General description
SX460 is a half-wave phase-controlled thyristor typeAutomatic Voltage Regulator (AVR) and forms part of theexcitation system for a brush-ess generator.
In addition to regulating the generator voltage, the AVRcircuitry includes under-speed and sensing loss protectionfeatures.Excitation power is derived directly from thegenerator temminals.
Positive voltage build up from residual levels is ensured bythe use ofefficient semiconductors in the power circuitry ofthe AVR.
The AVR is linked with the main stator windings and theexciterfield windings to provide closed loop control of theoutput voltage with load regulation of+/-1.0%.
In addition to being powered from the main stator, the AVRalso derives a sample voltage from the output windings forvoltage control purposes. In response to this samplevoltage, the AVR controls the power fed to the exciter fieldand hence the main field, to maintain the machine outputvoltage within the specified limits, compensating for load.speed, temperature and power factor of the generator.
A frequency measuring circuit continually monitors thegenerator output and provides output under -speedprotection ofthe excitation system, by reducing the outputvoltage proportionally with speed below a pre -settablethreshold. Amanual adjustment is provided for factonysetting ofthe under frequency roll off point, (UFRO).Thiscan easily be changed to 50 or 60 Hz in the field by push-on link selection.
Provision is made for the connection ofa remote voltagetrimmer, allowing the user fine control ofthe generator’soutputTechnical specification
INPUT
Voltage
FrequencyPhase
OUTPUT
VoltageCurrent
Resistance
Jumper selectable95-132V ac or190-264V ac
50-60 Hz nominal
max 90V dc at 207V acinputcontinuous4Adcintermittent 6 A for 10 secs15 ohms minimum
REGULATION
+/-1.0% (see note 1)
THERMAL DRIFT
0.05% per deg. C change in AVR ambient (note 2)
TYPICALSYSTEM RESPONSE20 msAVR response80 msFiled current to 90%Machine Volts to 97%300 ms
EXTERNALVOLTAGE ADJUSTMENT+/-10% with 1 k ohm 1 watt trimmer (see note 3)UNDER FREQUENCY PROTECTION95% Hz (see note 4)Set pointSlope170% down to 30 Hz
UNIT POWER DISSIPATION
10 watts maximum
BUILD UP VOLTAGE
4 Volts @ AVR terminals