New life for old thyristor power rectifiers using contemporary digital control

The paper presents information on a control and monitoring system retrofit of two unreliable 1978 14 MW rectifiers used in a sodium chlorate plant. Reasons for the upgrade and expectations of the new system are discussed. Alternate solutions considered and the rationale supporting the choices made are reviewed. The paper summarizes the project from the initial investigation through the design process and selection of equipment. Justification of the expenditure, issues of mating old and new equipment, problems overcome during the implementation and the lessons learned are described. In closing, the suitability of this approach for other rectifier installations is addressed.