I am trying to understand buck boost transformers in more detail and have some questions and know this is the place so here goes correct me if I am wrong: A buck boost transformer is basically an auto transformer, a transformer with a voltage primary winding and secondary are connect togerther to provide a buck or boost in voltage, but here is the part I am trying to understand when I look in catalogs it indicates the primary voltage as 120x240 and the secondary at 12/24, 16/32, or 24/48 so how by connecting one of the phases on the primary and the secondary togerther do you get say 208 up to 230 volts? It is my understanding that the transformer comes shipped as a insulating transformer 120x240 and a secondary of 12/24 or 16/32 but when you apply 208 volts to the primary and connect the windings you can end up with 230V? how is the kva rating determined? this is the part that stumps me and I was hoping someone could help or point me in the direction of some good literature. thanks.