Patient care is a 24×7 job for medical teams, so clinics and hospitals alike depend on tools that ensure power stays on in the case of an emergency outage. Despite the important role power plays in supporting life-saving equipment, ensuring the electricity that IT resources rely on is both dependable and clean can sometimes be an afterthought.

In truth, power sags, surges, and outages are not only unavoidable, but more than capable of damaging valuable IT equipment and medical imaging devices, and bringing procedures to a halt. That’s why planning and deploying a robust power protection solution is absolutely vital.

An uninterruptible power system (UPS) is the central component of any well-designed power protection architecture, and no clinic can afford to leave its IT assets and critical care equipment unprotected from power issues.

Why Power Protection Matters

Power outages can be troublesome, even when they don’t very last long. Losing power for as little as a quarter-second can trigger events that may keep equipment unavailable for anywhere from 15 minutes to many hours. Some experts believe the US economy loses between $200 billion and $570 billion a year due to power outages and other disturbances.

Clean utility power is also hard to come by. In practice, electrical power can vary widely enough to cause significant problems for IT equipment and medical lab devices. According to current US standards, for example, voltage can vary up to 8.3% from absolute specifications. This means that utility services promising 208-phase voltage actually deliver a range anywhere from 191 to 220 volts.

Additionally, power in the United States is only 99.9% reliable, which translates into a likely 9 hours of utility outages every year. Today’s storage systems, servers, and network devices use components so miniaturized that they falter and fail under power conditions earlier-generation equipment easily withstood.

Generators and surge suppressors provide some security in avoiding power spikes and keeping systems operational during longer utility outages, but a UPS will serve to deliver this support while providing a wider range of protection against other common issues such as power loss, under-voltage, and brownout conditions. The UPS also bridges the power gap while the generator starts, and stabilizes the generator’s output while it is online.

What Is a UPS?

Put simply, a UPS is a device that provides backup power when utility power fails, either long enough for critical equipment to shut down gracefully so that no data is lost, or long enough to keep required loads operational until a generator comes online. A UPS also conditions incoming power so that all-too-common sags and surges don’t damage sensitive electronic gear.

Types of UPS

UPS devices come in three major varieties, which are also known as topologies:

Single-conversion systems. In normal operation, single-conversion systems feed incoming utility AC power to electronic equipment. If the AC input supply falls out of the predefined limits, the UPS utilizes its inverter to draw current from the battery, and also disconnects the AC input supply to prevent backfeed from the inverter to the utility. The UPS stays on battery power until the AC input returns to normal tolerances or the battery runs out of power, whichever happens first. Two of the most popular single-conversion designs are standby and line-interactive UPSs.

Diagram of the internal design of a line-interactive UPS.

Internal design of a line-interactive UPS. (Click to enlarge)

Standby UPS units allow electronic equipment to run off utility power until the UPS detects a problem, at which point it switches to battery power. Some standby UPS designs incorporate transformers or other devices to provide limited power conditioning as well.

Line-interactive UPS units regulate input utility voltage up or down as necessary before allowing it to pass through to protected equipment. They use their battery to guard against frequency abnormalities.

Double-conversion systems. As the name suggests, these devices convert power twice. First, an input rectifier converts AC power into DC and feeds it to an output inverter. The output inverter then processes the power back to AC before sending it on to electronic equipment. This double-conversion process isolates critical loads from raw utility power, ensuring that the equipment receives only clean, reliable electricity.

Diagram of the internal design of a double-conversion UPS.

Internal design of a double-conversion UPS. (Click to enlarge)

In normal operation, a double-conversion UPS continually processes power twice. If the AC input supply falls out of predefined limits, however, the input rectifier shuts off and the output inverter begins drawing power from the battery instead. The UPS continues to use battery power until the AC input returns to normal tolerances or the battery runs out of power, whichever occurs sooner. In case of a severe overload of the inverter, or a failure of the rectifier or inverter, the static switch bypass path is turned on quickly, to support the output loads.

Multi-mode systems. Multi-mode systems combine features of both single- and double-conversion technologies while providing substantial improvements in both efficiency and reliability.

Under normal conditions, the system operates in suspended mode, saving energy and money while also keeping voltage within safe tolerances and resolving common anomalies found in utility power.

If AC input power falls outside of preset tolerances for suspended mode, the system automatically, and instantly, transitions to double-conversion mode, completely isolating electronic equipment from the incoming AC source. If AC input power falls outside the tolerances of the double-conversion rectifier, or goes out altogether, the UPS uses the battery to keep supported loads up and running. When the generator comes online, the UPS switches to double-conversion mode until input power stabilizes, then transitions back to high-efficiency mode.

