A UPS (Uninterruptible Power Supply) is an electrical apparatus that provides emergency power to a load when the input power source or utility power fails. It is a battery-powered electronic device that continues to supply electricity to the load for a certain period of time during a utility failure how when the line voltage varies outside the normal limits.
A UPS helps to ensure that your running devices continues to function without any disruption when the utility energy goes off. It protects hardware such as computers, data centers, telecommunication equipment and other electrical equipment where an unexpected power disruption could cause injuries, fatalities, serious business disruption or data loss. Just like inverters, a UPS is powered by batteries and lasts for a very short period of time. In order to prevent loss of unsaved data on a desktop computer due to a brief power outage, a UPS is pivotal. The on-battery run time of a UPS is
relatively short but sufficient to start a standby power source or properly shut down the protected equipment. The primary purpose and advantage of a UPS is that it provides limited power to a computer so that it can stay running long enough for the operating system running to shut down neatly and for the utility power or an alternative power comes on.
Also referred to as an Offline UPS, this is the most basic type of UPS and the most common type used for personal computers. This type of UPS is ideal for environments where electrical isolation is necessary, or for equiupments that are very sensitive to power fluctuations. Power starts by being fed through various circuits that control surge and line-noising filtering. The output of a standby UPS is almost always a simulated sine-wave as this makes them cheaper to produce. The primary source of power of a Standby UPS is line power from the utility, and the secondary power source is the battery. It is called a Standby UPS because the battery and inverter are normally not supplying power to the equipment. The battery charger uses line power to charge the battery, and the battery and inverter are waiting wait on standby until they are needed. When the AC power goes out, the transfer switch changes to the secondary power source. When the line power is restored, the UPS switches back. A typical transfer time is between 2 ms and 10 ms depending on the amount of time it takes to detect the utility voltage and turn on the inverter.
This type of UPS is best suitable for sensitive and expensive equiptments that requires a true sine wave power. The online UPS is more expensive than the Standby UPS and may be necessary when the power environment is noisy such as in industrial settings, for larger equipment loads like data centers, or when operation from an extended-run backup generator is necessary. The online UPS always runs off its battery, thereby using its inverter. For this reason, this type of UPS is sometimes called a double-conversion UPS. They convert raw power to refined power through a double conversion. They change it from an unclean alternative current to a direct current, clean it and then convert it back to an alternative current. This design means that there is no transfer time in the event of a power failure-if the power goes out, the inverter keeps charging along and only the battery charger fails. A double conversion UPS or online UPS provides a layer of insulation from power quality problems. It allows control of output voltage and frequency regardless of input voltage and frequency. The online UPS provides an electrical firewall between the incoming utility power and sensitive electronic equipment. An online UPS always delivers all or at least a portion of the output power through its inverter even under normal line conditions, and therefore provides true uninterruptible power with 0 ms transfer time. The online UPS has an improved and greater battery charger/rectifier, and the batteries are always connected to the inverter, so that no power transfer switches are necessary. When there is a power loss, the rectifier simply drops out of the circuit and the batteries keep the power steady and unchanged. When the power is restored, the rectifier resumes carrying most of the load and begins charging the batteries. This continuous on-line double-conversion operation provides voltage regulation and sine wave output. It isolates connected equipment from most power problems, including blackouts, overvoltages, transient voltage surges, electromagnetic line noise, harmonic distortion, electrical impulses and frequency variations. The advantages of a double-conversion on-line UPS is that it operates less often from battery when the input voltage is highly distorted or wildly fluctuating; it can regulate output frequency and even perform frequency conversion from 50Hz to 60Hz and vice versa; it is more compact and lightweight.
