Yes i understand this... and i think that is what is happening here, up to a point... because things are behaving strange

lets say 10 hz

my field coil has 3 ohms also and 22mh

so at ten hertz the reactance impedance should be 1,4 ohms

so the impedance should be around 4 ohms this should make at least 3 amps flow having 13v, but i'm getting 260ma ..

Is very strange for me... Seems like the armature add a kind of extra impedance to the change of the current direction-- but i'm not sure if this is the case.. .will keep experimenting,

i'm going to try adding a capacitor in parallel or a diode to the field coil and check what happens!

Oh and the most stranger behavior is that at a frequency higher than 10khz the amps start to get higher... at 100khz i get 1,20 amps...

I don't know if is the meter witch is crap... i'm going to try with the other meter witch can measure dc or ac current...

Thanks Donald