Primary current expectation in unloaded toroidal transformer
Ferrite cores saturate at a given magnetic flux, this is a nice feature because the transformer limits the amount of power that can be sourced from mains. Apparently from your graph this starts to happen at 30VAC as 0.02A * 150V = 30VAC. If you need more power you will need a different transformer. 


Source: https://www.coilgun.info/theorymath/saturation.htm