ATEX approved Class C insulated dry type mining transformers are extremely robust in construction and are used in applications either in an open cast mine environment or underground, at the base of a mine, where it would not be possible to use a liquid filled transformer. To keep height and losses to a minimum both 3 and 5 limb cores are employed. Minimum periodic maintenance is required.
These are dry type naturally air cooled flameproof ATEX, Class C insulated  transformers, fin tank design by Transmag. We exclusively own the tooling equipment for the manufacture of these tanks.

Illustrated

Right - top 10 kV // 3.3 kV, 3 phase, 50 Hz, Rating: 4.5 MVA - courtesy of Baldwin & Francis Ltd

Centre - 10 kV // 3.3 kV, 3 phase, 50 Hz, Rating: 2.5 MVA

Bottom - Dual 5.5 – 10 kV, // 1100 Volts, 3 phase, 50 Hz, 5 Limb core design