6-Month Maintenance for 3-Phase Induction Motors Guide

Low-voltage three-phase induction motors are the backbone of industrial operations. But like any hardworking machine, they need regular maintenance to stay reliable. In this blog, we’ll walk through a human-friendly, step-by-step checklist for performing a complete 6-month periodic maintenance inspection.

This guide is ideal for electricians, maintenance engineers, and plant technicians looking to maximize motor performance and lifespan.


1.1 Isolate Power

Before doing anything, isolate power at the substation drawer to ensure zero electrical energy is available during the maintenance process.

1.2 Lockout/Tagout (LOTO)

Apply the lockout/tagout procedure. Each technician should receive a personal lock to secure the power source.

1.3 Local Isolation

Also isolate the local start/stop station to double-confirm that the motor cannot start accidentally.

1.4 Verify Zero Energy

Use a voltage tester to confirm no live voltage exists. Always wear appropriate personal protective equipment (PPE).


Inspect the motor for any obvious signs of damage or wear:

  • Housing and terminal box
  • Cooling fins and fan cover
  • Cable gland
  • Signs of overheating, corrosion, oil leaks, or dust build-up

3.1 Winding Continuity / Resistance Test

Use a digital multimeter or ohmmeter to test:

  • UV, VW, and UW winding pairs
  • Ensure resistance values are within ±10%
  • Record values and compare with fingerprint/reference values

3.2 Insulation Resistance Test

Use a 500V or 1,000V insulation tester (megger):

  • Test between U, V, or W to Earth (if terminals are connected)
  • If disconnected, test between UV, VW, UW
  • Acceptable resistance is over 1 MΩ
  • Record results for trending and comparison

Use a clamp-type earth resistance tester to check ground connection:

  • Confirm resistance is within standard (usually <5Ω or <2Ω)
  • Record measured values for future reference

5.1 Retightening

Inspect and retighten any loose control or power connections in the substation drawer.

5.2 Test Protection Devices

  • Test overload relays and contactors
  • Confirm trip settings match the motor’s full-load current
  • Simulate fault if safe to ensure proper trip function

5.3 Verify Logic and Interlocks

Double-check the control logic and any interlock conditions are functioning correctly.


  • Remove all LOTO tags and locks only after verifying all systems are secure
  • Reconnect terminals and control wiring properly
  • Restore power and perform a test run
  • Observe for any abnormal sounds, vibration, or temperature rise

  • Follow manufacturer’s lubrication schedule (typically every 4,000 working hours)
  • Use correct grease type as recommended
  • Wipe off excess grease and seal the grease nipple after application

Use a thermal camera to scan while the motor is running:

  • Inspect winding temperature
  • Scan terminal connections
  • Check bearing heat levels
  • Document anomalies for future analysis

You can download the complete 6-month motor checklist from here

Performing this 6-month maintenance checklist not only prevents breakdowns but also ensures optimal efficiency and safety. Regular testing, inspections, and lubrication are essential habits for any facility using low-voltage three-phase motors.

Stay safe, stay efficient, and let knowledge enlighten your world.

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