I have a transformer that is 3 phase and rated at:

45KVA
H.V=600v, L.V= 208/120

I assumed because of the two different output voltages (208 and 120) that the transformer was a 3 winding model with two secondary coils. Is a 3 winding transformer the only way to achieve two different output voltages or can this be done by other methods such as tapping the secondary coil?

 

The LV values are probably dependent on the way the primary or secondary windings are connected - either in star or delta configuration. To allow you to connect in either configuration you would need each secondary winding terminal to be available (3x2=6 wires).

Notice that 208/120 = 1.732 = sqrt(3)