Answer:
(1) Load type and frequency converter selection. Frequency converters cannot be used normally under all circumstances, so it is necessary to have a better understanding of loads, environmental requirements and frequency converters. Different loads carried by motors have different requirements for frequency converters.
1) Fans and water pumps. These are the most common loads, and the requirements for frequency converters are the simplest. As long as the frequency converter capacity is equal to the motor capacity, it can be used (air compressors, deep water pumps, silt pumps, and fast-changing musical fountains require larger capacity).
2) Crane loads. This type of load is characterized by a large impact when starting, so the frequency converter is required to have a certain margin. At the same time, when heavy objects are lowered, there will be energy feedback, so a brake unit should be used or a shared bus should be used.
3) Uneven loads. Some loads are sometimes light and sometimes heavy. At this time, the frequency converter capacity should be selected according to the heavy load situation, such as rolling mill machinery, crushing machinery, mixers, etc.
4) Large inertia loads. For example, centrifuges, punching machines, and rotary kilns in cement plants have large inertia, so they may oscillate during startup and have energy feedback when the motor decelerates. A frequency converter with a slightly larger capacity should be used to speed up startup and avoid oscillation. Use a brake unit to eliminate feedback energy.
(2) Long-term low-speed operation. Due to the high heat generated by the motor, the fan cooling capacity is reduced. Therefore, it is necessary to increase the reduction ratio or use a 6-level motor to make the motor run at a higher frequency.
(3) The installation location of the frequency converter must meet the requirements of the standard environment, otherwise it is easy to cause failures or shorten the service life; the distance between the frequency converter and the drive motor is generally not more than 50m. If a longer distance is required, it is necessary to reduce the carrier frequency or add an output reactor option for normal operation.
