Abstract : This paper details the features, usage, and adjustment methods of Siemens MM series frequency converters. It also discusses the application of CNC systems and frequency converters in semi-automatic high-speed railway bearing internal and external raceway ultra-precision machines and CNC reciprocating double-end face grinders, highlighting precautions for frequency converter use. Keywords : Frequency converter, ultra-precision machine, double-end face grinder, dresser 0 Introduction The Siemens MM12-MM750/3 series is a series of frequency converters for controlling the speed of three-phase AC motors. Different models are available, with power ranging from 120W for single-phase input to 7.5kW for three-phase input. This series of frequency converters utilizes microprocessor control and IGBT technology, offering reliability and flexibility. It employs selectable high-frequency and medium-frequency pulse width modulation to achieve ultra-quiet motor operation, and comprehensive protection functions provide protection for both the frequency converter and the motor. In the semi-automatic high-speed railway bearing inner and outer raceway ultra-precision machine independently developed by our company, Siemens frequency converters MM75/3 are used to control the oscillation motor and MM400/3 are used to control the workpiece shaft motor, so that the oscillation frequency and workpiece shaft speed can be arbitrarily adjusted according to process requirements during processing. In addition, frequency converter technology has also been used in bearing equipment such as CNC reciprocating double-end face grinders, and good results have been achieved. 1 Features of MM series frequency converters The features of MM series frequency converters are: (1) Easy to install, program and use. (2) Closed-loop control with proportional integral (PI) control loop function. (3) Strong parameter function, which makes the frequency converter usable in almost all applications through settings. (4) Built-in permanent memory stores the set parameters. (5) Wide speed range, "hard" mechanical characteristics, adjustable frequency of 0～400Hz, and constant torque speed regulation characteristics. (6) The acceleration/deceleration time can be set by the user, and the time from 0 to f[sub]max[/sub] and from f[sub]max[/sub] to 0 can be set between 0 and 650s. (7) The output frequency (motor speed) can be controlled by one of the following methods: ① Frequency setting value given by the panel; ② High-resolution analog setting value (voltage input); ③ External potentiometer to control motor speed; ④ Fixed frequency via binary input; ⑤ Serial port control. (8) Cooling fan with software control. (9) Fast current limit (FCL) enables reliable trip-free operation. [b][align=center]For more details, please click: Practical Techniques for Siemens MM Series Frequency Inverters[/align][/b]