SPX Transformer Solutions ships one of its most complex large power units

Posted: December 11, 2018


SPX Transformer Solutions recently tested and shipped a 280 MVA, 236.5kV to 112.75 kV three winding autotransformer to a new large power customer in the western United States. The customer was eager to find a U.S.-based supplier, qualified to meet their requirements for large power transformers. With active channel partner engagement, visits from the territory manager to discuss SPXTS as a large power provider and our proven quality on medium power, we were given the opportunity to bid and subsequently win the business away from the incumbent foreign supplier.


Core and coil assembly with in-tank LTCs, wired up and ready for tanking. This 280 MVA, 236.5kV to 112.75 kV large power transformer was unique due to a number of characteristics needing to be designed into the unit to accommodate its application in the field.

Designed to be used as a system tie to connect two transmission lines with different voltages, the transformer synchronously combines several design and manufacturing complexities to achieve the desired results. This unique combination includes:

  • Existing pad requires transformer to meet strict dimensional specifications – used internal arrestors to limit transformer voltage and size
  • Transformer supplies power to auxiliary equipment that needs to run 24/7/365 – designed with a loaded tertiary and series transformer for constant voltage flow to auxiliary equipment
  • Limited allowable short circuit current specifications required to protect auxiliary equipment – manufactured with an air core reactor to increase impedance of the tertiary winding
  • Application required high side voltage regulation while under load – achieved by including three in-tank tap changers
  • Application also required low side voltage regulation while de-energized – accomplished by incorporating de-energized tap changer (DETC) with taps on the common low voltage winding

The core and coil weight of the new Waukesha® transformer came in at 83% of the existing competitor’s unit. During a visit to the Waukesha plant, the customer was delighted with the quality of the transformer and appreciated the support and effort to provide a positive experience.