The problem of light load and heavy load in frequency converter selection

Everyone must have encountered the problem of light and heavy loads during the selection process of frequency converters. So what is light load and what is heavy load? How to determine and select various types of loads?
Today, I will share with you the selection experience related to light and heavy loads.

light load
In various centrifugal fans, water pumps, and oil pumps, as the impeller rotates, the resistance generated by air or liquid within a certain speed range is roughly proportional to the square of the rotational speed n. Centrifugal fans, pumps, and other loads can be selected according to the light load (LO) power of the frequency converter, ensuring that the power corresponding to the light load of the frequency converter is not less than the rated power of the motor.

Heavy load
Friction loads such as conveyor belts, mixers, extruders, etc; Gravity loads such as cranes and hoists; Air compressors, Roots blowers, ball mills, injection molding machines, reciprocating plug pumps, etc. The above constant torque load can be selected according to the frequency converter overload (HO) power, ensuring that the power corresponding to the frequency converter overload is not less than the rated power of the motor.

Selection Examples
Question: How to select a power module for a conveyor belt motor with a rated voltage of 380V, power of 5.5kw, and current of 11.6A without overload

Answer: As a constant torque load, it should be selected according to the power of the heavy load (HO), as shown in the following figure. Select the power module model 6SL3210-1PE21-8UL0 (without integrated filter) PM240-2 from sample D31.3 to drive.