The grinding electrical spindle is a new technology that integrates the machine tool spindle with the spindle motor, emerging in the CNC machine tool field. 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, which includes the electrical spindle itself and its accessories: the electrical spindle, high-frequency variable-frequency device, oil mist lubricator, cooling unit, built-in encoder, tool changer, and more.

The motor rotor serves directly as the machine tool's spindle, with the spindle unit's housing being the motor base. In conjunction with other components, this achieves an integrated design between the motor and the machine tool's spindle.

Currently, with the rapid development and improvement of electrical transmission technology (such as variable frequency speed regulation technology and motor vector control technology), the mechanical structure of high-speed CNC machine tool main drive systems has been greatly simplified, and belt drives and gear drives have basically been eliminated. The machine tool spindle is directly driven by an internally mounted motor, thereby reducing the length of the machine tool's main drive chain to zero, achieving the "zero drive" of the machine tool.

This drive structure, where the spindle motor is integrated with the machine tool's spindle, allows the spindle component to be relatively independent of the machine's transmission system and overall structure. Consequently, it can be made into a "spindle unit," commonly referred to as an "electric spindle." Since the electric spindle predominantly uses AC high-frequency motors at present, it is also known as a "high-frequency spindle." Due to the absence of intermediate transmission stages, it is sometimes called a "direct drive spindle."