The main components of planetary transmission include sun gear, planetary gear, ring gear, planetary carrier, pin shaft and bearing, which belong to NGW transmission type (Fig. 1). Asteroid gearbox is usually composed of one stage to multi-stage planetary transmission in series (one stage output is the next stage input). Wind power planetary gearbox is usually composed of three to five planetary transmission.

The planetary transmission of wind power is characterized by low speed, high torque and frequent positive and negative commutation (continuously adjusting the whole fan or blade to get the proper orientation), which causes highly accumulated fatigue damage to the planetary structure of planetary carrier and gear parts. A strange failure occurred in a batch of early developed products, i.e. the left (high-speed end) of the pin shaft emerged, and the emerging pin shaft even interfered with the right spoke plate of the previous stage planetary carrier, and even stuck seriously, which directly affected the cleanliness of the lubricating oil and the normal transmission of the planetary structure.

As the failure usually occurs within one year of product use, and the probability of occurrence in the same batch is high, detailed cause analysis is carried out urgently, and corrective measures are taken. The maintenance plan needs to disassemble the gearbox, redesign and manufacture some parts, so the maintenance cost is relatively high. Therefore, the author thinks it is necessary to analyze and sort out the problems and exchange experience with peers.