Why does the three phase asynchronous motor start Mars when it starts?

Three phase asynchronous motor rotor winding is aluminum bar or copper bar and short circuited ring welding. Last time a customer friend asked me what the reason was when the squirrel cage three-phase asynchronous motor started to spark. Today, Da LAN motor Xiaobian gives you a brief summary.
There may be several reasons for the emergence of cage type three phase induction motors when they start.
1. Mechanical friction.
When the rotor has a “sweeping chamber” or a rotating part collides with a non rotating part, the spark may erupt due to mechanical friction. This often occurs when motor bearings are damaged or overhauled.
Two. The squirrel cage strip is caused by the broken bar.
Rotor squirrel cage welding head or squirrel cage strip outlet is not far away, easy to fracture or remove welding. If the fracture appears to be unconnected, the two ends are subjected to centrifugal force after starting. Because the force is not uniform, the fracture head is disconnected. The large current produced in the rotors squirrel cage will produce arc light and out of Mars. It seems that when welding electrodes suddenly touch “ground” to break off the arc. When the gap is bigger, the ends are not at all contacted, or when the ends of the broken ends are connected, the Mars will disappear again.
Three, lead insulation bad cause.
380V motor, sometimes because of a certain phase lead insulation bad, when starting, the lead vibration and the shell connected (ground) broken time, also because of cutting off the grounding current to produce sparks, from the outlet of Mars.
No matter what causes Mars, the power should be cut off first, the motor is stopped to find out the cause, after eliminating the hidden danger and then start, so as not to cause greater loss. However, if the squirrel cage strip is not welded seriously, it can operate normally after starting, and does not continue to take the Mars, and the current is normal. In order to avoid the impact of production, it can continue to run, but it is necessary to avoid opening and stopping. After the standby motor is ready, the defective motor will be stopped and repaired.