After the equipment has experienced the aging of various electrical components in the initial stage, and the grinding and adjustment of mechanical parts, it has begun to enter a relatively stable period of normal operation. At this time, physical failures of various components are relatively rare, but sporadic failures are not excluded. The occurrence of faults, therefore, during this period, it is necessary to keep a record of equipment operation for reference when troubleshooting. At the same time, we must insist on a comprehensive mechanical and electrical inspection and verification of the equipment every 6 months. During this period, the occurrence rate of electromechanical failures is small, and most of them can be eliminated. The relatively stable operation period is longer, generally 7-10 years.