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UPS(Uninterruptible power supply)
UPS , Short for uninterruptible power supply, a power supply that includes a battery to maintain power in the event of a power outage. Typically, a UPS keeps a computer running for several minutes after a power outage, enabling you to save data that is in RAM and shut down the computer gracefully.
An uninterruptible power supply (UPS), also known as a battery back-up, provides emergency power and, depending on the topology, line regulation as well to connected equipment by supplying power from a separate source when utility power is not available. It differs from an auxiliary or emergency power system or standby generator, which does not provide instant protection from a momentary power interruption. A UPS, however, can be used to provide uninterrupted power to equipment, typically for 5–15 minutes until an auxiliary power supply can be turned on, utility power restored, or equipment safely shut down.
Off line/ standby UPS:
The Offline / Standby UPS (SPS) offers only the most basic features, providing surge protection and battery backup. Usually the Standby UPS offers no battery capacity monitoring or self-test capability, making it the least reliable type of UPS since it could fail at any moment without warning. These are also the least expensive, selling for as little as US$40. The SPS may be worse than using nothing at all, because it gives the user a false sense of security of being assured protection that may not work when needed the most.
With this type of UPS, a user's equipment is normally connected directly to incoming utility power with the same voltage transient clamping devices used in a common surge protected plug strip connected across the power line. When the incoming utility voltage falls below a predetermined level the SPS turns on its internal DC-AC inverter circuitry, which is powered from an internal storage battery. The SPS then mechanically switches the connected equipment on to its DC-AC inverter output. The switch over time is stated by most manufacturers as being less than 4 milliseconds, but typically can be as long as 25 milliseconds depending on the amount of time it takes the Standby UPS to detect the lost utility voltage.
Line interactive UPS:
The Line-Interactive UPS is similar in operation to a Standby UPS, but with the addition of a multi-tap variable-votage autotransformer.This is a special type ofelectrical trasformer that can add or subtract powered coils of wire, thereby increasing or decreasing the magnetic field and the output voltage of the transformer.
This type of UPS is able to tolerate continuous undervoltage brownouts and overvoltage surges without consuming the limited reserve battery power. It instead compensates by auto-selecting different power taps on the autotransformer. Changing the autotransformer tap can cause a very brief output power disruption, so the UPS may chirp for a moment, as it briefly switches to battery before changing the selected power tap.
Autotransformers can be engineered to cover a wide range of varying input voltages, but this also increases the number of taps and the size, weight, complexity, and expense of the UPS. It is common for the autotransformer to only cover a range from about 90v to 140v for 120v power, and then switch to battery if the voltage goes much higher or lower than that range.
In low-voltage conditions the UPS will use more current than normal so it may need a higher current circuit than a normal device. For example to power a 1000 watt device at 120 volts, the UPS will draw 8.32 amps. If a brownout occurs and the voltage drops to 100 volts, the UPS will draw 10 amps to compensate. This also works in reverse, so that in an overvoltage condition, the UPS will need fewer amps of current.
UPS Power supply- Presentation:
