Abstract : Combining the mechanical characteristics of wastewater treatment equipment and the destructive factors in the production site, this paper elaborates on the basic requirements for maintaining frequency converters. Keywords : mechanical characteristics, destructive factors, maintenance 1 Introduction In the automatic control system of wastewater treatment plants, a considerable portion of the production equipment is equipped with frequency converters. The production site is often attacked and disturbed by destructive factors such as corrosive gases, humidity, sunlight, high temperature, vibration, lightning strikes, power grid surges, and dust. These hazardous factors directly pose potential hidden dangers to the safe and reliable operation of frequency converters. Therefore, it is essential to correctly understand the mechanical characteristics of wastewater treatment plants and to understand and be familiar with some basic requirements for the application and maintenance of frequency converters to ensure the safe operation of frequency converters in harsh environments. 2 Mechanical Equipment of Wastewater Treatment According to the relevant wastewater treatment process, there are two types of production machinery that can be equipped with frequency converters: (1) Constant power load, i.e., PM=T[sub]L[/sub]·n This type of equipment mainly includes the filter belt drive mechanism of sludge scraper and sludge dewatering machine, dosing screw pump, and sludge screw pump. Such equipment has two characteristics: ● It generates a frictional load torque during operation, and its direction of action is always opposite to the direction of rotation. ● It operates at low speed, such as the sludge scraper in the sedimentation tank, with an average linear velocity in the range of 1 to 2 m/min. Therefore, when the frequency converter drives a constant torque load, the torque at low speed must be large enough and have sufficient torque overload capacity. (2) Pump and blower loads The characteristic of this type of load is that the resistance generated is proportional to the square of the rotational speed n. It is worth noting that at high speed, the required motor power increases too quickly with the rotational speed and is proportional to the cube of the rotational speed n. Under normal circumstances, the frequency converters of submersible pumps and blowers basically operate below the power frequency range. Correctly understanding the torque characteristics of production machinery is the basis for rationally selecting and maintaining frequency converters. [b][align=center]For details, please click: Application and Maintenance of Frequency Converters for Sewage Treatment Equipment[/align][/b]