Abstract : From the perspective of mechatronics and the overall performance of variable frequency speed control systems, achieving optimal matching between asynchronous motors and frequency converters is a crucial issue that urgently needs to be addressed in AC speed control systems composed of motors and frequency converters. Three-phase asynchronous motors utilize frequency converters for speed regulation, avoiding the limitations of power grid supply. Their parameter configuration and performance requirements are no longer constrained by power grid supply in many aspects. However, due to the limitations of the power electronic devices used in frequency converters, the converter output contains a large number of harmonics. These numerous output harmonics act on the motor, causing significant changes in the motor's output parameters, and in severe cases, leading to motor malfunction or shortened lifespan. Therefore, studying the matching problem between frequency converters and three-phase asynchronous motors is of great significance not only for the various performance indicators of variable frequency speed control systems but also for the design of both frequency converters and three-phase asynchronous motors. The following analysis examines the matching problem between frequency converters and three-phase asynchronous motors from the perspective of overall efficiency. Efficiency Analysis of Three-Phase Asynchronous Motors under Power Grid Supply Under power grid supply , it is assumed that only the fundamental frequency exists in the grid, and harmonics are negligible. As we know from the principles of electric motors, when a three-phase asynchronous motor runs at a stable speed *n*, the changes in magnetic flux per pole in the air gap and the speed are relatively small, while the iron loss and mechanical loss are very variable, becoming constant losses. The stator and rotor copper losses are proportional to the square of the current and change significantly, known as variable losses. The motor efficiency reaches its maximum when the constant losses equal the variable losses. Generally speaking, the larger the motor capacity, the higher the efficiency. Since the efficiency and power factor of a three-phase asynchronous motor are highest near its rated power, the motor capacity should be matched to the load when selecting a motor. If the motor capacity is much larger than the load, it not only increases the cost of the motor itself but also reduces its efficiency and power factor during operation. Conversely, if the load exceeds the motor capacity, the temperature rise of the motor will exceed the allowable value, affecting its lifespan and even damaging the motor. Due to the presence of harmonics and the constantly changing operating conditions, the selection of frequency converters and motors becomes a problem in variable frequency drive (VFD) power supply. [b][align=center]For more details, please click: Efficiency Issues of Frequency Converters and Motors[/align][/b]