Reactance is the only thing really limiting current flow in the primary...without it (which can be simulated by shorting the secondary) only the resistance of t

Reactance is the only thing really limiting current flow in the primary...without it (which can be simulated by shorting the secondary) only the resistance of the wire would limit current flow. The subsequent joule heating of the transformer would result in thermal runaway without it. The main advantage of this setup is to drastically reduce interwinding capacitance and DC leakage current.