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UBC Theses and Dissertations

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UBC Theses and Dissertations

Maximum torque per Ampere and maximum torque per Voltage operation of brushless DC motor drive systems with extended switching schemes Zhou, Jinhe


Hall-sensor-controlled brushless dc (BLDC) motors are widely used in many electromechanical applications due to their simplicity, low cost, and good torque-speed characteristics. The conventional commutation methods include the 120-degree and 180-degree switching logics. For these commutation methods, the maximum torque per Ampere (MTPA) and maximum torque per Voltage (MTPV) control schemes are often considered to achieve the optimal properties. Previously, many analytical and numerical implementations of MTPA and MTPV have been developed and widely applied. However, the common limitations such as deviation from the optimal operation due to machine parameters and high computational cost of controllers necessitate further research and improvements. In this thesis, three simple and novel control schemes have been proposed. Firstly, a hybrid MTPA/MTPV method is proposed based on the equations of 180-degree operation to combine the advantages of both methods. This hybrid method is shown to achieve high efficiency in steady state and fast response during electromechanical transients. Secondly, a numerical implementation of the MTPA and MTPV strategies has been developed for BLDC motors with 120-degree commutation to achieve better torque-speed characteristics compared with the conventional implementations. Thirdly, the switching logic has been extended to cover any conduction angle between 120 and 180 degrees while maintaining the MTPA optimal property. This proposed method is demonstrated to achieve up to 10% higher maximum achievable phase voltage than the conventional 120-degree operation from the same dc source voltage. Since the new methods are simple and computationally efficient, it is envisioned that they may be easily adopted in many applications utilizing Hall-sensor controlled BLDC motors where higher efficiency and faster transient response are desirable.

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