Negative voltage is created when electrons flow towards the negative electrode, also 90 degree out of phase, during the first 90 degrees negative voltage aoppear on the wfc, but no electron flow, [=strange] they are 'clustered', only voltage gets propagated to the wfc - after 90, electrons flow to the wfc.
now, why does the magnetic field created by the primary, create a positive emf in the negative choke [towards the wfc], and a negative emf on the negative side of the secondary , [towards the 2nd choke]?
A potential difference on 2nd choke tries to form: negative on transformer side, positive on the wfc side. [sum 0v?]