Comparison of brushless DC motors with trapezoidal and sinusoidal back-EMF

For analysis of electromechanical systems with brushless DC (BLDC) motors and power electronic drives it is essential to have a sufficiently accurate model of the machine. This paper compares the BLDC motors with sinusoidal and trapezoidal back-EMF waveforms and presents an improved detailed model for the 120° BLDC motor-inverter system with trapezoidal back-EMF. The established model is shown to be more accurate in comparison to the typical models that assume sinusoidal back-EMF. The presented studies are based on a typical industrial BLDC and include measurements and simulations using various detailed models developed in two different simulation packages.