A practical guide to performing root cause analysis (RCA) on rotating electrical machines, so the same failure does not repeat.
Simply repairing or rewinding a failed motor without understanding why it failed often leads to repeat breakdowns. Each repeat failure increases cost, erodes confidence and may cause collateral damage to connected equipment.
Root Cause Analysis (RCA) is a structured process to identify the underlying technical and process contributors to a failure, so that corrective and preventive actions can be implemented.
Common modes include insulation breakdown, bearing failure, rotor bar cracks, mechanical misalignment, contamination, cooling issues and electrical supply problems.
Each mode leaves characteristic evidence: for example, insulation tracking, localised discoloration, fluted bearings from stray currents or distinct vibration signatures.
1. Stabilise the situation and collect as-found data (protection trips, SCADA logs, operating conditions).
2. Perform systematic visual inspection and photographic documentation before any cleaning.
3. Carry out electrical and mechanical testing (IR/PI, surge, tan-delta, vibration, alignment, oil or grease analysis as applicable).
4. When required, conduct laboratory analysis (metallurgical examination, insulation sectioning, contamination analysis).
5. Map findings to likely failure mechanisms using standards, experience and failure databases.
The true root cause is often a combination of technical and process factors—incorrect protection settings, inadequate cooling air, poor maintenance intervals, improper lubrication or unsuitable motor selection for the duty.
Documenting these links clearly helps both engineering and operations teams understand what must change to avoid repetition.
A good RCA report does more than describe damage; it explains the sequence of events and recommends specific actions such as protection setting changes, design upgrades, maintenance plan revisions or operator training.
RKELC provides detailed failure investigation reports referencing IEEE/IEC/API guidelines where relevant, so recommendations are aligned with recognised standards.
You should consider formal RCA when a failure has high financial impact, safety implications, frequent repetition on a fleet, or when warranty and insurance discussions depend on clear evidence.
Engaging a specialist early—before evidence is lost—significantly improves the quality of conclusions.
Whether you are planning a maintenance strategy, investigating a failure, or building a predictive maintenance programme, RKELC can support you with NABL-accredited testing, workshop repairs, engineering studies and on-site services across power generation, oil & gas, metals & mining, marine and process industries.
Key Takeaways
Essential insights and actionable points extracted from the article for quick reference.
Simply repairing or rewinding a failed motor without understanding why it failed often leads to repeat breakdowns. Each repeat failure increases cost,...
Common modes include insulation breakdown, bearing failure, rotor bar cracks, mechanical misalignment, contamination, cooling issues and electrical su...
1. Stabilise the situation and collect as-found data (protection trips, SCADA logs, operating conditions).
The true root cause is often a combination of technical and process factors—incorrect protection settings, inadequate cooling air, poor maintenance in...