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Differences in UPS Topology

UPS TopologyThe importance of implementing a UPS system to protect network, data information and video assets from power issues cannot be understated. Even short power outages can pose huge issues for organizations, with as little as a quarter-second incident shutting down network equipment for minutes to hours. That can cost a business big money. Some experts believe the U.S. economy loses between $200 billion and $570 billion a year due to power outages and other electrical disturbances.

So, what is a UPS and why is it a crucial element in your power landscape? The bottom line is simple; it provides backup power when utility power shuts down, and saves critical equipment and systems from losing data until generators come online, or power is restored. The UPS will also condition incoming power to help quell common sags and power surges that may damage systems.

However, there are varied options for users, and matching the power solution to the correct application may prove confusing. But an understanding of the different technology definitions and their applications can help both user and integrator make an informed decision. 

 Understanding the 3 Types of UPS

The three major types of UPS system configurations are online double-conversion, line-interactive and offline (also called standby and battery backup). These UPS systems are defined by how power moves through the unit.

Single-conversion systems feed incoming utility AC power to various equipment. If the AC input supply drops below its predefined power limits, the inverter used by the UPS will pull current from a battery. At the same time, in order to eliminate backfeed from the inverter to the utility, the AC input supply is automatically disconnected. The battery will continue to power the UPS until the normal power tolerances return or the battery fails. The most common single-conversion options are line-interactive and standby. The line-interactive UPS can regulate incoming utility voltage up or down depending on need, prior to allowing it to pass through to protected equipment, using their battery to guard against frequency abnormalities.

Equipment can run off utility power until the UPS detects a problem using a standby UPS. If an issue is detected it switches to battery power. Some standby UPS designs may include transformers or other devices that provide limited power conditioning.

While the single-conversion solutions offer intermediate levels of power protection, double-conversion systems are the ultimate in power options. An online UPS uses a "double-conversion" method of accepting AC input, rectifying to DC for passing through the rechargeable battery (or battery strings), then inverting back to 120 V/230 V AC for powering the protected equipment. This double-conversion process isolates critical loads from incoming utility power completely, ensuring that equipment receives only clean, reliable electricity. This is the most common type of UPS above 10 kVA.

A double-conversion UPS will offer continual power processing twice during normal operations. If AC input supplies fall out of their predefined limits, it will also shut down the input rectifier allowing the output inverter to begin drawing power from a battery source. A true double-conversion online UPS is also the optimal solution for critical applications. However, the term “online” is not an indication that the UPS is plugged in and “powered” up. It simply describes how an online UPS continually regenerates new, clean AC power through its continuous duty inverter and seamlessly operates on AC or DC (battery) power. The double-conversion UPS also has several layers of protective circuits that further safeguard connected equipment and ensure it is always receiving 100% conditioned and regulated AC power that can provide long periods of battery runtime by adding extra battery packs.

Considerations Before Selecting a UPS

Because a standby UPS offers only the most basic level of protection, the majority of organizations choose to deploy either a line-interactive or a double-conversion online model. Once you understand the technology behind the different UPS options, there are several operational questions that must be asked to ensure the right device for the application.

Work with your consultant to map out the power landscape that the UPS is being considered to protect. From blackouts, sags and surges to under- and over-voltage conditions, switching transients and harmonic distortion, know the critical issues and prioritize the solution. You must also know the equipment being protected to determine the most effective UPS option. The fact that a double-conversion online UPS is the only platform that offers zero transfer time to the battery makes it the optimum solution for sensitive and mission-critical equipment. This type of unit safeguards equipment from all nine common power problems, offering the highest level of protection.

Finally, consider the total cost of ownership for your UPS system. While a double-conversion online UPS may consume more energy over the life of the system than a line-interactive model, it offers a superior level of protection for sensitive equipment and is less susceptible to downtime.

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