SX440 AUTOMATIC VOLTAGE
REGULATOR (AVR)
SPECIFICATION, INSTALLATION AND ADJUSTMENTS
GENERAL DESCRIPTION
The SX440 is a half-wave phase-controlled thyristor type
Automatic Voltage Regulator (AVR) and forms part of the
excitation system for a brushless generator.
In addition to regulating the generator voltage, the AVR
circuitry includes underspeed and sensing loss protection to
ensure safe, reliable control of the generator. Excitation power
is derived directly from the generator terminals.
Positive voltage build up from residual levels is ensured by
the use of efficient semiconductors in the power circuitry of
the AVR.
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%.
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 underspeed protection
of the excitation system, by reducing the output voltage
proportionally with speed below a presettable 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 push-on wire link selection.
Overvoltages caused by open circuit sensing terminals are
avoided by sensing loss detection circuitry which reduces the
generator terminal voltage to a safe fixed level.
Provision is made for the connection of a remote voltage
trimmer, allowing the user fine control of the generator's
output.
Accessories are available for this AVR. Please refer to factory
for further details.
TECHNICAL SPECIFICATION
INPUT
Voltage 170-250 V ac max
Frequency 50-60 Hz nominal
Phase 1
Wire 2
OUTPUT
Voltage max 90 V dc at 207 V ac input
Current Continuous 4 A dc
Transient 6 A for 10 seconds
Field Resistance 15 Ω minimum
REGULATION (See Note 1) +/- 1%
THERMAL DRIFT
(after 10 min)
1% for 40°C change in AVR ambient
TYPICAL SYSTEM RESPONSE
Field current to 90% 80ms
Machine Volts to 97% 300ms
EXTERNAL VOLTAGE ADJUSTMENT (see note 2)
+/- 8% with 1 K Ω trimmer
UNDER FREQUENCY PROTECTION
Set Point (See Note 3) 95% Hz
Slope 170% down to 30 Hz
UNIT POWER DISSIPATION
12 watts maximum
BUILD UP VOLTAGE
3.5 Vac @ AVR terminals
ACCESSORY INPUT
+/- 1V = +/- 13% change in output volts
QUADRATURE DROOP SENSITIVITY
Maximum sensitivity (10 Ω Burden)
0.07A for 5% droop @ 0p.f.
ENVIRONMENTAL
Vibration 20-100 Hz 50mm/sec
100 Hz-2 kHz 3.3g
Relative Humidity 0-60°C 95%
Operating Temperature -40°C to + 70°C
Storage Temperature -55°C + 80°C
NOTES
1) With 4% engine governing
2) External trim range is reduced to +/- 5% with 1 K
Ω trimmer when 3 phase sensingis fitted.
3) Factory set, semi-sealed, jumper selectable.
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