Cyndi Nyberg
Former Technical Support Specialist
Electrical Apparatus Service Association
St. Louis, MO
In the paper "A New Look at Thermography: More Options for Sales/Service and Profit," Cyndi Nyberg explores the expanded applications and benefits of infrared thermography (IR) for service centers. In the current economic climate, service centers are seeking ways to enhance their service offerings and increase profitability, while end users aim to reduce costs and downtime. Predictive and preventative maintenance have become crucial in the industry, and IR thermography offers a valuable tool for monitoring the condition of electric motor systems and detecting potential problems before catastrophic failures occur.
Infrared thermography is an electronic method that converts thermal energy into a digital readout or picture. Infrared radiation is emitted by any object above absolute zero, and thermal imaging detects this radiation, assigning specific colors to different temperatures. Basic IR equipment includes handheld spot radiometers for quick surface temperature checks and infrared cameras that produce thermal images. These cameras can display temperature variations in color or black and white, with dark colors representing cooler temperatures and bright colors indicating hotter surfaces.
Thermography is traditionally used to detect high-resistance joints in switchgear and motor control centers (MCCs), but it also has niche applications in monitoring the entire motor system, including driven equipment, MCCs, cable runs, protective devices, and power supplies. The paper emphasizes that IR should be used in conjunction with other tests and technologies, such as vibration analysis, current analysis, insulation resistance testing, and visual inspection, to provide a complete picture of the motor system's condition.
In the service center, IR can be employed to test for open rotors, assess the condition of stator cores and windings, and identify issues such as broken rotor bars, incomplete soldered connections, and shorted laminations. For example, core loss testing involves using a loop test or core loss tester to detect localized core damage, which appears as hot spots on thermal images. Testing windings with IR can reveal unbalanced heating, shorts, connection problems, and grounds. Similarly, IR can identify open or cracked rotor bars, shorted laminations, and high-resistance joints in armatures.
Thermography is also useful for inspecting bearings, which can overheat due to under- or over-lubrication, excessive load, improper fits or clearances, or reaching the end of their life. IR can detect bearing problems by comparing the surface temperatures of the drive end (DE) and opposite drive end (ODE). Additionally, IR can be used for no-load testing of motors, synchronous motor heating, restricted airflow, unbalanced voltage, transformers, belts and pulleys, couplings, drives, gearboxes, brush contact, and cold spots.
The paper highlights the importance of establishing baseline conditions for equipment and monitoring temperature trends over time. IR inspections are fast and easy to perform, making them a valuable part of a comprehensive predictive maintenance program. Training and safety are crucial for effective thermography, and the paper references standards such as NFPA 70B, NFPA 70E, and ASTM E1934, which provide guidelines for qualification, safety practices, and proper procedures.
Key Points Covered:
- Definition and basics of infrared thermography
- Traditional and niche applications of IR in service centers and field environments
- Importance of using IR in conjunction with other tests and technologies
- Service center uses of IR for testing cores, windings, rotors, bearings, and shop equipment
- Establishing baseline conditions and monitoring temperature trends
- Training and safety considerations for effective thermography
- Standards and guidelines for qualification and safety practices
Key Takeaways:
- Infrared thermography is a valuable tool for predictive and preventative maintenance.
- IR can detect problems in electric motor systems before catastrophic failures occur.
- Using IR in conjunction with other tests provides a complete picture of equipment condition.
- Service centers can employ IR for various tests and assessments, improving reliability and reducing costs.
- Establishing baseline conditions and monitoring trends are essential for effective maintenance.
- Proper training and adherence to safety standards are crucial for successful thermography.
- IR inspections are fast, easy, and can significantly enhance maintenance programs.
Related Reference and Training Materials
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