If you need a voltage regulation and power protection for moderate loads, particularly for commercial or office applications, a line-interactive UPS is your best bet. A line-interactive UPS conditions and regulates the AC power from the utility, generally using only one main power converter. This type of UPS smoothes and regulates the input AC voltage by a filter and a tap-changing transformer. It provides automatic voltage regulation (AVR) to keep equipment working through low-voltage and high-voltage conditions without draining battery power. The bi-directional inverter/charger is always connected to the output and uses a portion of AC power to keep the battery charged. When the input source fails, the transfer switch disconnects the AC input and the battery inverter then feeds the load. A line-interactive UPS maintains the inverter in line and redirects the battery’s DC current path from the normal charging mode to supplying current when power is lost. Here, the separate battery charger, inverter and source selection switch have all been replaced by a combination inverter/converter, which both charges the battery and converts its energy to AC for the output as required. The AC line power is the primary source of power while the battery is the secondary source of power. This type of UPS system uses automatic voltage regulation to correct abnormal voltages without switching to battery. It detects when voltage crosses a preset low or high threshold value and uses transformers to boost or lower the voltage by a set amount to return it to the acceptable range. It had advanced surge suppression and line noise filtering components to shield your equipment from damage by any electromagnetic noise. Its selected models include switched outlet banks that can be controlled independently, connectors that accept optional battery packs for extended runtime and an accessory card slot for an SNMP card to enable remote monitoring and control. A line-interactive UPS has a low power consumption, less costly to operate, highly reliable, faster response to a power failure, production of less heat and more efficient because less power conversion is performed when acceptable AC input is present. This type of UPS is an appropriate choice where the AC power is unstable or highly distorted, because battery power will be used too often to keep the UPS output within specifications. It is also best suitable when Power Factor Correction (PFC) is requires and the load equipment does not perform this function.
Similar to the double conversion on-line ups, the Delta conversion On-line UPS has the inverter supplying the load voltage. However, the additional Delta converter also contributes power to the inverter output. The additional Delta converter delivers a portion of the energy directly to the load and provides power factor correction. In other words, the Delta transformer and Delta converter work together. The Delta Converter moves components of the power from input to the output through the use of the power factor correction. This type of UPS acts with dual purpose. The first is to control the input power characteristics. This active front end draws power in a sinusoidal manner, minimizing harmonics reflected onto the utility. This ensures optimal conditions for utility lines and generator systems and reduces heating and system wear in the power distribution system. The second function of the Delta Converter is to charge the battery of the UPS by drawing power and converting it to the appropriate DC charging voltage. In a Delta Conversion On-line UPS, both the delta converter and the main converter are bi-directional devices; they have the ability to change AC power to DC power and simultaneously DC power to AC power. In other words, they can each do the same primary functions as both of the double conversion devices with some
A UPS provides backup only for a short period of time, so do not expect it to run all day. Most UPS units are engineered to provide you a backup time of around 10 to 20 minutes. It is especially useful for devices that can lose data when they turn off unexpectedly, such as computers. If you need battery backup power to outlast longer outages, many network/server UPS systems allow you to expand runtime by connecting optional external battery packs. So, when purchasing a UPS, make sure to choose the UPS that meets your backup time demands. Also, make sure the manufacturer of the brand of the UPS you want to buy has provided a way for you to replace the internal battery without replacing the entire unit. UPS batteries usually stop working long before the rest of the UPS, so you’ll get more years of service out of it if you can replace the battery yourself.
A UPS has so many outlets, so when purchasing one, you need to put into consideration how many devices you currently have plugged in and how many are truly considered essential which need to be powered by the UPS. Many UPS units provide at least eight plugs, but also check how many of them are actually powered by the battery. It is also imperative to note that UPS units more than more outlets costs more, so be prepared to pay extra if you want the unit with more outlets Also, if you are using wired data connections, look for a UPS that provides protection for them as well. This includes both old-fashioned modem and newer Ethernet connections.
After knowing how many outlets you need, the next decision to make is deciding on how large of a VA capacity you need. The VA is a way of describing the total power capacity of the battery. Every UPS comes with a VA rating, usually like a 800VA o4 1500VA. The higher the VA rating, the more power the UPS can supply both in terms of powering multiple devices simultaneously and lasting for a longer period of time.
When buying a UPS, be sure to add the watts of the equipment load and make sure it’s less than the rating of the UPS. Depending on the equipment load, you could get a UPS with less than 500 watts which are relatively inexpensive; 500W to 1.4W which can be used to power equipment with lighter loads; 1.5Kw TO 3KW that are perfectly able to service multiple computers and other similar equipment, and finally, more than 3K Watts that can be used to power industrial units, factory equipment, computer rooms and other larger equipment.