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Power Dense Single Core Three-Phase Transformer


TECHNOLOGY AREA(S): Electronics, 

OBJECTIVE: Reduce the size and weight of single-core three-phase transformers for use on Navy Shipboard power distribution systems. 

DESCRIPTION: Isolation transformers are used on U.S. naval ships to provide galvanic and ground fault isolation between electrical components of the ship service electrical distribution system. This functionality is critical to the survivability of the ship’s power distribution system, as transformers both prevent certain casualties from affecting other aspects of the system and suppress electrical interference and noise between devices. The U.S. Navy is keenly interested in achieving space and weight savings within the DDG 51 design wherever possible. The three-phase isolation transformers currently in use are large and heavy. These transformers are widely used in many spaces throughout the ship. Space, maintenance, acquisition, and weight savings can all be achieved through new and innovative product development. DDG 51 class ships currently utilize banks of three dry-type, single-phase 60 Hz transformers, rated at 37.5 kVA per transformer, to provide input isolation within vital loads of the ship service electrical power distribution system. Electrical power of this system is Type 1 60 Hz power, rated at 440 Vrms, three-phase, ungrounded, and is in accordance with the power requirements of MIL-STD-1399-300B Department of Defense Interface Standard: (Section 300b) Electric Power, Alternating Current. A single core three-phase transformer would need to replicate the electrical properties and tolerances, and meet the physical construction requirements of the current single-phase transformer bank design per phase. The transformer can be configured to be bulkhead or deck mounted, and able to be mounted horizontally or vertically. The Not To Exceed (NTE) dimensions and weight of the transformer shall be 95 in.x 71 in x 63 in and 1100lbs respectively. The combined power rating for the three-phase transformer design would be 194.85 kVA, to meet the power handling requirements of the existing transformer banks. The new transformer design would also be required to meet all Navy test and qualification standards including shock, vibration, airborne noise levels, and enclosure design. Qualification shall be in accordance with Grade B shock of MIL-STD-901D Shock tests High Impact, Shipboard Machinery Equipment, MIL-STD-1310D Shipboard Bonding, Grounding, and other Techniques for Electromagnetic Compatibility and Safety, drip proof in accordance with IP 22, and in accordance with MIL-E-917E Electric Power Equipment Basic Requirements. Single core three-phase transformers have been used in electric power distribution grids and to power larger electric motors. The commercial units used do not meet Military Standards and U.S. Navy shipboard requirements. Smaller units have been used onboard naval vessels but are not Navy-qualified and only used on non-vital loads. The development goal of this SBIR topic is to miniaturize and militarize this technology for implementation in a naval context. The design should incorporate innovative design aspects, such as novel material selection, to maximize the weight and space savings achieved by this project. 

PHASE I: Develop a conceptual design for an affordable, compact, and durable single core three-phase transformer for application to naval ships. Present the salient features of the performance as well as the physical and functional characteristics of the proposed system(s). Using best practices, develop electrical models to predict system performance and provide justification for the model assumptions. Using the results from the modeling, assess the feasibility of the proposed solution to meet the performance goals and metrics. The Phase I Option, if exercised, will include the initial design specifications and capabilities description to build a prototype solution in Phase II. 

PHASE II: Develop, fabricate, demonstrate, and deliver a prototype scaled to fit within the projected scope of the transformer as identified in the Description. Demonstrate that the same technology can support full-scale operation for shipboard power distribution. In a laboratory environment, demonstrate through test and validation that the prototype successfully powers a load and galvanic isolation of the source from the load. Ensure that Operational Testing of the prototype mimics shipboard operation. Perform Standard Environmental Qualification Testing of the prototype. Perform all analyses and efforts required to refine the prototype into a useful technology for the Navy. Provide detailed drawings and specifications. Document the final product in a drawing package. Develop a Phase III installation plan. 

PHASE III: Support the Navy in transitioning the single core three-phase transformer to Navy use. Develop installation and maintenance manuals for the transformers to support the transition to the Fleet. Isolation transformers within electrical distribution systems are used on Navy and civilian naval vessels and in commercial applications. Thus, the same potential demand exists in commercial shipping and cruise liners. 


1. “MIL-STD-1399(NAVY) Department of Defense Interface Standard Section 300B Electric Power, Alternating Current.” Washington, D.C.: Department of Defense, 24 April 2008.

KEYWORDS: Input Transformer; Electrical Power Distribution; Three-Phase Power; Isolation Transformer; Galvanic Isolation; Miniaturization; Single Core 

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