Tamini Trasformatori S.r.l.

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.

In electric arc furnaces, which use long arcs and high values of secondary voltage, it is often helpful to introduce an additional reactor with the purpose of:

• Arc stability and power regulation
• Optimisation electrodes consumption
• Limitation of current during smelting process
• Reduction of flicker on the feeding network.

The reactors are series connected with the furnace transformers and have some regulation taps (for the reactance regulation) operated with either an onload tap changer (OLTC), for maximum flexibility, or with a de-energized tap changer (DETC). 

Distribution transformers MV/LV type for energy distributions are usually three or single phase, oil immersed, with different cooling method (K/L) ONAN - (K/L) ONAF with detachable radiators or corrugated tank (depending on transformer size and ambient temperature), with conservator technology or sealed construction (with or without nitrogen/air filling).

These transformers can be manufactured either with off-circuit tap changer or on-load tap changer, for environments with risk of explosion (ATEX) or for off-shore application. Furthermore transformers for railway application with various loading cycles can be manufactured.