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IR Inspections of Electric Motors
Tip written by: Infraspection Institute

Despite the important role they play in a commercial facility, electric motors tend to be both out-of-sight and out-of-mind until they fail. Infrared thermography can be used as a cost-effective diagnostic tool for detecting problems within electric motor systems.

Thermal image shows defective connection within motor junction box

Many infrared inspection programs include motor control circuits but overlook the motor itself. Evidence of several conditions which can lead to premature motor failure can be detected with a thermal imager. The following are suggestions for thermographically inspecting motors.

• With cover removed, inspect electrical connections at the motor junction box. This should be done in conjunction with the regularly scheduled inspection of the facility’s electrical system.
• Inspect motor casing for localized hotspots which may be indicative of short circuits within motor windings
• Qualitatively compare individual motors to similar motors under similar load
• When possible, qualitatively compare inboard and outboard bearings for each motor. If a large Delta T is present, it may be indicative of misalignment or a rotor balance problem. If both bearings are hot, the bearings may be worn or improperly lubricated.

Because no complicated analysis is required, infrared inspections typically can be performed rapidly and at a fraction of the cost of other types of motor testing. Additionally, infrared can detect evidence of misalignment at lower thresholds than those detectable by vibration analysis and motor current signature analysis.

Lastly, infrared inspections of motor bearings and stator should be performed monthly by experienced, certified infrared thermographers who thoroughly understand the theory and operation of electric motors.

Infrared inspection of electric motors is one of the many topics covered in the Level I Infraspection Institute Certified Infrared Thermographer^® training course. For information on thermographer training including our Distance Learning courses, visit us online at www.infraspection.com or call us at 609-239-4788.