Determine Power Requirements of Uninterruptible Power Supply

Electronics, Instrumentation & Electrical Database

Determine Power Requirements of Uninterruptible Power Supply UPS

Continued from:

• Determine the purpose of the UPS.
  • of Selecting and designing a Uninterruptible Power Supply UPS

Determine the power requirements: After determining the specific purpose(s) for an UPS, the next step is to determine the facility power requirements. This task is often laborious but is essential because it sets the stage for the remainder of the selection process. Undefined power requirements, or oversight of any initial conditions, could result in the selection of a system that is not capable of meeting the needs of the facility, costly budget overruns, and delays in completing the project. In addition, there is usually significant growth in the number of Uninterruptible Power Supply UPS loads as a manufacturing plant is developed. This must be accounted for in the sizing of the UPS. The first question to answer is how much power is needed. Power requirements can be divided into two categories, critical and non-critical. Critical power can be thought of as power for items such as emergency lighting for evacuation of personnel, security systems, central computing systems, signaling systems, medical equipment, and other functions that could cause loss of productivity, or result in injury or a life threatening situation. Non-critical power is used for functions such as general lighting, escalators, coffee makers, etc. Once the power requirements are defined, the next step is to determine how much (if any) to oversize the unit. Over sizing serves two purposes. First, it provides the capability to efficiently and effectively handle surges in power requirements due to peak demands caused by starting machinery, switching power supplies, etc. Secondly, it provides for growth. Over time, power demands may rise due to the addition of equipment or personnel, increases in productivity, and other reasons. Over sizing the UPS ensures it will have the capacity to handle the increased load without the expense of retrofitting the system, which is more costly in the long run. A general rule of thumb in over sizing is to increase the initial power requirement by 30 percent. If over sizing cannot be justified, the Uninterruptible Power Supply UPS should be selected and the installation designed such that future expansion can be accommodated at the least possible cost.

Continue Select the type of UPS.

References: “Joint Departments of the Army, Uninterruptible Power Supply System Selection, Installation, and Maintenance for Command, Control, Communications, Computer, Intelligence, Surveillance, and Reconnaissance (C4ISR) Facilities, 31 May 2002.”