Ecmweb 13072 Promotransientvoltagewaveform
Ecmweb 13072 Promotransientvoltagewaveform
Ecmweb 13072 Promotransientvoltagewaveform
Ecmweb 13072 Promotransientvoltagewaveform
Ecmweb 13072 Promotransientvoltagewaveform

Tip of the Week: Are Your Motors Getting Hit by Transients?

March 27, 2017
A power monitor can provide the data to determine when a transient event occurred and how long it lasted.

By definition, transient voltage events don’t last long. But a single event, if of sufficient magnitude, can destroy a motor. So can events of smaller magnitude that go unnoticed as they cause winding insulation to deteriorate.

We call a voltage event a transient when it lasts only momentarily. The voltage event may be a spike or a dip. A spike can do things like cause overheating or simply punch a hole in the insulation of conductors or motor windings. A voltage dip also can cause overheating, because the motor is going to demand more current when that dip occurs.

Suppose someone asks you if a given motor has been experiencing transient voltage events. How would you know? If lightning struck the building yesterday, you could probably say “yes” with reasonable confidence. But without instrumentation, you really have no way of knowing if that motor got hit by transients or not.

These random transient voltages (i.e., waveform notching) were recorded at a 480V service entrance with a power monitor.

You can’t hook up a digital multimeter (DMM) and have it look backward in time to measure an event that already happened. The only way to know if an event happened is to look at measurements that have been recorded. You want to do this with something more than the high-low recording feature on a DMM. For one thing, that DMM can’t tell you how many transient events it saw (if, indeed, it was fast enough to capture any).

You need something that is fast enough to capture each transient event, and you need something that will tell you when each occurred and how long it lasted. It would be nice to know not only the magnitude of each transient but also what its waveform looked like.

A power monitor fits the bill. It’s unlikely you can have it watch all of your motors, but you can have it watch your critical motor feeders.

If you have any large motors that start across the line but you haven’t been able to get management to spring for a soft starter, a report generated from the power monitor data will show what those motors are doing to the rest of your equipment via the power distribution system.

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.

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