Furnace transformers are used to feed electric furnace used to melt and refine materials. Furnace transformers are associated with very high secondary currents and wide output voltage regulation in order to cope with the furnace needs.

Furnace transformers are separated with normal power transformer with its characteristic of massive secondary currents. As an example a 30 MVA unit at 150 V would result in a secondary current of 115 kilo Ampere. For these high secondary currents special bushings are required to connect to the bus-bars.