of a Stand-by or Line-interactive COTS UPS will look, on paper, to be less expensive than a true Online, rugged UPS. That perception, however, masks the true total cost of ownership.

The lifecycle cost of the true Online, rugged UPS will be much lower as it has been designed to operate in a military environment subject to shock, vibration, EMI, and harsh temperature conditions. It has been manufactured and tested to meet these application requirements. By definition, they will last much longer than a COTS product designed for use in a commercial, air conditioned server room. It is therefore important that other considerations besides initial purchase price be factored in to your UPS selection criteria, including:

  • How often am I replacing an UPS due to failure?
  • Do I have to replace my UPSs during every Tech Refresh?
  • How much am I spending on my spare UPS inventory?
  • What is the logistics and supply chain cost to rush out a replacement when an UPS fails?
  • What is the impact of downtime while we wait for a replacement UPS?

A COTS UPS with a much lower initial cost can end up being much more expensive to replace several times during the lifespan of a single rugged UPS. The initial investment in a rugged UPS may be 2-5 times higher than a COTS UPS, but if your rugged UPS lasts 5-10 years and you are replacing your COTS UPS every 1-2 years (or less), the COTS UPS will cost much more over the life of your system.

The purchase price is the most obvious expense, but the logistics involved in maintaining spare inventory and shipping replacements can quickly add up. Components that fail regularly are stocked in higher quantity in anticipation of frequent failures and replacements, so if you use a COTS UPS, you may be already stocking 2-3 times more COTS UPSs than you would if you used a rugged UPS.

Most deployed systems are in remote locations where delivery is difficult, dangerous and expensive. In some cases the cost alone of shipping a replacement could well exceed the value of the COTS UPS.

The most expensive hidden cost, however, may be system downtime while waiting for a replacement COTS UPS. UPSs are a critical component of IT and network architecture because military personnel rely on their electronic systems, and those systems can be rendered useless if they don’t have dependable, reliable power.

NOVA Power Difference
NOVA Power Solutions is focused on solving problems encountered during the generation, distribution and use of electrical energy. Recent studies indicate that greater than 80% of electronic systems failures are power supply related. Further that greater than 95% of power supply failures are directly or indirectly related to the power quality of the primary electrical system. NOVA Power Solutions power conditioning solutions eliminate 98% of distributed electrical system anomalies, increasing system reliability and electrical generation efficiency.

NOVA Power Solutions power conversation solutions optimize load side electrical efficiency further and thus enhance reliability and allow for the use of a wide spectrum of electronic solutions to meet your requirements.

NOVA Power has established itself as a premier provider of mission-critical rugged UPS, Power Conditioners, and Battery Backup Modules, with over 40,000 units presently deployed in the world’s harshest environments. Our solutions protect mission-critical systems worldwide for applications where “up time” and reliability is absolute and unconditional.

In Conclusion – Make Sure You Have the Right Tool for the Job
The inexpensive COTS UPS’s manufactured by large power supply manufacturers for residential and commercial applications may not be an appropriate, or may not be the cost-wise choice for military applications. The technology may be inadequate, the mechanical and electrical design may be incapable of passing strict military-standards, and the hidden life cycle costs may be considerably higher than a UPS specifically designed for military applications and harsh environments – a rugged UPS. Standby, or Offline, and Line-Interactive UPSs compromise power protection for cost. A true online, double-conversion UPS is the best protection for sensitive electronic equipment. It best protects both your load from electrical disturbances, and your closed electrical system from harmful load harmonics.

The U.S. DoD has commissioned hundreds of military standards detailing the different electrical, mechanical, and environmental conditions products used in military applications must pass. These standards typically far exceed the technical specifications of COTS UPSs, and compliance to these standards requires a rugged UPS.

While a COTS UPS may have a lower initial investment than a rugged UPS, you may pay more over the total life cycle of the UPS for the COTS UPS. If the COTS UPS can’t survive the harsh environment since it wasn’t designed to pass the military standards, your sparing and logistics costs to replace that inventory is going to be high, but so is your system downtime as you deal with a failure or wait for a replacement.

When choosing an uninterruptible power supply, power conditioner, battery backup or power distribution system for military applications or other harsh settings, it’s mission-critical that reliability and survivability in all operating environments be considered in the context of the true life cycle costs of the purchasing decision. The UPS with the lowest initial investment may cost much more over the life of the system when replacement, sparing, logistics and downtime costs are considered.