This paper presents a simple core loss modeling approach for an inductor of three-phase voltage source converter (VSC) under pulse width modulation (PWM) technique. The inductor core loss calculation in PWM VSCs is challenging since the current ripple and its duty cycle are varying in each switching cycle. To calculate the core loss, however, generating the loss map as a common method is complicated and time consuming. This paper presents a new modeling method in which the minor B-H loops are categorized according the average dc bias and ac current ripple. The core loss is then modeled via calculating the power loss of averaged minor B-H loop in each category. On the other hand, unlike the loss map method, the presented model needs less iteration to find the core loss. Moreover, in this paper, the effect of dc pre-magnetization is investigated by measuring its influence on the core. As a case study, the core loss of an inductor has been calculated and the experimental results are presented. The inductor is designed with a toroidal Kool Mu powder core for a 5 kW three-phase PWM VSC.