Analysis of brushless DC motor in operation with magnetic saturation using FE method

In general, a brushless dc (BLDC) motor is designed to operate in an unsaturated operating area of the laminated steels under the rated current. In some applications, however, it needs to utilize the BLDC motor in an overload operation within a certain period, for example, using in an electric-bicycle. This operation leads to nonlinear behavior in the saturation region. This paper presents a study on effects of magnetic saturation in the BLDC motor when the overload operation is concerned. In this work, the outer rotor BLDC motor was used. The finite element (FE) analysis is applied to study torque and flux density in air-gap according to rotor positions. The relationship between torque and current is deduced to indicate the unsaturated- and saturated area.