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Uninterruptible Power Supply (UPS): Review and Buying Guide

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Uninterruptible Power Supply (UPS): Review andOwnershipGuide UNINTERRUPTIBLE POWER SUPPLY THEORY OF OPERATION, SELECTION CONSIDERATIONS, REVIEWS, AND SCHEMATICS <---------------------------------------------------------------------------------------------------------------------------> Home Tutorial Topologies SMPS diamond Thermal diamond Software PCB diamond Computer PSU UPS Circuit Transformers Formulas EE Reference Inverters Generators Solar WHAT IS UPS? An uninterruptible power supply (UPS) is a battery-powered electronic device that continues to supply electricity to the load for a unrepealable period of time during a utility failure or when the line voltage varies outside the normal limits. Its typical using is PC replacement power. Larger permanently wired devices can be used to feed servers and other equipment, or plane an unshortened home. Besides the backup, most models moreover provide surge protection and power conditioning. The generic standard for UPS replacement power supply systems is IEC 62040 series. Needless to say, plane a unenduring power outage could result in loss of unsaved data on a desktop computer that was running or reset you modem. That's why an UPS is a must in home and office. From a technical standpoint, to make a power supply uninterruptible, you need an energy storage replacement battery, an AC-DC charger and a DC-AC inverter. TYPES OF UPS. There are three main types of UPS: Standby (off-line), Line Interactive and Online. Each of these types supplies energy from the shower when the grid fails, but under normal conditions they process the power differently. Note that unlike home generators, none of them needs any moving parts. A Standby UPS (SPS) includes a transfer relay. It switches the load to the battery-powered inverter when the primary AC is out of range. A typical transfer time is between 2 ms and 10 ms depending on the value of time it takes to snift the lost utility voltage and turn on the inverter. During this time the current to the load is momentarily interrupted. That's why listing such devices as "uninterruptible" is somewhat misleading. Today's PC include an internal switching-mode PSU which inherently provides unrepealable hold up ("ride through") time. For a reference, SMPS PSU for personal computers are required to provide at least 16 ms hold-up time at rated load (this number corresponds to one trundling of 60Hz input). Since it is greater than normal UPS transfer time, most PCs are not unauthentic by a transition from mains to UPS. On the positive side, since SPS inverter operates in standby mode and starts up only when the input source fails, it has the highest efficiency (95-98%) and reliability. Because it is moreover the cheapest UPS power supply (under $0.10 per rated volt-amp), it became the most worldwide replacement product used for desktop PCs. Note, in some older systems the inverter generated square-wave type output rather than a sinusoidal one, which could rationalization problems to some sensitive equipment. An example of a popular standby model with good reviews is CyberPower CP750LCD. The Ferroresonant type of standby UPS has an spare ferroresonant transformer that shapes output voltage and stores some energy for a smoother transfer. Its main drawback is instability when it is loaded by an SMPS with a PFC front end. For this reason such systems are no longer wontedly used. A Line Interactive UPS under normal conditions smooths and to some stratum regulates the input AC voltage by a filter and a tap-changing transformer. The bi-directional inverter/charger is unchangingly unfluctuating to the output and uses a portion of AC power to alimony the shower charged. When the input source fails, the transfer switch disconnects AC input, and the battery/inverter then feeds the load. The typical efficiency of this type is 90-96%. It is currently the most worldwide diamond in 0.5-5 kVA power range. An example of Line Interactive type is Tripp Lite AVR550U. An Online UPS unchangingly delivers all or at least a portion of the output power through its inverter plane under normal line conditions, and therefore provides true uninterruptible power with 0 ms transfer time. An example of online type is CyberPower OL1000RTXL2U. This type is increasingly expensive. Its main applications are small servers and networks, but nowadays it is used in homes as well. There are two main types of on-line UPS: double conversion and delta conversion. A Double Conversion online UPS is continuously processing the whole power through a series unfluctuating AC-DC rectifier/charger and DC-AC inverter. An spare shirk switch allows you to support the loads directly from an AC source under some fault conditions (such as the inverter failure). Although such a type provides PFC and largest output voltage quality than other designs, the double energy processing results in reduced efficiency (80-90 % typical). This type is worldwide for hair-trigger applications. A Delta Conversion online UPS includes an spare "Delta Converter" that delivers a portion of the energy directly to the load and provides power factor correction. Such partial bypassing the rectifier / inverter stages during normal operation results in higher efficiency (up to 97%). For most desktop applications an SPS type is sufficient. However, if you want to stave plane unenduring power interruptions, squint for a line interactive type. Among main domestic suppliers Tripp Lite probably is the only one that unmistakably states the types of its models. Various performance and test requirements, such as the limits on the width and elapsing of deviation of the output voltage winning for switching mode (SMPS) PSU loads are specified by IEC 62040-3 standard. Note that manufacturers of small thingamabob UPS power supplies for PCs usually ventilate their systems by volt-ampere (VA) rating. A typical maximum real power in watts of such replacement power supply is only 60% of its nameplate VA rating. Such default ratio between watts and VA is based on an old non-PFC computer PSU that used to have power factor between 0.6 and 0.7. So, when you are ownership a UPS power unit, make sure that the net wattage of your loads does not exceed 60% of the its VA rating. To find your required wattage add nameplate currents of all devices you want to replacement and multiply the result by 120. Note that technically, this will requite you volt-amps rather than watts. However, today's electronics have nearly unity power factor. So, your watts will be scrutinizingly the same. For example, if your system draws 2.5 A, then it consumes up to 2.5x120=300 watt. In this specimen you need to select a replacement device rated for at least 300/0.6=500 VA. Although UPS sources are often cheap, small and convenient, they are not suitable for all applications. Their worldwide disadvantage is a relatively short runtime. That's why most data sheets state it at half load. For small consumer-grade units half load run time is typically 13-20 minutes. Note that this foible is not linear. At full load you may get only 1/3 of half-load life. If you are looking for a longer replacement consider electric generators. SELECTION GUIDES AND TUTORIALS FOR CONSUMERS UPS POWER SUPPLY REVIEWS- MODELS AND MANUFACTURERS BACKUP UPS DESIGN GUIDES AND SCHEMATICS Types and specification of uninterrupted systems Selecting a UPS for stand-alone single-phase computer replacement power LAPTOP COMPUTER's BATTERY GUIDE UPS reviews and ownership guide Best models- four top rated devices comparison and tests USER REVIEWS: APC BE550G Belkin F6C550-AVR 550VA Tripp Lite 550SER 550VA Reference diamond of an offline UPS with a microcontroller and AC sine wave generation APC UPS 250_400_600 schematic (download and save the file- it opens only locally) SBS and On-line UPS: overview and tutorial Disclaimer, Disclosure and Terms of Use | Contact Us | About Us | Privacy ©2005, 2017 Lazar Rozenblat