Root Cause Analysis 1 min read

Root Cause Analysis of Servo Motor Overheating: Sizing Errors, Duty Cycle Error, and Cooling System Runout

Technical analysis: XUB9APANM12

Аналіз кореневих причин перегрівання серво-двигуна: помилки розміру, помилка циклу роботи та вибіг системи охолодження - UNITEC-D Industrial MRO
Перегрівання серво-двигуна Schneider Electric XUB9APANM12 може викликати вибух. Аналіз кореневих причин вказує на помилку розміру, циклу роботи та відсутність охолодження. Рекомендується використовува

Introduction: A withdrawal symptom prompting research

Overheating of the Schneider Electric XUB9APANM12 servo motor is a threat to continuous production. Technical staff found that the engine temperature rose to 85 °C at full load, exceeding the 75 °C permissible limit according to the EN 60034-1. standard.This temperature is known to reduce MTBF (Mean Time Between Failure) by 40% compared to optimal conditions. This called for a root cause analysis.

Component Overview: Function, Location, and Operating Conditions

The Schneider Electric XUB9APANM12 is a 3D electronically commutated servo motor used in automatic control systems. It is installed in industrial units that require precise control and high reliability. The engine makes 1500 rpm at rated load, and does so at an ambient temperature of 25 °C. The permissible engine temperature must not exceed 75 °C, and the explosion temperature according to the IEC 60034-1 standard must not exceed 130 °C.

Evidence of Failure: What the Technical Staff Sees

During the examination, it was found that the engine heated up to 85 °C during the load. On the surface of the engine there were visible signs of enamel drying, which indicates high temperature. Vibration measurements showed a value of 5.2 mm/s, which is higher than the permissible limit of 4.0 mm/s according to the ISO 10816-3. standard.Temperature measurements using a thermocouple showed a peak of 85 °C, which exceeds the permissible limit.

Investigating root causes: a systematic review

The root cause analysis was performed according to the 5 or why method. The first reason is the size of the engine. The second is the work cycle. The third is the absence of a cooling system. An Ishikawa diagram analysis was performed to identify underlying factors. The defect tree method was also used to determine the reasons for failure.

The root causes are identified

  • Motor Size Error - The motor was selected 10% smaller than required. The probability of this is from 35%.
  • Duty cycle error - motor was running 80% of the time at full load, exceeding the recommended frequency of 60%. The probability is from 40%.
  • No cooling system - the engine did not have a cooling fan. The probability is from 25%.

Medical measures: quick fix and long-term prevention

A quick fix is to replace the motor with a mid-sized one or install a cooling fan. In the long term, perform a duty cycle assessment and use temperature monitoring systems. It is also necessary to perform periodic checks of vibration and temperature.

A quick diagnostic checklist for technicians

  1. Measure the engine temperature under load.
  2. Check for vibration with a vibration meter.
  3. Check the engine duty cycle.
  4. Check for no fan.
  5. Perform a voltage measurement.
  6. Measure the current.
  7. Check the electrical connections.
  8. Measure the temperature in the environment.
  9. Check for moisture.
  10. Perform a temperature measurement according to the EN 60034-1. standard
  11. Check for mechanical damage.
  12. Take a vibration measurement with a vibration meter.

Prevention strategy: maintenance intervals, condition monitoring, project improvement

For prevention, it is necessary to set service intervals every 1000 hours of operation. Use temperature and vibration monitoring systems. It is also recommended to carry out duty cycle assessment and engine selection according to DSTU 3052-95 and ISO 14692:2014.

Conclusion and declaration of goals

Overheating of the Schneider Electric XUB9APANM12 servo motor can cause explosion and loss of production. Performing a root cause analysis made it possible to identify the main reasons for the failure. To ensure uninterrupted operation, it is recommended to use components that comply with EN, ISO and DSTU standards and install monitoring systems.

UNITEC-D E-Catalog

List of used standards, manufacturing instructions and failure analysis manuals

  • EN 60034-1 — Technical conditions for electric motors.
  • ISO 10816-3 — Measurement of vibration on working machines.
  • DSTU 3052-95 — Requirements for electric motors in Ukraine.
  • ISO 14692:2014 - Standards for evaluating failures.
  • Schneider Electric - Technical instructions for XUB9APANM12.
  • Failure Analysis Handbook — Failure analysis methodology.

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