Eco-mode technology for uninterruptible power supplies (UPS) has been around for quite some time, probably a decade or so. But the technology has never really taken off because the gains it delivered in energy efficiency were not great enough to offset the risk it presented in terms of power availability. But now the tide is turning, as recent advancements in UPS technology are changing that equation.
UPSs are intended to provide reliable, “clean” power to its intended load, such as IT systems in a data center, even in the event of a power failure or disruption in the main power source. Most UPS systems do this by performing a double power conversion. They take in AC power from the main power source, rectify it to DC to perform filtering and to charge the UPS battery, then convert the power back to AC.
Through this process, the power output is always conditioned, meaning it’s isolated from any spikes, brownouts or harmonic distortions in the main power source. And in the event of a failure, the battery backup kicks in instantaneously.
This clean, reliable power does come at a price, however, because a small amount of power is lost in the conversion process. Traditional eco-mode UPSs seek to reduce or eliminate this power loss by bypassing the conversion process and connecting the load directly to the main power source. The UPS is effectively running in standby mode, kicking in only if there’s a serious disruption to the main power supply.
While that does indeed save energy, it comes at the expense of reliability because it takes a few milliseconds to transfer to the double-conversion mode. That can be enough to negatively impact the load, such as in data centers and manufacturing plants. What’s more, while in eco-mode the UPS battery is not constantly charging, which presents the risk that it will not be fully available when needed.
Schneider Electric has developed a new form of eco-mode, called ECOnversion, that offers a sort of happy medium between the two extremes. With ECOnversion, the power inverter runs constantly to perform whatever conditioning may be necessary to the main power source, such as harmonic compensation. It also constantly charges the UPS battery.
ECOnversion mode stops short of doing the full double conversion when it’s not warranted, but because the converter is always running, it can kick in immediately when there’s a power disruption; there’s no delay that can impact the load. And in ECOnversion mode the load is never exposed directly to unconditioned utility power, as is the case with standard eco-mode.
So, ECOnversion fully addresses the reliability and availability issues that have long hampered traditional UPS eco-mode while also delivering increased efficiency. While standard, bypass eco-mode usually delivers efficiency of 98% to 99% (compared to base UPS efficiency of 94% to 97%), ECOnversion will deliver efficiency that may drop below 99% depending on the connected load, but it’s a small price to pay for the increased reliability. (For more details, check out the article I co-wrote on the technology for Datacenter Dynamics.)
ECOnversion isn’t the only new technology that offers improved UPS reliability. We’ve also made some changes to the power conversion technology inside the UPS to reduce wear and tear on the conversion components – and thus increase the mean time between failure (MTBF) for the UPS as a whole.
I’ll save the details for a future post but basically the improvement has to do with the way we divide the voltage into four levels as opposed to the previous two. That means each activity the UPS has to perform is happening at a lower voltage level. Because failure rates are directly related to the voltage the UPS has to withstand, we are confident the four-level topology will reduce the MTBF for our UPSs.
Combine that with ECOnversion technology and it’s pretty clear that the UPS world is seeing a new level of reliability, availability and efficiency. To learn more, click here to read Schneider Electric Application Note #187, “Galaxy VM High Efficiency Modes.” And I’d love to know what you think about whether this new approach to eco-mode will make you more likely to use the technology in your own facilities. Please feel free to comment below.