Extended Control of Hall-sensor-controlled Brushless DC Motors with Limited Current Measurements

Hall-sensor-controlled brushless dc (BLDC) motors are widely utilized in industrial automation and light transportation applications due to their simplicity and favorable torque-speed characteristics. The traditional commutation schemes include the 120° and 180° switching logics that can be performed directly from the Hall sensor signals. The the 120° scheme is the most common because it naturally emulates the maximum torque per Ampere (MTPA) operation. Recently, a new control method has been proposed that extends the operation from 120° to 180° continuously while keeping the MTPA property. However, this method requires continuous measurement of all phase currents, which makes its implementation more costly. This paper presents a method that requires measurement of only the lower transistor currents, which can be easily achieved with just three current sensors with respect to the same common ground. The presented experimental results demonstrate the effectiveness of the proposed control technique and its benefits.