Study On Variable-frequency And Adjustable-speed System Of Power Magnetic Suspending Spindle For NC Machine Tools

Nowadays the development of NC machine tool has the trend to high speed, high efficiency and high precision. So NC machine tool puts forward high demands for spindle drive, such as large power and much wider range of adjustable speed. And at the same time, it also needs the localization function and protective capability.To achieve the requirements above, many NC machine tools spindle adopt AC spindle drive system, and use common asynchronous motor or Ac variable-frequency motor as spindle drive motor, at the same time the constant power automatic speed regulating can be carried out by applying the method of infinite speed vatiation. With the vector transform AC motor can obtain the performance as DC motor. For AC motor has characteristics of nonlinear and strong coupling, it's difficult to control. As the requirement of the motor technology becoming higher and higher, especially the development of DSP technology provides powerful supports for advanced control theory and complicated control methods.In this thesis, to obtain the variable-frequency and adjustable-speed of Power Magnetic Bearing Spindle for NC machine tools, applying DSP as control center, designed a kind of variable-frequency and adjustable-speed system. In this system, the form of main circuit is a kind of classic one, called AC-DC-AC voltage inverter. It uses IPM as Inverter parts to control turn on or off. In the front of the system, three phases uncontrolled rectifier part provide power for IPM and power module. The power module can supply four isolated power for IPM drive circuit, at the same time, it also put out power to the speed sensor and electric sensors. In the processing of circuit design, adopting many anti-jamming factors, which ensure the system working steadily.The experimental device that supports on-line debugging is a variable-frequency and adjustable-speed system especially designed for the power magnetic suspending spindle. The system applied advanced SVPWM control technique which can complete the real-time and precise control for spindle revolving. In the design of system, all the groupwares adopt modularized concept, it's convenient for debugging, assembling and maintaining.