The negative power can also come from the fact that the cosine of angles above 90° is negative mathematically and the oscilloscope follows the math rules. cos(103°)= 0.2249
Yes, that was my initial take on that, too, because cos(77°) = cos(103°). However, Itsu is insisting that sometimes the current really is lagging behind the voltage by more than 90°. Perhaps his current probe is getting saturated by the external magnetic field or his scope makes a phase measurement error when the signal level is too low or a commonmode signal is confusing the scope. Repositioning, shielding the contactless current probe should eliminate such modes of error. Substituting a CSR for the current probe should do it, too. Finally, commonmode signals can be attenuated by a CMC as you've described. Also, in theory, at the LC resonance frequency, the amplitude should be the highest and the the current should lag the voltage by 90°. However, Itsu's system does not manifest the highest amplitude at 90°.
