The AS440 AVR for Stamford generators is a half-wave phase-controlled thyristor type AVR that plays a crucial role in the excitation system of a brushless generator. It employs Surface Mount Technology (SMT), offering a high integration of features within a compact AVR footprint.

The AVR ensures a positive voltage build-up from residual levels by utilizing efficient semiconductors in its power circuitry. The power and voltage sensing circuits are equipped with separate terminals, allowing excitation power to be derived directly from the stator winding for basic applications or from an auxiliary winding if sustained short circuit performance is necessary.

The AVR connects with the main stator windings and exciter field windings, providing closed-loop control of the output voltage with a load regulation of +/- 1.0%. The voltage sensing terminals of the AVR continuously monitor the output windings to regulate voltage. Based on this feedback, the AVR controls the power fed to the exciter field, and subsequently the main field, to maintain the generator’s output voltage within specified limits, compensating for load, speed, temperature, and power factor variations.

Additionally, a frequency measuring circuit continuously monitors the generator output, providing under-speed protection by reducing the output voltage proportionally with speed below a pre-set threshold. The under frequency roll-off point (UFRO) can be manually adjusted in the field to either 50 or 60 Hz via a push-on link selection.

Over-excitation conditions are safely managed by a protection circuit within the AVR, and provisions are made for connecting a remote voltage trimmer, enabling fine control of the generator’s output. An analogue input allows for connection to a Power Factor controller or other external devices with compatible output. The AVR also supports droop CT connection, facilitating parallel operation with other similarly equipped generator.