MTPA Control Concept of BLDC Motor Using 2-step Voltage Level for High Efficiency

Abstract

BLDC motor has the high efficiency, high power density, low acoustic noise, and low maintenance cost due to the removal of the mechanical commutators and brushes. In the general design and driving control technology about BLDC motor, the square waveform phase current has been known as the ideal current waveform to get high torque production and high efficiency driving characteristics. But in here, the kinematic vector characteristics of magnetic force between stator and rotor pole is not considered. Conventionally recommended square wave current has no consideration about this vector angular feature of magnetic force. This paper studied about this vector potential separation of magnetic force during torque production to generate maximum torque per ampere (MTPA). The modified current waveform for MTPA is suggested by this study. In addition, this paper also suggests 2-step voltage control method for MTPA and high efficiency driving. The optimal voltage control condition is derived by DOE (Design of Experiments) and RS (Response Surface). This suggested control method is validified by finite element analysis (FEA) using voltage source operation to simulate real driving condition. As a result, the suggested control method can be a good driving control technology to maximize the output torque per ampere and improve the driving efficiency.