Oil-filled transformers have traditionally been the most commonly used option in electrical grids, but a number of issues in relation to the environment, fire hazards, control of leaks and general maintenance, have resulted in the evolution and increased use of dry-type transformers in areas such as shopping malls, public buildings, hospitals, tunnels, banks and other sites. Two classes of open coil Class H dry-type transformers are available: Low-Low Typically used to convert low voltages such as 440V/220V or 220V/440V in commercial or industrial buildings with equipment operating at different voltage levels. Medium-Low: Typically used in shopping malls, buildings and industries where fire hazards must be minimized. Efficient: They are designed at very low no-load loss levels in order to ensure maximum efficiency performance, which translates into energy savings, and thus to the protection of the environment and a reduction of operating costs.