In the fault of micromotor, the fault caused by electrical connection accounts for a large proportion, and it is easy to find the fault point. The following five traditional methods are usually used to judge whether the electrical connection points are in good contact:

① Visual inspection: check the connection point for discoloration, arc burn mark, fracture, etc

② Hammering inspection: that is, tap the connection point with a small hammer to see if there is any abnormal sound

③ Fastening bolt: retighten all electrical connection points. If there is looseness, it is poor contact.

④ Feeler gauge inspection: measure the tightness of the two joint surfaces, and the gap is poor contact.

⑤ Electrical inspection: measure the DC resistance of motor with double arm bridge, compare the records over the years (pay attention to convert to the same temperature), and the difference between them is poor contact.