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9 OPERATION
9.1 VOLTAGE REGULATOR
It compares the actual output voltage from the alternator with the theoretical adjusted value through the trimpot of voltage
adjustment P1, plus the external voltage adjustment (if any). The error is processed by the sensing loop whose value
determines the thyristor firing angle which may vary from 0 to 180°, thus controlling the output voltage of the alternator.
9.2 POWER CIRCUIT CONNECTION
The alternator voltage or the auxiliary winding voltage is connected to the terminals 3 and E3/4. This rectified voltage is
applied, in a controlled fashion, to the alternator exciter field.
9.3 FIELD FLASHING
Generation begins through the residual voltage of the alternator. Once the voltage has reached about 10% of the
nominal voltage, the regulator controls the alternator voltage causing it to rise through the initial ramp in approximately 3
seconds. When the alternator reaches its nominal value, the PID control loop will maintain the alternator output voltage
constant within the adjusted value.
9.4 U/F OPERATION
This operation is determined by trimpot P5, jumper J1 and associated components. The J1 jumper determines the
operating frequency (50 or 60 Hz), following the logic below:
▪
J1 closed on 60 Hz = 60 Hz
▪
J1 closed on 50 Hz = 50 Hz
Trimpot P5 determines the set point of the U/F mode, which can be from the nominal frequency (Fn) down to 1/3 of Fn,
the value of which comes out of the factory adjusted to 10% below Fn. For operation at 60 Hz it is adjusted to 54 Hz and
for operation at 50 Hz it is adjusted to 45 Hz (see Figure 9.1), the value of which can be changed based on each
application requirements.
U/f
14 l Automatic Voltage Regulator – GRT7-TH4E / GRT7-TH4PE
U
n
Frequency (Hz)
45
50
Figure 9.1: U/F operation
U
n
U/f
Frequency (Hz)
54
60
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