Resumo:
The main objective of this dissertation is to present the development of an automatic
voltage regulator for brushless excitation system.
The brushless excitation of synchronous machine is an attractive solution for problems
related to slip rings cooling. The brushless excitation eliminates the need for brushes, a
commutator and slip rings. For this, exciter stationary DC field induces AC three-phase
voltage into the rotating exciter armature. This armature is attached to generator shaft and
connected to a rotating three-phase bridge rectifier. The DC voltage of the rotating rectifier
is applied to the field of the synchronous generator.
The automatic regulator was developed with most advanced microcontroller technology
together with Programable Logical Controller (PLC). The power electronics part is fitted
with an IGBT (Insulated Gate Bipolar Transistor) semicondutor. The power circuit for the
excitation is explained and the signal of the PWM chopper circuit is analyzed.
The operation of the brushless excitation system of synchronous generator is presented. All
the operating modes of the regulator are careffuly explained. Many tests were realized and
the results are presented in this work.
A methodology for Diode Monitoring is also presented in this dissertation. This monitoring
is needed in brushless excitation and can only be done indirectly, because the diode bridge
is part of the rotor. In this way, a software for this monitoring is proposed.
