AC and DC Furnace Transformers for Metallurgy
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 over-voltages, significant harmonic content and the 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 over-voltages 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.
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.
Product scope:
- Rated power up to 360 MVA (the highest rating ever built);
- L.V. current up to 140 kA.
We are also able to offer:
- 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.
- Regulating transformers, with either stepped or stepless regulation of the output voltage.
Series Reactors for Furnace Applications
Series reactors connected to Furnace Transformer are often used to stabilize the arc current. In order to achieve better efficiency of the melting process, series reactors may have tappings to adjust the reactance in coordination with arc furnace needs.
Series reactors can be designed as Gapped-Core Reactors or Coreless Reactors (with core-frame).
Product scope:
- Up to 150 Mvar.
Reactors are used in the furnace operation with the purpose of:
- Arc stability and power regulation;
- Optimization of electrodes consumption;
- Limitation of current during the melting process;
- Reduction of flicker on the feeding network.
The reactor can be also assembled:
- Inside the main transformer tank;
- Entirely separated from the transformer;
- Located next to the transformer (On Board Reactor).
Rectifier Transformers
The rectifier transformer is the link between the electrical grid and the AC/DC converter. Therefore, it has the aim to provide the number of phases, the voltage shifts needed to realize the conversion and to adjust the rectifier input to vary the DC output voltage. To do it, the rectifier transformer is often coupled with components as regulating transformers (or autotransformers), saturable reactors and interphase transformers.
Product scope:
- Rated power up to 140 MVA;
- L.V. current up to 150 kA.
Rectifier Transformers face high operating currents combined with a huge amount of harmonic content due to the distorted waveform caused by the semiconductor converters connected to the transformer. Typical applications are for DC arc furnaces, electrolysis, scrap melting furnaces, aluminum smelter, graphitizing furnaces, traction substations, metal refining and inverters for variable speed drives.
Distribution Transformers for Industrial Applications
Distribution transformers for industrial applications are used wherever it is necessary to connect systems for transmission, distribution, and utilization of electrical energy, which function at different voltages, in order to transfer large quantities of active and reactive energy between these systems.
HV/MV Transformers
Distribution transformers are used to interconnect high voltage and medium voltage systems. These transformers can be manufactured either with off-circuit tap changer or on-load tap changer (with the different cooling method). Furthermore, transformers for railway application with various loading guide can be manufactured as well.
Product Scope:
- System voltage up to 420 kV;
- Power rating up to 400 MVA.
MV/MV and MV/LV Distribution Transformers
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 the off-shore application. Furthermore, transformers for railway application with various loading cycles can be manufactured.
Product Scope:
- System voltage up to 52 kV;
- Power rating up to 30 MVA.
– So, we highly recommend studying beneficial ramifications of selecting the appropriate transformer based on your customized needs. We are always at your disposal to discuss critical details of selecting the core component of your mill, the transformer. Contact us…
