The Electric Spindle is a new technology that has emerged in the CNC machine tool field over the past few years, integrating the machine tool spindle with the spindle motor. The high-speed CNC machine tool main transmission system eliminates belt and gear drives. The machine tool spindle is directly driven by an internal motor, thereby reducing the length of the machine tool's main transmission chain to zero, achieving "zero transmission" for the machine tool. This drive structure, which combines the spindle motor with the machine tool spindle, makes the spindle component relatively independent from the machine tool's transmission system and overall structure, allowing it to be made into a "spindle unit," commonly known as the "Electric Spindle" or "Motor Spindle." The Electric Spindle boasts compact structure, light weight, low inertia, minimal vibration, low noise, and rapid response, which can reduce gear drives, simplify the machine tool's external design, facilitate spindle positioning, and is an ideal structure in high-speed spindle units.