{"id":160,"date":"2026-07-08T08:51:59","date_gmt":"2026-07-08T08:51:59","guid":{"rendered":"https:\/\/industrialelectricmotor.net\/?p=160"},"modified":"2026-07-08T08:51:59","modified_gmt":"2026-07-08T08:51:59","slug":"how-to-troubleshoot-electric-motor-failures","status":"publish","type":"post","link":"https:\/\/industrialelectricmotor.net\/fr\/how-to-troubleshoot-electric-motor-failures\/","title":{"rendered":"How to Troubleshoot Electric Motor Failures"},"content":{"rendered":"
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Korea Ever-Power \u00b7 Maintenance Guide \u00b7 Fault Diagnosis<\/span><\/p>\n

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How to Troubleshoot Electric Motor Failures:
\n10 Common Issues and Their Causes<\/span><\/h1>\n

Most electric motor failures give advance warning through measurable changes in current, vibration, temperature, or noise before the motor actually fails. Recognising these early signals and identifying their root cause accurately allows maintenance teams to correct problems before an unplanned shutdown. This guide covers the 10 most common electric motor troubleshooting issues found in three-phase induction motors, their diagnostic indicators, and the corrective actions that fix them.<\/p>\n

Overheating<\/span>
\nBearing Failure<\/span>
\nVibration<\/span>
\nWinding Insulation<\/span>
\nPhase Loss<\/span><\/div>\n<\/div>\n<\/div>\n

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Issue 01<\/div>\n
Motor will not start<\/div>\n<\/div>\n
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Issue 02<\/div>\n
Overheating<\/div>\n<\/div>\n
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Issue 03<\/div>\n
Excessive vibration<\/div>\n<\/div>\n
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Issue 04<\/div>\n
Noisy bearings<\/div>\n<\/div>\n
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Issue 05<\/div>\n
Phase current imbalance<\/div>\n<\/div>\n
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Issue 06<\/div>\n
Low insulation resistance<\/div>\n<\/div>\n
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Issue 07<\/div>\n
Motor runs slow<\/div>\n<\/div>\n
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Issue 08<\/div>\n
Reduced starting torque<\/div>\n<\/div>\n
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Issue 09<\/div>\n
Phase loss operation<\/div>\n<\/div>\n
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Issue 10<\/div>\n
Shaft seal leakage<\/div>\n<\/div>\n<\/div>\n

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\"Electric<\/p>\n
Quality inspection and testing \u2014 systematic measurement of current balance, insulation resistance, vibration, and bearing temperature at regular intervals is the most effective electric motor troubleshooting strategy, catching developing faults before they cause unplanned downtime.<\/div>\n<\/div>\n

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Before You Troubleshoot<\/div>\n

Before starting any electric motor troubleshooting work, isolate the motor from the electrical supply using the local disconnect switch and apply lockout\/tagout (LOTO) procedure. Verify isolation with a voltage tester at the motor terminals. Allow the motor frame to cool to a safe touch temperature before working near the fan cover or terminal box. All measurements requiring motor operation should be performed with appropriate PPE and with the driven load secoupled where possible.<\/p>\n<\/div>\n<\/div>\n

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10 Common Electric Motor Problems and Their Solutions<\/h2>\n

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01<\/div>\n
Motor Will Not Start<\/div>\n<\/div>\n
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Possible Causes<\/div>\n
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  • No supply voltage at motor terminals (blown fuse, open circuit breaker)<\/li>\n
  • Incorrect terminal wiring (supply connected to wrong terminals)<\/li>\n
  • Supply voltage too low to produce sufficient starting torque<\/li>\n
  • Overload relay tripped and not reset<\/li>\n
  • Seized bearing preventing shaft rotation<\/li>\n
  • Driven load seized or locked mechanically<\/li>\n<\/ul>\n<\/div>\n
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    Diagnostic Steps<\/div>\n

    Measure supply voltage at motor terminals with motor in start command state. Confirm all three phases present and within 5% of rated voltage. Check overload relay status and reset if tripped. Try to rotate shaft by hand with supply isolated \u2014 resistance indicates mechanical seizure. Measure insulation resistance to rule out winding short circuit.<\/p>\n<\/div>\n<\/div>\n<\/div>\n

