A novel PM BLDC motors inverter topology for extending constant power region

In many fields just like traction, high-speed -servo and home appliances, motor needs to keep constant torque operation in low speed region and to keep constant power operation in high speed region. There are many papers detailed PMSM flux-weakening adopt d-q axis resolution to obtain constant power speed region, and there are also many method and algorithm, but few papers discuss the trapezoidal wave BLDCM flux weakening characteristic. This paper analyzes one of the important causes of BLDCM flux weakening performance narrow, circulating current produced in traditional driver inverter circuit system brings on reverse torque in BLDCM inverter, which imposes dramatically restriction in flux weakening operation region. A novel drive inverter topology is proposed. Both of the traditional drive inverter and the novel drive inverter are analyzed and compared. It is demonstrated that the novel drive inverter topology can eliminate the circulating current in driver inverter. Experimental result shows that the novel drive inverter topology can effectively extend PM BLDCM flux-weakening speed region by eliminating circulating current to avoid reverse torque. The new topology can be used in surface mount BLDC motors without remodeling motor structure.