Stamford SX 440


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SX440 is a half-wave phase-controlled thyristor type
Automatic Voltage Regulator (AVR) and forms part of the
excitation system for a brush-less generator.


In addition to being powered from the main stator, the
AVR also derives a sample voltage from 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.
A frequency measuring circuit continually monitors the
generator output and provides output under-speed
protection of the excitation system, 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 easily be changed to 50 or 60 Hz in the field by pushon
link selection.
Provision is made for the connection of a remote voltage
trimmer, allowing the user fine control of the generator’s
An analogue input is provided allowing connection to a
Newage Power Factor controller or other external devices
with compatible output.
The AVR has the facility for droop CT connection, to allow
parallel running with other similarly equipped generators.