Design Consideration of High Power High Current Twelve Pulse Thyristor Controlled Rectifiers

High power high current thyristor controlled rectifiers are widely used in industries, particularly in electrolysis processes like metal refining, chlorination plants, electroplating, hydrogen production, etc. Other special application includes metallurgical processes, heating applications and electric tractions including nuclear research. In this paper, design consideration of 3.4 MW at 10 kA, twelve pulse, thyristor controlled rectifier units utilized for nuclear research application have been discussed. Nuclear reactor converts fission energy into electrical energy which is fed to the grid network. Determination of safety margins of nuclear reactor is the most crucial requirement as far as the safety of nuclear reactor is concerned. Generally, nuclear reactor safety margin is initially evaluated using well-proven computer codes and then validated by conducting appropriate experiments in simulated test facilities. In those experimental test facilities, nuclear fuel bundle is simulated incorporating metallic cluster of identical geometry with suitable power scaling. Low resistance metallic cluster is directly heated by DC current of the order of 10-50 kA to achieve the output power in MW, needed for generating experimental database. Rectifiers should have capability to generate a typical nuclear reactor power profile/transient for simulating nuclear reactor conditions. The paper describes technical specifications, design considerations and implementation aspects, commissioning and operational experience of 3.4 MW, 10 kA, twelve pulse thyristor controlled rectifiers. The various operating parameters observed during experimentation are also presented.