The reason why the motor is running weakly?

     The 350KW main motor of an aluminum wire drawing machine, the operator reported that the motor could not pull the wire. After arriving at the site, the test machine found that the motor had a significant blocking sound. The aluminum wire was loosened from the traction wheel. The motor can rotate and there is no obvious abnormality. As long as the aluminum wire of the traction wheel is tightened, even if it is just held by a hand, the motor can't turn, and the armature current increases sharply.

Measure the insulation of the motor windings and check the carbon brushes and no obvious problems are found. After disconnecting the motor from the equipment, run a single machine, and test that the excitation current and armature current are within the normal range. I have encountered similar faults twice before, once because of the speed encoder, and once because of the virtual welding of a thermistor on the controller main board. This time there was no virtual welding and replacing the encoder did not solve the problem.

 No electrical problems were found for the time being. At that time, it was initially judged that there might be a problem with the mechanical part of the equipment, but the mechanics opened the equipment box and checked and found no problems. So I can only continue to search for electrical problems. This investigation really found a little problem. It was found that the motor had an insignificant sense of pause when it was rotating at a low speed. It would be difficult to see it if you were not careful. Later, I applied a little force on the motor connector and found that the armature current increased sharply, which ruled out the mechanical problems of the equipment.

     After checking the motor and motor bearings again and no obvious problems are found, consider the problem with the controller. There is no problem to check the controller parameters, and there is no obvious problem when the controller is disassembled. I have no choice but to let a professional repair station do a test. After their inspection, there was a real problem, saying that there was a problem with the rectifier module inside. After waiting for three days, the controller with the changed module was installed.

After the hopeful start-up test, the problem remained. Asking the maintenance point and providing various solutions to solve the problem is of no avail. It does not seem to be the fault caused by the controller. At that time, there was nothing to do, and I planned to give up, and then I went to the manufacturer for after-sales service. Before giving up, I plan to struggle again. I plan to check the inside of the motor again. There is a lot of dust in the motor, and my hands are covered with dust. So the new colleague asked the newcomer to find a hair dryer to blow it on, but the little colleague looked nervous and said that he broke the motor wire. At that time, I was excited, how much wind could blow such a thick line, it should be a motor problem, so hurry up and check it out.

    Sure enough, the connection between the commutating windings of the motor was broken, and the two wires were connected by terminals. In the past, the maintenance terminal was not pressed well, and the connection became hot after a long time. Because there was a layer of wax tube at the bottom of the motor, I didn’t see it when I checked it. He accidentally touched it when he blew it. opened. It should be the problem here, don't mention that feeling too excited. After the motor is sent to the outside for repair, install and test the machine, and the problem is solved.

By Jessica