Abstract : This paper studies a motor operating efficiency optimization controller embedded in a general-purpose frequency converter based on a search algorithm. Using a simplified motor model, a SC algorithm based on constant output power is proposed. Simulation results show that the motor deviates almost from its operating point after optimization, demonstrating the effectiveness of the algorithm. Keywords : Frequency converter; Controller; Efficiency optimization; SC Induction motors are typically controlled by frequency converters for variable frequency speed regulation. Frequency converters can be divided into general-purpose and special-purpose types. Special-purpose frequency converters employ complex control strategies, such as vector control, to achieve static and dynamic performance similar to DC speed control systems. General-purpose frequency converters typically use a constant V/f control method, approximately keeping the air gap flux constant. General-purpose frequency converters are mostly used in applications where speed regulation performance requirements are not high, such as open-loop speed regulation systems for fans and pumps. Their control algorithms and system structures are simple and easy to implement, and they account for the majority of induction motor speed regulation systems. Energy-saving general-purpose frequency converters embed a motor efficiency optimization controller within the frequency converter to obtain the optimal V/f value. Efficiency optimization controllers can be divided into two categories: loss model-based efficiency optimization controllers (LMC) and search algorithm-based efficiency optimization controllers (sc). LMC solves the efficiency-optimal objective function derived from the motor loss model online to achieve rapid optimization. The optimization effect mainly depends on the accuracy of the model. Motor parameters must be identified online, which makes the hardware and algorithm very complex and limits practical application. SC takes advantage of the fact that the total loss, input power, stator current and efficiency of the motor are globally concave or convex functions with respect to variables at a certain static operating point. It uses a one-dimensional search algorithm to obtain the extreme points of total loss, input power, stator current or efficiency, and obtains the optimal V/f value, so that the motor can run at high efficiency. This type of efficiency optimization controller algorithm is simple, has low hardware requirements and is easy to implement. In the search process, the motor operating point must be kept stable. sc must know the speed information, that is, it requires speed closed loop. In reference [4], sc is performed under speed closed loop conditions. In most practical systems, the speed is open-loop, making it impossible to accurately know the motor parameters and thus impossible to observe the motor speed. In such systems, maintaining a relatively stable operating point for the motor is crucial for the practical application of the efficiency optimization controller. (See full text: Research on Efficiency Optimization Controllers in General-Purpose Frequency Converters)