Block Diagram - Pegasus GRT7-TH4 R2 Manual De Instalación, Operación Y Mantenimiento

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4.3 BLOCK DIAGRAM

The structure of the regulator is shown on Figure 4.3.
Figure 4.3: Block diagram of the GRT7-TH4 R2 voltage regulator
The principle of operation is based on the comparison of the RMS sensing voltage with the reference voltage, adjusted by
the sum of the values of Vad trimpot and the external trimpot. The error is processed by the sensing loop and its value
determines the firing angle of the thyristor, which can vary from 0 to 180°, thus controlling the output voltage of the
alternator. With zero degree firing, the result is zero volts on the output side of the rectifier, and 180 degrees results in
maximum output of the half wave rectifier.
Generation starts through the alternator residual voltage. After the voltage has reached approximately 10% of the nominal
value, the regulator controls the voltage of the alternator, taking it through an initial ramp up of approximately 1 second
until reaching nominal voltage. From this point on, the sensing loop will maintain the output voltage of the alternator
constant within the adjusted value.
Figure 4 shows the control diagram of the GRT7-TH4 R2 voltage regulator. The control it's based in ST1A, shown by IEEE,
and applied to systems where the rectifier is fed from the output of the alternator (Type ST – Static Excitation Systems),
directly or through auxiliary coils or through a transformer.
Figure 4.4: Control diagram GRT7-TH4 R2
Automatic Voltage Regulator – GRT7-TH4 R2 l 15