Safety Voltage Transformer
A safety voltage transformer produces such a low secondary voltage that an insulation fault or touching live components do not cause harm to people. Safety voltage transformers are defined in standard EN 61558. When designing safety voltage transformers, the secondary voltage must be below the limits of extra-low voltage, which is 50 V with alternating voltage and 120 V with direct voltage.
SELV (Safety Extra Low Voltage) and PELV (Protective Extra Low Voltage) systems are used in protective voltage transformers.
Safety voltage transformer with SELV system:
Safety voltage transformer with PELV system: