Question

please explain in depth during power design the impact of changing distance from UPS to each server room for power design. explain the impact of voltage drop because of this change.

Answer 1

The power in Data Center comes from a large UPS running on AC current. The UPS can supply 80 kilowatts at 480 volts. As the UPS draws AC power it's converting some of that energy to DC power in the event of a power outage.

The UPS provides power to several circuit breakers in Data Center. These breakers run at 30 amps and 208 volts -- this means they can handle 6240 watts, though should be subjected to no more than 4992 watts to stay within that "80% or lower" safety zone. If you expect your servers to run at 600 watts max (say in extreme conditions), then seven or eight is your limit.

Another way to look at it is if you've got servers running at 3.3 amps, you wouldn't want more than seven plugged into each breaker.

So, the servers are plugged in to rack-mounted power strips, which then hook into these circuit breakers. The data center isn't powering on just the servers -- there are an electrical requirements for the foundation of the data center as well:

• Air handlers/cooling/heating/ventilation
• Lighting
• UPS systems and generators
• Fire suppression systems
• Alarm systems

How much power this data center consumes depends on many factors -- the primary ones are size, number of servers, air control strategies, and how many other devices are hooked up in Data Center.

However, for the sake of argument, let's say there are 40 critical servers drawing 400 watts, which totals 16000 watts, or 16 kilowatts. Since the UPS can supply five times that amount, this leaves plenty of breathing room for the other elements in the data center.

When a power outage hits, the UPS employs a power inverter to convert its stored DC power to AC current so all components in Data Center can be kept running. The good news is that many things like chillers or air conditioners can be set to reduce power or turn off entirely if need be in order to preserve the more important systems during this scenario.

Of course, how long a UPS can run depends on how long the power is off. Eventually, given enough time, every UPS out there will grind down to a halt if it's not fed fresh AC current. However, with luck, a good UPS can keep a data center afloat long enough for the main grid to be repaired and brought back up, or at least give IT staff enough time to fail over to a disaster recovery site. You do have one, right?