This chapter develops a circuit model description for three common types of phase-shifting transformer. This is useful in order to understand the regulation behavior of such devices, that is, how much the output voltage magnitude and phase change when the unit is loaded as compared with the no-load voltage output. The chapter finds how the phase angle depends on tap position, a relationship that can be nonlinear. The latter analysis is carried out for the standard types of fault for two of the phase-shifting transformers. A Delta HV (H) winding and zigzag LV (X) winding transformer is analyzed. The complex currents are calculated as well as the terminal positive/negative and zero sequence impedances. Although explicit expressions for these impedances are given in terms of 2-winding impedances, they can also be obtained directly from a program, which calculates the magnetic field associated with complex currents. These impedances are then used to obtain fault currents for a short-circuit analysis.