Diagram of the internal design of a multimode UPS.

Internal design of a multi-mode UPS. (Click to enlarge.)

Multimode UPS units are designed to dynamically strike an ideal balance between efficiency and protection. Under normal conditions, they provide maximum efficiency. When problems occur, however, they automatically sacrifice some efficiency to deliver maximum levels of protection.

Choosing the Right UPS

The medical industry has requirements for two unique UPS solutions based on how they are deployed. These two classifications are based on different safety requirements. Systems deployed to protect patient-contact systems, such as electrocardiographs or patient monitors, require certification to UL 60601 or IEC 60601 standards, while UPS systems protecting IT equipment and most imaging equipment only require UL 1778 certification. No matter which safety certification is required, be sure to consider the following issues during your selection process:

Topology. Question number one is deciding among a single-conversion, double-conversion, or multi-mode UPS to protect critical data and processes. The answer depends largely on how important energy efficiency is for the clinic relative to protection.

Single-conversion UPS units are more efficient than double-conversion devices, but offer less protection. That makes them a good fit for loads with a higher tolerance for power anomalies. More specifically, standby UPS units (the most basic type of single-conversion UPS) are generally the best option for smaller applications, like desktop and point-of-sale solutions, while line-interactive UPS units are typically preferable for smaller server, storage, and network applications located in facilities with access to relatively trouble-free AC utility power.

Double-conversion UPS devices, which provide the highest levels of protection, are less efficient but are usually the standard choice for protecting mission-critical systems.

Multimode UPS units, although they may be more expensive than either single- or double-conversion systems, are the best choice for organizations looking to achieve an optimal blend of both efficiency and protection.

Single-phase versus three-phase. When the utility generates power, it is at the three-phase level. This type of power is available to almost all commercial and industrial organizations, as they are typically large consumers of power. Three-phase power uses three separate “phase” wires, which allow higher power to be delivered to a single point or load. Most homeowners only have single-phase power available to them, as homes are typically small power users. Single-phase power is delivered through either one or two phase wires, which are derived from the utility three-phase power system using transformers.

Power Rating. The power rating of a UPS is the amount of load, in volt-amperes (VA), that it is designed to support. UPS units are available with ratings as low as 300 VA and as high as 5,000,000 VA or more. When evaluating appropriate UPS ratings for facilities, operators typically follow these steps:

1) Make a list of all the equipment a UPS will be protecting.

2) Determine how many volts and amps every device on the list draws.

3) Multiply volts by amps for each device to arrive at a VA figure.

4) Add all of the VA figures together.

5) Multiply that sum by 1.2, to build in room for growth.

6) Ensure that the UPS selected has a rating equal to or greater than the final number reached in step 5, unless there is more precise load data for the equipment needing protection.

Form Factor. UPS equipment comes in a range of form factors that fit into two master categories: rack-mounted and freestanding. The largest UPS units aren’t available in rack-mounted form factors, so organizations with substantial power requirements almost always use freestanding devices. For those with more modest needs, deciding between rack-mounted and freestanding models is largely a matter of design philosophy. Some organizations use rack-mounted models in an effort to consolidate as much hardware as possible in their enclosures. Others prefer to maximize the amount of rack space available for IT or medical equipment by using freestanding units. From a technical and financial standpoint, neither approach is inherently superior to the other.

Power distribution units. An essential component of any power quality infrastructure, power distribution units (PDUs) distribute power to downstream IT or medical equipment. Most companies use both floor-mount PDUs, which provide primary distribution to the equipment, and rack-mount PDUs (also known as ePDUs), which distribute power to individual servers and medical equipment in the rack. PDUs can be equipped with optional devices like surge suppression and individual breaker monitoring systems to monitor energy use.

The Case for UPS Systems

Hospitals today invest large sums of money in their IT infrastructure and diagnostic imaging equipment, as well as the power required to keep it functioning. They count on this investment to keep them productive and competitive. Leaving that infrastructure defenseless against electrical dips, spikes, and interruptions can be costly for staff and patients.

A well-built power protection solution, featuring high-quality, highly efficient UPS hardware, can help keep IT applications available, power costs manageable, and data safe. By familiarizing themselves with the basics of what a UPS does and how to choose the right one for their needs, facility operators can ensure that critical systems always have the clean, reliable electricity they need to drive long-term success.

Chris Loeffler is a product manager for several UPS platforms in Eaton’s Critical Power Systems group. Ed Spears is a marketing manager in Eaton’s Power Quality Solutions organization in Raleigh, NC. For more information, contact 24×7 editorial director John Bethune at [email protected]