What is a Line-Interactive Ups?
The line-interactive UPS is similar to a off-line UPS, but with the addition of a multi-tap variable-voltage autotransformer. This is a special type of transformer that can add or subtract powered coils of wire, thereby increasing or decreasing the magnetic field and the output voltage of the transformer. Additional filtering is provided in this UPS result in lower transient loss. Lline interactive UPS is used for small business and departmental servers and webs.
The block diagram is shown below.
Line-Interactive UPS is able to tolerate continuous under voltage brownouts and overvoltage surges without consuming the limited reserve battery power. It instead compensates by automatically selecting different power taps on the autotransformer. This has become popular even in the cheapest UPSs because it takes advantage of components already included. To gain the buck/boost feature, all that is required is two separate switches so that the AC input can be connected to one of the two primary taps, while the load is connected to the other, thus using the main transformer’s primary windings as an autotransformer. The battery can still be charged while “bucking” an overvoltage, but while “boosting” an under voltage, the transformer output is too low to charge the batteries.