At its core, the Automatic Voltage Regulation (AVR) system within a UPS is a masterwork of electronics engineering. Designed to maintain a steady voltage output despite fluctuations in incoming power, the AVR’s Boost and Trim (or Buck) functionalities are what enable this stabilization. How does it work?
When the incoming AC voltage dips below a set threshold, indicating undervoltage or a brownout, the AVR Boost function springs into action. Technically speaking, the AVR contains an autotransformer, a type of transformer with a single winding in which at least three electrical connection points (or taps) are exposed. When a low voltage is detected, the AVR switches to a tap that results in a higher output voltage, effectively ‘boosting’ the voltage to an appropriate level. Conversely, when there’s an overvoltage, the Trim or Buck function is activated. Here, the AVR shifts the connection to a tap that delivers a lower output voltage, ‘trimming’ or ‘bucking’ down the excessive voltage to protect connected devices.
In either scenario, the transition is seamless, often occurring in milliseconds, and without the need to switch to battery mode. This rapid response not only safeguards connected equipment from voltage abnormalities but also conserves battery life by reducing the frequency of battery usage. By utilizing the physics of transformer design and advanced electronics, the AVR in UPS systems ensures a consistent and clean power output.