原、副线圈的匝数比为N1:N2=2:1,原线圈接220V,则,副线圈电压为110V
P=U^2/R R=U^2/P 算R=605
当原线圈接180V时,副线圈电压为90V
P=U^2/R得出 P=8100/605
I=U/R=90/605