ABB UNITROL / Synpol D is an excitation and generator-control product family used to regulate field current, terminal voltage, and associated generator operating functions. Its architecture can combine automatic voltage regulator hardware, control boards, power supplies, I/O cards, measurement interfaces, and communication components. Technical characteristics vary by part number and include signal interface, supply requirements, board revision, measurement function, control role, electrical ratings, and system compatibility. The collection represents control, sensing, power, and interface layers within UNITROL and Synpol D excitation systems. Functionally, these components support voltage regulation, excitation control, measurement processing, protection interaction, and communication with plant control equipment. Replacement selection should match the exact system generation, board number, hardware revision, electrical specification, and installed excitation architecture to maintain compatibility with the existing generator control system.
