AVR AS480 | Generic

The AS480 is a half wave phase controlled AVR which forms part of the excitation system of the brushless generator. The design employs Surface Mount Technology (SMT), custom mouldings and heatsinks to produce a compact AVR assembly. The AVR also incorporates an interface to the optional Excitation Boost System (EBS) for use where short-circuit current maintenance is required. The AVR is linked with the main stator windings and the exciter field windings to provide closed loop control of the output voltage with load regulation of +/- 1.0%. The AVR voltage sensing terminals continuously sample the output windings for voltage control purposes. In response to this sample voltage, the AVR controls the power fed to the exciter field, and hence the main field, to maintain the machine output voltage within the specified limits, compensating for load, speed, temperature and power factor of the generator. Positive voltage build up from residual levels is ensured by the use of efficient semiconductors in the power circuitry of the AVR. A frequency measuring circuit continually monitors the generator output frequency and provides under-speed protection of the excitation system. This is done by reducing the output voltage proportionally with speed below a pre-settable threshold. A manual adjustment is provided for factory setting of the under frequency roll off point, (UFRO). This can be changed to 60Hz (or 50Hz) in the field by push-on link selection. A wide range of stability settings are available to compensate for machine sizes and applications. A ‘slow’ setting is available for applications involving single/twin cylinder engines and where lamp-flicker could be a problem. Provision is made for the connection of a remote voltage trimmer, allowing the user fine control of the generator’s output voltage.