Electrical Troubleshooting Quiz — Nov. 19, 2019
A few years ago, an addition was made to the plant. This addition contains three heavily automated lines. They are like older lines, but have robotics replacing manual operation tasks, such as lifting sheet metal blanks into the feeder tray.
All three lines ran reliably until last year. Then, one of the four 30-hp motors on Line Two failed. The motor was replaced and sent to a motor shop for analysis. The shop reported the motor had spun a bearing, which is what the electricians who removed it had said.
Shortly after that, the main board of a controller on Line One smoked out. Other failures have occurred periodically since then. What is going on?
These failures indicate damage from at least one transient event. To prevent future events:
- Install soft starts or VFDs on larger motors to prevent “across the line” starting transients.
- Analyze your transient voltage suppression system (TVSS) against current engineering standards (e.g., make it multi-stage).
Ask that motor shop if they have kept any records that show evidence of bearing pitting. If so, you have inadequate bonding. And thus, undesired current is flowing through motor bearings and electronics.
Fixing the bonding and TVSS should prevent further damage. But what about the damage already done? Keep in mind that interrupted production is orders of magnitude more expensive than scheduled repairs are. It is probably cheaper to replace all controllers and other electronics, rather than to let them run to failure. Perform ultrasonic testing and thermographic imaging to find other looming failures.
About the Author
Mark Lamendola
Mark is an expert in maintenance management, having racked up an impressive track record during his time working in the field. He also has extensive knowledge of, and practical expertise with, the National Electrical Code (NEC). Through his consulting business, he provides articles and training materials on electrical topics, specializing in making difficult subjects easy to understand and focusing on the practical aspects of electrical work.
Prior to starting his own business, Mark served as the Technical Editor on EC&M for six years, worked three years in nuclear maintenance, six years as a contract project engineer/project manager, three years as a systems engineer, and three years in plant maintenance management.
Mark earned an AAS degree from Rock Valley College, a BSEET from Columbia Pacific University, and an MBA from Lake Erie College. He’s also completed several related certifications over the years and even was formerly licensed as a Master Electrician. He is a Senior Member of the IEEE and past Chairman of the Kansas City Chapters of both the IEEE and the IEEE Computer Society. Mark also served as the program director for, a board member of, and webmaster of, the Midwest Chapter of the 7x24 Exchange. He has also held memberships with the following organizations: NETA, NFPA, International Association of Webmasters, and Institute of Certified Professional Managers.