With the continuous improvement of productivity, the improvement of machine tool structure and the enlargement of processing range, the speed and power of machine tool spindle are required to be constantly improved, the speed range of spindle is also constantly expanded, the constant power speed range of spindle is larger, and the spindle with automatic tool changing quasi-stop function is also required.

In order to achieve the above requirements, the spindle drive should be driven by stepless speed regulation system. Generally speaking, the spindle drive requires only speed control, and a small number of position control requirements, so the spindle control system only has speed control loop.

Because the spindle needs a wide range of constant power speed regulation, it is unreasonable to use permanent magnet motors, which often use separate excitation DC servo motor and cage induction AC servo motor.

There is no need for screw or other linear motion mechanism in the spindle rotation of CNC machine tools. There is a great difference between the spindle drive and the feed drive of CNC machine tools.

In the early years, DC spindle drive system was mostly used in NC machine tools, but due to the restriction of DC motor commutation, the range of constant power speed regulation of most systems is very small. With the development of microprocessor technology and high power transistor technology, the AC spindle drive system has been applied to the spindle drive of NC machine tools since the early 1980s. At present, the new CNC machine tools at home and abroad basically use AC spindle drive system, AC spindle drive system will completely replace DC spindle drive system. This is because unlike DC motors, AC motors are not limited in high speed and large capacity, and the performance of AC spindle drive system has reached the level of DC drive system, even in terms of noise, and the price is lower than that of DC spindle drive system.