Computer-aided design and analysis of new fan motors

This paper presents a design for a new DC brushless motor with an interior rotor for the cooling fan. The design differs fundamentally from conventional configurations using motors with exterior rotors, the difference being in the motor structure, where the arrangement for the rotor, the stator, and the blades in the fan gives the fan motor a higher stall torque, better efficiency, and reduced noise. The paper first models the fan motor analytically with an equivalent magnetic circuit, then develops a design to meet the desired performance, and follows with a finite-element analysis (FEA) for refinement and verification of this preliminary design. The FEA result confirms the accuracy of the analytical model. With other considerations such as the reduction of waste material taken into account, two other finite-element models are created, based on the foregoing design example, but with different parameters. The paper compares output characteristics of these three models to provide a brief reference for factors to be considered in motor design.