Motor Diagnostics (2)

2. Electric Motor

The primary purpose of the electric motor is to convert electrical energy to mechanical torque. As a result, it has both electrical and mechanical components that must be considered.

Electric motors include mechanical and electrical components.

The first review is mechanical.
The primary mechanical problems include:

  • Bearings
  • Bad or worn shaft or bearing housings
  • Vibration issues

Each of these can be detected using:

  • Motor current signature analysis will detect the more severe problems.
  • Vibration analysis will detect the faults earliest but requires a fair amount of experience.
  • Infrared will detect problems when they are severe.
  • Ultrasonics will detect the more severe problems

Electrical faults include:

  • Winding shorts including turn to turn and coil to coil
  • Insulation to ground faults
  • Winding contamination
  • Rotor faults including casting voids and broken rotor bars
  • Air gap faults including an eccentric rotor

The winding tests to detect these problems include:

  • MCA and MCSA will detect all of the faults
  • Vibration will detect late-stage faults
  • Insulation to ground will only detect ground faults
  • Surge testing will only detect winding shorts in the first few turns of the winding
  • All other testing will only detect late stage faults.

to be continued…..

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