Why is the Rogowski coil an alternative to traditional CTs?

Named after their inventor, Walter Rogowski, the Rogowski style of coils was first developed in 1912. They function as a measurement tools that determine the current moving through a conductor that has been inserted within the flexible Rogowski loop.

Rogowski coils allows the observer to accurately examine the changes in current over a given period. To utilize the output, you may need to “integrate” the raw voltage output. We’ll talk about what this means in a minute, but first we need to explain a little more about the coils themselves.

The Rogowski coil is a closed loop configuration that is wound over a nonmagnetic, constant cross-sectional area. The extreme flexibility of the coil allows it to be wrapped around cables and bus bars without disrupting the power or adding an energy burden to the line that is being measured.

The linear output and flexibility of the coil provide for more versatile functioning than the traditional CTs; however, there are some downsides. Even though you can measure high amperage with no saturation, the coil inductance displaces the phase +90 degrees with respect to the input current.

The Rogowski coil is a useful alternative to traditional CTs because it:

1. Enables the consumer to span a broad range of amperages and frequencies from Hz to MHz.

2. Is often less expensive to implement than CTs capable of similar measurement, which enables you to lower the cost of construction.

3. Offers great physical flexibility as well as a smaller size (than CTs capable of similar measurement).

4. May require “integration” if your measuring device doesn’t support them passively.