1. INTRODUCTION
Brushless dc (BLDC) motors are increasingly used in industrial automation, instrumentation, and many equipment and servo applications. Such motors generally have good torque-speed characteristics, fast dynamic response, high efficiency, long life, and etc. A typical BLDC motor consists of a permanent magnet synchronous machine (PMSM) (with either sinusoidal or trapezoidal back-EMF) driven by an inverter as depicted in Fig. 1. The detailed modeling of such machine-inverter system, wherein the switching of each transistor and diode is represented, has been investigated in the literature quite well [1], [2] and may be readily carried out using a number of available simulation packages [3], [4], [5]. However, it is often assumed that the machine's back-EMF is perfectly sinusoidal, where in practice may not be true for many motors. Including the back EMF harmonics increases the model accuracy and is needed for further studies and derivation of average-value models [6],[7].