A 6-Wire 3-Phase Inverter Topology for Improved BLDC Performance and Harmonics

The growing demand for motor applications such as household appliances and industrial automation has caused a surge on interest in the brushless DC (BLDC) motor due to its relatively small size and efficiency [1]. Reduced torque ripple, enhanced efficiency, and cost-effectiveness from the implementation of sinusoidal control, particularly field oriented control (FOC), for BLDC motor drives has led to faster industry adoption [2]. The phase windings of a typical three-phase, three-wire BLDC motor are connected in either wye of delta configuration. This paper presents an implementation of a three-phase, six-wire BLDC motor and corresponding driver wherein the phase windings are isolated from each other and independently driven. Three full bridges are implemented to drive the modified BLDC motor resulting in a three-level modified sine-wave drive where attenuation of the multiples of the third harmonic is achieved. The increased voltage swing inherently formed by full bridges enabled the motor to be driven at much higher speeds without over-modulation or applying advanced techniques such as field weakening. A design example and its performance are also presented.