Abstract: A power plant has effectively replaced the frequency converters of the main and auxiliary motors of the air preheater with permanent magnet motors, achieving the soft start function. At the same time, the PLC in the control cabinet has been eliminated, significantly simplifying the motor start-up and interlock logic. This has prevented auxiliary machine load reduction due to frequency converter interlock alarm faults and conflicts between PLC and DSC logic. Moreover, when defects occur, the causes are easier to trace, thereby enhancing the overall operational stability and reliability of the air preheater system.