Tom Bishop, P.E.
EASA Senior Technical Support Specialist
Determining the source of noise in an electric motor is often more challenging than correcting it. A methodical investigative approach, however, can narrow the possibilities and make it easier to resolve the issue—with one caveat. If the noise is due to something in the motor design (e.g., a manufacturing defect or anomaly), a solution may be impossible or impractical. With that in mind, let’s review the primary sources of noise in electric motors—magnetic, mechanical, and windage—as well as their causes and ways to reduce or eliminate them.
Areas examined in this article include:
- Magnetic noise
- Slip noise
- Skewing
- Unequal air gap
- Mechanical noise
- Loose stator core
- Bearings
- Airborne noise
- Windage noise
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ANSI/EASA AR100
More information on this topic can be found in ANSI/EASA AR100
EASA Technical Manual
More information on this topic can be found in EASA's Technical Manual- Section 2: AC Machines
- Section 5: Electronics
- Section 7: Electrical Testing
- Section 8: Bearings
- Section 9: Lubrication
- Section 10: Mechanical
Related Reference and Training Materials
Principles of Medium & Large AC Motors (NEMA Standards)- Section 2: Motor Enclosures
- Section 3: Typical Motor Applications
- Section 4: Safety & Handling Considerations
- Section 5: Basic Motor Theory
- Section 6: Motor Standards
- Section 8: Squirrel Cage Rotors
- Section 12: Test & Inspection Procedures
- Section 13: Motor Alignment, Vibration & Noise
- Section 15: Synchronous Machines
Principles of Medium & Large AC Motors (IEC Standards)- Section 2: Motor Enclosures
- Section 3: Typical Motor Applications
- Section 4: Safety & Handling Considerations
- Section 5: Basic Motor Theory
- Section 6: Motor Standards
- Section 8: Squirrel Cage Rotors
- Section 10: Bearings & Lubrication
- Section 12: Test & Inspection Procedures
- Section 13: Motor Alignment, Vibration & Noise
- Section 15: Synchronous Machines
Root Cause Failure Analysis- Section 1: Root Cause Methodology
- Section 2: Bearing Failures
- Section 3: Stator Failures
- Section 4: Shaft Failures
- Section 5: Rotor Failures
- Section 6: Mechanical Failures
- Section 10: Case Studies
Fundamentals of DC Motors & Operation Tips- Section 6: Commutators
- Section 8: Ventilation & Accessories
- Section 9: Motor Assembly & Final Testing
- Section 11: Failure Analysis
Mechanical Repair Fundamentals of Electric Motors- Section 2: Motor Applications & Enclosures
- Section 7: Shafts
- Section 8: Rotors
- Section 9: Motor Assembly
- Section 11: Motor Dynamics
- Section 12: Vibration & Motor Geometry
- Section 13: Shaft/Bearing Currents
- Section 15: Failures in Mechanical Components
- Section 16: Miscellaneous Repairs
Fundamentals of Pump Repair- Section 2: General Pump Repair Procedures
- Section 8: Pump Reliability
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