Abstract: A sealed core-coil assembly in a submersible transformer includes a coil assembly having an inner coil with inner, outer, upper, and lower surfaces, and an outer coil with inner, outer, upper, and lower surfaces, a core assembly including a core window and core column of a magnetically-permeable material, the core column and core window having inner side surfaces, and an expandable sealing member including an inner cavity that is fillable or evacuatable so that a compliant insulation material is positioned in the inner cavity to block passage of water and prevent the formation of a loop of water, which otherwise would act like an electrical short in a submerged transformer.

Abstract: A transformer core for a dry-type transformer includes a laminated construction having several groups of stacked laminations that form a step-lap sequence of laminations. Each group in the step-lap sequence has a mean length different than an adjacent group in the step-lap sequence and has at least two identical laminations per group, wherein at least one group has at least four identical laminations. Methods of assembling a transformer core are also provided, as are other aspects.

Abstract: A tap changer assembly of a dry-type transformer. The tap changer assembly includes a first molding including multiple taps, a semi-conductive coating applied to the first molding, a conductive shield provided overtop some of the semi-conductive coating, a grounding member comprising a ring of bosses interconnected by a grounding conductor connected to the conductive shield, a second molding applied over at least a portion of the conductive shield and the grounding conductor, the second molding forming a molded sealing surface, a conductive cover coupled to the ring of bosses; and a sealing member sealing a space between the molded sealing surface and the conductive cover. Dry-type transformers and methods of forming a tap changer assembly of a dry-type transformer are provided, as are numerous other aspects.

Abstract: In some embodiments, a connection bar is provided for connecting multiple high voltage coils of a dry-type transformer along a top or bottom of the dry-type transformer. The connection bar includes (1) an electrically insulating body having a plurality of openings, each opening sized to receive at least one of high voltage terminals of the transformer; (2) an electrical connection pathway within the electrically insulating body configured to create a predetermined electrical connection between multiple high voltage coils of the transformer; (3) external connector terminals embedded within and extending from the electrically insulating body, the external connector terminals connected to the electrical connection pathway; and (4) a ground shield embedded within the electrically insulating body and configured to shield high voltage terminals of each high voltage coil of the transformer. Numerous other aspects are provided.