A fail-safe transformer is a transformer that is designed in such a way that it assumes a safe state in the event of a fault and no dangerous voltages or operating states occur. The aim is to protect people, systems and connected devices from damage.

Typical fail-safe features include galvanic isolation between the primary and secondary sides, particularly robust insulation and defined switch-off or limiting mechanisms in the event of overload, short circuit or overheating. In the event of a fault, the energy transfer is either interrupted or reduced to a safe level.

Fail-safe transformers are primarily used in safety-critical applications, for example in control systems, medical technology, railroad technology or industrial systems, where a failure must not have any dangerous consequences.

The term “fail-safe” does not describe a specific type of transformer, but a safety principle in which the system specifically switches to a safe state in the event of a fault.