Soft Start for transformer
Transformer primary windings can take an inrush of excessive current when voltage is supplied. If the AC voltage is activated at the peak of the waveform then there is no problem; if the AC voltage is activated at a zero cross there can be problems: -



It only affects the transformer primary current and is due to the magnetization of the core. It won't increase the output voltage i.e. it won't generate an excessive secondary voltage so there is no worries in this respect but, it can blow primary fuses occasionally.