Electronics Protection Online - A Complete Guide to Enclosures and Protection

Electronics Protection

The Cost of Power Protection
Pedro Robredo, Product Line Manager
Eaton Corp.

All the electronics in an organization, from desktop to data center, require continuous, clean power. Anything less puts the business at risk for data corruption, equipment damage and downtime. For virtually all organizations, this requirement is met by having one or more UPSs, whether that’s a central UPS that serves an entire building or data center, distributed UPSs placed closer to the equipment being protected, or both. If UPS technology in the organization is even five years old, it’s costing more than it should. If it’s 10 years old, the company could be leaving tens of thousands of dollars on the table.

In a one megawatt data center, a 10-year-old UPS could be wasting 150 kW or more of utility power and dissipating a lot of added heat. Replacing that vintage equipment with high-efficiency UPSs can free up about 120 kW of power to support new IT equipment and reduce the burden on cooling systems. For example, replacing just one 550 kW UPS from a redundant UPS configuration with a higher-efficiency model could save more than $40,000 in power and cooling bills each year, while eliminating 190 tons of CO2 emissions and netting substantial utility company rebates.

Changing the Game in UPS Efficiency
Until recently, 96 or 97 percent energy efficiency was the upper limit in a double-conversion UPS. For every dollar spent on utility power, three to seven cents of it was used or dissipated as heat by the UPS. That does not sound like much, but it adds up. New energy-saving UPSs can deliver up to 99 percent efficiency, providing more usable power for every utility dollar. These UPSs achieve this high efficiency by intelligently adapting to the quality of the utility power and operating in energy-saving mode most of the time. In contrast, traditional double-conversion UPSs process utility power through an inverter and rectifier every millisecond of the day, converting it from AC to DC and back to AC again, dissipating heat and wasting power at every stage.

Until recently, there were trade-offs to increasing energy efficiency including power surges and slow reaction times. Any engineer who has dealt with UPSs in the past has no doubt heard plenty of hype about high-efficiency UPSs despite their disadvantages. Now, a single, high-efficiency UPS can have 99 percent efficiency and premium protection.

Even slight gains in efficiency deliver significant potential savings in power and cooling. The table 1 shows an example for a UPS supporting loads of various sizes. For a 250 kW load, a company can save about $4,000 per percentage point of efficiency gain, enough to pay for the UPS in three to five years.

Five Questions to Ask Before Selecting a High Efficiency, Multi-Mode UPS
1. Does the UPS sacrifice protection to gain high efficiency?
Some high-efficiency UPSs force a trade-off between power savings and power quality. Internal design, topology, profoundly affects efficiency and protection levels. Line-interactive UPSs are efficient, but they only offer limited voltage regulation, surge suppression and battery backup. Premium, double-conversion UPSs do the most processing to deliver clean power, but at a cost to efficiency. New multi-mode UPSs offer the best of multiple topologies in one UPS.

2. How is the UPS achieve so efficient?
Conventional multi-mode or eco-mode UPSs usually operate in one of two ways. They either run in standby mode or run in line-interactive mode. Stand by UPS can take too long to respond to power conditions. Damaging surges or transient power problems could still reach valuable electronics. The second type of UPS is faster to repond, but consumes more energy. This type of UPS tends to be no better than 96 to 98 percent efficient.

Multi-mode technology resolves both issues. In this newer type of UPS, the inverter is continuously charged but not processing power. The inverter remains connected, running all controls and synchronized with the input power, so the UPS can transition to double-conversion mode without delay and without compromising efficiency. Inverter filtering components are connected to the load all the time, providing surge conditioning comparable to double-conversion mode.

3. How efficient is the UPS when lightly loaded?
Average efficiency in the real world can be quite different from stated efficiency. Manufacturers usually state UPS efficiency ratings at full load, but most UPSs are markedly less efficient under lighter loads, which is how they’re likely to be used. Since many IT systems use dual-bus architecture for redundancy, the typical data center loads each power bus, and each corresponding UPS, at less than 50 percent capacity, often as little as 20 to 40 percent.

As a result, it is important to know UPS efficiency across the entire load range, not just under theoretical ideal UPS operating conditions. While many UPSs drop off markedly in their efficiency under light loads, others can perform at 99 percent efficiency even when lightly loaded, as much as 15 percentage points better than a traditional UPS.4. Just how quickly does the UPS detect and respond to power events?
Look for a UPS that is very quick to detect and respond to power problems, ideally within two to four milliseconds, for two key reasons: minimizing inrush current and preventing disruption to downstream static switches. If, for example, a data center has A and B side power systems for redundancy, it probably has static switches in the power infrastructure to extend this A/B redundancy to single-corded loads. If an upstream UPS takes too long to change state, either from high-efficiency mode to double-conversion mode or back again, these downstream static switches could mistakenly perceive a disruption in power and switch between A and B power sources. To prevent these unwanted and unnecessary transfers from occurring, the UPS must have a faster detection/transfer time than the static switch.Look closely at a vendor’s claim that a UPS changes modes in a stated number of milliseconds. The number sometimes doesn’t include all the steps involved. Transition time is a function of two factors, how fast the UPS can turn on its inverter, and how fast it can turn off the static switch, which opens the door for power to flow through the UPS internal circuitry. Only when both have been accomplished is a UPS online in double-conversion mode.5. What extras does the UPS offer for maximum protection?
High-efficiency UPSs have been proven reliable under prolonged and repeated power problems far greater than the typical commercial site would experience. Even so, some multi-mode UPSs offer options for locking in double-conversion mode under user-specified conditions. Also look for a UPS that knows the difference between an upstream and downstream fault. The UPS should respond differently depending on the origin of the power problem.Closing Thoughts
Utility costs account for 20 to 30 percent of data center operating costs. According to IDC, for every dollar spent on new IT hardware, an additional 50 cents is spent on power and cooling, more than double the ratio five years ago. The good news is engineers have improved the efficiency of power protection systems. With a more efficient allocation of power, not only are the utility bills and total operating costs reduced, but the business can achieve more with available backup power and cooling systems, delaying the point where those systems would have to be upgraded to accommodate expansion. With a lower carbon footprint, high-efficiency UPSs also help advance corporate sustainability initiatives.For more information please visit www.eaton.com.