Stator design consideration of a brushless DC motor for robust rotor position detection in inductive sense start-up

This paper presents a method to improve three-phase brushless DC (BLDC) motor design for easier application of inductive sense start-up algorithms. Using the experimental results of motor start-up, a failure analysis of the successful and unsuccessful motors identifies the root cause of failure. The unsuccessful motors had smaller inductance difference when energized by a positive test current than when energized by a negative test current. Finite-element method (FEM) analysis then is used to examine the effect of the stator geometry on the sensitivity of the inductance to the permanent magnet polarity. A modified stator design is obtained through FEM study. The performance improvement is verified by current rise simulation.