Maximum Protection/Maximum Efficiency: Balancing Data Center Availability, Efficiency and Capacity
The data center is at a critical stage in its evolution. During the high-growth years of 2003-2008, many organizations scrambled to keep up with capacity demands, often compromising long-term planning and efficiency for speed of deployment. When the 2008 global economic crisis hit and capacity demands eased, those organizations found themselves with a smaller budget, a mix of infrastructure generations and an incomplete picture of what they had and how it was being used.
The data center is at a critical stage in its evolution. During the high-growth years of 2003-2008, many organizations scrambled to keep up with capacity demands, often compromising long-term planning and efficiency for speed of deployment. When the 2008 global economic crisis hit and capacity demands eased, those organizations found themselves with a smaller budget, a mix of infrastructure generations and an incomplete picture of what they had and how it was being used.
Now that budgets have returned to more “normal” levels and the world becomes more social, mobile and cloud-based, businesses looking to use technology to support and spur growth face one of the biggest data center dilemmas today – increasing efficiency levels (maximum efficiency) while maintaining or improving availability (maximum protection) in increasingly dense and dynamic computing environments.
Traditionally, availability of IT systems has been viewed as the most important metric on which to evaluate data centers. That shifted slightly in 2008 as IT organizations began to look seriously at energy efficiency in terms of cost savings as well as environmental responsibility. Energy efficiency dominated industry discussions until a rash of well-publicized data center outages in 2009 led to increased downtime.
As the pendulum begins to swing back to availability – with renewed focus being placed on the frequency and cost of downtime, it is important that data center professionals remember that no two organizations – and therefore, data centers – are the same. Each organization has its own set of priorities, and as the most important strategic asset, the data center needs to reflect those business priorities and objectives.
For some data centers, this may very well mean taking a more reasonable and balanced approach to optimizing availability, efficiency and capacity of their data centers. However, for some data centers, efficiency and scalability may take priority, while for others, the assurance of high availability might be the primary objective. The approach data center professionals take with their UPS solutions should be based on the priority (or priorities) identified by the organization.
Maximum Protection UPS Design
For those organizations that deem maximum protection as their top concern, a robust UPS design is required. The key to protecting your data center’s availability starts with ensuring you have the highest quality power at all times. As you explore UPS options that provide maximum protection, you should seek out a UPS solution that offers the following benefits and characteristics.
- Built-in electrical isolation for proper safety and performance.
- Handles a stack-up of multiple adverse conditions at once without compromising your connected IT load.
- Maintains online operation without transfer to bypass during DC ground fault conditions.
- Fuse-less continuous duty bypass design for fault management and to allow fault coordination of the distribution system.
There are many options to consider in deploying the right maximum protection configuration for your environment. Transformer-based UPS systems are highly robust and excel at providing the highest capacities and levels of availability while simplifying external and internal voltage transformation, as well as fault management.
For high-power enterprise data centers and other critical applications, a state-of-the-art transformer-based UPS still provides an edge in availability. Transformers within the UPS provide integrated fault management and galvanic isolation as well as greater compatibility with critical power distribution system requirements that should be considered when designing a high-availability UPS system.
When additional capacity is needed, additional modules are added to the system in either a centralized or distributed bypass architecture. In a centralized bypass architecture there is a single system level bypass and no module level bypass. In a distributed bypass architecture each UPS has its own bypass that must act in concert to take the system to bypass. Of the two, centralized bypass has higher mean time between failures (MTBF), so it is typically the configuration of choice in a maximum protection system.
Maximum Efficiency UPS Design
If your organization is focused on data center efficiency then energy costs, power density and future growth should be the top concerns on your mind when it comes to UPS solutions. A UPS solution designed for high efficiency can reduce both operating and capital expenditures, helping drive a low total cost of ownership. As you search for a UPS solution that can maximize efficiency, look for an offering that provides the following benefits and characteristics.
- Optimized design for high efficiency to minimize operating costs.
- Small footprint with high power density.
- Lower costs for installation and deployment.
- Performance tuned to today’s IT loads.
- Scalable architecture to allow cost-effective growth.
A distributed bypass architecture will typically have a smaller footprint, so it is usually the configuration of choice for a maximum efficiency system.
UPS Economization
There are UPS operating modes to consider that can improve efficiency further. One such option is the use of active eco-mode, which accomplishes improved efficiency by powering the bulk of the critical load thru the bypass path. When power problems are detected, the UPS automatically switches back to double-conversion mode.
In double-conversion UPS systems, the rectifier and inverter are designed to run continuously with the rectifier directly powering the inverter. The incoming AC is rectified to DC, which is then converted back to AC by the UPS inverter, resulting in a low-distortion, regulated stable AC output voltage waveform. This process can be up to 96 percent efficient.
The active eco-mode approach pushes efficiency above 98 percent in some cases. It keeps the inverter and rectifier in an active state, which means the inverter is kept in an active state and ready to accept the load immediately. As a result, the transfer to the inverter can be accomplished almost seamlessly. When the UPS senses bypass power quality falling outside accepted standards, the bypass opens and transfers power immediately back to the inverter until bypass anomalies are corrected. Once bypass power anomalies end, the critical load can be automatically returned to active inverter eco-mode.
Not all UPS economization modes are created equal. Due to technology limitations, some UPSs have to turn off the inverter before turning on the bypass or turn off the bypass before turning on the inverter. This is commonly referred to as an interrupted transfer. In active eco mode the UPS controls the inverter to have zero current passing through it. This zero current mode takes only one control instruction cycle for the inverter to produce current for voltage regulation mode which is the normal mode of operation. It is due to this technique that going into or suspending active eco-mode operation can be made without any interruption to the load.
Active eco-mode operation is similar to the operation used for transfer. During transfer of the load from bypass to inverter the inverter matches the bypass voltage and phase angle. The inverter then increases it’s frequency to lead the bypass effectively moving the load to the inverter. When the static switch is turned off the load is isolated from the bypass source and the transfer is completed. Active eco-mode operation also connects both the bypass and the inverter simultaneously to the load. The difference is that the inverter matches the bypass voltage and frequency in a manner that allows the inverter to remain connected to the load.
As the complexity of data center environments continues to grow, data center managers are confronting concerns about maintaining or improving availability and increasing efficiency and reducing costs. There are many options to consider in the area of power system design that affect efficiency, availability and scalability. The key is to base any decision on broader organization priorities and decide if you need maximum protection, maximum efficiency, or a balanced approach to both.