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    02<\/div>\n
    Overheating \u2014 Motor Frame Too Hot to Touch<\/div>\n<\/div>\n
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    Possible Causes<\/div>\n
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    • Motor overloaded beyond nameplate rating<\/li>\n
    • Cooling fins blocked with dust or debris<\/li>\n
    • Ambient temperature above rated maximum (typically 40\u00b0C)<\/li>\n
    • Fan cover damaged, restricting airflow<\/li>\n
    • Supply voltage imbalance causing unequal phase currents<\/li>\n
    • Frequent starting cycles exceeding thermal capacity<\/li>\n<\/ul>\n<\/div>\n
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      Diagnostic Steps<\/div>\n

      Measure all three phase currents with clamp meter. If any current exceeds nameplate value, the load is too high. Measure supply phase-to-phase voltages \u2014 imbalance above 2% causes significant overheating. Clean cooling fins with compressed air. Measure ambient temperature at the motor air inlet. Check fan cover for obstruction or damage.<\/p>\n<\/div>\n<\/div>\n<\/div>\n

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      03<\/div>\n
      Excessive Vibration<\/div>\n<\/div>\n
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      Possible Causes<\/div>\n
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      • Shaft misalignment with driven machine<\/li>\n
      • Unbalanced coupling or pulley<\/li>\n
      • Loose hold-down bolts (motor or driven machine)<\/li>\n
      • Worn or damaged bearings<\/li>\n
      • Bent shaft from mechanical impact<\/li>\n
      • Foundation resonance at running frequency<\/li>\n<\/ul>\n<\/div>\n
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        Diagnostic Steps<\/div>\n

        Measure vibration velocity at both bearing housings and at the baseplate. A vibration velocity above 2.8 mm\/s RMS (IEC 60034-14 Grade A) requires investigation. If vibration reduces when load is disconnected, the driven machine or coupling is the likely source. Frequency spectrum analysis identifies the dominant frequency \u2014 1x rpm indicates unbalance or misalignment; 2x rpm indicates angular misalignment or coupling issues.<\/p>\n<\/div>\n<\/div>\n<\/div>\n

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        04<\/div>\n
        Noisy Bearings \u2014 Grinding, Squealing, or Rumbling<\/div>\n<\/div>\n
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        Sound and Probable Cause<\/div>\n\n\n\n\n\n\n\n
        Intermittent grinding<\/td>\nHard particle contamination in grease<\/td>\n<\/tr>\n
        Continuous rumble<\/td>\nRaceway spalling from fatigue or overload<\/td>\n<\/tr>\n
        High-pitched squeal<\/td>\nGrease starvation or wrong grease type<\/td>\n<\/tr>\n
        Rhythmic clicking<\/td>\nBall or roller damage (flat spot)<\/td>\n<\/tr>\n
        Roughness at low speed<\/td>\nVFD bearing current fluting<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n
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        Corrective Action<\/div>\n

        Schedule bearing replacement at next planned maintenance window. For grease starvation: add correct grease type and quantity through grease nipple if fitted (re-greasable bearings only). For VFD current fluting: implement bearing current protection (insulated NDE bearing or shaft grounding brush). Do not continue running a motor with bearing damage beyond the next maintenance opportunity \u2014 a failed bearing can damage the stator bore through rotor contact.<\/p>\n<\/div>\n<\/div>\n<\/div>\n

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        05<\/div>\n
        Phase Current Imbalance<\/div>\n<\/div>\n
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        Cause Identification by Measurement<\/div>\n

        Measure phase-to-phase supply voltages at the motor terminals (not at the panel \u2014 voltage drop in cables can create imbalance that is invisible at the panel). Also measure all three phase currents under full load.<\/p>\n

        Voltage imbalance present<\/strong> \u2192 supply network problem; check transformer tap settings, check for high-resistance connections in switchgear<\/p>\n

        Voltage balanced, current imbalanced<\/strong> \u2192 motor winding fault; measure winding resistance on each phase \u2014 deviation above 2% indicates partial turn short or open circuit<\/div>\n<\/div>\n

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        Why Imbalance Is Damaging<\/div>\n

        A supply voltage imbalance of 3.5% can cause current imbalance of 15 to 25%, because induction motor current is highly sensitive to voltage asymmetry. The phase carrying the highest current heats most rapidly. NEMA MG1 and IEC 60034-26 recommend derating motor output power when voltage imbalance exceeds 1%. At 5% voltage imbalance, derate to 75% of nameplate power to avoid overheating of the hot phase winding.<\/p>\n<\/div>\n<\/div>\n<\/div>\n

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        06<\/div>\n
        Low Insulation Resistance \u2014 Below 1 M\u03a9<\/div>\n<\/div>\n
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        Possible Causes<\/div>\n