On Field Weakening Performance of a Brushless Direct Current Motor with Higher Winding Inductance: Why Does Design Matter?

Abstract

This paper comprises the design, analysis, experimental verification and field weakening performance study of a brushless direct current (BLDC) motor for a light electric vehicle. The main objective is to design a BLDC motor having a higher value d-axis inductance, which implies an improved performance of field weakening and a higher constant power speed ratio (CPSR) operation. Field weakening operation of surface-mounted permanent magnet (SMPM) BLDC motors requires a large d-axis inductance, which is characteristically low for those motors due to large air gap and PM features. The design phases of the sub-fractional slot-concentrated winding structure with unequal tooth widths include the motivation and the computer aided study which is based on Finite Element Analysis using ANSYS Maxwell. A 24/20 slot-pole SMPM BLDC motor is chosen for prototyping. The designed motor is manufactured and performed at different phase-advanced currents in the field weakening region controlled by a TMS320F28335 digital signal processor. As a result of the experimental work, the feasibility and effectiveness of field weakening for BLDC motors are discussed thoroughly and the contribution of higher winding inductance is verified.