HT Motor Problem appears after Disassembly and Reassembly

Electrical engineering root cause analysis (RCA) related to HT motor problem appears after disassembly and reassembly.

Note: This root cause analysis (RCA) is from real-time scenarios that happened in industries during the tenure of two or three decades ago. These articles will help you to improve your troubleshooting skills and knowledge.

HT Motor Problem

The crew disassembled a 3.3.KV 400 KW 3000 RPM Journal Bearing Motor, completed DOR change tasks and assembled it back.

On energizing with workshop test 400 V supply, the rotor instead of running at the magnetic center after few seconds of axial wandering moved axially to the extreme.

The shaft collar hitting the bearing end stopped further shaft axial movement – misbehavior indeed!

Author Root Cause Analysis

Since the problem appears after disassembly, obviously reassembly errors are most likely.

Close motor inspection showed no match marks on the end shields!

Possibly, the left end shield has gone to the right and vice versa.

Motor disciplined!

Motor disassembly after careful match marking and assembling back solved the problem.

The sheepishly grinning electrical crew leader said, “Sir, I assumed the end-shields are interchangeable; hence, I disassembled the motor without match marks.”

The author explained, “Never assume; always be sure. Assume really splits as “ASS-U-Me”; i.e. it makes an ass of you and me, as it did this time!”

Author: S. Raghava Chari

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