2022 Fault Zone Series: Part 6 Air Gap

Returning to the Fault Zone approach to electric motor troubleshooting we continue this series with Air Gap. When PdMA refers to the Air Gap Fault Zone, it is referring to faults resulting in a non-symmetric air gap between the rotor and stator. With the improved precision design and alignment of today’s motors the air gap between the rotor and stator has never been smaller, providing more opportunity for air gap issues to become severe.

Like in other fault zones a variety of root causes should be considered when trying to get ahead of an air gap fault. Air gap faults, if not identified as the root cause may result in a motor failure blamed on another fault zone. The following are some potential indications or sources of air gap faults:

  • Increased Vibration
  • Increasing Air Gap Related Frequency Peaks on Current Spectrum
  • Rotor/Stator Rub Marks
  • Increased Motor Temperature
  • Pole-to-Pole Inductance Pattern Variations on Rotor Influence Check
  • Loose or Overly Tightened Hold Down Bolts on Foot Mounted Motors

Note that many of the fault indications above are based on a comparison to a baseline or trend. Remember…Trend is Your Friend.

For more examples of Air Gap anomalies and alarm standards applied to your electric motor reliability view our Air Gap Fault Zone Diagnostic Tool on our website at https://pdma.com/diagnostic-tools/fault-zone-air-gap/