What is a Rogowski Coil?

Patrick Roland

A Rogowski coil is a simple device used to measure alternating current or high speed electrical currents. Its unique design sets it apart from other measuring devices both structurally and performance-wise. These coils are utilized in many fields and are sought after for the accuracy they provide. Recently, Rogowski coils have received a lot of competition from simpler sensors utilizing similar technology.

Man with a drill
Man with a drill

The Rogowski coil design is unique because of its air core, as opposed to previous measuring devices that utilized an iron core. The air core comes courtesy of a single wire being looped several times until it makes a tight coil, looking similar to a miniature wound up garden hose. This coil is then formed into a circular shape that is wrapped around the conductor that needs its current measured. The design of this coil also is unique because the ends of the wire, or the terminals, are on the same side, creating a complete loop around the conductor.

The winding of the Rogowski coil wire is the most important element of the entire device. The wound loops of the coil must be spaced uniformly, or they will run the risk of picking up magnetic interference. The more interference that enters the coil's sphere, the less accurate its measurements will be.

A Rogowski coil measures the alternating electrical current by attaching each of the leads to an integrator circuit. The coil picks up the output current coming off the conductor and sends the data back to the integrator circuit. The result is a map of current patterns and, if properly calibrated, a measurement of the amount of current.

Rogowski coils are used in many industries to measure currents. Electric power transmission and welding, where powerful currents are frequently used, are two of the most popular uses of the coil. Its ability to fit over an active conductor, because of its lightweight construction, allows it to be applied to practically any conductor.

The Rogowski coil has seen a great deal of competition in the alternating current measurement field. Using low-cost circuit board technology and electronic sensors, newer components are able to measure a conductor's current accurately. These cheaper, lighter measuring devices have threatened the coil's decades of dominance in the field of current measurement.

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