Uninterruptiblepower systems (UPS’s) are often being referred to merely as a “batteries in abox”. While in fact, they are very complex systems which perform numerousfunctions. Those important functions ensure clean power and continuous uptimeto sensitive electronic equipment.However, without propermaintenance, UPS’s are subject to failure, sincecritical components wear out from normal use. Performing regular service by trained and experienced personnel is crucial to minimize the riskof failure. Performing regular service enhances your own knowledge aboutthe power system.
Understanding how the main elements of your UPS function isof vital importance. This knowledge enables you to more easily identify, andavoid, potential failures and unwanted delays. Allow us to introduce youto four primary components of each UPS: 1. Battery This main component can be compared to a “heart”of UPS system. When the system senses a loss of powerfrom the primary source the battery “kicksin”. The main purpose of batteries is to support the connected loadduring a utility power failure. This component is the most critical UPScomponent since it guarantees system reliability. Nevertheless, the battery isoften considered as a maintenance-free product that doesn’t require muchattention or inspection.
Such a mistake can prove costly and can potentially causea power failure.Depending on the UPS configuration, each UPScontains at least one battery string. In order to increase runtime and/orredundancy, multiple battery strings can be added. Since the battery stringsare serially connected, asingle bad battery can cause failure of the entire battery string.Experience shows that up to 20% of UPS failures happen due to a bad battery. This factunderlines the need and importance of regular inspection and maintenance. The most commonly used batteries in UPS’sare valve regulated lead acid (VRLA) batteries, including Geland AGM (Absorbed Glass Mat) batteries. A VRLA batteryuses a one-way, pressure-relief valve system.
This means that the oxygennormally produced on the positive plate is absorbed by the negative plate. Thissuppresses the production of hydrogen at the negative plate. Water (H2O) isproduced instead, retaining the moisture within the battery. This type ofbattery never needs watering, and they should never be opened as this wouldexpose them to excess oxygen from the air. In addition to damaging thebatteries, opening also voids the warranty.AGM(Absorbed Glass Mat) batteriesAGM batteriescompletely absorb electrolyte in separators, consisting of matted glass fibers.Significant advantage is that they are spill proof, meaning they don’t leakacid like a flooded design of battery, if tipped on their side. The AGMbatteries glass mats are wrapped around the positive plate, which helps preventdamage from vibration and extend cycling.
The battery strings are packedtightly in the case partitions, which also protects their power producingcomponents. UPS batteries usuallyhave a life expectancy between four and six years, although individual qualityand charging technology can impact the projected lifespan. In the rightapplication, AGM batteries can have over twice the life cycle of conventionalflooded batteries.
Gelor Gelled Electrolyte batteriesInstead of thetraditional liquid form, electrolyte in a Gel battery is permanently locked ina highly viscous gelled state. Because there is no electrolyte in a liquidstate, this type of battery will also not leak if tipped on its side. Thethick, gelled electrolyte and tightly packed strings also protect the battery’spower producing components. Gel battery designs have a superior deep dischargeresiliency and, if used in the right applications, can deliver over two tothree times the life cycle of an AGM battery.
2. Rectifier A UPS rectifier performs two very importantroles: charging the batteries and converting incoming utility power from AC toDC. Ifpower loss occurs, the rectifier simply drops out of the circuit and thebatteries keep the power steady and unchanged. When power is restored, therectifier resumes carrying most of the load and begins charging the batteries,though the charging current may be limited to prevent the high-power rectifierfrom overheating the batteries. Weutilize a sophisticated charging method that prevents unnecessary charging ofthe batteries, which significantly slows the wearing-out process. 3. Inverter The inverter within a UPS accepts the DCfrom the DC buss, which is supplied by the rectifier and the battery. During apower outage, the rectifier no longer provides current to the D/C buss, leavingthe batteries to support the load.
But if power is not restored before thebatteries wear out, the system runs the risk of dropping the load unless anexternal power source such as a generator kicks in. If power lossoccurs,the batteries drive the inverter, which continues to run. When poweris restored, either from the utility or a generator, the rectifierdelivers direct current (DC) to the inverter. The inverter runs fulltime.
4. Staticbypass Astatic bypass is fitted to almost all On-line UPS. It forms the second line of defense.
Should the inverter fail, the static bypass ensures the load dropsautomatically onto the mains input feed. Thiscomponent automatically closes the circuit and allows the incoming power todivert around the rectifier, batteries and inverter. Although the power supplyis not conditioned, the static bypass lets critical systems continuefunctioning even if the UPS’s internal components fail.A static bypass is in almost all cases part of the UPS internal circuitry andmay be invoked manually using an external switch. In larger UPS, itsynchronizes the UPS output with the mains cycle before switching, so it maytake a few seconds to engage. When you get familiar withthe primary UPS components, you are able to make more educated decisions andkeep your systems performing optimally.
We recommend scheduling at leasttwo preventative maintenance visits yearly. These service visits,which include a comprehensive range of inspections, are designed to ensure theongoing health of the critical UPS components.