The self-supporting rectifier frame is built of aluminum profiles having specially designed channels for most effective cooling by de-ionized water or a glycol mixture flowing inside. The inside water channels are routed and welded in such a way that extensive outside hose connections are not needed anymore. Semiconductor and fuses are cooled on both sides by high efficiency cooling boxes.
Except the joint to the transformer bushing the complete rectifier structure is without any bolted conductor connection. The clear design allows easy and quick access to every rectifier component. For long-term best conductivity in the rectifier all contact areas are nickel-plated. Each semiconductor path is equipped with a high-speed current limiting fuse for selective isolation in case of a failure. If desired, the built-in redundancy allows nominal load operation even with one or more semiconductor per leg out of service. In such a case the striker pin with its micro-switch or a Rogowski-type fuse supervision identify the faulty element.
To eliminate the risk for a secondary flashover the semiconductor stack is designed with ABB’s unique "plasma containment" protection. Additionally arc resistant phase barriers eliminate the risk of a phase-to-phase flashover. Electrically the rectifier is protected against hole-storage effect surges and overvoltage disturbances coming from the network by a suitable rated capacitor circuit arrangement. All phases are tested in our inhouse power testing facility to ensure safe operation of the rectifier.