Abstract: This paper analyzes the control characteristics of the frequency converter and proposes the feasibility and necessity of retrofitting the B2012A gantry planer with a sensorless speed control frequency converter. The selection criteria for the frequency converter are also given. Keywords : Speed ​​regulation; AC frequency converter; Control characteristics; Sensorless speed control frequency converter 1 Necessity of Retrofitting the Speed ​​Regulation System of a Gantry Planer The gantry planer is an indispensable machine tool for manufacturing heavy machinery, with a very wide processing range. It is mainly used to process various planes, inclined planes, and grooves, and is particularly suitable for processing large and narrow mechanical parts. Our factory uses two B2012A gantry planers to process the machine base and press frame of printing machinery, as well as the bed of various punch presses. It has three feed directions: main worktable, left spindle, and right spindle. The drive system is a closed-loop system of voltage and magnetic adjustment of an AC amplifier. The control components are numerous and complex, and the components are aging. During use, the control level and accuracy are relatively backward, and the control system frequently malfunctions, causing considerable difficulties in maintenance and continuously increasing maintenance costs. The speed control system of the gantry planer urgently needs to be upgraded. 2. Feasibility of Upgrading the Gantry Planer with Variable Frequency Technology AC speed control transmissions, such as asynchronous motor speed reduction and wound-rotor asynchronous motor rotor resistance speed control, have been widely used, but they have some shortcomings in terms of speed range, stability, reliability, and maintainability. With the continuous development and progress of electronic technology, and the proposal and improvement of new control theories, high-performance variable frequency speed control transmissions have developed rapidly. Rotor cascade speed control of wound-rotor asynchronous motors, commutatorless motor speed control using frequency converters, and variable frequency speed control of squirrel-cage asynchronous motors have been successively put into practical use, completing the foundation of AC speed control transmission with variable frequency speed control as the mainstream. The application of modern vector technology has enabled AC speed control transmissions to also possess the high performance of DC speed control. The commutator of a DC motor is its main weak point, limiting its key technical specifications such as unit capacity, overload capacity, maximum voltage, and maximum speed. It also causes considerable trouble in the manufacturing and maintenance of DC motors, thus restricting their application. In contrast, the squirrel-cage asynchronous motor in AC variable frequency speed control is simple in structure, robust and durable, reliable in operation, easy to maintain, has low transmission inertia, and good dynamic performance. Its unit capacity, voltage rating, and maximum speed are all superior to those of DC motors. Currently, high-performance AC variable frequency speed control systems are fully comparable to DC speed control systems and can be used in situations where DC motors are unsuitable. In recent years, the development of AC variable frequency speed control has been rapid, and its superior speed control performance has enabled it to replace traditional DC speed control systems. With the development of electronic components and the emergence of integrated circuits, the price of frequency converters has decreased significantly, and their economic efficiency has continuously improved, providing an increasingly broad market for their application. We have analyzed and compared the advantages and disadvantages of DC speed control systems and variable frequency speed control systems in detail, and used variable frequency technology to upgrade the original speed control system. [b][align=center]For details, please click: Variable Frequency Technology Retrofit of BZO12A Gantry Planer[/align][/b]