Multiple Input Voltages

Transformers can be designed for multiple input voltages by means of taps and / or multiple input windings.
However, it should be noted that the additional winding space typically leads to larger core sizes compared to a transformer of similar power designed for a single input voltage. An exception is when the input winding is divided into two equal parts, allowing the user to optionally connect them in series or parallel, requiring only a little additional winding space for insulation.

Note:
A sometimes-observed mistake is that users, in transformers with two input windings intended for optional series or parallel connection, connect only one input winding in applications with a lower network voltage. This leads to overheating and destruction of the primary winding at rated load and should be strictly avoided. This also affects the fusing. (This error may not be immediately noticed at partial load or no-load operation!)