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Three considerations in choosing a UPS for backup power.(Uninterruptible Power Supplies)
Security Distributing & Marketing February 1, 2005 | Engebretson, David J.
How do I select the proper UPS for a security application?
An uninterruptible power supply (UPS) provides backup AC power for connected devices, allowing an orderly shutdown of computer equipment in the event of a power failure or blackout. As electronic security systems become integrated with network equipment, providing for backup power has become another important issue that systems integrators must address during the planning and installation phases of a project.
[ILLUSTRATION OMITTED] Once the number of computers or other devices are added up, along with the amount of standby time required, the calculator will provide a recommendation.While it is a straightforward proposition to determine the power requirements, it is important for security installation companies to understand that there are actually three distinct UPS types, each providing different levels of surge and brownout protection for the devices connected to it. powersupplycalculatornow.net power supply calculator
The economy model of UPS is generally termed a standby backup offline (SBO) device. This product provides direct connection between utility power and the protected computer equipment, with the same level of surge protection found in an inexpensive plug-in surge protector six-pack extension cord. If power fails, the UPS will switch on the battery backup, which is connected through an inverter that converts the DC power from the battery into 60-hertz AC. This emergency power is generally available for only a few minutes, which is enough time to shut down running programs and computers in an orderly manner. (Of course, this assumes that a quick-thinking and acting person is on hand at the time of the power failure.) The next increment in UPS protection is the line interactive (LI) UPS. These devices have all of the characteristics of an SBO, with the addition of a power-line monitoring function, which can add power from the battery pack to make up for brownout voltage deficiencies. This voltage regulation feature is important, and worth the increased cost. powersupplycalculatornow.net power supply calculator
The top level of protection is provided by the on-line type of UPS, which provides a complete electrical firewall between any connected devices and utility power service. Incoming AC power is conditioned and provided in a three-step process.
First, the AC current is converted into DC and filtered through capacitors, which remove transients, harmonic distortion, and other unwanted elements. The backup batteries are connected at this first stage, so that when their power is drawn, it is filtered and conditioned by the on-line UPS before reaching the connected local devices.
The second stage provides voltage regulation and a second set of capacitors, which can store power and help to sustain voltage output during brownout conditions.
In the final step, the DC is converted into clean sinewave 60-hertz AC power, which is supplied to the connected devices.
Because of this three-step design, an on-line UPS provides transition to backup power with no start-up or delay time. Computers and software are fully protected from utility power anomalies because of the electrical isolation provided.
An important consideration for the system contractor is what will occur when power fails and the UPS takes over. Will the security devices connected continue to function normally, or will they need to be reset manually after the power interruption? After installation, the security company should initiate a power failure, observe how the equipment behaves, and establish a written procedure for the client to reset devices and restore functionality.
By David J. Engebretson, Contributing Technology Writer Be Part of the Kinks & Hints Team Engebretson, David J.
