Protections - U/F Operation; Block Diagram - WEG AVR-A-OPT-06 400Hz Manual De Instalación, Operación Y Mantenimiento

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4.2 PROTECTIONS – U/F OPERATION
Erro! Fonte de referência não encontrada.Figure 4.1 shows the curves for voltage variation as a function of frequency
variation. For nominal frequency operation, U/F is disabled. When rotation decreases (for ex. when shutting down),
excitation diminishes, reducing the output voltage of the alternator. The drop follows a straight line of 7,5 V/HZ.
The U/F trimpot determines the trigger point of the U/F mode, which can be the nominal frequency (Fn) down to 1/3 of Fn,
and leaves the factory adjusted to 10% below Fn. For operation in 400Hz it is adjusted to 360Hz (see Figure 4.1). These
values can be altered according to the needs of each application.
ATTENTION
1. Do not set the U/F protection below 20 % of the rated alternator frequency. The configuration should be done
according to Figure 4.1 to avoid problems when shutting down.
2. The frequency limited by U/F is the frequency of the waveform that is at the power supply input of the
regulator and not at the sensing input (output voltage of the alternator).

4.3 BLOCK DIAGRAM

The structure of the regulator is shown on Figure 4.2.
14 l Automatic Voltage Regulator – AVR-A-OPT-06 400Hz
Figure 4.1: Actuation point for U/F protection
Figure 4.2: Block diagram of the AVR-A-OPT-06 voltage regulator