Source: Cat One Cat Two Motor Technology Day Ginseng
Working in a repair shop, because of the same major, the two of them naturally have more topics about faulty motors, and Ms. Shen also has the privilege and opportunity to see motor failure cases. Their unit undertook a set of H355 2P 280kW cast aluminum rotor motor, the customer said that there was obvious vibration during the debugging process, and the bearing did not work, but due to the time requirements of heating, the manufacturer could only turn to the nearest repair unit, that is, the unit where the old W was located.
Combined with the measures already taken by the customer, the shaft can be pulled out manually during dismantling and maintenance. Detect the core size of the rotor core hole and the shaft of the motor, and the two are obviously clearance fit, and the minimum clearance is 0.08mm on one side. The repair unit reported the problem to the manufacturer, and they conducted a comprehensive review of the process of the problem. Because of my best friend W, Ms. Shen has a little understanding of the process of the problem, coupled with my own analysis of the problem, and shares the case with you.
1. Description of the appearance of the fault
●There are circumferential scratches in the circumferential direction of the shaft, but it does not have much impact on the original machining surface, according to the data provided by the manufacturer, the shaft processing size is not too problematic, and the diameter of the shaft hole is obviously out of tolerance.
●While the size of the rotor shaft hole is too large, it can be found that the shaft hole at one end is seriously damaged, and there are obvious signs of pot bottom at the end of the iron core;
●There are obvious solid friction marks in the axial direction of the shaft hole, which should be caused by the shaft exit process;
●The surface of the rotor is all blackened, which is obviously the state after heating; This rotor slot is badly serrated.
2. Analysis and judgment based on faults
From the verification situation, it was found that the rotor shaft had been heated and withdrawn, this process led to the damage and enlargement of the shaft hole diameter, after the standard shaft was inserted again, the rotor centrifugation occurred during the operation of the motor, and the shaft had periodic and non-periodic collisions, and the final result was motor vibration. The problem may occur in the test phase of the motor, or in the use phase of the motor, but it is a fatal blow to the motor itself.
3 Analysis results from the manufacturer
When the rotor of the motor fails to meet the balance control requirements in the dynamic balance process, check that the rotor has a horseshoe problem, exit the shaft by oil stuffing and cold pressing, and then wear the correction tooling (similar to a false shaft) to shape the cast aluminum rotor core, after the shaping is completed, the shaft and the core are bonded relatively tightly and cannot be withdrawn, and the shaft is forcibly withdrawn by cold pressing, which ultimately causes the core hole to be seriously damaged and deformed, and the diameter of the shaft hole is also seriously out of tolerance; The cause of the blackening of the rotor is the heating of the shaft and rotor during the initial shaping.
Similar problems may be encountered by different motor manufacturers, but the repair process is sometimes more difficult to control than the normal production and processing technology, because each case will have its own personalized characteristics, but how to solve the problem is the effective integration of technology and management.
The above unofficial content represents personal views only.