First, the condensation and electrical breakdown problems that may be caused by the motor start-stop process, as well as the large current and temperature rise caused by repeated starting, will not be elaborated here. Second, each start and stop of the motor is a process of changing its inertia state. In particular, when the motor goes from static to moving, the bearing system and rotor part of the motor are subjected to greater impact, which directly affects the mechanical properties of the motor. According to the characteristics of motor starting and forward and reverse rotation, some motor shaft materials, bearing selection, and shaft extension shape may require special safety design. 

For example, crane motors that frequently rotate forward and reverse need to select tapered shaft extensions, and positioning keys should be used to strengthen the fixation between the stator core and the base. For slightly larger motors, their bearings should be one size larger than ordinary series motors, and cylindrical roller bearings with better tolerance should be used. 

Therefore, for intermittent work, including motors with periodic work, special attention should be paid to the problems they may face, and necessary measures should be taken. Specific contents such as higher winding insulation level, moisture-proof heating device, special shaft extension, etc.

Wolong Nanyang Explosion Protection, Flameproof three-phase asynchronous motor, crane motors