AC or DC Furnace Transformers

The Electric Arc Furnace and Ladle Furnace Transformers are the key equipment in a steel plant, therefore specific engineering solutions are adopted in order to guarantee over time the best performances under the dielectric, thermal and mechanical stresses which daily involve these transformers.

Furnaces transformer’s life is affected by heavy stresses during operation. Frequent on and off switching, high magnitude inrush currents, high operation currents, often close to short circuit values, fast transient overvoltages, significant harmonic content and elevated number of operations carried out by the on load tap changer are the everyday challenges for a furnace transformer.

Electrical stresses are due to overvoltages generated both by the melting process and by transient state resulting from a sudden disconnection of HV circuit breakers, especially if vacuum-type ones are installed. Tamini pays special attention to this issue adopting a specific design and manufacturing procedures to guarantee a stronger transformer insulating structure.

Moreover during furnace operation, the transformers undergo thermal and mechanical stresses due to the continuous daily steel melting process. Continuous stresses and vibrations might make the windings loose if they are not properly treated and robustly clamped. In order to avoid any inconvenience due to such heavy and frequent stresses, Tamini has adopted improved procedures for windings pressing and thermal treatment operation.

Different solutions can be adopted according to the customer requirements:

  • Single or double core 'booster' solution
  • LV delta closure either inside or outside the tank
  • LV bushings either in copper bars or water-cooled pipes
  • LV outlets either on the top cover of the transformer tank or on the lateral side.
Tamini also provides:

  • Special furnace transformers as Submerged Arc Furnace (SAF), Electroslag Remelting (ESR) and Smelter Transformers used to power furnaces for the production of special iron alloys.These alloys often require the deployment of three single-phase furnace transformers instead of a single three-phase transformer in order to balance the total phase impedance through an equilateral-triangle layout of the units or in applications of modern steel processes.
  • Regulating transformers, with either stepped or stepless regulation of the output voltage, for those applications/processes where a fine regulation is needed.

Product Scope

  • Rated power up to 360 MVA (the highest rating ever built)
  • L.V. current up to 140 kA