Maximum Torque per Ampere and Maximum Efficiency Control Methods based on V/f Control for IPM Synchronous Motors

This paper discusses maximum torque per ampere (MTPA) and maximum efficiency control methods based on the Volt per Hertz (V/f) control for an interior permanent magnetic synchronous motor (IPMSM). The V/f control is inherently a position sensorless method, and therefore it is simpler than conventional methods such as the sensorless vector control method. In addition, the MTPA and the maximum efficiency controls can be achieved by controlling the reactive power without requiring knowledge of the magnet pole position. The MTPA control can reduce the copper loss in IPMSMs and achieve high efficiency. Furthermore, the maximum efficiency control further improves the efficiency after implementation of the MTPA, which tends to reduce both the copper and iron losses. In this study, the validity of the MTPA methods is confirmed by simulation and experimental results. From the experimental results, the output current is reduced by 76% after the MTPA is implemented to control the reactive power. In addition at 0.6p. u. torque and 1.0p. u. motor speed, the simulation results demonstrate that the maximum efficiency control can further reduce the total losses.