© Cummins 2008 1 TD_AS480 AVR_04.08_02_GB
AS480 AUTOMATIC VOLTAGE
REGULATOR (AVR)
SPECIFICATION INSTALLATION AND ADJUSTMENTS
General description
Technical specification
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.
Operation with 110Vac sensing is possible, replace the hand
trimmer link with fixed resistor. The hand trimmer option cannot
be used in this configuration. The generator overload capability
is reduced in 110V operation.
The AVR has the facility for droop CT connection, to allow
parallel running with other similarly equipped generators.
Over excitation conditions are limited to a safe period by a
protection circuit within the AVR. Once activated by a sustained
over-excitation condition, the generator voltage is reduced to a
low level until reset. Stopping the generator or removing power
from the AVR will perform the necessary reset.
Connections are provided to interface to the optional Excitation
Boost System. This incorporates a small externally mounted
rotary power supply which provides excitation power in the event
of heavy overloads or short circuits. The EBS is short term rated
and responds to signals from the AVR to deliver excitation power
when required. A separate overload protection system within the
EBS electronic module protects the generator against sustained
overloads.
SENSING and POWER INPUT
Voltage 100-264 V ac 1 phase
Frequency 50-60 Hz nominal
OUTPUT
Voltage 82 V d.c. @ 200 Va.c power input.
Voltage 45 V d.c. @ 110 Va.c power input.
Current continuous 5A (see note 1).
transient 7.5A for 10 secs.
Resistance 15 ohms min
REGULATION
+/- 1.0% (see note 2)
THERMAL DRIFT
0.03% per deg. C change in AVR ambient (see note 3)
TYPICAL SYSTEM RESPONSE
AVR response 20ms
Field current to 90% 80 ms
Machine Volts to 97% 300ms
EXTERNAL VOLTAGE ADJUSTMENT
+/-10% with 1 k ohm 1 watt trimmer (see note 4)
Increasing resistance lowers voltage.
Fixed 15kOhm resistor enables 110V sensing
UNDER FREQUENCY PROTECTION
Set point 94 -98% Hz (see note 5)
UNIT POWER DISSIPATION
12 watts maximum
BUILD UP VOLTAGE
4 Volts @ AVR terminals
QUADRATURE DROOP INPUT
10 ohms burden
Max. sensitivity: 0.07 A for 5% droop 0PF
Max. input: 0.33 A
OVER EXCITATION PROTECTION
Set point 67 Vdc +/-3% (fixed)
Time delay 10-15 seconds (fixed)
ENVIRONMENTAL
Vibration 20-100 Hz 50mm/sec
100Hz – 2kHz 3.3g
Operating temperature -40 to +70C (note 6)
Relative Humidity 0-70C 95% (note 7)
Storage temperature -55 to +80C
NOTES
1. De-rate by 20% if mounted external to generator.
2. Inclusive of 4% engine governing.
3. After 2 minutes warm-up.
4. Generator de-rate may apply. Check with factory.
5. Factory set, semi-sealed, jumper selectable.
6. De-rate output current by 5% per deg. C above 60C.
7. Non condensing.
(34 pages)
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