用电机测试工具诊断定子松动情况
Preliminary investigation results
A 6.6 kV motor used at a petrochemical plant to cool gases produced during a vapor-phase polymerization process has developed abnormal symptoms. An abnormal vibration was detected during a vibration test. A subsequent no-load test also revealed the abnormal vibration. The root cause of the vibration remains undetermined. We contacted a team at Instrument Resource in Bangkok, Thailand, to conduct further investigations into the motor in an attempt to determine the cause of the abnormal vibration.
Motor circuit analysis (MCA™) was performed using ALL-TEST PRO 7 PROFESSIONAL™ . Through a series of tests, the AT7™ identified the problem after executing the DYN test function. This specialized test is designed to verify the integrity and health of the stator and rotor. The test requires rotating the motor shaft. ALL TEST Pro’s patented dynamic stator and rotor characterization test revealed an imbalance in the dynamic stator characteristics.
Dynamic signature analysis
The green line represents the stator characteristics, indicating the deviation of the average value during the rotation of each phase. The two black dashed lines represent the rotor signature, including the upper and lower signatures.
The motor has been disassembled. Loose stator slot wedges were found. These loose stator slots caused excessive vibration and imbalance in the dynamic stator signature.
After repairing and reassembling the motor, a set of tests was conducted using the AT7™. Subsequent tests showed that the dynamic stator signal was no longer unbalanced, indicating that the stator was in good health.
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