Abstract: Tap changing apparatus for switching the turns ratio between the primary and secondary windings of a three-phase transformer. The tap changer includes three mounting boards, one for each phase of the transformer. Each board contains a plurality of stationary contacts arranged in a circular pattern around an axis of rotation and connected to taps from various sections of the transformer windings. A movable contact assembly is associated with each set of stationary contacts and is rotatable around the center axis of each respective contact set. Each movable contact assembly is affixed to a worm gear which operates to rotate the movable contacts between successive stationary contacts in each respective contact set.

Abstract: A three-phase transformer including tap changing apparatus for switching the turns ratio between the primary and secondary windings of the transformer. The tap changer includes a mounting board on which three contact sets are mounted; each set having a plurality of stationary contacts arranged in a circular pattern. A circular-shaped operating member, with a movable contact assembly affixed thereto, is associated with each contact set and is pivotable around the center of the stationary contact set to allow the movable contact assembly to sequentially engage successive stationary contacts. A connecting bar is coupled to each operating member in spaced relation from its axis of rotation, causing all three operating members to rotate together.

Abstract: Tap changing apparatus for connection to the windings of a three-phase power transformer. The tap changer includes a mounting board on which three sets of stationary contacts, arranged in a circular pattern, are mounted. A rotating contact assembly is associated with each set of stationary contacts and may be pivoted around the center of the stationary contact set for engagement with one of the stationary contacts. An operating bar extends across each set of stationary contacts and is coupled to the rotating contacts by rack and pinion assemblies. When the operating bar is moved in one direction, the rotating contacts are turned in a counterclockwise direction. When the operating bar is moved in the other direction, the rotating contacts are turned in the clockwise direction. The operating bar is moved by a rack and pinion assembly which is connected to a rotating shaft.