Abstract. This paper presents the design optimization and accurate electromagnetic field analysis of an 18-12 there phase Brushless dc motor (BLDCM) by using a three-dimensional Finite-Element analysis. Proposed motor will provide a wide range of air-gap flux control by a dc assisted field winding which is replaced with the permanent magnet in the rotor structure. In proposed BLDCM a simple dc current control is used and no brushes or slip rings are required to perform this control. To achieve the required performance within a specified space envelope, the physical dimensions of the proposed configuration were optimized; subject to maximize the average output power. Proposed 18-12 BLDCM configuration has been compared with a 9-6 BLDCM configuration. To evaluate the motor performance, the numerical techniques have been utilized. In the numerical part, 3-D Finite Element (FE) analysis has been carried out using a MagNet CAD package (Infolytica Corporation Ltd.) for two type of BLDCM to confirm the accuracy and the efficacy of the proposed design procedure. The analysis results demonstrate the effectiveness of the proposed machine design methodology. Keywords: FE Analysis; Field analysis; Brushless Dc Motor ­­­