The grinding electrical spindle is a new technology in the CNC machine tool field that integrates the machine tool spindle with the spindle motor. Alongside linear motor technology and high-speed tooling technology, it propels high-speed machining into a new era. The electrical spindle is a set of components, including the electrical spindle itself and its accessories: the electrical spindle, high-frequency inverter, oil mist lubricator, cooling unit, built-in encoder, tool changing unit, and more. The motor's rotor directly serves as the machine tool's spindle, with the spindle unit's housing being the motor base, and in conjunction with other components, achieving integration between the motor and the machine tool spindle.

Currently, with the rapid development and continuous improvement of electrical transmission technology (such as variable frequency speed regulation technology and motor vector control technology), the mechanical structure of the high-speed CNC machine tool's main drive system has been greatly simplified, and belt drive and gear drive are basically eliminated. The machine tool spindle is directly driven by an internally mounted motor, thereby shortening the length of the machine tool's main drive chain to zero, achieving "zero transmission" in the machine tool. This drive structure, where the spindle motor and the machine tool spindle are combined into one, makes the spindle component relatively independent from the machine tool's transmission system and overall structure, thus allowing it to be made into a "spindle unit," commonly known as the "electric spindle." As the electric spindle mainly uses AC high-frequency motors at present, it is also called the "high-frequency spindle." Due to the absence of intermediate transmission stages, it is sometimes referred to as the "direct drive spindle."