The leakage magnetic flux in the motor is an unnecessary parameter that does not affect the generation of torque. Although there is a formula for calculating the inductance due to the leakage magnetic flux, there is a difference between the formula and the actual measured value because it is difficult to consider the saturation phenomenon of the stator core generated in the motor. In the case of WFSM, the field flux changes according to the field current, so the entire flux flowing through the stator core changes. These factors make the difference between the value obtained from the theoretical calculation of the leakage inductance and the actual measured leakage inductance value. In this paper, the effects of core saturation and field current on leakage inductance are analyzed. Based on the analyzed data, we derived the equation considering the saturation and the field current from the existing leakage inductance formula. Newly derived formulas analyze the effects of field current and saturation on leakage inductance.