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EA321
3
SECTION 2 : GENERAL DESCRIPTION
2.1
EA321 is a three phase sensed Automatic
Voltage Regulator and forms part of the
excitation system for a brush-less generator.
Excitation power is derived from a three-phase
permanent magnet generator (PMG), to isolate
the AVR control circuits from the effects of
nonlinear loads and to reduce radio frequency
interference
on
the
generator
terminals.
Sustained generator short circuit current is
another feature of the PMG system.
2.2
The AVR senses the voltage in the main
generator winding and controls the power fed to
the exciter stator and hence the main rotor to
maintain the generator output voltage within the
specified limits, compensating for load, speed,
temperature and power factor of the generator.
2.3
Soft start circuitry is included to provide a smooth
controlled build up of generator output voltage.
2.4
A frequency measuring circuit continually
monitors the shaft speed of the generator and
provides under-speed protection of the excitation
system by reducing the generator output voltage
proportionally with speed below a pre-settable
threshold. A further enhancement of this feature
is an adjustable volt per Hertz slope to improve
engine recovery time on turbo charged engines.
Soft start circuitry is included to provide a smooth
controlled build up of generator output voltage.
2.5
Uncontrolled excitation is limited to a safe period
by internal shutdown of the AVR output device.
This condition remains latched until the generator
has stopped.
2.6
Provision is made for the connection of a remote
voltage trimmer, allowing the user fine control of
the generator’s output.
2.7
An
analogue
input
is
provided
allowing
connection to a controller or other external
devices with compatible output.
2.8
The AVR has the facility for droop CT connection,
to allow parallel running with other similarly
equipped generators.
NOTE :
(1) Derate linearly from 3.7A at 50
˚C to 2.7A at 70 ˚C.
(2) The stated voltage regulation may not be
maintained in the presence of certain transmitted
radio signals. Any change in regulation will fall
within the limits in criteria B of S.EN.61000-6-2 :
2001.
(3) After 10 minutes.
(4) Applies to Mod status E onwards. Generator
de-rate may apply. Check with factory. Factory set,
semi-sealed, jumper selectable.
(5) Any device connected to the analogue input must
be fully looting (galvanically isolated from ground),
with an insulation strength of 500 Vac.
(6) Non condensing.
SECTION 3 : SUMMARY OF AVR CONTROLS
CONTROL
FUNCTION
DIRECTION
VOLT
To adjust generator output voltage
Clockwise increases output voltage
STABILITY
To prevent voltage hunting
Clockwise increase the damping effect
UFRO
To set the UFRO knee point
Clockwise reduces the knee point frequency
DROOP
To set the generator droop to 5% at 0 pf
Clockwise increases the droop
TRIM
To optimize analogue input sensitivity
Clockwise increases the gain or sensitivity
EXC
To set the over excitation cut off level
Clockwise increase the cut off level
DIP
To set the frequency related voltage dip
Clockwise increases the voltage dip
DWELL
To set the Hz related recovery time
Clockwise increases the recovery time
I LIMIT
To set the stator current limit
Clockwise increases the current limit
OVER V
To set the over voltage trip level
Clockwise increases the trip level
RAMP
To set the no load voltage RAMP up time
Clockwise increases the voltage ramp time
RMS
To set 3 phase RMS detected
