115 Norfolk Avenue

Bristol, VA 24201



115 Norfolk Avenue      CONTACT US
Bristol, VA 24201         276.466.8200

Mine-Duty Transformers Products

Line Power Manufacturing Corporation’s Parts and Rebuild Division, a part of Electro-Mechanical Corporation, has been a leader for over 50 years in re-engineering and rebuilding electrical apparatus. Located in its own modernized 50,000 square foot facility in Bristol, Virginia, with a competent staff of electrical engineers, application specialists and factory technicians, Line Power’s Parts and Rebuild Division looks forward to assisting you with your replacement parts and rebuild needs.

Mine-Duty Transformers


Line Power Manufacturing is the leading specialist in design and manufacturing of mine-duty transformers. Our people, knowledge and experience can provide a reliable, cost-effective transformer that will provide years of trouble-free service. Line Power vacuum pressure impregnated (VPI) transformers combine a performance proven Dry-Type transformer design with the environmental protection of a polyester coil encapsulation process. This combination ensures reliable transformer operation in hostile environments containing moisture, dust, dirt, chemicals and other contaminants.

The VPI process fully penetrates and seals the coils into a high strength composite unit for complete environmental protection. Since the coil protection is created using vacuum pressure impregnation rather than molding, maximum design flexibility is achieved to allow conformance to the most stringent application requirements. The vacuum impregnation of the varnish eliminates winding voids to reduce corona generation due to insulation voids.

Benefits of Line Power vs. Cast Coil

  • Lower initial cost
  • Flexibility of design
  • Elimination of cracking concerns
  • Higher thermal overload available Cast = 17% @ 80 / 115 C rise VPI = 30% @ 80 / 150 C rise
  • Less weight for easier handling and installation
  • Smaller dimensions to save valuable floor space
  • Outstanding environmental protection

Line Power Step-Lapped Miter Core Transformers


A Dry-Type transformer consists of four main parts: the coils, the core, the structural frame and the terminals. The purpose of the core is to provide a path for the magnetic flux with which the windings are linked. The core is used to transfer energy from the primary windings to the secondary windings. When voltage is applied to the primary, current flows producing a magnetic field (flux.) Secondary voltage is induced due to the coupling of the secondary to the magnetic field. In a step-lapped miter core, the core steel is miter cut and step stacked in groups of 5 to 7 laminations at a time. In this arrangement, the grain orientation of the core steel lines up with the direction of the flux. The flux then flows parallel with the direction of the grain orientation.

Along with less heat to dissipate and lower sound, the greatest benefit of using step-Lapped, miter core transformers is in the energy savings. In a typical mining power center with a 2500 kVA transformer, the annual savings Can be as much as $2235 based on an average electricity cost of $.08 per killowat hour (KWH.)