Failure Modes of Brushless Excitation System and Refurbishment Approach for Life Extension

Brushless excitation system was introduced four decades ago to get rid of commutator problems of DC Exciter for turbine generator in power plants. But new problems appeared in rotating rectifier circuits and permanent magnets of this system. Failure of the exciters can have impact on the power production. Condition-based maintenance built on online condition monitor and off-line condition assessment has taken importance to safeguard the system.This paper presents different types of troubles experienced on brushless exciters and permanent magnet generators in various power plants. Condition monitor and condition assessment techniques adopted for these machines are dealt. Case studies on unexpected failure of BL Exciters of a 32 MW and 40 MW turbine generators in industry sector and refurbishment methods are narrated. Anatomy of the brushless exciter is given for the benefit of fresh service engineers which will help link the health checkup test results with the components. A brief on the efforts put in indigenous development of rotating electronic components and monitors of these machines to meet the customer’s necessity is given.