BLDC motor for fan application with automatically optimized commutation angle

Brushless DC motors are often used in fan applications due to their easy speed controllability, high efficiency and long life time expectation. These motors are electronically commutated; the commutation point is determined by Hall-sensors or sensorless (mainly by the so called back EMF method). In case of constant commutation angle, this angle can be optimized only for one operating point. Through this optimization, motor current and power consumption can be reduced. However, if the motor works in another operating point (different supply voltage, speed and/or torque), its efficiency will be lower than that of a motor with a commutation angle optimized for this new operating point. This paper describes methods for the automatic optimization of motor efficiency by changing the commutation angle.