1 phase pre-circuit transformer according to IEC/EN61558-2-13 (autotransformer) for general applications without the need of a galvanic isolation, e.g. for transforming typical mains voltage to other voltages needed by tools, machinery or other devices.
VT pre-circuit transformers and other autotransformers do not provide any electrical protection due to the lack of galvanic isolation between input and output windings.