耦合电感#
$$
u_1=L_1\frac{di_1}{dt}+M\frac{di_2}{dt}\\
\ \\
u_2=L_2\frac{di_2}{dt}+M\frac{di_1}{dt}
$$
$$
注：若为异名端耦合，则为"-"
$$串联耦合电路#
$$
注：若为异名端相连，则为"+"
$$并联耦合电路#
$$
\dot{U}=Z_1\dot{I_1}\pm Z_M\dot{I_2}\\
\dot{U}=\pm Z_M\dot{I_1}+Z_2\dot{I_2}\\
\dot{I_3}=\dot{I_1}+\dot{I_2}\\
注：同名端并联为"+"，异名端并联为"-"
$$三支路耦合电路#
$$
注：同名端相连为"-"，异名端并联为"+"
$$理想变压器#
$$
\frac{u_1}{N_1}=\frac{u_2}{N_2}\\
\frac{i_1}{N_2}=-\frac{i_2}{N_1}
$$$$
二次侧阻抗折算至一次侧：R_{eq}=\frac{u_1}{i_1}=\frac{n \cdot u_2}{\frac{i_2}{n}}=n^2 \cdot Z_L
$$
