Exploring flux-weakening effect for a REPM brushless DC motor

It is well known that armature reaction can achieve some flux-weakening. Our exploration shows that something else achieves far more flux-weakening. That something else is the magnetic flux variation of corresponding conduction phase windings as the conduction angle varies. In the full paper, we explain our exploration in some detail; in this abstract, we just add some pertinent remarks to listing the three topics of explanation. The first topic is: the equivalent air-gap magnetic flux density analysis method. In this topic, we analyze the relations between anticipated conduction angle and the operating speed or torque of a brushless DC motor (BLDCM), as summarized in Figs.2 through 5. The second topic is: the space magnetic force analysis method. In this topic, we study the influence of armature reaction on the flux-weakening effect through analyzing the space magnetic force of BLDCM's stator and rotor. The third topic is: experimental results and their analysis. The theoretical analysis shows that, compared with magnetic flux variation, armature reaction has far smaller de-magnetizing effect during flux-weakening operation; the BLDCM's rotation speed has only 11.87% rise, indicating that armature reaction is weak in demagnetization. Also in this topic, we did experiments with the 40 W/27 V REPM BLDCM, experimental results; as shown in Fig.9, its flux weakening operating region achieves 2.58. The experimental results are in good agreement with theoretical analysis.