Extended Operation of Brushless DC Motors Beyond 120° Under Maximum Torque Per Ampere Control

Hall-sensor-controlled brushless dc (BLDC) motors are widely used in many electromechanical applications due to their simplicity and good torque-speed characteristics. The conventional commutation methods include the 120° and 180° switching logics that can be derived directly from the Hall sensor signals. The 120° switching method is the most common due to its natural approximation of the maximum torque per Ampere (MTPA) operation, while the 180° switching method offers a higher available phase voltage for the same dc voltage. Both methods are typically used with additional pulse-width modulation to control the motors from a fixed dc source. Recently, attention has been given to the operation of BLDC motors with conduction angles between 120° and 180° (e.g., 150°, 160°, etc.), where some benefits may be gained. This paper proposes a new methodology that continuously extends the operation from 120° to 180°, while maintaining the MTPA property. Simulations and experimental results based on a typical industrial BLDC motor demonstrate the proposed control methodology and its benefits over the conventional alternative methods.