It typically converts the higher voltage of the mine's power grid (e.g., 660V, 1140V) to a Safety Extra-Low Voltage (SELV) required by the lighting system, most commonly 127V.

It is an Isolation Transformer. Its secondary winding (output side) is electrically isolated from the earth and the primary winding (input side).

Its design purpose is primarily to supply lighting loads (e.g., incandescent lamps, LED lights). The load characteristics are relatively stable, and the capacity is usually small (from a few kVA to several tens of kVA).

Although it also possesses certain mining protection features (like moisture resistance, shock resistance), its primary focus is on providing a safe power source, not necessarily handling high concentrations of explosive gases.