Abstract : This article introduces a design scheme for a frequency converter for small and medium power AC high-speed motors. It elaborates on the control principle and implementation method of the frequency converter, provides the programming approach for speed control, and points out the control characteristics of the motor at different speeds. Keywords : High-speed motor; Frequency converter; Variable frequency speed regulation; Step wave control 0 Introduction High-speed motors, besides using special materials and processes, operate on the same electromagnetic principle as three-phase AC motors, with three coil windings. When voltages of the same amplitude, frequency, and phase difference of 120° are applied to the three windings, the motor begins to rotate. The speed of a high-speed motor is determined by the frequency of the signal applied to the windings; changing the frequency of the voltage applied to the windings adjusts the motor speed. Therefore, the speed regulation problem of a motor is essentially a problem of voltage frequency regulation, hence AC motor speed controllers are often called frequency converters. Although many mature technologies are available for AC motor frequency converters, and there are many commercially available frequency converter products, most employ high-power, high-precision control designs, resulting in high costs. This paper proposes a design concept for a frequency converter using a microcontroller. The circuit is simple, economical, practical, and has a wide frequency conversion range, making it highly valuable for application. 1. Working Principle There are various methods to implement a three-phase AC frequency converter, but the most commonly used is the "AC-DC-AC" conversion method, as shown in Figure 1. The AC power, after rectification, becomes the DC operating voltage V[sub]d[/sub] of the frequency converter. By controlling the switching sequence and frequency of the six MOS power transistors V1, V2, V3, V4, V5, and V6, voltages of different amplitudes and frequencies can be generated on the three windings of the motor, thereby achieving motor control. Therefore, the core of the AC frequency converter is the control of the six MOS power transistors V1, V2, V3, V4, V5, and V6, and the quality of this control method directly affects the quality of the controller. Obviously, when V1 is on, V2 must be off; similarly, when V3 is on, V4 is off, and when V5 is on, V6 is off. If every 30... A set of trigger pulses following a specific pattern is applied to V1 through V6, causing the MOSFETs to turn on sequentially. After every 12 sets of pulses, the MOSFETs cycle through V1 to V6 once in a 360° sequence. Table 1 lists the conduction status of each MOSFET within one cycle. (Full text download : Design and Implementation of High-Speed ​​Motor Frequency Converter)