Protect Yourself from Power Interruptions with a UPS

How reliable is reliable enough? Typically 99.99% reliability is considered darn good. However, in a year 8,760 hours long, that 0.01% outage is 52 minutes long. Most would agree that in business, an outage of nearly an hour is a big de

• A one-minute outage requires 99.9998% reliability
• A one-second outage requires 99.999997% reliability

Computers can shut down, losing hours of work or bringing a process to a halt with a power interruption of only one cycle in length (1/60th of a second). Clearly, it is impossible to provide 100% reliability. A lot of things that are beyond our control affect our ability to bring electricity to a business. Ice storms, traffic and construction accidents and animals, to name a few. Where reliability is mission -critical, uninterruptible power is required.

Even when a back-up generator is used to provide power during an outage, a couple of minutes can elapse before the generator cranks and begins feeding power to emergency circuits. To provide a continuous flow of short-duration back-up power, Uninterruptible Power Supplies (UPS), sometimes called Standby Power Supplies (SPS), are needed. UPS also provide excellent surge protection and power filtering.

UPS come in a wide range of types and sizes. The most common type — found mostly in small to mid-size systems — use batteries to provide direct current (DC) power to an electronic inverter that produces alternating current (AC) power on demand. Small systems designed to power a personal computer are available from consumer electronics and computer stores as well as from Jackson EMC. For more information, see the Lightning Pro Surge Protection equipment pages. While larger systems that can power an entire office or computer-aided manufacturing (CAM) facility are available, smaller, individual units may be more cost-effective, especially for retrofit in an existing facility.

UPS capacities are specified in Volt-Amps or Watts. This is the maximum power that the device can deliver. Most manufacturers size the UPS battery capacity to supply about 1/2 the rated Volt-Amp capacity for 10 to 15 minutes — long enough to ride through brief outages or long enough to save your work and shut the equipment down. Higher-capacity units can provide the same power for a longer time. When selecting a UPS, you can't simply go by the nameplate rating of the equipment to be powered. The actual power drawn is needed. Contact a UPS manufacturer or Jackson EMC for more assistance.

Large-capacity UPS systems have typically used rotary systems with a combination of AC and DC motors driving an AC generator. When the power fails, batteries power the DC motor to spin the generator to serve the load. Development of flywheel energy storage systems to replace the batteries in a UPS looks promising.