Abstract : This paper describes the AC speed regulation methods of asynchronous motors, the basic requirements and mechanical characteristics of variable frequency speed regulation, and realizes stepless speed regulation of asynchronous motors through variable frequency control modification. Keywords : Asynchronous motor; Speed ​​regulation; Variable frequency speed regulation; Frequency converter; Shot blasting machine 0 Introduction Our company imported the NL-150W shot blasting machine from Japan for surface shot blasting of die-cast aluminum parts for motorcycle engines to remove burrs and prepare for large-scale CNC precision machining. The speed of the shot blasting motor was fixed. Later, the company introduced a new model that required stepless speed regulation of the shot blasting speed within the rated range for different aluminum parts. To meet the process requirements, the NL-150W shot blasting machine was modified for variable frequency control. 1. AC Speed ​​Control Method The speed of an AC asynchronous motor is: N = N1(1-S) = 60f1/Pn(1-S) N1: Synchronous speed (r/min) f1: Stator power supply frequency (Hz) Pn: Number of pole pairs S: Slip That is, the speed of an asynchronous motor can be controlled through three methods: changing the power supply frequency, changing the number of pole pairs, and changing the slip. [b][align=center]For details, please click: Variable Frequency Control Retrofit of NL-150W Shot Blasting Machine[/align][/b]