Moly-Cop 15MVA Furnace Transformer

Following the short circuit failure of one of their two specialist furnace transformers, Moly-Cop urgently required the installation of a replacement. It was decided that an existing spare transformer that had been in storage for 15 years could be modified to suit the special requirements of the furnace.


  • Reworking the external bus bar arrangement and fitting a new off circuit tap changer and HV cable box
  • Transformer overhaul, including installation and commissioning of the transformer in a very short timeframe, reducing disruption to site production
  • Engagement with site personnel to coordinate the multi-discipline site installation requirements


After initial inspection a detailed work schedule and execution plan was established and agreed with onsite personnel to match the site specific production initiatives.

Given the age of the transformer and the time it had been in storage it was in need of major repair and upgrading to meet the demands of the critical role it has in production.

Modifications and upgrades included the following:

  • Replacement of compound cable box with new plug in type to suit site cabling
  • Modification of the transformer design to suit an off circuit tap switch including removing the existing on load tap changer which was not fit for service repair.
  • Redesign and accommodation of a pumped water cooler sourced from a separate on-site transformer.
  • Design and manufacture of external busbar system to configure the correct vector connection and couple it to existing site bus-work
  • Inspection and processing of the core and coils together with the supply of new transformer oil
  • Refurbishment of the existing conservator and pipework
  • Reconfiguration of a new control box, wiring and auxiliary protection devices.

The busbar design required significant engineering to ensure the weight of the busbar was supported and to minimise stress on the transformer bushings. Flexible connections were manufactured from copper sheet punched and formed to individually align with the multiple bushings of the transformer.  This high current externally connected structure required support both at the top and bottom with the bottom supports designed to accommodate for uneven floor and alignment to the existing busbar.

Close coordination with the site personnel was required to ensure delivery of the project within the agreed schedule as well as to coordinate both transformer specific design changes and modifications to accommodate the new larger footprint of the transformer

Through close participation with the site personnel and coordination by the project team this turnkey, labour intensive, multi-discipline project was successfully delivered in a short timeframe.

Find out more about Ampcontrol’s transformer engineering and manufacturing capabilities